Papers on sea level in small island countries

This is a list of papers on sea level changes in small island countries such as Maldives. Emphasis is on the sea level observations, not its consequences. There are plenty of papers dealing with vulnerability of the island countries but so far only couple of such papers are included here. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (November 17, 2011): Merrifield (2011) and Becker et al. (2012) added.

Sea level variations at tropical Pacific islands since 1950 – Becker et al. (2012) “The western tropical Pacific is usually considered as one of the most vulnerable regions of the world under present-day and future global warming. It is often reported that some islands of the region already suffer significant sea level rise. To clarify the latter concern, in the present study we estimate sea level rise and variability since 1950 in the western tropical Pacific region (20°S–15°N; 120°E–135°W). We estimate the total rate of sea level change at selected individual islands, as a result of climate variability and change, plus vertical ground motion where available. For that purpose, we reconstruct a global sea level field from 1950 to 2009, combining long (over 1950–2009) good quality tide gauge records with 50-year-long (1958–2007) gridded sea surface heights from the Ocean General Circulation Model DRAKKAR. The results confirm that El Niño-Southern Oscillation (ENSO) events have a strong modulating effect on the interannual sea level variability of the western tropical Pacific, with lower/higher-than-average sea level during El Niño/La Niña events, of the order of ± 20–30 cm. Besides this sub-decadal ENSO signature, sea level of the studied region also shows low-frequency (multi decadal) variability which superimposes to, thus in some areas amplifies current global mean sea level rise due to ocean warming and land ice loss. We use GPS precise positioning records whenever possible to estimate the vertical ground motion component that is locally superimposed to the climate-related sea level components. Superposition of global mean sea level rise, low-frequency regional variability and vertical ground motion shows that some islands of the region suffered significant ‘total’ sea level rise (i.e., that felt by the population) during the past 60 years. This is especially the case for the Funafuti Island (Tuvalu) where the “total” rate of rise is found to be about 3 times larger than the global mean sea level rise over 1950–2009.” M. Becker, B. Meyssignac, C. Letetrel, W. Llovel, A. Cazenave, T. Delcroix, Global and Planetary Change, Volumes 80-81, January 2012, Pages 85-98, doi:10.1016/j.gloplacha.2011.09.004.

A Shift in Western Tropical Pacific Sea Level Trends during the 1990s – Merrifield (2011) “Pacific Ocean sea surface height trends from satellite altimeter observations for 1993–2009 are examined in the context of longer tide gauge records and wind stress patterns. The dominant regional trends are high rates in the western tropical Pacific and minimal to negative rates in the eastern Pacific, particularly off North America. Interannual sea level variations associated with El Niño–Southern Oscillation events do not account for these trends. In the western tropical Pacific, tide gauge records indicate that the recent high rates represent a significant trend increase in the early 1990s relative to the preceding 40 years. This sea level trend shift in the western Pacific corresponds to an intensification of the easterly trade winds across the tropical Pacific. The wind change appears to be distinct from climate variations centered in the North Pacific, such as the Pacific decadal oscillation. In the eastern Pacific, tide gauge records exhibit higher-amplitude decadal fluctuations than in the western tropical Pacific, and the recent negative sea level trends are indistinguishable from these fluctuations. The shifts in trade wind strength and western Pacific sea level rate resemble changes in dominant global modes of outgoing longwave radiation and sea surface temperature. It is speculated that the western Pacific sea level response indicates a general strengthening of the atmospheric circulation over the tropical Pacific since the early 1990s that has developed in concert with recent warming trends.” Merrifield, Mark A., 2011: A Shift in Western Tropical Pacific Sea Level Trends during the 1990s. J. Climate, 24, 4126–4138, doi: 10.1175/2011JCLI3932.1. [Full text]

Patterns of Indian Ocean sea-level change in a warming climate – Han et al. (2010) “Global sea level has risen during the past decades as a result of thermal expansion of the warming ocean and freshwater addition from melting continental ice. However, sea-level rise is not globally uniform. Regional sea levels can be affected by changes in atmospheric or oceanic circulation. As long-term observational records are scarce, regional changes in sea level in the Indian Ocean are poorly constrained. Yet estimates of future sea-level changes are essential for effective risk assessment. Here we combine in situ and satellite observations of Indian Ocean sea level with climate-model simulations, to identify a distinct spatial pattern of sea-level rise since the 1960s. We find that sea level has decreased substantially in the south tropical Indian Ocean whereas it has increased elsewhere. This pattern is driven by changing surface winds associated with a combined invigoration of the Indian Ocean Hadley and Walker cells, patterns of atmospheric overturning circulation in the north–south and east–west direction, respectively, which is partly attributable to rising levels of atmospheric greenhouse gases. We conclude that—if ongoing anthropogenic warming dominates natural variability—the pattern we detected is likely to persist and to increase the environmental stress on some coasts and islands in the Indian Ocean.” Weiqing Han, Gerald A. Meehl, Balaji Rajagopalan, John T. Fasullo, Aixue Hu, Jialin Lin, William G. Large, Jih-wang Wang, Xiao-Wei Quan, Laurie L. Trenary, Alan Wallcraft, Toshiaki Shinoda & Stephen Yeager, Nature Geoscience 3, 546 – 550 (2010), doi:10.1038/ngeo901. [Full text]

Wind Effects on Past and Future Regional Sea Level Trends in the Southern Indo-Pacific – Timmermann et al. (2010) “Global sea level rise due to the thermal expansion of the warming oceans and freshwater input from melting glaciers and ice sheets is threatening to inundate low-lying islands and coastlines worldwide. At present the global mean sea level rises at 3.1 ± 0.7 mm yr⁻¹ with an accelerating tendency. However, the magnitude of recent decadal sea level trends varies greatly spatially, attaining values of up to 10 mm yr⁻¹ in some areas of the western tropical Pacific. Identifying the causes of recent regional sea level trends and understanding the patterns of future projected sea level change is of crucial importance. Using a wind-forced simplified dynamical ocean model, the study shows that the regional features of recent decadal and multidecadal sea level trends in the tropical Indo-Pacific can be attributed to changes in the prevailing wind regimes. Furthermore, it is demonstrated that within an ensemble of 10 state-of-the-art coupled general circulation models, forced by increasing atmospheric CO₂ concentrations over the next century, wind-induced redistributions of upper-ocean water play a key role in establishing the spatial characteristics of projected regional sea level rise. Wind-related changes in near-surface mass and heat convergence near the Solomon Islands, Tuvalu, Kiribati, the Cook Islands, and French Polynesia oppose—but cannot cancel—the regional signal of global mean sea level rise.” Timmermann, Axel, Shayne McGregor, Fei-Fei Jin, 2010, J. Climate, 23, 4429–4437, doi: 10.1175/2010JCLI3519.1.

The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal analysis of island change in the Central Pacific – Webb & Kench (2010) “Low-lying atoll islands are widely perceived to erode in response to measured and future sea-level rise. Using historical aerial photography and satellite images this study presents the first quantitative analysis of physical changes in 27 atoll islands in the central Pacific over a 19 to 61 yr period. This period of analysis corresponds with instrumental records that show a rate of sea-level rise of 2.0 mm yr⁻¹ in the Pacific. Results show that 86% of islands remained stable (43%) or increased in area (43%) over the timeframe of analysis. Largest decadal rates of increase in island area range between 0.1 to 5.6 ha. Only 14% of study islands exhibited a net reduction in island area. Despite small net changes in area, islands exhibited larger gross changes. This was expressed as changes in the planform configuration and position of islands on reef platforms. Modes of island change included: ocean shoreline displacement toward the lagoon; lagoon shoreline progradation; and, extension of the ends of elongate islands. Collectively these adjustments represent net lagoonward migration of islands in 65% of cases. Results contradict existing paradigms of island response and have significant implications for the consideration of island stability under ongoing sea-level rise in the central Pacific. First, islands are geomorphologically persistent features on atoll reef platforms and can increase in island area despite sea-level change. Second, islands are dynamic landforms that undergo a range of physical adjustments in responses to changing boundary conditions, of which sea level is just one factor. Third, erosion of island shorelines must be reconsidered in the context of physical adjustments of the entire island shoreline as erosion may be balanced by progradation on other sectors of shorelines. Results indicate that the style and magnitude of geomorphic change will vary between islands. Therefore, island nations must place a high priority on resolving the precise styles and rates of change that will occur over the next century and reconsider the implications for adaption.” Arthur P. Webb and Paul S. Kench, Global and Planetary Change, Volume 72, Issue 3, June 2010, Pages 234-246, doi:10.1016/j.gloplacha.2010.05.003. [Full text]

Submerged reef terraces of the Maldives (Indian Ocean) – Fürstenau et al. (2009) “There is limited knowledge about the record of sea-level rise from the last glacial maximum (LGM) until the onset of Holocene reef growth in the Maldives archipelago. Multibeam data show that atoll slopes between 130 and 55 mbsl (meters below sea level) are characterized by a step-like morphology. In parts, these terraces show a raised rim and a crenate geometry. Atoll margin features can be interpreted as successive reef-growth and -drowning stages, which are attributable to changes in the rate of sea-level rise. These changes can tentatively be correlated to known records of global sea-level change since the LGM. In addition to terraces between 97 and 55 mbsl, which can be associated with the initiation of meltwater pulses MWP-1A and -1B, several reef-drowning stages between 94 and 68 mbsl are proposed. As the Maldives can be considered a tectonically stable, far-field site, the submerged reef terraces inferred from the first multibeam dataset for this region likely represent a valuable archive for global deglacial sea-level history in the Indian Ocean.” Jörn Fürstenau, Sebastian Lindhorst, Christian Betzler and Christian Hübscher, Geo-Marine Letters, Volume 30, Number 5, 511-515, DOI: 10.1007/s00367-009-0174-2.

Late Quaternary reef growth and sea level in the Maldives (Indian Ocean) – Gischler et al. (2008) “Based on rotary drilling and radiometric and U-series dating, we present the first comprehensive data on Holocene reef anatomy and sea-level rise as well as nature and age of underlying Pleistocene limestone in the Maldives. Holocene reefs in Rasdhoo Atoll, central Maldives, are composed of four facies including (1) robust-branching coral facies, (2) coralline algal facies, (3) domal coral facies, and (4) detrital sand and rubble facies. Branching coral and coralline algal facies predominate the marginal reefs and domal corals and detrital facies preferentially occur in a lagoon reef. In addition, microbialite crusts are found in lower core sections of marginal reefs. Microbialites formed during the early Holocene in reef cavities. Holocene reef thickness ranges from 14.5 m to > 22 m. Reef growth started as early as 8.5 kyr BP. Marginal reefs accreted in the keep-up mode with rates of > 15 m/kyr. Rate of sea-level rise significantly slowed down from 7–6 kyr BP and subsequently gradually rose with rates < 1 m/kyr. The lagoon reef accreted in the catch-up mode with rates of around 4 m/kyr. Even though no indications of a higher than present sea level were found during this study, it is not entirely clear from the data whether the sea gradually rose to or exceeded present level in the late Holocene. Submarine cementation in Holocene reefs studied is rather weak, presumably as a consequence of high accretion-rates, i.e., short time available for consolidation. Pleistocene coral grainstone was encountered in one core at 14.5 m below present level and three U-series dates indicate deposition during marine isotope stage 5e ca. 135 kyr BP.” Eberhard Gischler, J. Harold Hudson and Andrzej Pisera, Marine Geology, Volume 250, Issues 1-2, 21 April 2008, Pages 104-113, doi:10.1016/j.margeo.2008.01.004.

Reef-island topography and the vulnerability of atolls to sea-level rise – Woodroffe (2008) “Low-lying reef islands on the rim of atolls are perceived as particularly vulnerable to the impacts of sea-level rise. Three effects are inferred: erosion of the shoreline, inundation of low-lying areas, and saline intrusion into the freshwater lens. Regional reconstruction of sea-level trends, supplementing the short observational instrumental record, indicates that monthly mean sea level is rising in the eastern Indian and western Pacific Oceans. This paper reviews the morphology and substrate characteristics of reef islands on Indo-Pacific atolls, and summarises their topography. On most atolls across this region, there is an oceanward ridge built by waves to a height of around 3 m above MSL; in a few cases these are topped by wind-blown dunes. The prominence of these ridges, together with radiocarbon dating and multi-temporal studies of shoreline position, indicate net accretion rather than long-term erosion on most of these oceanward shores. Less prominent lagoonward ridges occur, but their morphology and continuity are atoll-specific, being a function of the processes operating in each lagoon. Low-lying central areas are a feature of many islands, often locally excavated for production of taro. These lower-lying areas are already subject to inundation, which seems certain to increase as the sea rises. Tropical storms play an important role in the geomorphology of reef islands in those regions where they are experienced. Topographical differences, as well as features such as emergence of the reef flat and the stability of the substrate, mean that islands differ in terms of their susceptibility to sea-level rise. Further assessment of variations in shoreline vulnerability based on topography and substrate could form the basis for enhancing the natural resilience of these islands.” Colin D. Woodroffe, Global and Planetary Change, Volume 62, Issues 1-2, May 2008, Pages 77-96, doi:10.1016/j.gloplacha.2007.11.001. [Full text]

Sea-level rise at tropical Pacific and Indian Ocean islands – Church et al. (2006) “Historical and projected sea-levels for islands in the tropical Pacific and Indian oceans are a subject of considerable interest and some controversy. The large variability (e.g. El Niño) signals and the shortness of many of the individual tide-gauge records contribute to uncertainty of historical rates of sea-level rise. Here, we determine rates of sea-level rise from tide gauges in the region. We also examine sea-level data from the TOPEX/Poseidon satellite altimeter and from a reconstruction of sea level in order to put the sparse (in space and time) tide-gauge data into context. For 1993 to 2001, all the data show large rates of sea-level rise over the western Pacific and eastern Indian Ocean (approaching 30 mm yr⁻¹) and sea-level falls in the eastern Pacific and western Indian Ocean (approaching − 10 mm yr⁻¹). Over the region 40°S to 40°N, 30°E to 120°W, the average rise is about 4 mm yr⁻¹. For 1950 to 2001, the average sea-level rise (relative to land) from the six longest tide-gauge records is 1.4 mm yr⁻¹. After correcting for glacial isostatic adjustment and atmospheric pressure effects, this rate is 2.0 mm yr⁻¹, close to estimates of the global average and regional average rate of rise. The long tide-gauge records in the equatorial Pacific indicate that the variance of monthly averaged sea-level after 1970 is about twice that before 1970. We find no evidence for the fall in sea level at the Maldives as postulated by Mörner et al. (2004). Our best estimate of relative sea-level rise at Funafuti, Tuvalu is 2 ± 1 mm yr⁻¹ over the period 1950 to 2001. The analysis clearly indicates that sea-level in this region is rising. We expect that the continued and increasing rate of sea-level rise and any resulting increase in the frequency or intensity of extreme sea-level events will cause serious problems for the inhabitants of some of these islands during the 21st century.” John A. Church, Neil J. White, and John R. Hunter, Global and Planetary Change, Volume 53, Issue 3, September 2006, Pages 155-168, doi:10.1016/j.gloplacha.2006.04.001. [Full text]

Have there been large recent sea level changes in the Maldive Islands? – Woodworth (2005) “The Maldive Islands are often used as case studies within research into the impacts of potential future sea level change. Therefore, if such studies are to be realistic, it is important that the past and future variations of sea level in the islands are understood as well as possible. That objective led a fieldwork team to the Maldives, and resulted in a conclusion that sea level in the islands fell by approximately 30 cm during the past few decades. In the present paper, the suggestion of such a fall has been examined from meteorological and oceanographic perspectives and found to be implausible. A number of met-ocean data sets and regional climate indices have been examined, at least one of which would have been expected to reflect a large sea level fall, without any supporting evidence being found. In particular, a suggestion that an increase in evaporation could have caused the fall has been demonstrated to be incorrect. Without any real evidence for a hitherto-unrecognised process which could lead to a sea level change as significant as that proposed by the fieldwork team, one concludes that a rise in sea level of approximately half a metre during the 21st century, as suggested by the Intergovernmental Panel on Climate Change Third Assessment Report, remains the most reliable scenario to employ in future studies of the islands.” Philip L. Woodworth, Global and Planetary Change, Volume 49, Issues 1-2, November 2005, Pages 1-18, doi:10.1016/j.gloplacha.2005.04.001.

Late Quaternary sea-level highstands in the central and eastern Indian Ocean: A review – Woodroffe (2005) “The relative sea-level history of several atolls in the central and eastern Indian Ocean, including the Cocos (Keeling) Islands, Chagos Archipelago, and the Maldives–Laccadive Archipelagoes, has been debated for over a century but takes on a particular significance in the face of anticipated climate change. For each of these central and eastern Indian Ocean atolls Pleistocene limestone is encountered at depths of 6–20 m below sea level. On the Cocos (Keeling) Islands this has been dated to Last Interglacial age. Conglomerate platform underlies the reef islands on Cocos within which a sequence of fossil microatolls of massive and branching Porites records a gradual fall of sea level relative to the atoll. In the Maldives, the significance of outcrops of ‘reef rock’ has been vigorously debated without resolving sea-level history. Although in situ Heliopora occurs on the reef flat of Addu Atoll, dated at around 2700 radiocarbon yrs BP, other evidence for higher sea level remains poorly constrained. Conglomerates of a similar age have been described from the Chagos Archipelago, but it has not been unequivocally demonstrated that they formed under conditions of relatively higher sea level. In contrast to reefs further west in the Indian Ocean, each of these atolls has living microatolls of massive Porites that have been constrained in their upward growth by sea level. Interpretation of the upper surface of two such specimens from the Cocos (Keeling) Islands indicates broad fluctuations in the sea surface over the past century; similar microatolls are described from the Maldives implying little change in sea level over recent years. Regardless of minor past fluctuations, most reef islands in the Maldives are particularly low-lying and appear vulnerable to inundation, and extracting a more detailed sea-level history remains an important challenge.” Colin D. Woodroffe, Global and Planetary Change, Volume 49, Issues 1-2, November 2005, Pages 121-138, doi:10.1016/j.gloplacha.2005.06.002.

Holocene sea-level changes in the Indo-Pacific – Woodroffe & Horton (2005) “Holocene sea-level reconstructions exist from many locations in the Indo-Pacific region. Despite being a large geographical region, the nature of Holocene sea-level change is broadly similar in all locations. Differences do exist, however, in the timing and magnitude of the Mid-Holocene High Stand (MHHS) and the nature of late Holocene sea level fall across the region. When the Indo-Pacific is subdivided into smaller regions, these discrepancies do not disappear, and in some cases the discrepancies are large within a single coastline. It is clear from this analysis that the fundamental criteria to produce accurate local relative sea-level curves are hardly ever met. There are serious problems associated with the correct interpretation of sea-level indicators and their relationship to mean sea level, and with the quality of age determinations. A consistent methodology throughout the Indo-Pacific for the analysis of sea level data is lacking. Future sea-level analysis from far field locations must involve the application of a consistent methodology in order to allow meaningful comparison between studies. This should help to resolve the ongoing debate about the magnitude and timing of the Mid-Holocene High Stand, and the nature of late Holocene sea-level fall across the region.” S. A. Woodroffe and B. P. Horton, Journal of Asian Earth Sciences, Volume 25, Issue 1, April 2005, Pages 29-43, doi:10.1016/j.jseaes.2004.01.009.

New perspectives for the future of the Maldives – Mörner et al. (2004) “Novel prospects for the Maldives do not include a condemnation to future flooding. The people of the Maldives have, in the past, survived a higher sea level of about 50–60 cm. The present trend lack signs of a sea level rise. On the contrary, there is firm morphological evidence of a significant sea level fall in the last 30 years. This sea level fall is likely to be the effect of increased evaporation and an intensification of the NE-monsoon over the central Indian Ocean.” Nils-Axel Mörner, Michael Tooley, and Göran Possnert, Global and Planetary Change, Volume 40, Issues 1-2, January 2004, Pages 177-182, doi:10.1016/S0921-8181(03)00108-5. [Full text]

Coral microatolls and 20th century sea level in the eastern Indian Ocean – Smithers & Woodroffe (2001) “Coral microatolls are discoid intertidal corals that are limited in their upward growth by subaerial exposure during low tides. Microatoll upper surface morphology preserves a filtered record of changes in the height of living coral (HLC), the upper limit to which corals can grow, and by proxy a historical record of former constraining water levels. Chronologies for these variations in HLC were established in this study using annual skeletal density bands revealed when skeletal slices were X-radiographed, supplemented by annual fluorescent bands visible when samples were illuminated with ultra-violet light. The upper surface morphologies of two large microatolls from separate reef-flat sites on the Cocos (Keeling) Islands are well correlated and indicate that the upper limit to coral growth has fluctuated by more than 5 cm since the early 1900s. The upper surfaces of these microatolls also indicate that there has been little net rise in sea level in the eastern Indian Ocean during the 20th century. Microatoll surface morphology suggests that average rates of sea-level rise in the eastern Indian Ocean over this period were less than 0.35 mm yr−1, a rate considerably lower than the rate of average global sea-level change determined from aggregated tide-gauge data. The broad surface undulations do not appear to correlate directly with either El Niño-Southern Oscillation events or occurrence of the Indian Ocean dipole mode of ocean-atmosphere circulation. Microatolls provide a simple and effective method for extrapolating broad variations in sea level beyond the tide-gauge record in remote mid-oceanic settings.” Scott G. Smithers and Colin D. Woodroffe, Earth and Planetary Science Letters, Volume 191, Issues 1-2, 30 August 2001, Pages 173-184, doi:10.1016/S0012-821X(01)00417-4.

Illuminating Sea-Level Fall around AD 1220–1510 (730-440 cal yr BP) in the Pacific Islands: Implications for Environmental Change and Cultural Transformation – Nunn (2000) “This paper focuses on the climatic transition between the Little Climatic Optimum (approximately AD 750–1300 or 1200-650 cal yr BP) and the Little Ice Age (approximately AD 1300–1800 or 650-150 cal yr BP) in the Pacific Islands. This transition was marked by rapid temperature and sea-level fall, and perhaps by sharply-increased precipitation associated with an increase in El Nino frequency. Examples from throughout the Pacific Islands demonstrate the possible and/or likely effects of sea-level fall at this time on inland horticulture through water-table fall; on coral reefs and lagoons through the emergence of reef surfaces and the consequent reduction of nearshore water circulation; on the emergence of reef islets and the conversion of tidal inlets to brackish lakes. The effects of such changes on human lifestyles are explored.” Patrick D. Nunn, New Zealand Geographer, Volume 56, Issue 1, pages 46–54, April 2000, DOI: 10.1111/j.1745-7939.2000.tb00559.x.

Holocene Sea-Level Record on Funafuti and Potential Impact of Global Warming on Central Pacific Atolls – Dickinson (1999) “Geomorphic features inherited from the mid-Holocene glacio-hydro-isostatic sea-level highstand that affected the central Pacific region influence the susceptibility of atoll islets to potentially enhanced wave erosion associated with rise in sea level from global warming. Shoreline morphology on multiple islets of Funafuti atoll in central Tuvalu reflects a relative mid-Holocene sea-level highstand 2.2–2.4 m above modern sea level. Typical islets are composed of unconsolidated post-mid-Holocene sediment resting disconformably on cemented coral rubble formed beneath now-emergent mid-Holocene reef flats. Exposed remnants of the lithified islet foundations serve as resistant buttresses protecting the flanks of atoll islets from wave attack. Islets lacking cemented mid-Holocene deposits as part of their internal structure are migratory sand cays with unstable shorelines. Any future sea-level rise ≥0.75 m, bringing high tide above the elevation of mid-Holocene low tide, might trigger enhanced wave erosion of stable atoll islets by overtopping the indurated mid-Holocene reef platforms. As analogous threshold relations are inferred for other central Pacific atolls, the risk of future inundation of island nations cannot be evaluated solely in terms of expected sea-level rise with respect to gross islet elevations.” William R. Dickinson, Quaternary Research, Volume 51, Issue 2, March 1999, Pages 124-132, doi:10.1006/qres.1998.2029.

Submarine topography of Maldivian atolls suggests a sea level of 130 metres below present at the last glacial maximum – Anderson (1998) “This present study reports the results of an echo sounding survey around four Maldivian atolls which suggests that local sea level was reduced to about 130 m below current levels during the last glacial maximum. At that time present-day atolls would have been exposed as large, steeply clifted islands.” R. C. Anderson, Coral Reefs, Volume 17, Number 4, 339-341, DOI: 10.1007/s003380050135.

Morphology and evolution of reef islands in the Maldives – Woodroffe (1992). From Mörner et al. (2004): “More recently, Woodroffe (1992) presented the first sea level curve for the Maldives. He claimed that the islands were predominantly formed by catch-up coral reef growth.” Woodroffe, C.D., 1992, Proc. 7th Int. Coral Reef Symp., Gaum 2, 1217– 1226.

Microatolls and recent sea level change on coral atolls – Woodroffe & McLean (1990) “MICROATOLLS are colonies of corals, commonly Porties, which are dead on top but living around their perimeter, and are found in intertidal environments on coral atolls. They can grow to several metres in diameter. Their upward growth is constrained by sea level through prolonged exposure at the lowest spring tides, and their dead upper surfaces have been limited by past sea levels. They act as natural recorders of sea level, which is of particular significance for coral atolls thought to be susceptible to inundation and erosion if sea level rises in response to global warming. X-radiographs of vertical slices through microatolls from the Maldives and Cocos (Keeling) Islands (Indian Ocean) and Kiribati (Pacific Ocean) record sea-level fluctuations over the past few decades. There is a high degree of reproducibility between adjacent corals, although on Cocos we noted geographical variation in the pattern of change around the atoll. The majority of microatolls sampled on these atolls record a slight fall in sea level over the past ten years.” Colin Woodroffe & Roger McLean, Nature 344, 531 – 534 (05 April 1990); doi:10.1038/344531a0.

Sea level rise: Some implications for Tuvalu – Lewis (1989) “Much current evidence suggests that global temperatures are slowly increasing. It is believed that this increase will be associated with a sea level rise. Tuvalu, approximately 1000 km north of Fiji in the South Pacific Ocean, is one of six countries, all of them island states, that could face total destruction when sea levels rise. If sea level rises occur anywhere near the extreme projections that have been made, we can write these nations off the map. (Pernetta, 1988). This paper examines possible implications to the people of Tuvalu.” James Lewis, The Environmentalist, Volume 9, Number 4, 269-275, DOI: 10.1007/BF02241827.

New research from last week 51/2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

History of climate modeling

History of climate modeling – Edwards (2010) “The history of climate modeling begins with conceptual models, followed in the 19th century by mathematical models of energy balance and radiative transfer, as well as simple analog models. Since the 1950s, the principal tools of climate science have been computer simulation models of the global general circulation. From the 1990s to the present, a trend toward increasingly comprehensive coupled models of the entire climate system has dominated the field. Climate model evaluation and intercomparison is changing modeling into a more standardized, modular process, presenting the potential for unifying research and operational aspects of climate science.” Paul N. Edwards, Wiley Interdisciplinary Reviews: Climate Change, DOI: 10.1002/wcc.95.

Winter warming delays spring phenology

Winter and spring warming result in delayed spring phenology on the Tibetan Plateau – Yu et al. (2010) “Climate change has caused advances in spring phases of many plant species. Theoretically, however, strong warming in winter could slow the fulfillment of chilling requirements, which may delay spring phenology. This phenomenon should be particularly pronounced in regions that are experiencing rapid temperature increases and are characterized by highly temperature-responsive vegetation. To test this hypothesis, we used the Normalized Difference Vegetation Index ratio method to determine the beginning, end, and length of the growing season of meadow and steppe vegetation of the Tibetan Plateau in Western China between 1982 and 2006. We then correlated observed phenological dates with monthly temperatures for the entire period on record. For both vegetation types, spring phenology initially advanced, but started retreating in the mid-1990s in spite of continued warming. Together with an advancing end of the growing season for steppe vegetation, this led to a shortening of the growing period. Partial least-squares regression indicated that temperatures in both winter and spring had strong effects on spring phenology. Although warm springs led to an advance of the growing season, warm conditions in winter caused a delay of the spring phases. This delay appeared to be related to later fulfillment of chilling requirements. Because most plants from temperate and cold climates experience a period of dormancy in winter, it seems likely that similar effects occur in other environments. Continued warming may strengthen this effect and attenuate or even reverse the advancing trend in spring phenology that has dominated climate-change responses of plants thus far.” Haiying Yu, Eike Luedeling, and Jianchu Xu, PNAS December 21, 2010 vol. 107 no. 51 22151-22156, doi: 10.1073/pnas.1012490107. [Full text]

Climate change has affected tundra ecosystem

Climate changes and its impact on tundra ecosystem in Qinghai-Tibet Plateau, China – Wang et al. (2010) “Alpine ecosystems in permafrost region are extremely sensitive to climate change. The headwater regions of Yangtze River and Yellow River of the Qinghai-Tibet plateau permafrost area were selected. Spatial-temporal shifts in the extent and distribution of tundra ecosystems were investigated for the period 1967–2000 by landscape ecological method and aerial photographs for 1967, and satellite remote sensing data (the Landsat’s TM) for 1986 and 2000. The relationships were analyzed between climate change and the distribution area variation of tundra ecosystems and between the permafrost change and tundra ecosystems. The responding model of tundra ecosystem to the combined effects of climate and permafrost changes was established by using statistic regression method, and the contribution of climate changes and permafrost variation to the degradation of tundra ecosystems was estimated. The regional climate exhibited a tendency towards significant warming and desiccation with the air temperature increased by 0.4–0.67°C/10a and relative stable precipitation over the last 45 years. Owing to the climate continuous warming, the intensity of surface heat source (HI) increased at the average of 0.45 W/m² per year, the difference of surface soil temperature and air temperature (DT) increased at the range of 4.1°C–4.5°C, and the 20-cm depth soil temperature within the active layer increased at the range of 1.1°C–1.4°C. The alpine meadow and alpine swamp meadow were more sensitive to permafrost changes than alpine steppe. The area of alpine swamp meadow decreased by 13.6–28.9%, while the alpine meadow area decreased by 13.5–21.3% from 1967 to 2000. The contributions of climate change to the degradation of the alpine meadow and alpine swamp was 58–68% and 59–65% between 1967 and 2000. The synergic effects of climate change and permafrost variation were the major drivers for the observed degradation in tundra ecosystems of the Qinghai-Tibet plateau.” Genxu Wang, Wei Bai, Na Li and Hongchang Hu, Climatic Change, DOI: 10.1007/s10584-010-9952-0.

Complex climate response of the trees in Pakistan

The dendroclimatic potential of conifers from northern Pakistan – Ahmed et al. (2010) “A collection of 28 tree-ring chronologies from six different species located in northern Pakistan were evaluated in terms of their potential for dendroclimatic reconstructions. 15 of the sites are new while the remaining 13 (all Juniperus excelsa M. Bieb.) have been reported earlier. Several species had trees attaining ages of around 700 years (Cedrus deodara (D. Don) G. Don, Pinus gerardiana Wall. ex D. Don., Pinus wallichiana A.B. Jacks and Picea smithiana (Wall.) Boiss.) but the juniper was clearly the oldest with some trees greater than 1000 years. Correlations between the site chronologies declined with increasing separation distance. This was consistently seen both between sites of the same species and between sites composed of different species. This led to a situation where a much stronger correlation occurred between two different species growing at the same site than between sites of the same species but separated by as little as 0.5 km. Such results highlight the obvious strong elevational gradients present in this mountainous region (where some elevations are over 7000 m). They also lend support to the practice of multi-species combinations for better spatial and temporal coverage. The best prospects for this appear to be C. deodara and P. gerardiana and are consistent with studies from neighbouring India. The comparison to 0.5° gridded climate data was strongest from the same two species though P. smithiana at one site was also highly significant. A general climate correlation pattern from all species was evident that starts with a strong negative relationship to temperature in the previous October, then turns towards positive during winter, before again becoming significantly negative by the current May. The previous October signal is thought to be a lag effect where hot temperatures (and low soil-moisture) stress the trees, thereby reducing reserves available for the following spring. Similarly, hot temperatures in late spring (May) lead to greater soil moisture losses and tree transpiration costs. Conversely, there is an extended strong positive precipitation correlation from late winter to spring (January–May). This ends abruptly and there is no evidence of a summer (June–September) monsoon signal seen in the rainfall correlation functions.” Moinuddin Ahmed, Jonathan Palmer, Nasrullah Khan, Muhammad Wahab, Pavla Fenwick, Jan Esper and Ed Cook, Dendrochronologia, 2010, doi:10.1016/j.dendro.2010.08.007.

Poleward energy transport with global warming increases

Increasing atmospheric poleward energy transport with global warming – Hwang & Frierson (2010) “Most state-of-the-art global climate models (GCMs) project an increase in atmospheric poleward energy transport with global warming; however, the amount of increase varies significantly from model to model. Using an energy balance model that diffuses moist static energy, it is shown that: (1) the increase in atmospheric moisture content causes most of the increase in transport, and (2) changes in the radiation budget due to clouds explain most of the spread among GCMs. This work also shows that biases in clouds, surface albedo, ocean heat uptake, and aerosols will not only affect climate locally but will also influence other latitudes through energy transport.” Hwang, Y.-T., and D. M. W. Frierson (2010), Increasing atmospheric poleward energy transport with global warming, Geophys. Res. Lett., 37, L24807, doi:10.1029/2010GL045440. [Full text]

Changes in lake size and amount in China related to climate change?

A half-century of changes in China’s lakes: Global warming or human influence? – Ma et al. (2010) “Lake size is sensitive to both climate change and human activities, and therefore serves as an excellent indicator to assess environmental changes. Using a large volume of various datasets, we provide a first complete picture of changes in China’s lakes between 1960s–1980s and 2005–2006. Dramatic changes are found in both lake number and lake size; of these, 243 lakes vanished mainly in the northern provinces (and autonomous regions) and also in some southern provinces while 60 new lakes appeared mainly on the Tibetan Plateau and neighboring provinces. Limited evidence suggested that these geographically unbalanced changes might be associated primarily with climate change in North China and human activities in South China, yet targeted regional studies are required to confirm this preliminary observation.” Ma, R., H. Duan, C. Hu, X. Feng, A. Li, W. Ju, J. Jiang, and G. Yang (2010), Geophys. Res. Lett., 37, L24106, doi:10.1029/2010GL045514.

A review of methane cycle in the future – lot of uncertainties

Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review – O’Connor et al. (2010) “We have reviewed the available scientific literature on how natural sources and the atmospheric fate of methane may be affected by future climate change. We discuss how processes governing methane wetland emissions, permafrost thawing, and destabilization of marine hydrates may affect the climate system. It is likely that methane wetland emissions will increase over the next century. Uncertainties arise from the temperature dependence of emissions and changes in the geographical distribution of wetland areas. Another major concern is the possible degradation or thaw of terrestrial permafrost due to climate change. The amount of carbon stored in permafrost, the rate at which it will thaw, and the ratio of methane to carbon dioxide emissions upon decomposition form the main uncertainties. Large amounts of methane are also stored in marine hydrates, and they could be responsible for large emissions in the future. The time scales for destabilization of marine hydrates are not well understood and are likely to be very long for hydrates found in deep sediments but much shorter for hydrates below shallow waters, such as in the Arctic Ocean. Uncertainties are dominated by the sizes and locations of the methane hydrate inventories, the time scales associated with heat penetration in the ocean and sediments, and the fate of methane released in the seawater. Overall, uncertainties are large, and it is difficult to be conclusive about the time scales and magnitudes of methane feedbacks, but significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out. We also identify gaps in our scientific knowledge and make recommendations for future research and development in the context of Earth system modeling.” O’Connor, F. M., et al. (2010), Rev. Geophys., 48, RG4005, doi:10.1029/2010RG000326.

Ozone layer protective measures are starting to have an effect

Evidence for the effectiveness of the Montreal Protocol to protect the ozone layer – Mäder et al. (2010) “The release of man-made ozone depleting substances (ODS, including chlorofluorocarbons and halons) into the atmosphere has led to a near-linear increase in stratospheric halogen loading since the early 1970s, which levelled off after the mid-1990s and then started to decline, in response to the ban of many ODS by the Montreal Protocol (1987). We developed a multiple linear regression model to test whether this already had a measurable effect on total ozone values observed by the global network of ground-based instruments. The model includes explanatory variables describing the influence of various modes of dynamical variability and of volcanic eruptions. In order to describe the anthropogenic influence a first version of the model contains a linear trend (LT) term, whereas a second version contains a term describing the evolution of Equivalent Effective Stratospheric Chlorine (EESC). By comparing the explained variance of these two model versions we evaluated, which of the two terms better describes the observed ozone evolution. For a significant majority of the stations, the EESC proxy fits the long term ozone evolution better than the linear trend term. Therefore, we conclude that the Montreal Protocol has started to show measurable effects on the ozone layer about twenty years after it became legally binding.” Mäder, J. A., Staehelin, J., Peter, T., Brunner, D., Rieder, H. E., and Stahel, W. A., Atmos. Chem. Phys., 10, 12161-12171, doi:10.5194/acp-10-12161-2010, 2010. [Full text]

Anthropogenic influence shows in China rainfall

Exploring the interplay between natural decadal variability and anthropogenic climate change in summer rainfall over China. Part 1: Observational evidence – Lei et al.(2010) “Summer rainfall over China has experienced substantial variability on longer timescales during the last century, and the question remains whether this is due to natural, internal variability or is part of the emerging signal of anthropogenic climate change. Using the best available observations over China, the decadal variability and recent trends in summer rainfall are investigated with the emphasis on changes in the seasonal evolution and on the temporal characteristics of daily rainfall. The possible relationships with global warming are reassessed. Substantial decadal variability in summer rainfall has been confirmed during the period 1958–2008; this is not unique to this period but is also seen in the earlier decades of the 20th century. Two dominant patterns of decadal variability have been identified, which contributes substantially to the recent trend of southern flooding and northern drought. More detailed analysis has shown that the decadal variability in the total summer rainfall is characterised by large changes in the seasonal cycle, and is composed of more complex changes in the intensity and frequency. Over the latter half of the 20th century increases in rainfall intensity and decreases in light rainfall frequency are seen country-wide and mainly the result of anthropogenic influences on the regional climate, both through warming and increased aerosol loading. The observed change in heavy rainfall frequency is mainly attributed to the decadal variability. Thus, global warming signals are most prominent over the northeast of China where heavy rainfall is lack, and the decadal variability signals are dominant over southern China. The interplay between anthropogenic climate change and natural decadal variability appears to have played an important role in shaping summer rainfall over China.” Yonghui Lei, Brian Hoskins, and Julia Slingo, Journal of Climate 2010.

Anthropogenic CO2 goes deep in Indian Ocean

Decadal increases in anthropogenic CO2 along 20°S in the South Indian Ocean – Murata et al.(2010) “We used high-quality data for dissolved inorganic carbon and related water properties in the Indian Ocean along 20°S (World Ocean Circulation Experiment Hydrographic Program line I3) and 24°S (I4) obtained 8 years apart (1995–2003/2004) to estimate decadal-scale increases of anthropogenic CO2 in the interior of the South Indian Ocean. Significant increases were detected to about 1800 m depth in the longitude range 35–45°E. In the upper thermocline subtropical subsurface water and Indian Central Water, anthropogenic CO2 increased an average of 7.9 ± 1.1 and 7.7 ± 0.5 μmol kg⁻¹, respectively, whereas in the lower thermocline Antarctic Intermediate Water, the increase was 3.8 ± 0.7 μmol kg⁻¹. A significant increase was also detected in Circumpolar Deep Water (2.5 ± 1.0 μmol kg⁻¹). The estimated uptake rate of anthropogenic CO2 along the I3/I4 line over this time interval was 1.0 ± 0.1 mol m−2 a⁻¹. Seasonal variations, which are influential in this ocean because of the Indian monsoon, did not affect detection of the anthropogenic CO2 signals. Comparisons with previous studies showed that increases of anthropogenic CO2 became larger in the most recent decade and that the CO2 uptake rate was similar to that in the South Pacific (1.0 ± 0.4 mol m⁻² a⁻¹) but higher than those in the South Atlantic (0.6 ± 0.1 mol m⁻² a⁻¹) and North Pacific (0.5 ± 0.1 mol m⁻² a⁻¹) Oceans. Deep penetration of anthropogenic CO2 is possibly associated with the higher uptake rate.” Murata, A., Y. Kumamoto, K. Sasaki, S. Watanabe, and M. Fukasawa (2010), J. Geophys. Res., 115, C12055, doi:10.1029/2010JC006250.

Primary controls of a coral bleaching event

Air-sea energy exchanges measured by eddy covariance during a localised coral bleaching event, Heron Reef, Great Barrier Reef, Australia – MacKellar & McGowan (2010) “Despite the widely claimed association between climate change and coral bleaching, a paucity of data exists relating to exchanges of heat, moisture and momentum between the atmosphere and the reef-water surface. We present in situ measurements of reef-water-air energy exchanges made using the eddy covariance method during a summer coral bleaching event at Heron Reef, Australia. Under settled, cloud-free conditions and light winds, daily net radiation exceeded 800 W m−2, with up to 95% of the net radiation during the morning partitioned into heating the water column, substrate and benthic cover including corals. Heating was exacerbated by a mid-afternoon low tide when shallow reef flat water reached 34°C and near-bottom temperatures 33°C, exceeding the thermal tolerance of corals, causing bleaching. Results suggest that local to synoptic scale meteorology, particularly clear skies, solar heating, light winds and the timing of low tide were the primary controls on coral bleaching.” MacKellar, M. C., and H. A. McGowan (2010), Geophys. Res. Lett., 37, L24703, doi:10.1029/2010GL045291. [Conference paper]

New England water table climate response increases flood risks

Heterogeneous water table response to climate revealed by 60 years of ground water data – Weider & Boutt (2010) “Recent findings suggest that climate change will lead to modifications in the timing and nature of precipitation, giving rise to an altered hydrologic cycle. The response of subsurface hydrology to decadal climate and longer-term climate change to date has been investigated via site specific analyses, modeling studies, and proxy analysis. Here we present the first instrumental long-term regional compilation and analysis of the water table response to the last 60 years of climate in New England. Ground water trends are calculated as normalized anomalies and analyzed with respect to regional compiled precipitation, temperature, and streamflow. The time-series display decadal patterns with ground water levels being more variable and lagging that of precipitation and streamflow pointing to site specific and non-linear response to changes in climate. Recent trends (i.e., last 10 years) suggest statistically significant increasing water tables, which could lead to a higher risk for flooding in New England.” Weider, K., and D. F. Boutt (2010), Geophys. Res. Lett., 37, L24405, doi:10.1029/2010GL045561.

Christmas Science

In science there are some christmas related things, such as the interpretation of the Star of Betlehem as a celestial object and the workload of Santa Claus from the point-of-view of physics. These can be considered as celestial objects which all in ancient Greece belonged to the field of meteorology. There are some other things in christmas also relating to meteorology and climate science.

In the Pacific Ocean there is a strong weather event known as El Niño. It has been most noticeable arnound christmas time and the name of the event referred to Christ child (El Niño is Spanish for little boy).

There is less industrial activity in christmas time. This causes a reduction in industrial pollution, which has been also observed from the atmosphere. For example Nottrodt et al. (1980) observed the atmosphere and noticed clear changes in atmospheric composition in December 24 and 25, 1976. They named christmas related reduction in industrial pollution as one possible explanation for the observation. Other similar results have been published by Bhugwant et al. (2000) and Madhavi Latha & Highwood (2006).

This is known more generally as the holiday effect and it has been observed also relating to some other holidays. For example Tan et al. (2009) studied how the holiday effect shows in atmospheric polluting substances during Chinese new year. They observed clear changes in the behavior of polluting substances. Most of the studied substances were reduced during the holiday but ozone concentration increased. Additionally, the traffic related pollution peaks during morning and evening rush-hours disappeared during the holiday.

There are also some additional emissions during christmas for example due to energy consumption of christmas lights and ham-cooking, and also due to over-eating and useless presents.

Here it’s -20°C and over 50 cm of snow. Merry christmas to all of you from this winter wonderland!

References:

Chatrapatty Bhugwant, Hélène Cachier, Miloud Bessafi and Jean Leveau, 2000, Impact of traffic on black carbon aerosol concentration at la Réunion Island (Southern Indian Ocean), Atmospheric Environment, Volume 34, Issue 20, 2000, Pages 3463-3473, doi:10.1016/S1352-2310(99)00405-7. [abstract]

K.H. Nottrodt, H.W. Georgii and K.O. Groeneveld, 1980, Temporal and spatial differences in the elemental composition of atmospheric aerosols, Science of The Total Environment, Volume 14, Issue 2, March 1980, Pages 113-128, doi:10.1016/0048-9697(80)90068-6. [abstract]

K. Madhavi Latha and E.J. Highwood, 2006, Studies on particulate matter (PM10) and its precursors over urban environment of Reading, UK, Journal of Quantitative Spectroscopy and Radiative Transfer, Volume 101, Issue 2, September 2006, Pages 367-379, doi:10.1016/j.jqsrt.2005.11.067. [abstract]

Pei-Hua Tan, Chia Chou, Jing-Yi Liang, Charles C.-K. Chou and Chein-Jung Shiu, 2009, Air pollution “holiday effect” resulting from the Chinese New Year, Atmospheric Environment, Volume 43, Issue 13, April 2009, Pages 2114-2124, doi:10.1016/j.atmosenv.2009.01.037. [abstract, full text]

New research from last week 50/2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Cloud cover over Australia changed very little since 1957

A high-quality monthly total cloud amount dataset for Australia – Jovanovic et al. (2010) “A high-quality monthly total cloud amount dataset for 165 stations has been developed for monitoring and assessing long-term trends in cloud cover over Australia. The dataset is based on visual 9 a.m. and 3 p.m. observations of total cloud amount, with most records starting around 1957. The quality control process involved examination of historical station metadata, together with an objective statistical test comparing candidate and reference cloud series. Individual cloud series were also compared against rainfall and diurnal temperature range series from the same site, and individual cloud series from neighboring sites. Adjustments for inhomogeneities caused by relocations and changes in observers were applied, as well as adjustments for biases caused by the shift to daylight saving time in the summer months. Analysis of these data reveals that the Australian mean annual total cloud amount is characterised by high year-to-year variability and shows a weak, statistically non-significant increase over the 1957–2007 period. A more pronounced, but also non-significant, decrease from 1977 to 2007 is evident. A strong positive correlation is found between all-Australian averages of cloud amount and rainfall, while a strong negative correlation is found between mean cloud amount and diurnal temperature range. Patterns of annual and seasonal trends in cloud amount are in general agreement with rainfall changes across Australia, however the high-quality cloud network is too coarse to fully capture topographic influences. Nevertheless, the broadscale consistency between patterns of cloud and rainfall variations indicates that the new total cloud amount dataset is able to adequately describe the broadscale patterns of change over Australia. Favourable simple comparisons between surface and satellite measures of cloudiness suggest that satellites may ultimately provide the means for monitoring long-term changes in cloud over Australia. However, due to the relative shortness and homogeneity problems of the satellite record, a robust network of surface cloud observations will be required for many years to come.” Branislava Jovanovic, Dean Collins, Karl Braganza, Doerte Jakob and David A. Jones, Climatic Change, DOI: 10.1007/s10584-010-9992-5. [full text]

Correlation between Arctic sea ice and NH snow cover

On the emergence of an Arctic amplification signal in terrestrial Arctic snow extent – Ghatak et al. (2010) “The impact of declining sea ice in amplifying surface air temperatures (SAT) over the Arctic Ocean is readily visible, and this “Arctic amplification” will become more pronounced as more sea ice is lost in the coming decades. The effect of sea ice loss on atmospheric temperatures and circulation patterns is of utmost significance as these changes will affect the terrestrial climate. Land-surface snow is vulnerable to these changes; hence, we search for any link between changes in Arctic sea ice and Northern Hemisphere snow cover. Analyses of observational data sets suggest that the increasing snow cover over Siberia during fall and early winter is correlated with the decreasing September Arctic sea ice over the Pacific sector. We also examine modeled covariance between sea ice and snow using historical and future simulations of the Community Climate System Model (CCSM3). Results indicate the emergence of a Siberian snow signal during the last half of the 21st century most strongly during late winter. Moreover, CCSM3 future simulations show diminishment of snow at a hemispheric scale outside of the Siberian region, which is correlated with the loss of Arctic sea ice. These results indicate that we may be seeing the first, albeit weak, signs of “Arctic amplification” on the terrestrial Arctic snowpack; that only a weak and therefore inconclusive signal would be expected at this time; and that the signal should strengthen over the coming decades.” Ghatak, D., A. Frei, G. Gong, J. Stroeve, and D. Robinson (2010), On the emergence of an Arctic amplification signal in terrestrial Arctic snow extent, J. Geophys. Res., 115, D24105, doi:10.1029/2010JD014007.

A 1000 year reconstruction of Norwegian sea temperatures

Response of Norwegian Sea temperature to solar forcing since 1000 A.D. – Sejrup et al. (2010) “We report on a 1000 year long oxygen isotope record in sediments of the eastern Norwegian Sea which, we argue, represents the temperature and transport of warm Atlantic waters entering the Nordic Sea basin via the North Atlantic Drift and the large-scale Meridional Overturning Circulation. The single-sample resolution of the record is 2.5–10 years and age control is provided by ²¹⁰Pb and ¹³⁷Cs dating, identification of historic tephra, and a 14C “wiggle-match” dating method in which the surface reservoir ¹⁴C age in the past is constrained rather than assumed, thereby eliminating a large source of chronological uncertainty. The oxygen isotope results indicate decade- to century-scale temperature variations of 1–2°C in the shallow (∼50 m deep) subsurface which we find to be strongly correlated with various proxies of past solar activity. The correlations are synchronous to within the timescale uncertainties of the ocean and solar proxy records, which vary among the records and in time with a range of about 5–30 years. The observed ocean temperature response is larger than expected based on simple thermodynamic considerations, indicating that there is dynamical response of the high-latitude ocean to the Sun. Correlations of our results with a gridded temperature reconstruction for Europe are greater in central Europe than in coastal regions, suggesting that the temperature and transport of warm Atlantic waters entering the Nordic Basin and the pattern of temperature variability over Europe are both the proximate responses to a change in the atmospheric circulation, consistent with a forced shift in the primary modes of high-latitude atmospheric variability.” Sejrup, H. P., S. J. Lehman, H. Haflidason, D. Noone, R. Muscheler, I. M. Berstad, and J. T. Andrews (2010), Response of Norwegian Sea temperature to solar forcing since 1000 A.D., J. Geophys. Res., 115, C12034, doi:10.1029/2010JC006264.

New interesting article from Lonnie Thompson

Climate Change: The Evidence and Our Options – Thompson (2010) “Glaciers serve as early indicators of climate change. Over the last 35 years, our research team has recovered ice-core records of climatic and environmental variations from the polar regions and from low-latitude high-elevation ice fields from 16 countries. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides some of the strongest evidence to date that a large-scale, pervasive, and, in some cases, rapid change in Earth’s climate system is underway. This paper highlights observations of 20th and 21st century glacier shrinkage in the Andes, the Himalayas, and on Mount Kilimanjaro. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds of years to multiple millennia, suggesting that climatological conditions that dominate those regions today are different from those under which these ice fields originally accumulated and have been sustained. The current warming is therefore unusual when viewed from the millennial perspective provided by multiple lines of proxy evidence and the 160-year record of direct temperature measurements. Despite all this evidence, plus the well-documented continual increase in atmospheric greenhouse gas concentrations, societies have taken little action to address this global-scale problem. Hence, the rate of global carbon dioxide emissions continues to accelerate. As a result of our inaction, we have three options: mitigation, adaptation, and suffering.” Lonnie G. Thompson, The Behavior Analyst, 2010, 33, 153-170, No. 2 (Fall). [full text]

Update of GISS surface temperature analysis

Global surface temperature change – Hansen et al. (2010) “We update the Goddard Institute for Space Studies (GISS) analysis of global surface temperature change, compare alternative analyses, and address questions about perception and reality of global warming. Satellite-observed night lights are used to identify measurement stations located in extreme darkness and adjust temperature trends of urban and periurban stations for nonclimatic factors, verifying that urban effects on analyzed global change are small. Because the GISS analysis combines available sea surface temperature records with meteorological station measurements, we test alternative choices for the ocean data, showing that global temperature change is sensitive to estimated temperature change in polar regions where observations are limited. We use simple 12 month (and n × 12) running means to improve the information content in our temperature graphs. Contrary to a popular misconception, the rate of warming has not declined. Global temperature is rising as fast in the past decade as in the prior 2 decades, despite year-to-year fluctuations associated with the El Niño-La Niña cycle of tropical ocean temperature. Record high global 12 month running mean temperature for the period with instrumental data was reached in 2010.” Hansen, J., R. Ruedy, M. Sato, and K. Lo (2010), GLOBAL SURFACE TEMPERATURE CHANGE, Rev. Geophys., 48, RG4004, doi:10.1029/2010RG000345. [full text]

McShane & Wyner thoroughly debunked

Annals of Applied Statistics made a discussion paper out of recently published McShane & Wyner (2010). Many scientists commented on the paper which got quite thoroughly debunked. Among commenters – for some strange reason – were also McIntyre & McKitrick who, not surprisingly, were completely in agreement with McShane & Wyner. Full papers here (see the bottom of the page).

Global warming effects on southern oscillation

The impact of global warming on the Southern Oscillation Index – Power & Kociuba (2010) “The Southern Oscillation Index (SOI)—a measure of air pressure difference across the Pacific Ocean, from Tahiti in the south-east to Darwin in the west—is one of the world’s most important climatic indices. The SOI is used to track and predict changes in both the El Niño-Southern Oscillation phenomenon, and the Walker Circulation (WC). During El Niño, for example, the WC weakens and the SOI tends to be negative. Climatic variations linked to changes in the WC have a profound influence on climate, ecosystems, agriculture, and societies in many parts of the world. Previous research has shown that (1) the WC and the SOI weakened in recent decades and that (2) the WC in climate models tends to weaken in response to elevated atmospheric greenhouse gas concentrations. Here we examine changes in the SOI and air pressure across the Pacific in the observations and in numerous WCRP/CMIP3 climate model integrations for both the 20th and 21st centuries. The difference in mean-sea level air pressure (MSLP) between the eastern and western equatorial Pacific tends to weaken during the 21st century, consistent with previous research. Here we show that this primarily arises because of an increase in MSLP in the west Pacific and not a decline in the east. We also show, in stark contrast to expectations, that the SOI actually tends to increase during the 21st century, not decrease. Under global warming MSLP tends to increase at both Darwin and Tahiti, but tends to rise more at Tahiti than at Darwin. Tahiti lies in an extensive region where MSLP tends to rise in response to global warming. So while the SOI is an excellent indicator of interannual variability in both the equatorial MSLP gradient and the WC, it is a highly misleading indicator of long-term equatorial changes linked to global warming. Our results also indicate that the observed decline in the SOI in recent decades has been driven by natural, internally generated variability. The externally forced signal in the June–December SOI during 2010 is estimated to be approximately 5% of the standard deviation of variability in the SOI during the 20th century. This figure is projected to increase to 40% by the end of the 21st century under the A2 SRES scenario. The 2010 global warming signal is already a major contributor to interdecadal variability in the SOI, equal to 45% of the standard deviation of 30-year running averages of the SOI. This figure is projected to increase to nearly 340% by the end of the 21st century. Implications that these discoveries have for understanding recent climatic change and for seasonal prediction are discussed.” Scott B. Power and Greg Kociuba, Climate Dynamics, DOI: 10.1007/s00382-010-0951-7. [full text]

Papers on Atlantic Multidecadal Oscillation and climate

This is a list of papers on Atlantic Multidecadal Oscillation and its effects to the climate. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

100-year mass changes in the Swiss Alps linked to the Atlantic Multidecadal Oscillation – Huss et al. (2010) “Thirty new 100-year records of glacier surface mass balance, accumulation and melt in the Swiss Alps are presented. The time series are based on a comprehensive set of field data and distributed modeling and provide insights into the glacier-climate linkage. Considerable mass loss over the 20th century is evident for all glaciers, but rates differ strongly. Glacier mass loss shows multidecadal variations and was particularly rapid in the 1940s and since the 1980s. Mass balance is significantly anticorrelated to the Atlantic Multidecadal Oscillation (AMO) index assumed to be linked to thermohaline ocean circulation. We show that North Atlantic variability had a recognizable impact on glacier changes in the Swiss Alps for at least 250 years.” Huss, M., R. Hock, A. Bauder, and M. Funk (2010), 100-year mass changes in the Swiss Alps linked to the Atlantic Multidecadal Oscillation, Geophys. Res. Lett., 37, L10501, doi:10.1029/2010GL042616. [Full text]

Evidence of multidecadal climate variability and the Atlantic Multidecadal Oscillation from a Gulf of Mexico sea-surface temperature-proxy record – Poore et al. (2009) “A comparison of a Mg/Ca-based sea-surface temperature (SST)-anomaly record from the northern Gulf of Mexico, a calculated index of variability in observed North Atlantic SST known as the Atlantic Multidecadal Oscillation (AMO), and a tree-ring reconstruction of the AMO contain similar patterns of variation over the last 110 years. Thus, the multidecadal variability observed in the instrumental record is present in the tree-ring and Mg/Ca proxy data. Frequency analysis of the Gulf of Mexico SST record and the tree-ring AMO reconstruction from 1550 to 1990 found similar multidecadal-scale periodicities (~30–60 years). This multidecadal periodicity is about half the observed (60–80 years) variability identified in the AMO for the 20th century. The historical records of hurricane landfalls reveal increased landfalls in the Gulf Coast region during time intervals when the AMO index is positive (warmer SST), and decreased landfalls when the AMO index is negative (cooler SST). Thus, we conclude that alternating intervals of high and low hurricane landfall occurrences may continue on multidecadal timescales along the northern Gulf Coast. However, given the short length of the instrumental record, the actual frequency and stability of the AMO are uncertain, and additional AMO proxy records are needed to establish the character of multidecadal-scale SST variability in the North Atlantic.” Richard Z. Poore, Kristine L. DeLong, Julie N. Richey and Terrence M. Quinn, Geo-Marine Letters, Volume 29, Number 6, 477-484, DOI: 10.1007/s00367-009-0154-6.

Arctic air temperature change amplification and the Atlantic Multidecadal Oscillation – Chylek et al. (2009) “Understanding Arctic temperature variability is essential for assessing possible future melting of the Greenland ice sheet, Arctic sea ice and Arctic permafrost. Temperature trend reversals in 1940 and 1970 separate two Arctic warming periods (1910–1940 and 1970–2008) by a significant 1940–1970 cooling period. Analyzing temperature records of the Arctic meteorological stations we find that (a) the Arctic amplification (ratio of the Arctic to global temperature trends) is not a constant but varies in time on a multi-decadal time scale, (b) the Arctic warming from 1910–1940 proceeded at a significantly faster rate than the current 1970–2008 warming, and (c) the Arctic temperature changes are highly correlated with the Atlantic Multi-decadal Oscillation (AMO) suggesting the Atlantic Ocean thermohaline circulation is linked to the Arctic temperature variability on a multi-decadal time scale.” Chylek, P., C. K. Folland, G. Lesins, M. K. Dubey, and M. Wang (2009), Arctic air temperature change amplification and the Atlantic Multidecadal Oscillation, Geophys. Res. Lett., 36, L14801, doi:10.1029/2009GL038777. [Full text]

Atlantic Warm Pool acting as a link between Atlantic Multidecadal Oscillation and Atlantic tropical cyclone activity – Wang et al. (2008) “Multidecadal variability of Atlantic tropical cyclone activity is observed to relate to the Atlantic Multidecadal Oscillation (AMO), a mode manifesting primarily in sea surface temperature (SST) in the high latitudes of the North Atlantic. In the low latitudes of the North Atlantic, a large body of warm water called the Atlantic Warm Pool (AWP) comprises the Gulf of Mexico, the Caribbean Sea, and the western tropical North Atlantic. AWP variability occurs on both interannual and multidecadal timescales as well as with a secular variation. The AWP multidecadal variability coincides with the signal of the AMO; that is, the warm (cool) phases of the AMO are characterized by repeated large (small) AWPs. Since the climate response to the North Atlantic SST anomalies is primarily forced at the low latitudes and the AWP is in the path of or a birthplace for Atlantic tropical cyclones, the influence of the AMO on Atlantic tropical cyclone activity may operate through the mechanism of the AWP-induced atmospheric changes. The AWP-induced changes related to tropical cyclones that we emphasize here include a dynamical parameter of tropospheric vertical wind shear and a thermodynamical parameter of convective instability. More specifically, an anomalously large (small) AWP reduces (enhances) the vertical wind shear in the hurricane main development region and increases (decreases) the moist static instability of the troposphere, both of which favor (disfavor) Atlantic tropical cyclone activity. This is the most plausible way in which the AMO relationship with Atlantic tropical cyclones can be understood.” Wang, C., S.-K. Lee, and D. B. Enfield (2008), Atlantic Warm Pool acting as a link between Atlantic Multidecadal Oscillation and Atlantic tropical cyclone activity, Geochem. Geophys. Geosyst., 9, Q05V03, doi:10.1029/2007GC001809. [Full text]

The Atlantic multidecadal oscillation and extreme daily precipitation over the US and Mexico during the hurricane season – Curtis (2008) “The tail of the distribution of daily precipitation for August–September–October was examined over the United States and Mexico in relation to the Atlantic Multidecadal Oscillation (AMO). As expected from previous studies linking the AMO to hurricane activity, Florida and the coastal Southeast US showed an increase in precipitation intensity when the Atlantic was in a warm phase (AMO+). Also during AMO+ Northwest Mexico was dry and exhibited a reduction of extreme events and the Mid-Atlantic Appalachian Mountains showed evidence of an increase in heavy precipitation compared to when the Atlantic was cool. It is proposed that the aforementioned decadal variations in extreme rainfall are forced by changes in the large-scale surface winds and air temperature in conjunction with the AMO. Namely, an anomalous cyclonic circulation is observed off the Southeast coast, leading to a reduction of moisture flux into the decaying North American monsoon, and an increase in moisture flux into the Mid-Atlantic. Further, the Mid-Atlantic shows a relatively strong increase in the mid-tropospheric lapse rate. Thus, the unique combination of low-level humidity, potential instability, and elevated topography are consistent with an enhanced risk of intense rainfall during AMO+.” Scott Curtis, Climate Dynamics, Volume 30, Number 4, 343-351, DOI: 10.1007/s00382-007-0295-0.

Impact of the Atlantic Multidecadal Oscillation on North Pacific climate variability – Zhang & Delworth (2007) “In this paper, we found that the Atlantic Multidecadal Oscillation (AMO) can contribute to the Pacific Decadal Oscillation (PDO), especially the component of the PDO that is linearly independent of El Niño and the Southern Oscillation (ENSO), i.e. the North Pacific Multidecadal Oscillation (NPMO), and the associated Pacific/North America (PNA) pattern. Using a hybrid version of the GFDL CM2.1 climate model, we show that the AMO provides a source of multidecadal variability to the North Pacific, and needs to be considered along with other forcings for North Pacific climate change. The lagged North Pacific response to the North Atlantic forcing is through atmospheric teleconnections and reinforced by oceanic dynamics and positive air-sea feedback over the North Pacific. The results indicate that a North Pacific regime shift, opposite to the 1976–77 shift, might occur now a decade after the switch of the observed AMO to a positive phase around 1995.” Zhang, R., and T. L. Delworth (2007), Impact of the Atlantic Multidecadal Oscillation on North Pacific climate variability, Geophys. Res. Lett., 34, L23708, doi:10.1029/2007GL031601. [Full text]

A Hemispheric Mechanism for the Atlantic Multidecadal Oscillation – Dima & Lohmann (2007) “The physical processes associated with the ~70-yr period climate mode, known as the Atlantic multidecadal oscillation (AMO), are examined. Based on analyses of observational data, a deterministic mechanism relying on atmosphere–ocean–sea ice interactions is proposed for the AMO. Variations in the thermohaline circulation are reflected as uniform sea surface temperature anomalies in the North Atlantic. These anomalies are associated with a hemispheric wavenumber-1 sea level pressure (SLP) structure in the atmosphere that is amplified through atmosphere–ocean interactions in the North Pacific. The SLP pattern and its associated wind field affect the sea ice export through Fram Strait, the freshwater balance in the northern North Atlantic, and consequently the strength of the large-scale ocean circulation. It generates sea surface temperature anomalies with opposite signs in the North Atlantic and completes a negative feedback. The authors find that the time scale of the cycle is associated with the thermohaline circulation adjustment to freshwater forcing, the SST response to it, the oceanic adjustment in the North Pacific, and the sea ice response to the wind forcing. Finally, it is argued that the Great Salinity Anomaly in the late 1960s and 1970s is part of AMO.” Dima, Mihai, Gerrit Lohmann, 2007: A Hemispheric Mechanism for the Atlantic Multidecadal Oscillation. J. Climate, 20, 2706–2719, doi: 10.1175/JCLI4174.1. [Full text]

Climate impacts of the Atlantic Multidecadal Oscillation – Knight et al. (2006) “The Atlantic Multidecadal Oscillation (AMO) is a near-global scale mode of observed multidecadal climate variability with alternating warm and cool phases over large parts of the Northern Hemisphere. Many prominent examples of regional multidecadal climate variability have been related to the AMO, such as North Eastern Brazilian and African Sahel rainfall, Atlantic hurricanes and North American and European summer climate. The relative shortness of the instrumental climate record, however, limits confidence in these observationally derived relationships. Here, we seek evidence of these links in the 1400 year control simulation of the HadCM3 climate model, which produces a realistic long-lived AMO as part of its internal climate variability. By permitting the analysis of more AMO cycles than are present in observations, we find that the model confirms the association of the AMO with almost all of the above phenomena. This has implications for the predictability of regional climate.” Knight, J. R., C. K. Folland, and A. A. Scaife (2006), Climate impacts of the Atlantic Multidecadal Oscillation, Geophys. Res. Lett., 33, L17706, doi:10.1029/2006GL026242. [Full text]

Atlantic Ocean Forcing of North American and European Summer Climate – Sutton & Hodson (2005) “Recent extreme events such as the devastating 2003 European summer heat wave raise important questions about the possible causes of any underlying trends, or low-frequency variations, in regional climates. Here, we present new evidence that basin-scale changes in the Atlantic Ocean, probably related to the thermohaline circulation, have been an important driver of multidecadal variations in the summertime climate of both North America and western Europe. Our findings advance understanding of past climate changes and also have implications for decadal climate predictions.” Rowan T. Sutton and Daniel L. R. Hodson, Science 1 July 2005,
Vol. 309 no. 5731 pp. 115-118, DOI: 10.1126/science.1109496. [Full text]

A tree-ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 A.D. – Gray et al. (2004) “We present a tree-ring based reconstruction of the Atlantic Multidecadal Oscillation (AMO) which demonstrates that strong, low-frequency (60–100 yr) variability in basin-wide (0–70°N) sea surface temperatures (SSTs) has been a consistent feature of North Atlantic climate for the past five centuries. Intervention analysis of reconstructed AMO indicates that 20th century modes were similar to those in the preceding ∼350 yr, and wavelet spectra show robust multidecadal oscillations throughout the reconstruction. Though the exact relationships between low-frequency SST modes, higher frequency (∼7–25 yr) atmospheric modes (e.g., North Atlantic Oscillation/Arctic Oscillation), and terrestrial climates must still be resolved, our results confirm that the AMO should be considered in assessments of past and future Northern Hemisphere climates.” Gray, S. T., L. J. Graumlich, J. L. Betancourt, and G. T. Pederson (2004), A tree-ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 A.D., Geophys. Res. Lett., 31, L12205, doi:10.1029/2004GL019932. [Full text]

The Atlantic Multidecadal Oscillation and its relation to rainfall and river flows in the continental U.S. – Enfield et al. (2001) “North Atlantic sea surface temperatures for 1856–1999 contain a 65–80 year cycle with a 0.4 °C range, referred to as the Atlantic Multidecadal Oscillation (AMO) by Kerr [2000]. AMO warm phases occurred during 1860–1880 and 1940–1960, and cool phases during 1905–1925 and 1970–1990. The signal is global in scope, with a positively correlated co‐oscillation in parts of the North Pacific, but it is most intense in the North Atlantic and covers the entire basin there. During AMO warmings most of the United States sees less than normal rainfall, including Midwest droughts in the 1930s and 1950s. Between AMO warm and cool phases, Mississippi River outflow varies by 10% while the inflow to Lake Okeechobee, Florida varies by 40%. The geographical pattern of variability is influenced mainly by changes in summer rainfall. The winter patterns of interannual rainfall variability associated with El Niño‐Southern Oscillation are also significantly changed between AMO phases.” Enfield, D. B., A. M. Mestas‐Nuñez, and P. J. Trimble (2001), The Atlantic Multidecadal Oscillation and its relation to rainfall and river flows in the continental U.S., Geophys. Res. Lett., 28(10), 2077–2080, doi:10.1029/2000GL012745. [Full text]

Is There a Dominant Timescale of Natural Climate Variability in the Arctic? – Venegas & Mysak (2000) “A frequency-domain singular value decomposition performed jointly on century-long (1903–94) records of North Atlantic sector sea ice concentration and sea level pressure poleward of 40°N reveals that fluctuations on the interdecadal and quasi-decadal timescales account for a large fraction of the natural climate variability in the Arctic. Four dominant signals, with periods of about 6–7, 9–10, 16–20, and 30–50 yr, are isolated and analyzed. These signals account for about 60%–70% of the variance in their respective frequency bands. All of them appear in the monthly (year-round) data. However, the 9–10-yr oscillation especially stands out as a winter phenomenon. Ice variability in the Greenland, Barents, and Labrador Seas is then linked to coherent atmospheric variations and certain oceanic processes. The Greenland Sea ice variability is largely due to fluctuations in ice export through Fram Strait and to the local wind forcing during winter. It is proposed that variability in the Fram Strait ice export depends on three different mechanisms, which are associated with different timescales: 1) wind-driven motion of anomalous volumes of ice from the East Siberian Sea out of the Arctic (6–7-yr timescale); 2) enhanced ice motion forced by winter wind anomalies when they align parallel to the Transpolar Drift Stream (9–10-yr timescale); 3) wind-driven motion of old, thick, and very low salinity ice from offshore northern Canada into the outflow region (16–20-yr timescale). Also, a marked decreasing trend in ice extent since around 1970 (30–50-yr timescale) is linked to a recently reported warming in the Arctic. The Barents Sea ice variability is associated with the nature of the penetration of Atlantic waters into the Arctic Basin, which is affected by two distinct mechanisms: 1) changes in the intensity of the northward-flowing Norwegian Current, which is linked to variability in the North Atlantic oscillation (NAO) pattern (9–10-yr timescale); and 2) changes in the upper-ocean temperature of the Norwegian Current waters, which is likely related to the advection of temperature anomalies by the ocean gyres (16–20-yr timescale). Ice variability in the Labrador Sea, on the other hand, appears to be mainly determined by thermodynamical effects produced by the local wind forcing, which is closely related to the NAO pattern (9–10-yr timescale), and by oceanic advection of ice anomalies into this sea from the Greenland–Irminger Sea by the East Greenland Current (6–7-yr timescale).” Venegas, Silvia A., Lawrence A. Mysak, 2000: Is There a Dominant Timescale of Natural Climate Variability in the Arctic?. J. Climate, 13, 3412–3434. [Full text]

Observed and simulated multidecadal variability in the Northern Hemisphere – Delworth & Mann (2000) “Analyses of proxy based reconstructions of surface temperatures during the past 330 years show the existence of a distinct oscillatory mode of variability with an approximate time scale of 70 years. This variability is also seen in instrumental records, although the oscillatory nature of the variability is difficult to assess due to the short length of the instrumental record. The spatial pattern of this variability is hemispheric or perhaps even global in scale, but with particular emphasis on the Atlantic region. Independent analyses of multicentury integrations of two versions of the GFDL coupled atmosphere-ocean model also show the existence of distinct multidecadal variability in the North Atlantic region which resembles the observed pattern. The model variability involves fluctuations in the intensity of the thermohaline circulation in the North Atlantic. It is our intent here to provide a direct comparison of the observed variability to that simulated in a coupled ocean-atmosphere model, making use of both existing instrumental analyses and newly available proxy based multi-century surface temperature estimates. The analyses demonstrate a substantial agreement between the simulated and observed patterns of multidecadal variability in sea surface temperature (SST) over the North Atlantic. There is much less agreement between the model and observations for sea level pressure. Seasonal analyses of the variability demonstrate that for both the model and observations SST appears to be the primary carrier of the multidecadal signal.” T. L. Delworth and M. E. Mann, Climate Dynamics, Volume 16, Number 9, 661-676, DOI: 10.1007/s003820000075. [Full text]

An oscillation in the global climate system of period 65–70 years – Schlesinger & Ramankutty (1994) “IN addition to the well-known warming of 0.5 °C since the middle of the nineteenth century, global-mean surface temperature records display substantial variability on timescales of a century or less. Accurate prediction of future temperature change requires an understanding of the causes of this variability; possibilities include external factors, such as increasing greenhouse-gas concentrations and anthropogenic sulphate aerosols, and internal factors, both predictable (such as El Niño) and unpredictable (noise). Here we apply singular spectrum analysis to four global-mean temperature records, and identify a temperature oscillation with a period of 65–70 years. Singular spectrum analysis of the surface temperature records for 11 geographical regions shows that the 65–70-year oscillation is the statistical result of 50–88-year oscillations for the North Atlantic Ocean and its bounding Northern Hemisphere continents. These oscillations have obscured the greenhouse warming signal in the North Atlantic and North America. Comparison with previous observations and model simulations suggests that the oscillation arises from predictable internal variability of the ocean–atmosphere system.” Michael E. Schlesinger & Navin Ramankutty, Nature 367, 723 – 726 (24 February 1994); doi:10.1038/367723a0.

New research from last week 49/2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

On the two degree limit

Three views of two degrees – Jaeger & Jaeger (2010) “Limiting global warming to 2°C above pre-industrial global mean temperature has become a widely endorsed goal for climate policy. It has also been severely criticized. We show how the limit emerged out of a marginal remark in an early paper about climate policy and distinguish three possible views of it. The catastrophe view sees it as the threshold separating a domain of safety from a domain of catastrophe. The cost-benefit view sees it as a strategy to optimize the relation between the costs and benefits of climate policy. The focal point view sees it as a solution to a complex coordination problem. We argue that the focal point view is the most appropriate. It leads to an emphasis on implementing effective steps toward a near-zero emissions economy, without panicking in the face of a possible temporary overshooting. After several decades of practical experiences, the focal point may or may not be redefined on the basis of knowledge gathered thanks to these experiences.” Carlo C. Jaeger and Julia Jaeger, Regional Environmental Change
DOI: 10.1007/s10113-010-0190-9. [full text]

Human activity shows in Europe temperatures in all seasons

Human activity and anomalously warm seasons in Europe – Christidis et al. (2010) “Seasonal mean temperatures averaged over the European region have warmed at a rate of 0.35–0.52 K/decade since 1980. The last decade has seen record-breaking seasonal temperatures in Europe including the summer of 2003 and the spring, autumn, and winter of 2007. Previous studies have established that European summer warming since the early twentieth century can be attributed to the effects of human influence. The attribution analysis described here employs temperature data from observations and experiments with two climate models and uses optimal fingerprinting to partition the climate response between its anthropogenic and natural components. These responses are subsequently combined with estimates of unforced climate variability to construct distributions of the annual values of seasonal mean temperatures with and without the effect of human activity. We find that in all seasons, anthropogenic forcings have shifted the temperature distributions towards higher values. We compute the associated change in the likelihood of having seasons whose temperatures exceed a pre-specified threshold. We first set the threshold equal to the seasonal temperature observed in a particular year to assess the effect of anthropogenic influences in past seasons. We find that in the last decade (1999–2008) it is extremely likely (probability greater than 95%) that the probability has more than doubled under the influence of human activity in spring and autumn, while for summer it is extremely likely that the probability has at least quadrupled. One of the two models employed in the analysis indicates it is extremely likely the probability has more than doubled in winter too. We also compute the change in probability over a range of temperature thresholds which enables us to provide updates on the likely change in probability attributable to human influence as soon as observations become available. Such near-real time information could be very useful for adaptation planning.” Nikolaos Christidis, Peter A. Stott, Gareth S. Jones, Hideo Shiogama, Toru Nozawa, Jürg Luterbacher, International Journal of Climatology, 2010, DOI: 10.1002/joc.2262.

Black carbon in Arctic snow probably has not contributed to rapid sea ice decline

Light-absorbing impurities in Arctic snow – Doherty et al. (2010) “Absorption of radiation by ice is extremely weak at visible and near-ultraviolet wavelengths, so small amounts of light-absorbing impurities in snow can dominate the absorption of solar radiation at these wavelengths, reducing the albedo relative to that of pure snow, contributing to the surface energy budget and leading to earlier snowmelt. In this study Arctic snow is surveyed for its content of light-absorbing impurities, expanding and updating the 1983–1984 survey of Clarke and Noone. Samples were collected in Alaska, Canada, Greenland, Svalbard, Norway, Russia, and the Arctic Ocean during 1998 and 2005–2009, on tundra, glaciers, ice caps, sea ice, frozen lakes, and in boreal forests. Snow was collected mostly in spring, when the entire winter snowpack is accessible for sampling. Sampling was carried out in summer on the Greenland Ice Sheet and on the Arctic Ocean, of melting glacier snow and sea ice as well as cold snow. About 1200 snow samples have been analyzed for this study. The snow is melted and filtered; the filters are analyzed in a specially designed spectrophotometer system to infer the concentration of black carbon (BC), the fraction of absorption due to non-BC light-absorbing constituents and the absorption Ångstrom exponent of all particles. This is done using BC calibration standards having a mass absorption efficiency of 6.0 m2 g−1 at 550 nm and by making an assumption that the absorption Angstrom exponent for BC is 1.0 and for non-BC light-absorbing aerosol is 5.0. The reduction of snow albedo is primarily due to BC, but other impurities, principally brown (organic) carbon, are typically responsible for ~40% of the visible and ultraviolet absorption. The meltwater from selected snow samples was saved for chemical analysis to identify sources of the impurities. Median BC amounts in surface snow are as follows (nanograms of carbon per gram of snow): Greenland 3, Arctic Ocean snow 7, melting sea ice 8, Arctic Canada 8, subarctic Canada 14, Svalbard 13, Northern Norway 21, western Arctic Russia 27, northeastern Siberia 34. Concentrations are more variable in the European Arctic than in Arctic Canada or the Arctic Ocean, probably because of the proximity to BC sources. Individual samples of falling snow were collected on Svalbard, documenting the springtime decline of BC from March through May. Absorption Ångstrom exponents are 1.5–1.7 in Norway, Svalbard, and western Russia, 2.1–2.3 elsewhere in the Arctic, and 2.5 in Greenland. Correspondingly, the estimated contribution to absorption by non-BC constituents in these regions is ~25%, 40%, and 50% respectively. It has been hypothesized that when the snow surface layer melts some of the BC is left at the top of the snowpack rather than being carried away in meltwater. This process was observed in a few locations and would cause a positive feedback on snowmelt. The BC content of the Arctic atmosphere has declined markedly since 1989, according to the continuous measurements of near-surface air at Alert (Canada), Barrow (Alaska), and Ny-Ålesund (Svalbard). Correspondingly, the new BC concentrations for Arctic snow are somewhat lower than those reported by Clarke and Noone for 1983–1984, but because of methodological differences it is not clear that the differences are significant. Nevertheless, the BC content of Arctic snow appears to be no higher now than in 1984, so it is doubtful that BC in Arctic snow has contributed to the rapid decline of Arctic sea ice in recent years.” Doherty, S. J., Warren, S. G., Grenfell, T. C., Clarke, A. D., and Brandt, R. E.: Light-absorbing impurities in Arctic snow, Atmos. Chem. Phys., 10, 11647-11680, doi:10.5194/acp-10-11647-2010, 2010. [full text]

On anthropogenic changes in upper ocean temperature

Can oceanic reanalyses be used to assess recent anthropogenic changes and low-frequency internal variability of upper ocean temperature? – Corre et al. (2010) “A multivariate analysis of the upper ocean thermal structure is used to examine the recent long-term changes and decadal variability in the upper ocean heat content as represented by model-based ocean reanalyses and a model-independent objective analysis. The three variables used are the mean temperature above the 14°C isotherm, its depth and a fixed depth mean temperature (250 m mean temperature). The mean temperature above the 14°C isotherm is a convenient, albeit simple, way to isolate thermodynamical changes by filtering out dynamical changes related to thermocline vertical displacements. The global upper ocean observations and reanalyses exhibit very similar warming trends (0.045°C per decade) over the period 1965–2005, superimposed with marked decadal variability in the 1970s and 1980s. The spatial patterns of the regression between indices (representative of anthropogenic changes and known modes of internal decadal variability), and the three variables associated with the ocean heat content are used as fingerprint to separate out the different contributions. The choice of variables provides information about the local heat absorption, vertical distribution and horizontal redistribution of heat, this latter being suggestive of changes in ocean circulation. The discrepancy between the objective analysis and the reanalyses, as well as the spread among the different reanalyses, are used as a simple estimate of ocean state uncertainties. Two robust findings result from this analysis: (1) the signature of anthropogenic changes is qualitatively different from those of the internal decadal variability associated to the Pacific Interdecadal Oscillation and the Atlantic Meridional Oscillation, and (2) the anthropogenic changes in ocean heat content do not only consist of local heat absorption, but are likely related with changes in the ocean circulation, with a clear shallowing of the tropical thermocline in the Pacific and Indian oceans.” L. Corre, L. Terray, M. Balmaseda, A. Ribes and A. Weaver, Climate Dynamics, DOI: 10.1007/s00382-010-0950-8.

Flood risk concerns 3x people and 10x assets by 2070s

A global ranking of port cities with high exposure to climate extremes – Hanson et al. (2010) “This paper presents a first estimate of the exposure of the world’s large port cities (population exceeding one million inhabitants in 2005) to coastal flooding due to sea-level rise and storm surge now and in the 2070s, taking into account scenarios of socio-economic and climate changes. The analysis suggests that about 40 million people (0.6% of the global population or roughly 1 in 10 of the total port city population in the cities considered) are currently exposed to a 1 in 100 year coastal flood event. For assets, the total value exposed in 2005 across all cities considered is estimated to be US$3,000 billion; corresponding to around 5% of global GDP in 2005 (both measured in international USD) with USA, Japan and the Netherlands being the countries with the highest values. By the 2070s, total population exposed could grow more than threefold due to the combined effects of sea-level rise, subsidence, population growth and urbanisation with asset exposure increasing to more than ten times current levels or approximately 9% of projected global GDP in this period. On the global-scale, population growth, socio-economic growth and urbanization are the most important drivers of the overall increase in exposure particularly in developing countries, as low-lying areas are urbanized. Climate change and subsidence can significantly exacerbate this increase in exposure. Exposure is concentrated in a few cities: collectively Asia dominates population exposure now and in the future and also dominates asset exposure by the 2070s. Importantly, even if the environmental or socio-economic changes were smaller than assumed here the underlying trends would remain. This research shows the high potential benefits from risk-reduction planning and policies at the city scale to address the issues raised by the possible growth in exposure.” Susan Hanson, Robert Nicholls, N. Ranger, S. Hallegatte, J. Corfee-Morlot, C. Herweijer and J. Chateau, Climatic Change, DOI: 10.1007/s10584-010-9977-4.

Vegetation might cause stronger negative feedback than previously thought

Quantifying the negative feedback of vegetation to greenhouse warming: A modeling approach – Bounoua et al. (2010) “Several climate models indicate that in a 2 × CO₂ environment, temperature and precipitation would increase and runoff would increase faster than precipitation. These models, however, did not allow the vegetation to increase its leaf density as a response to the physiological effects of increased CO₂ and consequent changes in climate. Other assessments included these interactions but did not account for the vegetation down-regulation to reduce plant’s photosynthetic activity and as such resulted in a weak vegetation negative response. When we combine these interactions in climate simulations with 2 × CO₂, the associated increase in precipitation contributes primarily to increase evapotranspiration rather than surface runoff, consistent with observations, and results in an additional cooling effect not fully accounted for in previous simulations with elevated CO₂. By accelerating the water cycle, this feedback slows but does not alleviate the projected warming, reducing the land surface warming by 0.6°C. Compared to previous studies, these results imply that long term negative feedback from CO₂-induced increases in vegetation density could reduce temperature following a stabilization of CO₂ concentration.” Bounoua, L., F. G. Hall, P. J. Sellers, A. Kumar, G. J. Collatz, C. J. Tucker, and M. L. Imhoff (2010), Geophys. Res. Lett., 37, L23701, doi:10.1029/2010GL045338.

Papers on lake effect and climate

This is a list of papers on the lake effect and how climate affects it. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

A New Look at Lake-Effect Snowfall Trends in the Laurentian Great Lakes Using a Temporally Homogeneous Data Set – Kunkel et al. (2009) “Snowfall data are subject to quality issues that affect their usefulness for detection of climate trends. A new analysis of lake-effect snowfall trends utilizes a restricted set of stations identified as suitable for trends analysis based on a careful quality assessment of long-term observation stations in the lake-effect snowbelts of the Laurentian Great Lakes. An upward trend in snowfall was found in two (Superior and Michigan) of the four snowbelt areas. The trends for Lakes Erie and Ontario depended on the period of analysis. Although these results are qualitatively similar to outcomes of other recent studies, the magnitude of the upward trend is about half as large as trends in previous findings. The upward trend in snowfall was accompanied by an upward trend in liquid water equivalent for Superior and Michigan, while no trend was observed for Erie and Ontario. Air temperature has also trended upward for Superior and Michigan, suggesting that warmer surface waters and less ice cover are contributing to the upward snowfall trends by enhancing lake heat and moisture fluxes during cold air outbreaks. However, a more comprehensive study is needed to definitely determine cause and effect. Overall, this study finds that trends in lake-effect snowfall are not as large as was believed based on prior research.” Kenneth E. Kunkel, Leslie Ensor, Michael Palecki, David Easterling, David Robinson, Kenneth G. Hubbard, Kelly Redmond, Journal of Great Lakes Research 35(1):23-29. 2009, doi: 10.1016/j.jglr.2008.11.003. [Full text]

Climatology of Lake-Effect Precipitation Events over Lake Champlain – Laird et al. (2009) “This study provides the first long-term climatological analysis of lake-effect precipitation events that developed in relation to a small lake (having a surface area of ≤1500 km2). The frequency and environmental conditions favorable for Lake Champlain lake-effect precipitation were examined for the nine winters (October–March) from 1997/98 through 2005/06. Weather Surveillance Radar-1988 Doppler (WSR-88D) data from Burlington, Vermont, were used to identify 67 lake-effect events. Events occurred as 1) well-defined, isolated lake-effect bands over and downwind of the lake, independent of larger-scale precipitating systems (LC events), 2) quasi-stationary lake-effect bands over the lake embedded within extensive regional precipitation from a synoptic weather system (SYNOP events), or 3) a transition from SYNOP and LC lake-effect precipitation. The LC events were found to occur under either a northerly or a southerly wind regime. An examination of the characteristics of these lake-effect events provides several unique findings that are useful for comparison with known lake-effect environments for larger lakes. January was the most active month with an average of nearly four lake-effect events per winter, and approximately one of every four LC events occurred with southerly winds. Event initiation and dissipation occurred on a diurnal time scale with an average duration of 12.1 h. In general, Lake Champlain lake-effect events 1) typically yielded snowfall, with surface air temperatures rarely above 0°C, 2) frequently had an overlake mesolow present with a sea level pressure departure of 3–5 hPa, 3) occurred in a very stable environment with a surface inversion frequently present outside the Lake Champlain Valley, and 4) averaged a surface lake–air temperature difference of 14.4°C and a lake–850-hPa temperature difference of 18.2°C. Lake Champlain lake-effect events occur within a limited range of wind and temperature conditions, thus providing events that are more sensitive to small changes in environmental conditions than are large-lake lake-effect events and offering a more responsive system for subsequent investigation of connections between mesoscale processes and climate variability.” Laird, Neil F., Jared Desrochers, Melissa Payer, 2009, J. Appl. Meteor. Climatol., 48, 232–250, doi: 10.1175/2008JAMC1923.1. [Full text]

Climate teleconnections related to El Niño winters in a lake-effect region of west-central New York – Grimaldi (2008) “A 64-year climatological record for the cold season in Syracuse, New York is analyzed for temperature and snowfall. Evidence suggests that El Niño winters are characterized by warmer temperatures and below normal snowfall during the first month of winter followed by colder temperatures and above normal snowfall for the second month of winter. Major snow events were more than five times more likely to occur for El Niño winters compared to climatology. It is suggested that the greater frequency of heavy snowfalls is related to both favorable dynamics and warmer lake/ocean temperatures which follow the mild early winter period.” Richard Grimaldi, Atmospheric Science Letters, Volume 9, Issue 1, pages 18–25, January/March 2008, DOI: 10.1002/asl.166. [Full text]

Hydroclimatic Analysis of Snowfall Trends Associated with the North American Great Lakes – Ellis & Johnson (2004) “Research over the past several decades has indicated that snowfall has increased dramatically over portions of the past century across those areas of the Great Lakes region of North America that are subject to lake-effect snowfall. Within this study, time series of annual midwinter snowfall within lake-effect areas show evidence of a clear increase in both snowfall and snowfall frequency through a 40-yr period beginning in the early 1930s and ending in the early 1970s. The goal of the work presented here is to determine to what extent the apparent increases in lake-effect snowfall actually modified the winter hydroclimate of the areas. Simple hydroclimatic analysis of midwinter precipitation to the lee of Lakes Erie and Ontario for the period of significant snowfall increases suggests that the changes were a product of 1) a shift toward more precipitation events that were snowfall rather than rainfall, 2) an associated decrease in midwinter rainfall, 3) an increase in the intensity of individual snowfall events, and 4) an increase in the snowfall/snow water equivalence ratio. The balance was a small increase in total precipitation confined to areas in close proximity to the lakes across northeastern Ohio and western New York, while areas outside the regions generally experienced an overall decrease in midwinter precipitation. While the cause(s) of the snowfall trends remains elusive, the results of the work presented here suggest that no great long-term regional change occurred in the true wintertime seasonal hydroclimate of the lake-effect areas. Rather, much of the touted snowfall increase simply came at the expense of rainfall events to produce only small changes in total precipitation over the time period of significant snowfall increase.” Ellis, Andrew W., Jennifer J. Johnson, 2004, J. Hydrometeor, 5, 471–486. [Full text]

Increasing Great Lake–Effect Snowfall during the Twentieth Century: A Regional Response to Global Warming? – Burnett et al. (2003) “The influence of the Laurentian Great Lakes on the climate of surrounding regions is significant, especially in leeward settings where lake-effect snowfall occurs. Heavy lake-effect snow represents a potential natural hazard and plays important roles in winter recreational activities, agriculture, and regional hydrology. Changes in lake-effect snowfall may represent a regional-scale manifestation of hemispheric-scale climate change, such as that associated with global warming. This study examines records of snowfall from several lake-effect and non-lake-effect sites throughout most of the twentieth century in order to 1) determine whether differences in snowfall trends exist between these settings and 2) offer possible linkages between lake-effect snow trends and records of air temperature, water temperature, and ice cover. A new, historic record of oxygen isotope [δ¹⁸O(CaCO₃)] data from the sediments of three eastern Finger Lakes in central New York is presented as a means of independently assessing changes in Great Lakes lake-effect snowfall. Results reveal a statistically significant increasing trend in snowfall for the lake-effect sites, whereas no trend is observed in the non-lake-effect settings. The Finger Lake oxygen isotope record reflects this increase in lake-effect snow through a statistically significant trend toward lower δ¹⁸O(CaCO₃) values. Records of air temperature, water temperature, and lake ice suggest that the observed lake-effect snow increase during the twentieth century may be the result of warmer Great Lakes surface waters and decreased ice cover, both of which are consistent with the historic upward trend in Northern Hemispheric temperature due to global warming. Given projected increases in future global temperature, areas downwind of the Great Lakes may experience increased lake-effect snowfall for the foreseeable future.” Burnett, Adam W., Matthew E. Kirby, Henry T. Mullins, William P. Patterson, 2003, J. Climate, 16, 3535–3542. [Full text]

Assessment of Potential Effects of Climate Change on Heavy Lake-Effect Snowstorms Near Lake Erie – Kunkel et al. (2002) “The potential effects of future climate change on the frequency of heavy lake-effect snowstorms in the Lake Erie snowbelt were assessed using recent transient simulations from two General Circulation Models (GCMs): the second-generation Hadley Centre (HadCM2) and the first generation Canadian Climate Centre (CGCM1) coupled ocean-atmosphere models. An analysis of historical heavy lake-effect snowstorms identified six weather conditions to be closely related to heavy lake-effect snowstorm occurrence: surface wind speed > 6 m/s, surface wind direction of south southwest to west northwest, surface air temperature in the range of −10°C to 0°C, lake surface to air temperature difference > 7°C, lower tropospheric stability (T_{lake − 850} >15°C), and a highly amplified middle tropospheric wave train. These criteria were applied to daily grid point data from the GCMs for two periods, the late 20th Century and the late 21st Century, to determine the relative frequency with which heavy lake-effect conditions were predicted. Surface conditions favorable for heavy lake-effect snow decreased in frequency by 50% and 90% for the HadCM2 and CGCM1, respectively, by the late 21st Century. This reduction was due almost entirely to a decrease in the number of occurrences of surface air temperature in the range of −10 to 0°C, which in turn was the result of an increase in average winter air temperatures. Other surface conditions favorable for lake-effect snow occurred at about the same frequency in the late 21st Century as in the late 20th Century, suggesting that lake-effect rain events may replace lake-effect snow events. Changes in the middle tropospheric wave train were also noted in both models. However, there were sizable biases in the simulation of the present-day climate, raising questions about the validity of the future projections.” Kenneth E. Kunkel, Nancy E. Westcott and David A.R. Kristovich, Journal of Great Lakes Research, Volume 28, Issue 4, 2002, Pages 521-536, doi:10.1016/S0380-1330(02)70603-5.

Synoptic mechanisms associated with snowfall increases to the lee of Lakes Erie and Ontario – Leathers & Ellis (1996) “Snowfall is a cyrospheric variable that impacts nearly every sector of society. Because of its societal importance, snowfall is a logical variable to be used as an indicator of potential global environmental change. This study investigates the mechanisms responsible for large observed snowfall increases across the eastern Great Lakes region of the USA. Results indicate that mean snowfall amounts across sections of western New York and north-western Pennsylvania have increased by up to 100 cm over the 60-year period encompassing the snowfall seasons 1930–1931 through to 1989–1990. A synoptic climatological approach is utilized to identify consistent synoptic-scale atmospheric patterns responsible for snowfall across the region. Nine synoptic types are identified as producing significan t snowfall in the study area; five with synoptic characteristics indicative of lake-effect snowfall and four evidencing characteristics of snowfall associated with cyclonic influence. An examination of the seasonal frequency of the nine synoptic types indicates a substantial increase in the frequency of the five lake-effect synoptic types and a long-term decrease in the numbers of cyclone synoptic types over the period 1950–1951 through to 1981–1982. Information concerning trends in the frequency and the intensity of each of the nine snowfall-producing synoptic types was combined to produce a modelled snowfall change due to frequency and intensity variations over the period. Trends in the frequency and intensity of the synoptic patterns associated with lake- effect snowfall explain the majority of the observed snowfall increase across the region. Variations in the synoptic types associated with cyclonically induced snowfall are shown to be unimportant to snowfall changes across the eastern Great Lakes area. Possible reasons for increases in the frequency and the intensity of the lake-effect synoptic types are discussed.” Daniel J. Leathers, Andrew W. Ellis, International Journal of Climatology, Volume 16, Issue 10, pages 1117–1135, October 1996, DOI: 10.1002/(SICI)1097-0088(199610)16:103.0.CO;2-4.

Temporal characteristics of USA snowfall 1945–1946 through to 1984–1985 – Leathers et al. (1993) “The temporal variability of USA snowfall is investigated for the period 1945–1946 through to 1984–1985 using linear trend and principal components analyses. The results of the linear trend analysis indicate that two regions of the USA evidence significant changes in monthly snowfall over the period. These areas include the Great Lakes/upper mid-west and high plains regions of the USA. In the Great Lakes/upper mid-west sector, positive linear trends are found in monthly snowfall totals for the mid-winter months (December, January, February). For the high plains region, positive linear trends are found for the month of December. Principal components analysis (PCA) is used with seasonal snowfall data in order to better understand the spatial and temporal nature of seasonal snowfall variations across the USA. The PCA isolates six spatially coherent regions in which seasonal snowfall varied similarly over the 40-year period. Only one of these regions, centred on the Great Lakes and upper mid-west, displays any long-term change in seasonal snowfall, a positive trend during the period 1945–1946 through to 1984–1985. These results are discussed in the context of man-induced and natural environmental changes.” Daniel J. Leathers, Thomas L. Mote, Karl C. Kuivinen, Stuart McFeeters, Douglas R. Kluck, International Journal of Climatology, Volume 13, Issue 1, pages 65–76, January/February 1993, DOI: 10.1002/joc.3370130105.

Spatiotemporal Trends in Lake Effect and Continental Snowfall in the Laurentian Great Lakes, 1951–1980 – Norton & Bolsenga (1993) “A new raster-based monthly snowfall climatology was derived from 1951–1980 snowfall station data for the Laurentian Great Lakes. An automated methodology was used to obtain higher spatial resolution than previously obtained. The increase in resolution was attained by using all available monthly snowfall data from over 1230 stations per year combined with a monthly lime step to produce high-resolution grids. These monthly grids were combined to produce snow-year grids. Multiyear average grids were created and compared. This technique minimizes traditional problems associated with missing data and variable length station records. The three 10-year average distribution maps presented here indicate a period of increasing snowfall. Windowing of the 30 seasonal grids revealed that increasing snowfall was attributable to an increase in lake effect snowfall and not to continental snowfall. The Great Lakes drainage basin was evaluated for trends within and between monthly and seasonal average snowfall through windowing of all 240 monthly grids. The graphical and statistical evaluation of these trends indicates a strong natural variation in the region’s snowfall and reveals an increasing trend during the study period.” Norton, D. C., S. J. Bolsenga, 1993, J. Climate, 6, 1943–1956. [Full text]

Numerical Study of the Influence of Environmental Conditions on Lake-Effect Snowstorms over Lake Michigan – Hjelmfelt (1990) “Numerical simulations are used to examine the influence of environmental parameters on the morphology of lake effect snowstorms over Lake Michigan. A series of model sensitivity studies are performed using the Colorado State University mesoscale model to examine the effects of lake–land temperature difference, surface roughness, atmospheric boundary layer stability, humidity, and wind speed and direction on the morphology of simulated storms. Four morphological types of lake effect snowstorms have been identified: (i) Broad area coverage, which may become organized into wind parallel bands or cellular convection; (ii) shoreline bands with a line of convection roughly parallel to the lee shore and a well developed land breeze on the lee shore; (iii) midlake band with low-level convergence centered over the lake; and (iv) mesoscale vortices with a well-developed cyclonic flow pattern in the boundary layer. The model is able to reproduce all four morphological types. Simulations varying environmental parameters independently define the thermodynamic and wind conditions for the occurrence of each morphological type. In particular, the limiting conditions of lake–land temperature difference, upwind wind speed stability, and humidity for development of a land breeze on the east side of Lake Michigan are defined for lake snow conditions. The effects of wind direction, surface roughness, and latent heat release are also described.” Hjelmfelt, Mark R., 1990, Mon. Wea. Rev., 118, 138–150. [Full text]

Quantitative Estimates of the Effect of Lake Michigan on Snowfall – Braham & Dungey (1984) “A climatological study of snowfall in the snowbelts of Michigan shows that decade-average amounts varied by a factor of 2 during the period from 1909/10 through 1980/81. The effect of Lake Michigan on total winter snowfall along its shores has been estimated. A long-term average effect of +10% is found for the Wisconsin shore south of Sheboygan, and an average of +60% for the Michigan shore, south of Hart, with a minimum effect in the 1930s and a maximum in the 1960s.” Braham, Roscoe R., Maureen J. Dungey, 1984, J. Climate Appl. Meteor., 23, 940–949. [Full text]

Lake Effect Snowfall to the Lee of the Great Lakes: Its Role in Michigan – Eichenlaub (1970) “Lake effect snowfalls contribute a significant proportion of the total winter snowfall in areas to the lee of the Great Lakes. In Michigan during the seasons 1957–58 through 1961–62 at least 30% of the seasonal snowfall in lee areas was derived from lake-atmosphere interactions. Evidence suggests that lake effect snowfall has significantly increased during the past several decades, particularly in southwestern Michigan and northern Indiana. While the observed changes cannot be definitely ascribed to any single factor, it seems likely that a general cooling of winter temperatures may be partially responsible for this climatic change.” Eichenlaub, Val L., 1970, Bull. Amer. Meteor. Soc., 51, 403–412. [Full text]

New research from last week 48/2010

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

South Africa apple and pear trees bloom earlier

Advance of apple and pear tree full bloom dates in response to climate change in the southwestern Cape, South Africa: 1973–2009 – Grab & Craparo (2010) “Studies from throughout the world have demonstrated that tree phenophases are becoming earlier in spring and are closely associated with rising temperatures. Despite many such studies from the Northern Hemisphere, similar comparative work has not been forthcoming from the Southern Hemisphere or from Africa. In addition, few studies have demonstrated the possible role of changes in precipitation and associated soil moisture to driving fruit tree phenophases. Here we provide changes of mean full bloom dates for three apple Malus domestica (Golden Delicious, Sayaka, Granny Smith) and one pear Pyrus communis (Bon Chrétien) cultivars in the southwestern Cape of South Africa. These phenological changes are correlated with temperature and precipitation changes in the same region between 1973 and 2009. Significant early spring (August/September) temperature increases of +0.45 °C/decade are associated with a mean full bloom advance of 1.6 d/decade over the last 37 years. Golden Delicious apple trees have the strongest sensitivity (+4.2 d/°C) to climate change in the region, whilst Granny Smith apple trees have the lowest (+2.4 d/°C). Although winter and early spring rainfall has also decreased over this time, such decreases are not significant. However, significant correlations are found for both temperature and rainfall when comparing with the mean full bloom dates, and it is proposed that both variables operate synergistically to influence mean full bloom dates in the southwestern Cape.” Stefan Grab and Alessandro Craparo, Agricultural and Forest Meteorology, doi:10.1016/j.agrformet.2010.11.001.

Urban cool islands within urban heat island

Derivation of Birmingham’s summer surface urban heat island from MODIS satellite images – Tomlinson et al. (2010) “This study investigates the summer (June, July, August) night urban heat island (UHI) of Birmingham, the UK’s second most populous city. Land surface temperature remote sensing data is used from the MODIS sensor on NASA’s Aqua satellite, combined with UK Met Office station data to map the average variation in heat island intensity over the Birmingham conurbation. Results are presented of average UHI events over four Pasquill-Gifford stability classes D, E, F, and G between 2003 and 2009, as well as a specific heatwave event in July 2006. The results quantify the magnitude of the Birmingham surface UHI as well as the impact of atmospheric stability on UHI development. During periods of high atmospheric stability, a UHI of the order of 5 °C is evident with a clear peak in the central business district. Also identified, are significant cold spots in the conurbation. In one city park, recorded surface temperatures are up to 7 °C lower than the city centre.” C. J. Tomlinson, L. Chapman, J. E. Thornes, C. J. Baker, International Journal of Climatology, DOI: 10.1002/joc.2261.

Sound wave climate science

The Sound of Climate Change – Munk (2010) “It came as a great shock in the 1960s that the oceans, like the atmosphere, have an active weather (i.e. ocean storms are called eddies). The traditional expedition mode of individual research vessels making independent measurements was no longer adequate. Ocean Acoustic Tomography was developed in direct response to the “eddie revolution”. Sound travels faster in warmer water; acoustic waves transmitted from ship to ship give information about the temperature and currents in the intervening waters. The transmission scale has widened over the years from 100 to 1000 to 10,000 km, approaching the antipodal scale of Ewing’s 1960 transmission from Perth (Australia) to Bermuda. In 1991 we successfully transmitted from a source ship on Heard Island in the Indian Ocean to receiver ships in the north and south Atlantic and Pacific Oceans. Brian Dushaw (personal communication, 2010) is planning to repeat Ewing’s experiment; he expects a reduction in travel time of approximately 10 s as confirmation of global ocean warming over the last fifty years. Sea level rose 15cm in the 20th century. The rate has since doubled; values up to 2m by 2100 are now being quoted. To make accurate predictions we must understand the melting processes of continental ice sheets. Floating ice sheets from Antarctic and Greenland glaciers cover huge ocean caverns that have not to date been accessible to observation. We propose probing these caverns with sound waves to study the ocean dynamics at the underside of the floating ice sheets: a daring venture.” Walter Munk, Tellus A, 2010, DOI: 10.1111/j.1600-0870.2010.00494.x.

Fish sperm not bothered by ocean acidification

Effect of ocean acidification on marine fish sperm (Baltic cod: Gadus morhua) – Frommel et al. (2010) “Ocean acidification, as a consequence of increasing marine pCO2, may have severe effects on the physiology of marine organisms. However, experimental studies remain scarce, in particular concerning fish. While adults will most likely remain relatively unaffected by changes in seawater pH, early life-history stages are potentially more sensitive – particularly the critical stage of fertilization, in which sperm motility plays a central role. In this study, the effects of ocean acidification (decrease of pHT to 7.55) on sperm motility of Baltic cod, Gadus morhua, were assessed. We found no significant effect of decreased pH on sperm speed, rate of change of direction or percent motility for the population of cod analyzed. We predict that future ocean acidification will probably not pose a problem for sperm behavior, and hence fertilization success, of Baltic cod.” Frommel, A. Y., Stiebens, V., Clemmesen, C., and Havenhand, J., Biogeosciences, 7, 3915-3919, doi:10.5194/bg-7-3915-2010, 2010. [full text]

Only rapid sea level rise will sink coastal marshes

Limits on the adaptability of coastal marshes to rising sea level – Kirwan et al. (2010) “Assumptions of a static landscape inspire predictions that about half of the world’s coastal wetlands will submerge during this century in response to sea-level acceleration. In contrast, we use simulations from five numerical models to quantify the conditions under which ecogeomorphic feedbacks allow coastal wetlands to adapt to projected changes in sea level. In contrast to previous sea-level assessments, we find that non-linear feedbacks among inundation, plant growth, organic matter accretion, and sediment deposition, allow marshes to survive conservative projections of sea-level rise where suspended sediment concentrations are greater than ∼20 mg/L. Under scenarios of more rapid sea-level rise (e.g., those that include ice sheet melting), marshes will likely submerge near the end of the 21st century. Our results emphasize that in areas of rapid geomorphic change, predicting the response of ecosystems to climate change requires consideration of the ability of biological processes to modify their physical environment.” Kirwan, M. L., G. R. Guntenspergen, A. D’Alpaos, J. T. Morris, S. M. Mudd, and S. Temmerman (2010), Limits on the adaptability of coastal marshes to rising sea level, Geophys. Res. Lett., 37, L23401, doi:10.1029/2010GL045489. [full text]

Regional sea ice decline in Antarctica contrasts overall increase

Ice core evidence for a 20th century decline of sea ice in the Bellingshausen Sea, Antarctica – Abram et al. (2010) “This study uses ice core methanesulphonic acid (MSA) records from the Antarctic Peninsula, where temperatures have been warming faster than anywhere else in the Southern Hemisphere, to reconstruct the 20th century history of sea ice change in the adjacent Bellingshausen Sea. Using satellite-derived sea ice and meteorological data, we show that ice core MSA records from this region are a reliable proxy for regional sea ice change, with years of increased winter sea ice extent recorded by increased ice core MSA concentrations. Our reconstruction suggests that the satellite-observed sea ice decline in the Bellingshausen Sea during recent decades is part of a long-term regional trend that has occurred throughout the 20th century. The long-term perspective on sea ice in the Bellingshausen Sea is consistent with evidence of 20th century warming on the Antarctic Peninsula and may reflect a progressive deepening of the Amundsen Sea Low due to increasing greenhouse gas concentrations and, more recently, stratospheric ozone depletion. As a first-order estimate, our MSA-based reconstruction suggests that sea ice in the Bellingshausen Sea has retreated southward by ∼0.7° during the 20th century. Comparison with other 20th century sea ice observations, reconstructions, and model simulations provides a coherent picture of Antarctic sea ice decline during the 20th century, although with regional-scale differences evident in the timing and magnitude of this sea ice decline. This longer-term perspective contrasts with the small overall increase in Antarctic sea ice that is observed in post-1979 satellite data.” Abram, N. J., E. R. Thomas, J. R. McConnell, R. Mulvaney, T. J. Bracegirdle, L. C. Sime, and A. J. Aristarain (2010), J. Geophys. Res., 115, D23101, doi:10.1029/2010JD014644.

70% chance for climate-carbon feedbacks being positive

Paleoclimatic warming increased carbon dioxide concentrations – Lemoine (2010) “If climate-carbon feedbacks are positive, then warming causes changes in carbon dioxide (CO2) sources and sinks that increase CO2 concentrations and create further warming. Previous work using paleoclimatic reconstructions has not disentangled the causal effect of interest from the effects of reverse causality and autocorrelation. The response of CO2 to variations in orbital forcing over the past 800,000 years suggests that millennial-scale climate-carbon feedbacks are significantly positive and significantly greater than century-scale feedbacks. Feedbacks are also significantly greater on 100 year time scales than on 50 year time scales over the past 1500 years. Posterior probability distributions implied by coupled models’ predictions and by these paleoclimatic results give a mean of 0.03 for the nondimensional climate-carbon feedback factor and a 90% chance of its being between −0.04 and 0.09. The 70% chance that climate-carbon feedbacks are positive implies that temperature change projections tend to underestimate an emission path’s consequences if they do not allow the carbon cycle to respond to changing temperatures.” Lemoine, D. M. (2010), J. Geophys. Res., 115, D22122, doi:10.1029/2010JD014725.

Detecting anthropogenic CO2 changes in Atlantic Ocean

Detecting anthropogenic CO₂ changes in the interior Atlantic Ocean between 1989 and 2005 – Wanninkhof et al. (2010) “Repeat observations along the meridional Atlantic section A16 from Iceland to 56°S show substantial changes in the total dissolved inorganic carbon (DIC) concentrations in the ocean between occupations from 1989 through 2005. The changes correspond to the expected increase in DIC driven by the uptake of anthropogenic CO₂ from the atmosphere, but the ΔDIC is more varied and larger, in some locations, than can be explained solely by this process. Concomitant large changes in oxygen (O₂) suggest that processes acting on the natural carbon cycle also contribute to ΔDIC. Precise partial pressure of CO₂ measurements suggest small but systematic increases in the bottom waters. To isolate the anthropogenic CO₂ component (ΔC_anthro) from ΔDIC, an extended multilinear regression approach is applied along isopycnal surfaces. This yields an average depth-integrated ΔC_anthro of 0.53 ± 0.05 mol m⁻² yr⁻¹ with maximum values in the temperate zones of both hemispheres and a minimum in the tropical Atlantic. A higher decadal increase in the anthropogenic CO₂ inventory is found for the South Atlantic compared to the North Atlantic. This anthropogenic CO₂ accumulation pattern is opposite to that seen for the entire Anthropocene up to the 1990s. This change could perhaps be a consequence of the reduced downward transport of anthropogenic CO₂ in the North Atlantic due to recent climate variability. Extrapolating the results for this section to the entire Atlantic basin (63°N to 56°S) yields an uptake of 5 ± 1 Pg C decade⁻¹, which corresponds to about 25% of the annual global ocean uptake of anthropogenic CO₂ during this period.” Wanninkhof, R., S. C. Doney, J. L. Bullister, N. M. Levine, M. Warner, and N. Gruber (2010), J. Geophys. Res., 115, C11028, doi:10.1029/2010JC006251.

Much of the dissolved organic carbon in ocean is from microbial methane hydrate consumption

Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans – Pohlman et al. (2010) “Marine sediments contain about 500–10,000 Gt of methane carbon, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined, but it releases relatively little methane to the ocean and atmosphere. Sedimentary microbes convert most of the dissolved methane to carbon dioxide. Here we show that a significant additional product associated with microbial methane consumption is methane-derived dissolved organic carbon. We use Δ¹⁴C and δ¹³C measurements and isotopic mass-balance calculations to evaluate the contribution of methane-derived carbon to seawater dissolved organic carbon overlying gas hydrate-bearing seeps in the northeastern Pacific Ocean. We show that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon. This methane-derived material is much older, and more depleted in ¹³C, than background dissolved organic carbon. We suggest that fossil methane-derived carbon may contribute significantly to the estimated 4,000–6,000 year age of dissolved organic carbon in the deep ocean, and provide reduced organic matter and energy to deep-ocean microbial communities.” John W. Pohlman, James E. Bauer, William F. Waite, Christopher L. Osburn & N. Ross Chapman, Nature Geoscience, Published online: 28 November 2010, doi:10.1038/ngeo1016.

Papers on ENSO effects in Europe

This is a list of papers on the El Niño-Southern Oscillation (ENSO) effects in Europe. Also papers on North-Atlantic (and NAO) link to ENSO are included. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (December 5, 2010): Brönnimann et al. (2004) added, thanks to Lars Rosenberg for pointing it out, see the comment section below.

Northern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10 – Seager et al. (2010) “Winter 2009/10 had anomalously large snowfall in the central parts of the United States and in northwestern Europe. Connections between seasonal snow anomalies and the large scale atmospheric circulation are explored. An El Niño state is associated with positive snowfall anomalies in the southern and central United States and along the eastern seaboard and negative anomalies to the north. A negative NAO causes positive snow anomalies across eastern North America and in northern Europe. It is argued that increased snowfall in the southern U.S. is contributed to by a southward displaced storm track but further north, in the eastern U.S. and northern Europe, positive snow anomalies arise from the cold temperature anomalies of a negative NAO. These relations are used with observed values of NINO3 and the NAO to conclude that the negative NAO and El Niño event were responsible for the northern hemisphere snow anomalies of winter 2009/10.” Seager, R., Y. Kushnir, J. Nakamura, M. Ting, and N. Naik (2010), Geophys. Res. Lett., 37, L14703, doi:10.1029/2010GL043830. [Full text]

An Atmospheric Teleconnection Linking ENSO and Southwestern European Precipitation – Shaman & Tziperman (2010) “Numerous studies have demonstrated statistical associations between the El Niño-Southern Oscillation (ENSO) and precipitation in the Mediterranean basin. The dynamical bases for these teleconnections have yet to be fully identified. Here we use observational analyses and model simulations to show how ENSO variability affects rainfall over southwestern Europe (Iberia, Southern France and Italy). We define a precipitation index for the region, named southwestern European Precipitation (SWEP). Observational analyses show that ENSO modulates SWEP during the September–December wet season. These precipitation anomalies are associated with changes in large-scale atmospheric fields to the west of Iberia that alter low-level westerly winds and onshore moisture advection from the Atlantic. The vorticity anomalies associated with SWEP variability are linked to ENSO through a stationary barotropic Rossby wave train that emanates from the eastern equatorial Pacific and propagates eastward to the Atlantic and Mediterranean. Solutions of the linearized barotropic vorticity equation produce such eastward propagating Rossby waves with trajectories that traverse the region of observed ENSO-related anomalies. In addition, these linearized barotropic vorticity equation solutions produce a dipole of positive and negative vorticity anomalies to the west of Iberia that matches observations and is consistent with the onshore advection of moisture. Thus, interannual variability of fall and early winter precipitation over southwestern Europe is linked to ENSO variability in the eastern Pacific via an eastward propagating atmospheric stationary barotropic Rossby wave train.” Jeffrey Shaman, Eli Tziperman, Journal of Climate 2010, doi: 10.1175/2010JCLI3590.1.

A 600 k.y. record of El Niño–Southern Oscillation (ENSO): Evidence for persisting teleconnections during the Middle Eocene greenhouse climate of Central Europe – Lenz et al. (2010) “The El Niño–Southern Oscillation (ENSO) is a globally important factor in today’s climate dynamics. Annually laminated oil shales from the maar lake of Messel (Germany) provide high-resolution sedimentological and paleoenvironmental data of a time interval of ∼600 k.y. during the Eocene greenhouse phase. Individual laminae consist of a light spring and summer algal layer (Tetraedron minimum layer) and a dark winter layer composed of terrigenous background sediment. Four sections were selected from the core of the Messel 2001 well in order to count varves and to measure total varve thickness and the thickess of light and dark laminae. Spectral analyses were done in order to detect possible cyclic fluctuations in varve thickness. Fluctuations are significant in the quasi-biennial (2.1–2.5 yr) and low-frequency band (2.8–3.5 yr, 4.9–5.6 yr), thus showing that algal growth as well as the background sedimentation were controlled by ENSO effects at least over a time interval of 600 k.y. This confirms the existence of a previously postulated robust Eocene ENSO. Significant peaks within a quasi-decadal (10–11 yr), interdecadal (17–26 yr), and multidecadal band (∼52 yr, ∼82 yr) show either the enduring influence of more or less cyclic instabilities or the influence of solar cycles.” Olaf K. Lenz, Volker Wilde, Walter Riegel, and Franz-Jürgen Harms, Geology, v. 38 no. 7 p. 627-630, doi: 10.1130/G30889.1.

Impact of the Stratosphere on the Winter Tropospheric Teleconnections between ENSO and the North Atlantic and European Region – Cagnazzo & Manzini (2009) “The possible role of stratospheric variability on the tropospheric teleconnection between El Niño–Southern Oscillation (ENSO) and the North Atlantic and European (NAE) region is addressed by comparing results from two ensembles of simulations performed with an atmosphere general circulation model fully resolving the stratosphere (with the top at 0.01 hPa) and its low-top version (with the top at 10 hPa). Both ensembles of simulations consist of nine members, covering the 1980–99 period and are forced with prescribed observed sea surface temperatures. It is found that both models capture the sensitivity of the averaged polar winter lower stratosphere to ENSO in the Northern Hemisphere, although with a reduced amplitude for the low-top model. In late winter and spring, the ENSO response at the surface is instead different in the two models. A large-scale coherent pattern in sea level pressure, with high pressures over the Arctic and low pressures over western and central Europe and the North Pacific, is found in the February–March mean of the high-top model. In the low-top model, the Arctic high pressure and the western and central Europe low pressure are very much reduced. The high-top minus low-top model difference in the ENSO temperature and precipitation anomalies is that North Europe is colder and the Northern Atlantic storm track is shifted southward in the high-top model. In addition, it has been found that major sudden stratospheric warming events are virtually lacking in the low-top model, while their frequency of occurrence is broadly realistic in the high-top model. Given that this is a major difference in the dynamical behavior of the stratosphere of the two models and that these events are favored by ENSO, it is concluded that the occurrence of sudden stratospheric warming events affects the reported differences in the tropospheric ENSO–NAE teleconnection. Given that the essence of the high-top minus low-top model difference is a more annular (or zonal) pattern of the anomaly in sea level pressure, relatively larger over the Arctic and the NAE regions, this interpretation is consistent with the observational evidence that sudden stratospheric warmings play a role in giving rise to persistent Arctic Oscillation anomalies at the surface.” Cagnazzo, Chiara, Elisa Manzini, 2009, J. Climate, 22, 1223–1238.

The role of the stratosphere in the European climate response to El Niño – Ineson & Scaife (2009) “El Niño/Southern Oscillation (ENSO) is the largest natural interannual climate signal in the tropics; oscillations between warm El Niño and cold La Niña phases occur every few years. The effects are felt not only in the centre of action, the tropical Pacific region, but around the globe. Observational studies show a clear response in European climate to ENSO in late winter. However, the underlying mechanisms of the link are not yet understood. Here we use a general circulation model of the atmosphere, that has been extended into the upper atmospheric layers, to provide end-to-end evidence for a global teleconnection pathway from the Pacific region to Europe via the stratosphere. We present evidence for an active stratospheric role in the transition to cold conditions in northern Europe and mild conditions in southern Europe in late winter during El Niño years. In our experiments, this mechanism is restricted to years when stratospheric sudden warmings occur. The response in European surface climate to the El Niño signal is large enough to be useful for seasonal forecasting.” S. Ineson & A. A. Scaife, Nature Geoscience 2, 32 – 36 (2009), doi:10.1038/ngeo381.

On ENSO impacts on European wintertime rainfalls and their modulation by the NAO and the Pacific multi-decadal variability described through the PDO index – Zanchettin et al. (2008) “While strong relationships have previously been established between the El Niño/Southern Oscillation (ENSO) and climate variability in many parts of the world, previous analyses of ENSO impacts on European rainfalls have been variable and inconclusive. In this paper, the role and apparent interactions of a range of known teleconnections are assessed. It is shown that ENSO events do indeed appear to impact European rainfalls and that these impacts are likely to also depend on the concurrent state of the North Atlantic Oscillation (NAO) and the Pacific Decadal Oscillation (PDO). In particular, it is demonstrated that ENSO impacts most significantly on European wintertime rainfalls during positive (warm) phases of the PDO.” Davide Zanchettin, Stewart W. Franks, Pietro Traverso, Mario Tomasino, International Journal of Climatology, Volume 28, Issue 8, pages 995–1006, 30 June 2008.

ENSO influence on Europe during the last centuries – Brönnimann et al. (2007) “El Niño/Southern Oscillation (ENSO) affects climate not only in the Pacific region and the tropics, but also in the North Atlantic-European area. Studies based on twentieth-century data have found that El Niño events tend to be accompanied in late winter by a negative North Atlantic Oscillation index, low temperatures in northeastern Europe and a change in precipitation patterns. However, many questions are open, for example, concerning the stationarity of this relation. Here we study the relation between ENSO and European climate during the past 500 years based on statistically reconstructed ENSO indices, early instrumental station series, and reconstructed fields of surface air temperature, sea-level pressure, precipitation, and 500 hPa geopotential height. After removing years following tropical volcanic eruptions (which systematically mask the ENSO signal), we find a consistent and statistically significant ENSO signal in late winter and spring. The responses to El Niño and La Niña are close to symmetric. In agreement with studies using twentieth-century data only, the ENSO signal in precipitation is different in fall than in late winter. Moving correlation analyses confirm a stationary relationship between ENSO and late winter climate in Europe during the past 300 years. However, the ENSO signal is modulated significantly by the North Pacific climate. A multi-field cluster analysis for strong ENSO events during the past 300 years yields a dominant pair of clusters that is symmetric and represents the ‘classical’ ENSO effects on Europe.” S. Brönnimann, E. Xoplaki, C. Casty, A. Pauling and J. Luterbacher, Climate Dynamics, Volume 28, Numbers 2-3, 181-197, DOI: 10.1007/s00382-006-0175-z. [Full text]

North Atlantic Winter SLP Anomalies Based on the Autumn ENSO State – Pozo-Vázquez et al. (2005) “The winter sea level pressure (SLP) anomalies in the Northern Hemisphere have been analyzed over the period 1873–2000 based on the ENSO state during the previous autumn. First, a set of extreme cold and warm ENSO events and periods that may be regarded as normal is selected using the SST data of the Niño-3 region. This selection is carried out for autumn and with the constraint that the ENSO event is well developed. For the winters following these selected autumn events, composites of Northern Hemisphere SLP anomalies have been obtained and compared to each other. A study of the consistency among events of the relationship between ENSO and SLP anomalies was also carried out. Results show the preference for a positive NAO-like SLP anomaly pattern in the North Atlantic region during the winters following autumns of strong cold ENSO events and, thus, suggest the existence of a potential source of predictability for the North Atlantic climate. An additional analysis of the winter North Atlantic Oscillation (NAO) index confirms this finding. The possible physical basis of this source of predictability for the North Atlantic climate is discussed.” Pozo-Vázquez, D., S. R. Gámiz-Fortis, J. Tovar-Pescador, M. J. Esteban-Parra, Y. Castro-DÍez, 2005, J. Climate, 18, 97–103, doi: 10.1175/JCLI-3210.1.

Extreme climate of the global troposphere and stratosphere in 1940–42 related to El Niño – Brönnimann et al. (2004) “Although the El Niño/Southern Oscillation phenomenon is the most prominent mode of climate variability1 and affects weather and climate in large parts of the world, its effects on Europe and the high-latitude stratosphere are controversial. Using historical observations and reconstruction techniques, we analyse the anomalous state of the troposphere and stratosphere in the Northern Hemisphere from 1940 to 1942 that occurred during a strong and long-lasting El Niño event. Exceptionally low surface temperatures in Europe and the north Pacific Ocean coincided with high temperatures in Alaska. In the lower stratosphere, our reconstructions show high temperatures over northern Eurasia and the north Pacific Ocean, and a weak polar vortex. In addition, there is observational evidence for frequent stratospheric warmings and high column ozone at Arctic and mid-latitude sites. We compare our historical data for the period 1940–42 with more recent data and a 650-year climate model simulation. We conclude that the observed anomalies constitute a recurring extreme state of the global troposphere–stratosphere system in northern winter that is related to strong El Niño events.” S. Brönnimann, J. Luterbacher, J. Staehelin, T. M. Svendby, G. Hansen & T. Svenøe, Nature 431, 971-974 (21 October 2004) | doi:10.1038/nature02982.

Predictability of Winter Climate over the North Atlantic European Region during ENSO Events – Mathieu et al. (2004) “The predictability of winter climate over the North Atlantic–European (NAE) region during ENSO events is investigated. Rather than employing traditional composite analyses, the authors focus on the impacts of six individual events: three El Niño events and three La Niña events. The investigation is based on the analysis of ensemble simulations with an atmospheric GCM forced with prescribed sea surface temperatures (SST) for the period December 1985–May 2001, and on observations. Model experiments are used to separate the respective roles of SST anomalies in the Indo-Pacific basin and in the Atlantic basin. A significant (potentially predictable) climate signal is found in the NAE region for all six ENSO events. However, there are notable differences in the impacts of individual El Niño and La Niña events. These differences arise not simply from atmospheric internal variability but also because the atmosphere is sensitive to specific features of the SST anomaly fields that characterize the individual events. The different impacts arise partly from differences in Indo-Pacific SST and partly from differences in Atlantic SST. SST anomalies in both ocean basins can influence tropical convection and excite a Rossby wave response over the North Atlantic. The evidence presented here for the importance of Atlantic Ocean conditions argues that, in the development of systems for seasonal forecasting, attention should not be focused too narrowly on the tropical Pacific Ocean.” Mathieu, P-P., R. T. Sutton, B. Dong, M. Collins, 2004, J. Climate, 17, 1953–1974. [Full text]

A high resolution AGCM study of the El Niño impact on the North Atlantic/European sector – Merkel & Latif (2002) “An atmospheric general circulation model (AGCM) sensitivity study has been performed with the ECHAM4 model forced by anomalous sea surface temperatures to investigate the role of the horizontal resolution (T42 versus T106) in determining the El Niño/Southern Oscillation (ENSO) response in the North Atlantic/European region. The higher resolution has been chosen in order to represent more realistically the transient eddy activity that is supposed to play a crucial role in the signal communication to regions remote from the tropical Pacific. In contrast to the T42 experiments, the T106 experiments reveal significant changes both in the mean of selected atmospheric variables (sea level pressure, temperature, precipitation) over Europe and in the transient and stationary wave activity. A cyclone tracking analysis reveals a southward shift of the North Atlantic low pressure systems in the winter season during El Niño events.” Merkel, U., and M. Latif (2002), Geophys. Res. Lett., 29(9), 1291, doi:10.1029/2001GL013726. [Full text]

Euro-Mediterranean rainfall and ENSO—a seasonally varying relationship – Mariotti et al. (2002) “Using observational datasets and atmospheric reanalyses, we show that interannual variability of rainfall in the Euro-Mediterranean sector is significantly influenced by ENSO in a way that is seasonally varying. Spatially coherent correlation patterns are found in central and eastern Europe during winter and spring, and in western Europe and the Mediterranean region during autumn and spring. A composite analysis of ENSO events indicates that during an El Nino western Mediterranean rainfall has a 10% increase (decrease) in the autumn preceeding (spring after) the mature phase of an event, corresponding to a rainy season arriving (retreating) earlier compared to the climatology. The atmospheric reanalyses show that an anomalous atmospheric circulation and moisture transport extending from the Atlantic Ocean into the Euro-Mediterranean region accompanies the observed rainfall anomalies. Multidecadal variations characterize the ENSO Euro-Mediterranean relationship during the 20th century.” Mariotti, A., N. Zeng, and K.-M. Lau (2002), Geophys. Res. Lett., 29(12), 1621, doi:10.1029/2001GL014248. [Full text]

The Association between ENSO and Winter Atmospheric Circulation and Temperature in the North Atlantic Region – Pozo-Vázquez et al. (2001) “The association among ENSO, the Northern Hemisphere sea level pressure (SLP), and temperatures in Europe has been analyzed during the period 1873–1995. In the first part, the SST of the Niño-3 region has been used to select extreme cold and warm ENSO events and periods that can be regarded as normal. The study was carried out for winter with the constraints that the ENSO events were well developed during the winter of study, and that they are extreme events. Composites of winter SLP and temperatures have been made for the selected cold and warm events as well as for normal cases and compared with each other. In the North Atlantic area, no statistically significant SLP anomaly patterns were found associated with warm events, while during cold events a statistically significant anomaly pattern resembling the positive phase of the North Atlantic oscillation (NAO) was found. The temperature analysis shows statistically significant negative anomalies during cold events over the Iberian Peninsula and positive anomalies over the British Isles and southern Scandinavia, consistent with the SLP anomalies. The SLP and temperatures have also been analyzed for spring. The patterns resemble those found for winter but the anomalies have lower amplitudes. For the completion of the composite analysis, the consistency among events of the relationship between ENSO and SLP as well as between ENSO and temperatures was examined. The results show that the significant patterns found in the composite analysis in the North Atlantic area are not the result of a few major events, but rather because both the SLP and temperature anomalies in this area during cold ENSO events are stable and qualitatively similar to those found during the positive phase of the NAO. The possible physical basis for this association between NAO and ENSO is discussed.” Pozo-Vázquez, D., M. J. Esteban-Parra, F. S. Rodrigo, Y. Castro-Díez, 2001, J. Climate, 14, 3408–3420. [Full text]

On the El Niño teleconnection to spring precipitation in Europe – Van Oldenborgh et al. (2000) “In a statistical analysis of more than a century of data, a strong connection was found between strong warm El Niño winter events and high spring precipitation in a band from southern England eastwards into Asia. This relationship is an extension of the connection mentioned by Kiladis and Diaz (1989. ‘Global climatic anomalies associated with extremes in the Southern Oscillation’, J. Climate, 2, 1069–1090), and is much stronger than the winter season teleconnection that has been the subject of other studies. Correlation coefficients between December–January (DJF) NIÑO3 indices and March–May (MAM) precipitation are higher than r=0.3 for individual stations, and as high as r=0.49 for an index of precipitation anomalies around 50°N from 5°W to 35°E. The lagged correlation suggests that southeast Asian surface temperature anomalies may act as intermediate variables.” Geert Jan Van Oldenborgh, Gerrit Burgers, Albert Klein Tank, International Journal of Climatology, Volume 20, Issue 5, pages 565–574, April 2000, DOI: 10.1002/(SICI)1097-0088(200004)20:53.0.CO;2-5.

Predictable winter climate in the North Atlantic sector during the 1997–1999 ENSO cycle – Dong et al. (2000) “The winters of 1997/98 and 1998/99 were marked by strikingly different weather conditions over the North Atlantic ocean and adjacent continents. We use a state‐of‐the‐art atmospheric general circulation model forced with observed sea surface temperatures (SSTs) to investigate the hypothesis that the anomalous conditions in the North Atlantic sector during the winters of 97/98 and 98/99 were related to the ENSO cycle and were therefore potentially predictable. We demonstrate that the major circulation anomalies observed in the North Atlantic sector are reproducible in both winters. We show further that these circulation anomalies were forced primarily by ENSO‐related SST anomalies in the Pacific Ocean, but that SST anomalies in the Atlantic Ocean also had an influence. Our results are encouraging for the prospects of useful seasonal predictions for wintertime in the North Atlantic sector.” Dong, B. ‐W., R. T. Sutton, S. P. Jewson, A. O’Neill, and J. M. Slingo (2000), Geophys. Res. Lett., 27(7), 985–988, doi:10.1029/1999GL010994.

The relationship between the North Atlantic Oscillation and El Niño‐Southern Oscillation – Huang et al. (1998) “We have applied a multiresolution cross‐spectral analysis technique to resolve the temporal relationship between the NAO and ENSO. The study shows significant coherence between NAO and Niño3 SST in about 70% of the warm ENSO events from 1900 to 1995, of which 33% and 37% are associated with a 5‐ to 6‐year period (E1) and a 2‐ to 4‐year period (E2) oscillation terms in the spectral decomposition, respectively. The dominant teleconnection pattern associated with changes in the mean atmospheric circulation during the initial winter of a typical E1 and E2 events is the positive phase of the Pacific/North American (PNA) pattern. Non‐coherence between the NAO and ENSO occurs during relatively weak Niño3 SST anomaly, with a teleconnection pattern which shows a strong negative phase of the NAO and a pattern which resembles a weak eastward shifted negative phase of the PNA pattern.” Huang, J., K. Higuchi, and A. Shabbar (1998), Geophys. Res. Lett., 25(14), 2707–2710, doi:10.1029/98GL01936. [Full text]

Variations in seasonal rainfall in Southern Europe during the present century: relationships with the North Atlantic Oscillation and the El Niño-Southern Oscillation – Rodó et al. (1997) “Analysis of data from seventeen rainfall stations in the Iberian Peninsula, Balearic Islands and Northern Africa has revealed significant El Niño-Southern Oscillation (ENSO) signals in Europe. Both North Atlantic Oscillation (NAO) and Southern Oscillation (SO) exert an influence on Iberian climate, but at different temporal and spatial scales. Though most of the peninsula is under NAO influence in winter, some stations in the eastern region show no connection with this phenomenon. The same is found for ENSO, with a positively correlated region appearing in the eastern part of Spain, while the rest of the peninsula remains insensitive. The correlation between ENSO and Iberian rainfall has increased towards the end of the present century, with strong positive signals spanning over half of the area studied. The percentage of springtime variability due to ENSO has similarly increased, reaching up to 50% in certain areas.
We also show how there are outstanding climatic sensors of these phenomena such as Lake Gallocanta, which manifests a positive response to ENSO while appears insensitive to NAO. Common long-term patterns are observed between SOI and an inferred lake level series, suggesting a constant influence of the low-frequency component of ENSO throughout the period considered. Lake drying phases every 14 years reflect the impact of this signal, approximately every four ENSO events.” X. Rodó, E. Baert and F. A. Comín, Climate Dynamics, Volume 13, Number 4, 275-284, DOI: 10.1007/s003820050165.

An ENSO impact on Europe? – Fraedrich (1994) A review article. “The possible influence of the El Niño/Southern Oscillation (ENSO) warm and cold extremes on mid-latitude circulation regimes in the North Atlantic/European sector is described in terms of a phenomenological, statistical and physical analysis of observational data. (1) The European circulation patterns (after Hess-Brezowsky, 1977) are combined to a binary set of cyclonic and anticyclonic (low and high pressure) centres of action. They reveal a regional ENSO response with predominantly cyclonic (anticyclonic) Grosswetter for warm (cold) ENSO events in winters at the peak of the episode. (2) Standard climate statistics of the same winter seasons (surface pressure, temperature and precipitation anomalies) supplement the Grosswetter phenomenology. They suggest a shift of the tail end of the cross Atlantic storm track and its rainbearing frontal systems from a more northern route (during warm events) to a more zonal orientation (in cold events). (3) Finally, the transient and stationary eddy–mean flow interaction is diagnosed from daily hemispheric 500 mb geopotential height fields. They are composited about most extreme anomalies in Europe (independent of ENSO) defined by the amplitude of the first simultaneous EOF of normalized monthly mean pressure, temperature and precipitation at 40 stations. Thus (upstream location and intensity of) dynamic sources of wave activity flux in the western North-Atlantic cyclogenesis area can be identified. They are associated with European climate anomalies and may represent the connection linking ENSO and Europe under favourable conditions.” Klaus Fraedrich, Tellus A, Volume 46, Issue 4, pages 541–552, August 1994. [Full text]

Climate anomalies in Europe associated with ENSO extremes – Fraedrich & Müller (1992) “Surface pressure, temperature and precipitation anomalies in Europe are composed for the El Niño-Southern Oscillation (ENSO) warm and cold extremes. During warm event winters, negative pressure departures at western and central European stations are associated with positive temperature and precipitation anomalies; the reverse signals are observed in northern Europe. During cold episodes the field of negative pressure deviations is shifted northward with positive temperature and precipitation anomalies, whereas higher pressure is observed over central Europe. This shift of the anomalies corresponds to a shift in the dominating cyclone track (deduced from weather maps), which may be interpreted as the response of the (sensitive tail end of the) cross-Atlantic storm track on the high-pressure anomalies occurring at times in the northern or central part of the North Atlantic/European sector during warm or cold ENSO winters, respectively.” Klaus Fraedrich, Klaus Müller, International Journal of Climatology, Volume 12, Issue 1, pages 25–31, January/February 1992. [Full text]

European grosswetter during the warm and cold extremes of the El Niñco/Southern Oscillation – Fraedrich (1990) “El Niňo/Southern Oscillation (ENSO) warm and cold events affect the synoptic climatology of the north-eastern Atlantic-European sector. The classification of cyclonic and anticyclonic European Grosswetter (1881–1987) is analysed for its response on 26 warm and 21 cold ENSO episodes. Bi-monthly ranked composites computed over idealized 2–year ENSO warm (cold) episodes show more days of cyclonic (anticyclonic) steering over Europe. This signal is largest in the winter months of January and February following the year of a warm or cold event. The distributions of the occurrence of cyclonic and anticyclonic Grosswetter days are significantly different for warm and cold event winters: (i) there is more variability between individual warm event winter months, whereas the response to cold episodes is relatively uniform; (ii) on average, cyclonic Grosswetter days are experienced on 60 per cent (46 per cent) of the 58 warm (cold) event winter. days-about 70 per cent (90 per cent) of the warm (cold) event winters realize more than 30 (< 36) days of cyclonic steering. Qualitatively corresponding results are obtained at a representative central European location for sunshine duration and the sum of daily negative temperatures, which characterize the winter strength." Klaus Fraedrich, International Journal of Climatology, Volume 10, Issue 1, pages 21–31, January/February 1990. [Full text]

The Association between the North Atlantic Oscillation and the Southern Oscillation in the Northern Hemisphere – Rogers (1984) “The North Atlantic Oscillation (NAO) and Southern Oscillation (SO) are compared from the standpoint of their association with Northern Hemisphere winter mean distributions of sea-level pressure (SLP) and 500 mb height. The NAO and SO are associated with significant SLP differences over much of the hemisphere except for Siberia and western North America. Significant SLP and 500 mb height differences occur in the NAO over the Atlantic Ocean and near Baja California, while in the SO they occur over the Pacific Ocean, India and the western Atlantic. Only over the latter region do large pressure and height variations consistently occur in the extremes of both oscillations; these are also associated with winter temperature variability over the southeastern United States. For example, during winter 1982–83, when the two oscillations simultaneously reached extremes, the NAO was associated with record December warmth east of the Mississippi River, but during January and February the SO dominated the height and air temperature distributions over the United States. The cospectrum of the NAO index and Darwin (Australia) pressure is largest at intermediate frequencies with periods of about 6 years, although the NAO itself has peak energy at 7.3 years. The NAO is characterized by a large trend toward lower index in the twentieth century through the 1960s; this is not associated with variations in the SO. In the 80 winters of data, simultaneous occurrences of particular modes of one oscillation with those of the other seem to occur by chance.” Rogers, Jeffery C., 1984, Mon. Wea. Rev., 112, 1999–2015. [Full text]

The Southern Oscillation. Part I: Global Associations with Pressure and Temperature in Northern Winter – van Loon & Madden (1981) The abstract doesn’t mention it, but the Europe situation is discussed in the paper, so see the full text. “We describe the global correlations between a measure of the Southern Oscillation and sea level pressure and surface air temperature in the northern winter. The stability of these correlations were tested on the Northern Hemisphere for an 80-year period, and it turned out that most stable correlation coefficients were found over India, the North Pacific Ocean, the Rocky Mountains, and the central and western North Atlantic Ocean. On the Southern Hemisphere most records are too short for a similar test, but the following may tentatively be said about the Southern Oscillation in middle and high southern latitudes: when pressure is low in lower latitudes over the South Pacific Ocean it tends to be high at higher latitudes of that ocean, high over East Antarctica and low in the belt of westerlies in the Indian and South Atlantic oceans. In the zonal average on both hemispheres the pressure gradients in this extreme of the oscillation tend to be steeper at lower latitudes and flatter at higher latitudes than in the other extreme. The apparent large-scale sympathetic variations between the SO and temperature are shown to occur over the relatively wide range of periods dust have been attributed to the SO itself.” van Loon, Harry, Roland A. Madden, 1981, Mon. Wea. Rev., 109, 1150–1162. [Full text]

Papers on global potential of bio-energy

This is a list of papers on the global potential of bio-energy. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

The global technical potential of bio-energy in 2050 considering sustainability constraints – Haberl et al. (2010) “Bio-energy, that is, energy produced from organic non-fossil material of biological origin, is promoted as a substitute for non-renewable (e.g., fossil) energy to reduce greenhouse gas (GHG) emissions and dependency on energy imports. At present, global bio-energy use amounts to approximately 50 EJ/yr, about 10% of humanity’s primary energy supply. We here review recent literature on the amount of bio-energy that could be supplied globally in 2050, given current expectations on technology, food demand and environmental targets (‘technical potential’). Recent studies span a large range of global bio-energy potentials from ≈30 to over 1000 EJ/yr. In our opinion, the high end of the range is implausible because of (1) overestimation of the area available for bio-energy crops due to insufficient consideration of constraints (e.g., area for food, feed or nature conservation) and (2) too high yield expectations resulting from extrapolation of plot-based studies to large, less productive areas. According to this review, the global technical primary bio-energy potential in 2050 is in the range of 160–270 EJ/yr if sustainability criteria are considered. The potential of bio-energy crops is at the lower end of previously published ranges, while residues from food production and forestry could provide significant amounts of energy based on an integrated optimization (‘cascade utilization’) of biomass flows.” Helmut Haberl, Tim Beringer, Sribas C Bhattacharya, Karl-Heinz Erb and Monique Hoogwijk, Current Opinion in Environmental Sustainability, 2010, doi:10.1016/j.cosust.2010.10.007.

Bioenergy potentials from forestry in 2050 An assessment of the drivers that determine the potentials – Smeets & Faaij (2007) “The purpose of this study was to evaluate the global energy production potential of woody biomass from forestry for the year 2050 using a bottom-up analysis of key factors. Woody biomass from forestry was defined as all of the aboveground woody biomass of trees, including all products made from woody biomass. This includes the harvesting, processing and use of woody biomass. The projection was performed by comparing the future demand with the future supply of wood, based on existing databases, scenarios, and outlook studies. Specific attention was paid to the impact of the underlying factors that determine this potential and to the gaps and uncertainties in our current knowledge. Key variables included the demand for industrial roundwood and woodfuel, the plantation establishment rates, and the various theoretical, technical, economical, and ecological limitations related to the supply of wood from forests. Forests, as defined in this study, exclude forest plantations. Key uncertainties were the supply of wood from trees outside forests, the future rates of deforestation, the consumption of woodfuel, and the theoretical, technical, economical, or ecological wood production potentials of the forests. Based on a medium demand and medium plantation scenario, the global theoretical potential of the surplus wood supply (i.e., after the demand for woodfuel and industrial roundwood is met) in 2050 was calculated to be 6.1 Gm³ (71 EJ) and the technical potential to be 5.5 Gm³ (64 EJ). In practice, economical considerations further reduced the surplus wood supply from forests to 1.3 Gm³ year^-1 (15 EJ year−1). When ecological criteria were also included, the demand for woodfuel and industrial roundwood exceeded the supply by 0.7 Gm³ year^-1 (8 EJ year^-1). The bioenergy potential from logging and processing residues and waste was estimated to be equivalent to 2.4 Gm³ year^-1 (28 EJ year^-1) wood, based on a medium demand scenario. These results indicate that forests can, in theory, become a major source of bioenergy, and that the use of this bioenergy can, in theory, be realized without endangering the supply of industrial roundwood and woodfuel and without further deforestation. Regional shortages in the supply of industrial roundwood and woodfuel can, however, occur in some regions, e.g., South Asia and the Middle East and North Africa.” Edward M. W. Smeets and André P. C. Faaij, Climatic Change, Volume 81, Numbers 3-4, 353-390, DOI: 10.1007/s10584-006-9163-x. [Full text]

A bottom-up assessment and review of global bio-energy potentials to 2050 – Smeets et al. (2007) “In this article, a model for estimating bioenergy production potentials in 2050, called the Quickscan model, is presented. In addition, a review of existing studies is carried out, using results from the Quickscan model as a starting point. The Quickscan model uses a bottom-up approach and its development is based on an evaluation of data and studies on relevant factors such as population growth, per capita food consumption and the efficiency of food production. Three types of biomass energy sources are included: dedicated bioenergy crops, agricultural and forestry residues and waste, and forest growth. The bioenergy potential in a region is limited by various factors, such as the demand for food, industrial roundwood, traditional woodfuel, and the need to maintain existing forests for the protection of biodiversity. Special attention is given to the technical potential to reduce the area of land needed for food production by increasing the efficiency of food production. Thus, only the surplus area of agricultural land is included as a source for bioenergy crop production. A reference scenario was composed to analyze the demand for food. Four levels of advancement of agricultural technology in the year 2050 were assumed that vary with respect to the efficiency of food production. Results indicated that the application of very efficient agricultural systems combined with the geographic optimization of land use patterns could reduce the area of land needed to cover the global food demand in 2050 by as much as 72% of the present area. A key factor was the area of land suitable for crop production, but that is presently used for permanent grazing. Another key factor is the efficiency of the production of animal products. The bioenergy potential on surplus agricultural land (i.e. land not needed for the production of food and feed) equaled 215–1272 EJ yr⁻¹, depending on the level of advancement of agricultural technology. The bulk of this potential is found in South America and Caribbean (47–221 EJ yr⁻¹), sub-Saharan Africa (31–317 EJ yr⁻¹) and the C.I.S. and Baltic States (45–199 EJ yr⁻¹). Also Oceania and North America had considerable potentials: 20–174 and 38–102 EJ yr⁻¹, respectively. However, realization of these (technical) potentials requires significant increases in the efficiency of food production, whereby the most robust potential is found in the C.I.S. and Baltic States and East Europe. Existing scenario studies indicated that such increases in productivity may be unrealistically high, although these studies generally excluded the impact of large scale bioenergy crop production. The global potential of bioenergy production from agricultural and forestry residues and wastes was calculated to be 76–96 EJ yr⁻¹ in the year 2050. The potential of bioenergy production from surplus forest growth (forest growth not required for the production of industrial roundwood and traditional woodfuel) was calculated to be 74 EJ yr⁻¹ in the year 2050.” Edward M.W. Smeets, André P.C. Faaij, Iris M. Lewandowski and Wim C. Turkenburg, Progress in Energy and Combustion Science, Volume 33, Issue 1, February 2007, Pages 56-106, doi:10.1016/j.pecs.2006.08.001.

Global Biomass Energy Potential – Moreira (2006) “The intensive use of renewable energy is one of the options to stabilize CO₂atmospheric concentration at levels of 350 to 550ppm. A recent evaluation of the global potential of primary renewable energy carried out by Intergovernmental Panel on Climate Change (IPCC) sets a value of at least 2800EJ/yr, which is more than the most energy-intensive SRES scenario forecast for the world energy requirement up to the year 2100. Nevertheless, what is really important to quantify is the amount of final energy since the use of renewable sources may involve conversion efficiencies, from primary to final energy, different from the ones of conventional energy sources. In reality, IPCC does not provide a complete account of the final energy from renewables, but the text claims that using several available options to mitigate climate change, and renewables is only one of them, it is possible to stabilize atmospheric carbon dioxide (CO₂) concentration at a low level. In this paper, we evaluate in detail biomass primary and final energy using sugarcane crop as a proxy, since it is one of the highest energy density forms of biomass, and through afforestation/reforestation using a model presented in IPCC Second Assessment Report (SAR). The conclusion is that the primary-energy potential for biomass has been under-evaluated by many authors and by IPCC, and this under-evaluation is even larger for final energy since sugarcane allows co-production of electricity and liquid fuel. Regarding forests we reproduce IPCC results for primary energy and calculate final energy. Sugarcane is a tropical crop and cannot be grown in all the land area forecasted for biomass energy plantation in the IPCC/TAR evaluation (i.e. 1280Mha). Nevertheless, there are large expanses of unexploited land, mainly in Latin America and Africa that are subject to warm weather and convenient rainfall. With the use of 143Mha of these lands it is possible to produce 164EJ/yr (1147GJ/hayr or 3.6W/m²on average) of primary energy and 90EJ/yr of final energy in the form of liquid fuel (alcohol) and electricity, using agricultural productivities near the best ones already achievable and biomass gasification technology. More remarkable is that these results can be obtained with the operation of 4,000 production units with unitary capacity similar to the largest currently in operation. These units should be spread over the tropical land area yielding a plantation density similar to the one presently observed in the state of São Paulo, Brazil, where alcohol and electricity have been commercialized in a cost-effective way for several years. Such an amount of final energy would be sufficiently large to fulfill all the expected global increase in oil demand, as well as in electricity consumption by 2030, assuming the energy demand of such sources continues to grow at the same pace observed over the last two decades. When sugarcane crops are combined with afforestation/reforestation it is possible to show that carbon emissions decline for some IPCC SRES scenarios by 2030, 2040 and 2050. Such energy alternatives significantly reduce CO₂emissions by displacing fossil fuels and promote sustainable development through the creation of millions of direct and indirect jobs. Also, it opens an opportunity for negative CO₂emissions when coupled with carbon dioxide capture and storage.” José Roberto Moreira, Mitigation and Adaptation Strategies for Global Change, Volume 11, Number 2, 313-333, DOI: 10.1007/s11027-005-9003-8.

Potential of biomass energy out to 2100, for four IPCC SRES land-use scenarios – Hoogwijk et al. (2005) “The availability of the resources is an important factor for high shares of biomass to penetrate the electricity, heat or liquid fuel markets. We have analysed the geographical and technical potential of energy crops for the years 2050–2100 for three land-use categories: abandoned agricultural land, low-productivity land and ‘rest land’, i.e. remaining no-productive land. We envisaged development paths using four scenarios resulting from different future land-use patterns that were developed by the Intergovernmental Panel on Climate Change in its Special Report on Emission Scenarios: A1, A2, B1 and B2. The geographical potential is defined as the product of the available area for energy crops and the corresponding productivity level for energy crops. The geographical potential of abandoned agricultural land is the largest contributor. For the year 2050 the geographical potential of abandoned land ranges from about 130 to 410 EJ yr⁻¹. For the year 2100 it ranges from 240 to 850 EJ yr⁻¹. The potential of low-productive land is negligible compared to the other categories. The rest land area is assumed to be partly available, resulting in ranges of the geographical potential from about 35 to 245 EJ yr⁻¹ for the year 2050 and from about 35 to 265 EJ yr⁻¹ in 2100. At a regional level, significant potentials are found in the Former USSR, East Asia and South America. The geographical potential can be converted to transportation fuels or electricity resulting in ranges of the technical potential for fuels in the year 2050 and 2100 equal to several times the present oil consumption.” Monique Hoogwijk, André Faaij, Bas Eickhout, Bert de Vries and Wim Turkenburg, Biomass and Bioenergy, Volume 29, Issue 4, October 2005, Pages 225-257, doi:10.1016/j.biombioe.2005.05.002.

Exploration of the ranges of the global potential of biomass for energy – Hoogwijk et al. (2003) “This study explores the range of future world potential of biomass for energy. The focus has been put on the factors that influence the potential biomass availability for energy purposes rather than give exact numbers. Six biomass resource categories for energy are identified: energy crops on surplus cropland, energy crops on degraded land, agricultural residues, forest residues, animal manure and organic wastes. Furthermore, specific attention is paid to the competing biomass use for material. The analysis makes use of a wide variety of existing studies on all separate categories. The main conclusion of the study is that the range of the global potential of primary biomass (in about 50 years) is very broad quantified at 33−1135 EJy⁻¹. Energy crops from surplus agricultural land have the largest potential contribution (0–988 EJy⁻¹). Crucial factors determining biomass availability for energy are: (1) The future demand for food, determined by the population growth and the future diet; (2) The type of food production systems that can be adopted world-wide over the next 50 years; (3) Productivity of forest and energy crops; (4) The (increased) use of bio-materials; (5) Availability of degraded land; (6) Competing land use types, e.g. surplus agricultural land used for reforestation. It is therefore not “a given” that biomass for energy can become available at a large-scale. Furthermore, it is shown that policies aiming for the energy supply from biomass should take the factors like food production system developments into account in comprehensive development schemes.” Monique Hoogwijk, André Faaij, Richard van den Broek, Göran Berndes, Dolf Gielen, and Wim Turkenburg, Biomass and Bioenergy, Volume 25, Issue 2, August 2003, Pages 119-133, doi:10.1016/S0961-9534(02)00191-5.

The contribution of biomass in the future global energy supply: a review of 17 studies – Berndes et al. (2003) “This paper discusses the contribution of biomass in the future global energy supply. The discussion is based on a review of 17 earlier studies on the subject. These studies have arrived at widely different conclusions about the possible contribution of biomass in the future global energy supply (e.g., from below 100 EJ yr⁻¹ to above 400 EJ yr⁻¹ in 2050). The major reason for the differences is that the two most crucial parameters—land availability and yield levels in energy crop production—are very uncertain, and subject to widely different opinions (e.g., the assessed 2050 plantation supply ranges from below 50 EJ yr⁻¹ to almost 240 EJ yr⁻¹). However, also the expectations about future availability of forest wood and of residues from agriculture and forestry vary substantially among the studies. The question how an expanding bioenergy sector would interact with other land uses, such as food production, biodiversity, soil and nature conservation, and carbon sequestration has been insufficiently analyzed in the studies. It is therefore difficult to establish to what extent bioenergy is an attractive option for climate change mitigation in the energy sector. A refined modeling of interactions between different uses and bioenergy, food and materials production—i.e., of competition for resources, and of synergies between different uses—would facilitate an improved understanding of the prospects for large-scale bioenergy and of future land-use and biomass management in general” Göran Berndes, Monique Hoogwijk, and Richard van den Broek, Biomass and Bioenergy, Volume 25, Issue 1, July 2003, Pages 1-28, doi:10.1016/S0961-9534(02)00185-X. [Full text]

Global bioenergy potentials through 2050 – Fischer & Schrattenholzer (2001) “This study explores the range of future world potential of biomass for energy. The focus has been put on the factors that influence the potential biomass availability for energy purposes rather than give exact numbers. Six biomass resource categories for energy are identified: energy crops on surplus cropland, energy crops on degraded land, agricultural residues, forest residues, animal manure and organic wastes. Furthermore, specific attention is paid to the competing biomass use for material. The analysis makes use of a wide variety of existing studies on all separate categories. The main conclusion of the study is that the range of the global potential of primary biomass (in about 50 years) is very broad quantified at 33−1135 EJy⁻¹. Energy crops from surplus agricultural land have the largest potential contribution (0–988 EJy⁻¹). Crucial factors determining biomass availability for energy are: (1) The future demand for food, determined by the population growth and the future diet; (2) The type of food production systems that can be adopted world-wide over the next 50 years; (3) Productivity of forest and energy crops; (4) The (increased) use of bio-materials; (5) Availability of degraded land; (6) Competing land use types, e.g. surplus agricultural land used for reforestation. It is therefore not “a given” that biomass for energy can become available at a large-scale. Furthermore, it is shown that policies aiming for the energy supply from biomass should take the factors like food production system developments into account in comprehensive development schemes.” Günther Fischer and Leo Schrattenholzer, Biomass and Bioenergy, Volume 20, Issue 3, March 2001, Pages 151-159, doi:10.1016/S0961-9534(00)00074-X. [Full text]

Evaluation of bioenergy potential with a multi-regional global-land-use-and-energy model – Yamamoto et al. (2001) “The purpose of this study is to evaluate the global bioenergy potential in the future using a multi-regional global-land-use-and-energy model (GLUE-11). The model covers a wide range of biomass flow including food chains from feed to meat, paper recycling, and discharge of biomass residues.

Through a set of simulations, the following results are obtained. (1) Supply potential of energy crops produced from surplus arable land will be available in North America, Western Europe, Oceania, Latin America, former USSR and Eastern Europe. However, the potential of energy crops will be strongly affected by the variation of parameters of food supply and demand such as animal food demand. (2) Bioenergy supply potential of biomass residues will be stable against a change of a food demand parameter. The ultimate bioenergy supply potential of biomass residues will be 265 EJ/year in the world in 2100. The practical potential of biomass residues in the world will be 114 EJ/year, which is equivalent to one-third of the commercial energy consumption in the world in 1990. (3) Concerning land uses, the global mature forest area will decrease by 24% between 1990 and 2100, because of growth of both population and wood biomass demand per capita in the developing regions. The mature forest, especially, will disappear by 2100 in some developing regions, such as Centrally Planned Asia, Middle East and North Africa, and South Asia.” Hiromi Yamamoto, Junichi Fujino and Kenji Yamaji, Biomass and Bioenergy, Volume 21, Issue 3, March 2001, Pages 185-203, doi:10.1016/S0961-9534(01)00025-3. [Full text]

The land cover and carbon cycle consequences of large-scale utilizations of biomass as an energy source – Leemans et al. (1996) “The use of modern biomass for energy generation has been considered in many studies as a possible measure for reducing or stabilizing global carbon dioxide (CO2) emissions. In this paper we assess the impacts of large-scale global utilization of biomass on regional and grid scale land cover, greenhouse gas emissions, and carbon cycle. We have implemented in the global environmental change model IMAGE the LESS biomass intensive scenario, which was developed for the Second Assessment Report of IPCC. This scenario illustrates the potential for reducing energy related emission by different sets of fuel mixes and a higher energy efficiency. Our analysis especially covers different consequences involved with such modern biomass scenarios. We emphasize influences of CO₂ concentrations and climate change on biomass crop yield, land use, competition between food and biomass crops, and the different interregional trade patterns for modern biomass based energy. Our simulations show that the original LESS scenario is rather optimistic on the land requirements for large-scale biomass plantations. Our simulations show that 797 Mha is required while the original LESS scenario is based on 550 Mha. Such expansion of agricultural land will influence deforestation patterns and have significant consequenses for environmental issues, such as biodiversity. Altering modern biomass requirements and the locations where they are grown in the scenario shows that the outcome is sensitive for regional emissions and feedbacks in the C cycle and that competition between food and modern biomass can be significant. We conclude that the cultivation of large quantities of modern biomass is feasible, but that its effectiveness to reduce emissions of greenhouse gases has to be evaluated in combination with many other environmental land use and socio-economic factors.” Rik Leemans, André van Amstel, Coos Battjes, Eric Kreileman and Sander Toet, Global Environmental Change, Volume 6, Issue 4, September 1996, Pages 335-357, doi:10.1016/S0959-3780(96)00028-3.

World potential of renewable energies. Actually accessible in the nineties and environmental impact analysis. – Dessus et al. (1992) “Large scale application of renewable energies is a major challenge for sustainable development and greenhouse gas emission control. Theoretical potential of those various energies may seem unlimited. In fact a reasonable evaluation taking into account economically available technologies and local considerations make it possible to define annual energy amounts relevant for each technology. Diversely distributed around the world but nowhere missing, renewable energies have an important annual potential since the nineties. They could indeed contribute to some 40% of the nowadays world energy consumption, mainly from wood, waste and hydro, but also from solar and wind energy.” Dessus, B, Devin, B, Pharabod, F, Houille blanche. Grenoble [HOUILLE BLANCHE.]. no. 1, pp. 21-70. 1992.