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Archive for May, 2012

New research from last week 21/2012

Posted by Ari Jokimäki on May 28, 2012

This week we have few paleoclimate studies. There’s atmospheric carbon dioxide record from Antarctic ice core, faint young sun problem review, the paper on storegga tsunami and 8.2 ka cold event, and one on the role of methane release in end-Triassic mass extinction. Also archaeology can contribute to modern climate science, but I wonder if climate archaeologists 5000 years from now will have a remarkable event to study?

Another thing I wonder is that will the water stay in Caspian Sea or will it just splash to surrounding land areas one day? And will the cattle in Brazil ever stop their GHG emissions (if that’s the correct expression for it)? Did they run out of possible causes for 2010 heat wave as they now have started to look if winter Arctic Oscillation caused summer Arctic Oscillation?

The pets are handling this climate situation quite well, as they are multiplying better then ever. Sorry, did I say pets? I meant pests, of course. Pine beetles are also thriving, at least as long as there are pines left. Tropical cyclones grow intense faster than they did before. Russian glaciers are losing ice and Finnish lake freezes later. But Antarctic ozone is rebounding, so we can soon stop putting sun tan lotion on penguins.

What archaeology can do for climate science?

Prospects and challenges for an archaeology of global climate change – Hudson et al. (2012)

Abstract: “Archaeology has a long history of research in reconstructing past environments and in attempting to understand the interactions between climate and human societies. So far, however, there has been little attempt by archeologists to employ this knowledge in the debate over current global climate change. This paper provides a broad overview of the relevance of archaeology to the problem of global climate change, yet also attempts to consider some of the challenges that require further debate. We propose five areas where archaeology may be able to make significant contributions to global climate change discourse: (1) the study not just of past social ‘collapse’ but of how ancient societies attempted to manage decline and recovery in the face of long-term environmental change; (2) the ability to rethink the nature/culture divide; (3) the use of public archaeology to further education and awareness on environmental links and impacts; (4) the study of social injustice and how it may affect societal responses to the environment; and (5) the building of common ‘intercultural’ responses to climate change. Challenges identified are (1) making clearer in public debate the relevance of archaeology to present and future climate change; (2) the contexts in which people really learn from the past; (3) how different (national) traditions of archeological research may affect our ability to relate archaeology to global climate change; and (4) how human-induced climate change on a global scale alters traditional historical approaches to human agency.”

Citation: Mark J. Hudson, Mami Aoyama, Kara C. Hoover, Junzō Uchiyama, Wiley Interdisciplinary Reviews: Climate Change, DOI: 10.1002/wcc.174.

Climate and weather are important for spatial expansion of pine beetle outbreaks

Climate and Weather Influences on Spatial Temporal Patterns of Mountain Pine Beetle Populations in Washington and Oregon – Preisler et al. (2012)

Abstract: “Widespread outbreaks of mountain pine beetle in North America have drawn the attention of scientists, forest managers, and the public. There is strong evidence that climate change has contributed to the extent and severity of recent outbreaks. Scientists are interested in quantifying relationships between bark beetle population dynamics and trends in climate. Process models that simulate climate suitability for mountain pine beetle outbreaks have advanced our understanding of beetle population dynamics; however, there are few studies that have assessed their accuracy across multiple outbreaks or at larger spatial scales. This study used the observed number of trees killed by mountain pine beetles per km2 in Oregon and Washington States over the past three decades to quantify and assess the influence of climate and weather variables on beetle activity over longer time periods and larger scales than previously studied. Influences of temperature and precipitation in addition to process model output variables were assessed at annual and climatological time scales. The statistical analysis showed that new attacks are more likely to occur at locations with climatological mean August temperatures greater than 15oC. After controlling for beetle pressure, the variables with the largest effect on the odds of an outbreak exceeding a certain size were minimum winter temperature (positive relationship) and drought conditions in current and previous years. Precipitation levels in the year prior to the outbreak had a positive effect, possibly an indication of the influence of this driver on brood size. Two-year cumulative precipitation had a negative effect, a possible indication of the influence of drought on tree stress. Among the process model variables, cold tolerance was the strongest indicator of an outbreak becoming epidemic size. A weather suitability index developed from the regression analysis indicated a 2.5 times increase in the odds of outbreak at locations with highly suitable weather versus locations with low suitability. The models were useful for estimating expected amounts of damage (total area with outbreaks) and for quantifying the contribution of climate to total damage. Overall, the results confirm the importance of climate and weather on the spatial expansion of bark beetle outbreaks over time.”

Citation: Preisler, Haiganoush Krikorian, Jeffrey Hicke, Alan Ager, and Jane L. Hayes. In press. Climate and Weather Influences on Spatial Temporal Patterns of Mountain Pine Beetle Populations in Washington and Oregon. Ecology.

Tropical cyclones now intensify 9 hours earlier than they did 25 years ago

Tropical cyclone intensification trends during satellite era (1986–2010) – Kishtawal et al. (2012)

Abstract: “Using International Best Track Archive for Climate Stewardship (IBTrACS, version v03r03) analysis during satellite era (1986–2010) we determined the trends of intensification of tropical cyclones (TC) over all the global basins, except the North Indian Ocean. Over all the basins, the rate of TC intensification from 64 kt to first peak of intensity maxima (global average value = 104 kt) was found to be positive. The above trends were significant for 4 out of 5 basins, except the North West Pacific. The trends indicate that the TCs now intensify from 64 kt to 104 kt nearly 9 hours earlier than they did 25 years back. The maximum reduction in intensification time is noticed over the North Atlantic Ocean where the average time needed for TC to intensify from 64 kt to 112 kt has reduced by nearly 20 hours during the past 25-year period.”

Citation: Kishtawal, C. M., N. Jaiswal, R. Singh, and D. Niyogi (2012), Tropical cyclone intensification trends during satellite era (1986–2010), Geophys. Res. Lett., 39, L10810, doi:10.1029/2012GL051700.

High resolution 1000-year ice core record of atmospheric carbon dioxide

Atmospheric CO2 over the last 1000 years: A high-resolution record from the West Antarctic Ice Sheet (WAIS) Divide ice core – Ahn et al. (2012)

Abstract: “We report a decadally resolved record of atmospheric CO2 concentration for the last 1000 years, obtained from the West Antarctic Ice Sheet (WAIS) Divide shallow ice core. The most prominent feature of the pre-industrial period is a rapid ∼7 ppm decrease of CO2 in a span of ∼20–50 years at ∼1600 A.D. This observation confirms the timing of an abrupt atmospheric CO2 decrease of ∼10 ppm observed for that time period in the Law Dome ice core CO2 records, but the true magnitude of the decrease remains unclear. Atmospheric CO2 variations over the time period 1000–1800 A.D. are statistically correlated with northern hemispheric climate and tropical Indo-Pacific sea surface temperature. However, the exact relationship between CO2 and climate remains elusive due to regional climate variations and/or uneven geographical data density of paleoclimate records. We observe small differences of 0 ∼ 2% (0 ∼ 6 ppm) among the high-precision CO2 records from the Law Dome, EPICA Dronning Maud Land and WAIS Divide Antarctic ice cores. However, those records share common trends of CO2 change on centennial to multicentennial time scales, and clearly show that atmospheric CO2 has been increasing above preindustrial levels since ∼1850 A.D.”

Citation: Ahn, J., E. J. Brook, L. Mitchell, J. Rosen, J. R. McConnell, K. Taylor, D. Etheridge, and M. Rubino (2012), Atmospheric CO2 over the last 1000 years: A high-resolution record from the West Antarctic Ice Sheet (WAIS) Divide ice core, Global Biogeochem. Cycles, 26, GB2027, doi:10.1029/2011GB004247.

Antarctic ozone shows signs of rebounding over the last decade

Changes of the Antarctic ozone hole: Controlling mechanisms, seasonal predictability, and evolution – Salby et al. (2012)

Abstract: “The ozone hole changes considerably from one year to the next. It varies between conditions in which springtime ozone is strongly depleted to others in which ozone is only weakly depleted. Those changes are shown to closely track anomalous planetary wave forcing of the residual circulation. The strong coherence with planetary wave forcing is consistent with similar coherence of springtime temperature, which modulates Polar Stratospheric Cloud (PSC). By controlling the lifetime of PSC, anomalous wave forcing determines the net activation of chlorine and bromine and, hence, springtime depletion of ozone during individual years. The strong coherence with planetary wave forcing affords long-range predictability. It supports a seasonal forecast of springtime depletion, which, through the ozone mass deficit, perturbs ozone across much of the Southern Hemisphere during subsequent months of summer. Conditioned upon wintertime wave structure, a hindcast of springtime depletion faithfully predicts the anomalous ozone observed. A reliable forecast of tropospheric planetary waves would thus enable springtime depletion to be predicted. The current evolution of Antarctic ozone is dominated by dynamically-induced changes. Representing its climate variability, those large changes obscure the more gradual evolution of springtime depletion, like that associated with the decline of chlorine. The strong dependence on planetary wave forcing, however, enables dynamically-induced changes of ozone to be identified accurately. Removing them unmasks the secular variation of Antarctic ozone, the part coherent over a decade and longer. Independent of dynamically-induced changes, that component discriminates to changes associated with stratospheric composition. It reveals a gradual but systematic rebound over the last decade. The upward trend is shown to be robust, significant at the 99.5% level. Uncertainty in this trend is thus small enough to make the probability of it arising through chance alignment of error less than 0.5%. The discriminated component mirrors the decline of effective stratospheric chlorine, representing a gradual return of springtime ozone toward its level in 1980 of 10–15%. It enables Antarctic ozone to be tracked relative to changes of chlorine, CO2, and other features of climate more reliably than is otherwise possible.”

Citation: Salby, M. L., E. A. Titova, and L. Deschamps (2012), Changes of the Antarctic ozone hole: Controlling mechanisms, seasonal predictability, and evolution, J. Geophys. Res., 117, D10111, doi:10.1029/2011JD016285.

Rapid sea level changes of the Caspian sea

Rapid Holocene sea-level changes along the Iranian Caspian coast – Kakroodi et al. (2012)

Abstract: “The Caspian Sea is well-known for its rapid sea-level change. During 1929–1995, a full sea-level cycle was observed. First, the sea level dropped ∼3 m with a lowstand in 1977, followed by a 3 m rise to 1995, after which the sea level has been relatively stable. These oscillations are a specific feature of the Caspian Sea and its sedimentary record. The main purpose of this study is to reconstruct the sea-level curve in the Holocene by using sedimentological and biostratigraphic analysis and radiocarbon dating along the Iranian part of the Caspian shore. Remote sensing images and historical maps show that two lagoons totally emerged, and the Gorgan delta prograded rapidly at a rate of around 160 m y−1 until the 1975 lowstand. Gorgan Bay was reduced in size considerably and the connection to the sea was blocked due to growth of a spit and change in base level. When sea level started to rise again, the coastal morphology rapidly changed and the Gorgan delta retrograded at the rate of around 140 m y−1. These sedimentary dynamics can be recognized in the preserved deposits. In addition to the recent dynamics, core data from the southeastern lowlands show four earlier highstands. Using characteristic barrier-lagoon deposits, early Holocene sea level rose until a highstand was reached of ca. −34 m. This phase was followed by fluvial deposition in the Gorgan delta associated with a base level fall. There is also an evidence of sea-level rise between 5000 and 2300 BP at ca. −27.7 m. On top of these deposits there is evidence of a highstand between 2700 and 2300 BP at ca. −23.5 m. The fourth highstand from the core data is dated to the Little Ice Age at ca. −24 m. Data from these last two highstands correspond well with other observations from the Caspian region.”

Citation: A.A. Kakroodi, S.B. Kroonenberg, R.M. Hoogendoorn, H. Mohammd Khani, M. Yamani, M.R. Ghassemi, H.A.K. Lahijani, Quaternary International, Volume 263, 14 June 2012, Pages 93–103,

Glaciers of Russian High Arctic are losing ice

Recent mass changes of glaciers in the Russian High Arctic – Moholdt et al. (2012)

Abstract: “Glaciers and ice caps are known to contribute significantly to present-day sea level rise, but there are still glaciated regions where little is known about modern changes in glacier mass. One of these regions is the Russian High Arctic archipelagos which has a total glaciated area of 51,500 km2. We have assessed the glacier mass budget of this region for a 6-year period between October 2003 and October 2009 using independent ICESat laser altimetry and GRACE gravimetry. Over this period we found that the archipelagos have lost ice at a rate of −9.1 ± 2.0 Gt a−1, which corresponds to a sea level contribution of 0.025 mm a−1. Approximately 80% of the ice loss came from Novaya Zemlya with the remaining 20% coming from Franz Josef Land and Severnaya Zemlya. Meteorological records of temperature and precipitation for the period 1980–2009 suggest that the recent climatic mass budget is not substantially different from the longer-term trend.”

Citation: Moholdt, G., B. Wouters, and A. S. Gardner (2012), Recent mass changes of glaciers in the Russian High Arctic, Geophys. Res. Lett., 39, L10502, doi:10.1029/2012GL051466.

Review of the research on faint young sun problem

The faint young Sun problem – Feulner (2012)

Abstract: “For more than four decades, scientists have been trying to find an answer to one of the most fundamental questions in paleoclimatology, the “faint young Sun problem.” For the early Earth, models of stellar evolution predict a solar energy input to the climate system that is about 25% lower than today. This would result in a completely frozen world over the first 2 billion years in the history of our planet if all other parameters controlling Earth’s climate had been the same. Yet there is ample evidence for the presence of liquid surface water and even life in the Archean (3.8 to 2.5 billion years before present), so some effect (or effects) must have been compensating for the faint young Sun. A wide range of possible solutions have been suggested and explored during the last four decades, with most studies focusing on higher concentrations of atmospheric greenhouse gases like carbon dioxide, methane, or ammonia. All of these solutions present considerable difficulties, however, so the faint young Sun problem cannot be regarded as solved. Here I review research on the subject, including the latest suggestions for solutions of the faint young Sun problem and recent geochemical constraints on the composition of Earth’s early atmosphere. Furthermore, I will outline the most promising directions for future research. In particular I would argue that both improved geochemical constraints on the state of the Archean climate system and numerical experiments with state-of-the-art climate models are required to finally assess what kept the oceans on the Archean Earth from freezing over completely.”

Citation: Feulner, G. (2012), The faint young Sun problem, Rev. Geophys., 50, RG2006, doi:10.1029/2011RG000375.

Freeze-up has been significantly delayed in a northern Europe lake

Changes in ice-season characteristics of a European Arctic lake from 1964 to 2008 – Lei et al. (2012)

Abstract: “The long-term ice record (from 1964 to 2008) of an Arctic lake in northern Europe (Lake Kilpisjärvi) reveals the response of lake ice to climate change at local and regional scales. Average freeze-up and ice breakup occurred on 9 November and 19 June, respectively. The freeze-up has been significantly delayed at a rate of 2.3 d per decade from 1964 onward (P < 0.05). No significant change has taken place in ice breakup. Annual average ice thickness has become smaller since the mid-1980s (P < 0.05). Air temperature during the early ice season significantly affected the ice thickness. The freeze-up date exhibits the highest correlation with the 2-month average daily minimum air temperature centered at the end of October, while the ice breakup date exhibits the highest correlation with the 2-month average daily maximal air temperature centered in mid May. A 1°C increase in the surface air temperature corresponds to a freeze-up later by 3.4 days and an ice breakup earlier by 3.6 days. Snow cover is a critical factor in lake-ice climatology. For cumulative November to March precipitation of less than 0.13 m, the insulating effect of the snow dominated, while higher rates of precipitation favored thicker ice due to the formation of snow ice. Variations in ice records of Lake Kilpisjärvi can serve as an indicator of climate variations across the northern Europe. The North Atlantic Oscillation (NAO) does not significantly affect the ice season there, although both the local air temperatures and winter precipitation contain a strong NAO signal.”

Citation: Ruibo Lei, Matti Leppäranta, Bin Cheng, Petra Heil and Zhijun Li, Climatic Change, 2012, DOI: 10.1007/s10584-012-0489-2.

Storegga tsunami happened during coldest times of 8.2 ka cold event

Green mosses date the Storegga tsunami to the chilliest decades of the 8.2 ka cold event – Bondevik et al. (2012)

Abstract: “Chlorophyll in dead plants ordinarily decomposes completely before permanent burial through exposure to light, water and oxygen. Here we describe 8000-year-old terrestrial mosses that retain several percent of its original chlorophyll. The mosses were ripped of the land surface, carried 50–100 m off the Norwegian coast of the time, and deposited in depressions on the sea floor by the Storegga tsunami. A little of the chlorophyll survived because, within hours after entraining it, the tsunami buried the mosses in shell-rich sediments. These sediments preserved the chlorophyll by keeping out light and oxygen, and by keeping the pH above 7—three factors known to favour chlorophyll’s stability. Because the green mosses were buried alive, their radiocarbon clock started ticking within hours after the Storegga Slide had set off the tsunami. Radiocarbon measurement of the mosses therefore give slide ages of uncommon geological precision, and these, together with a sequence of ages above and below the boundary, date the Storegga Slide to the chilliest decades of the 8.2 ka cold event at 8120–8175 years before AD 1950. North Atlantic coastal- and fjord- climatic records claimed to show evidence of the 8.2 cold event should be carefully examined for possible contamination and disturbance from the Storegga tsunami.”

Citation: Stein Bondevik, Svein Kristian Stormo, Gudrun Skjerdal, Quaternary Science Reviews, Volume 45, 29 June 2012, Pages 1–6,

Agronomically important pests in California might be making more generations during a year with climate change

Climate Change and Voltinism in Californian Insect Pest Species: Sensitivity to Location, Scenario and Climate Model Choice – Ziter et al. (2012)

Abstract: “Experimental studies of the impact of climatic change are hampered by their inability to consider multiple climate change scenarios, and indeed often consider no more than simple climate sensitivity such as a uniform increase in temperature. Modelling efforts offer the ability to consider a much wider range of realistic climate projections and are therefore useful, in particular, for estimating the sensitivity of impact predictions to differences in geographical location, and choice of climate change scenario and climate model projections. In this study we used well-established degree-day models to predict the voltinism of 13 agronomically important pests in California, USA. We ran these models using the projections from three Atmosphere-Ocean Coupled Global Circulation Models (AOCGCMs or GCMs), in conjunction with the SRES scenarios. We ran these for two locations representing northern and southern California. We did this for both the 2050s and 2090s. We used ANOVA to partition the variation in the resulting voltinism among time period, climate change scenario, GCM, and geographical location. For these 13 pest species, the choice of climate model explained an average of 42% of the total variation in voltinism, far more than did geographical location (33%), time period (17%) or scenario (1%). The remaining 7% of the variation was explained by various interactions, of which the location by GCM interaction was the strongest (5%). Regardless of these sources of uncertainty, a robust conclusion from our work is that all 13 pest species are likely to experience increases in the number of generations that they complete each year. Such increased voltinism is likely to have significant consequences for crop protection and production.”

Citation: Carly Ziter, Emily A. Robinson, Jonathan A. Newman, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02748.x.

Methane release might not have caused end-Triassic mass extinction

No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction – Lindström et al. (2012)

Abstract: “Profound changes in both marine and terrestrial biota during the end-Triassic mass extinction event and associated successive carbon cycle perturbations across the Triassic-Jurassic boundary (T-J, 201.3 Ma) have primarily been attributed to volcanic emissions from the Central Atlantic Magmatic Province and/or injection of methane. Here we present a new extended organic carbon isotope record from a cored T-J boundary succession in the Danish Basin, dated by high-resolution palynostratigraphy and supplemented by a marine faunal record. Correlated with reference C-isotope and biotic records from the UK, it provides new evidence that the major biotic changes, both on land and in the oceans, commenced prior to the most prominent negative C-isotope excursion. If massive methane release was involved, it did not trigger the end-Triassic mass extinction. Instead, this negative C-isotope excursion is contemporaneous with the onset of floral recovery on land, whereas marine ecosystems remained perturbed. The decoupling between ecosystem recovery on land and in the sea is more likely explained by long-term flood basalt volcanism releasing both SO2 and CO2 with short- and long-term effects, respectively.”

Citation: Sofie Lindström, Bas van de Schootbrugge, Karen Dybkjær, Gunver Krarup Pedersen, Jens Fiebig, Lars Henrik Nielsen and Sylvain Richoz, Geology, v. 40 no. 6 p. 531-534, doi: 10.1130/G32928.1.

GHG emissions from cattle industry might be Brazil’s most important opportunity for emissions mitigation

Estimating greenhouse gas emissions from cattle raising in Brazil – Bustamante et al. (2012)

Abstract: “The study estimated, for the first time, the greenhouse gas emissions associated with cattle raising in Brazil, focusing on the period from 2003 to 2008 and the three principal sources: 1) portion of deforestation resulting in pasture establishment and subsequent burning of felled vegetation; 2) pasture burning; and 3) bovine enteric fermentation. Deforestation for pasture establishment was only considered for the Amazon and Cerrado. Emissions from pasture burning and enteric fermentation were accounted for the entire country. The consolidated emissions estimate lies between approximately 813 Mt CO2eq in 2008 (smallest value) and approximately 1,090 Mt CO2eq in 2003 (greatest value). The total emissions associated with Amazon cattle ranching ranged from 499 to 775 Mt CO2eq, that of the Cerrado from 229 to 231 Mt CO2eq, and that of the rest of the country between 84 and 87 Mt CO2eq. The full set of emissions originating from cattle raising is responsible for approximately half of all Brazilian emissions (estimated to be approximately 1,055 Mt CO2eq in 2005), even without considering cattle related sources not explicitly estimated in this study, such as energy use for transport and refrigeration along the beef and derivatives supply chain. The potential for reduction of greenhouse gas emissions offered by the Brazilian cattle industry is very high and might constitute Brazil’s most important opportunity for emissions mitigation. The study offers a series of policy recommendations for mitigation that can be implemented by public and private administrators at a low cost relative to other greenhouse gas reduction options.”

Citation: Mercedes M. C. Bustamante, Carlos A. Nobre, Roberto Smeraldi, Ana P. D. Aguiar, Luis G. Barioni, Laerte G. Ferreira, Karla Longo, Peter May, Alexandre S. Pinto and Jean P. H. B. Ometto, Climatic Change, 2012, DOI: 10.1007/s10584-012-0443-3.

Negative winter Arctic Oscillation might have caused the strongly positive AO during summer of 2010

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme summer weather – Otomi et al. (2012) [FULL TEXT]

Abstract: “In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the “memory” of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.”

Citation: Yuriko Otomi, Yoshihiro Tachibana and Tetsu Nakamura, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1386-0.


The Total Quantity of Aqueous Vapor in the Atmosphere – Abbe (1894) [FULL TEXT]

Abstract: No abstract.

Citation: Abbe, C., 1894, Mon. Wea. Rev., 22, 539–541. doi:;2.

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Papers on global warming detection from global temperature series

Posted by Ari Jokimäki on May 25, 2012

This is a list of papers on global warming detection from global temperature series (i.e. papers that estimate if global warming signal can be statistically significantly distinguished from random noise). The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

UPDATE (July 24, 2013): Foster & Rahmstorf (2011) added.

A Bayesian approach to detecting change points in climatic records – Ruggieri (2012) “Given distinct climatic periods in the various facets of the Earth’s climate system, many attempts have been made to determine the exact timing of ‘change points’ or regime boundaries. However, identification of change points is not always a simple task. A time series containing N data points has approximately Nk distinct placements of k change points, rendering brute force enumeration futile as the length of the time series increases. Moreover, how certain are we that any one placement of change points is superior to the rest? This paper introduces a Bayesian Change Point algorithm which provides uncertainty estimates both in the number and location of change points through an efficient probabilistic solution to the multiple change point problem. To illustrate its versatility, the Bayesian Change Point algorithm is used to analyse both the NOAA/NCDC annual global surface temperature anomalies time series and the much longer δ18O record of the Plio-Pleistocene.” Eric Ruggieri, International Journal of Climatology, DOI: 10.1002/joc.3447.

Global temperature evolution 1979–2010 – Foster & Rahmstorf (2011) “We analyze five prominent time series of global temperature (over land and ocean) for their common time interval since 1979: three surface temperature records (from NASA/GISS, NOAA/NCDC and HadCRU) and two lower-troposphere (LT) temperature records based on satellite microwave sensors (from RSS and UAH). All five series show consistent global warming trends ranging from 0.014 to 0.018 K yr−1. When the data are adjusted to remove the estimated impact of known factors on short-term temperature variations (El Niño/southern oscillation, volcanic aerosols and solar variability), the global warming signal becomes even more evident as noise is reduced. Lower-troposphere temperature responds more strongly to El Niño/southern oscillation and to volcanic forcing than surface temperature data. The adjusted data show warming at very similar rates to the unadjusted data, with smaller probable errors, and the warming rate is steady over the whole time interval. In all adjusted series, the two hottest years are 2009 and 2010.” Grant Foster and Stefan Rahmstorf 2011 Environ. Res. Lett. 6 044022 doi:10.1088/1748-9326/6/4/044022. [Full text]

Detecting abrupt climate changes on different time scales – Matyasovszky (2011) “Two concepts are introduced for detecting abrupt climate changes. In the first case, the sampling frequency of climate data is high as compared to the frequency of climate events examined. The method is based on a separation of trend and noise in the data and is applicable to any dataset that satisfies some mild smoothness and statistical dependence conditions for the trend and the noise, respectively. We say that an abrupt change occurs when the first derivative of the trend function has a discontinuity and the task is to identify such points. The technique is applied to Northern Hemisphere temperature data from 1850 to 2009, Northern Hemisphere temperature data from proxy data, a.d. 200–1995 and Holocene δ18O values going back to 11,700 years BP. Several abrupt changes are detected that are, among other things, beneficial for determining the Medieval Warm Period, Little Ice Age and Holocene Climate Optimum. In the second case, the sampling frequency is low relative to the frequency of climate events studied. A typical example includes Dansgaard–Oeschger events. The methodology used here is based on a refinement of autoregressive conditional heteroscedastic models. The key element of this approach is the volatility that characterises the time-varying variance, and abrupt changes are defined by high volatilities. The technique applied to δ18O values going back to 122,950 years BP is suitable for identifying DO events. These two approaches for the two cases are closely related despite the fact that at first glance, they seem quite different.” István Matyasovszky, Theoretical and Applied Climatology, Volume 105, Numbers 3-4 (2011), 445-454, DOI: 10.1007/s00704-011-0401-4.

Testing for Deterministic Trends in Global Sea Surface Temperature – Barbosa (2011) “Long-term variability in global sea surface temperature (SST) is often quantified by the slope from a linear regression fit. Attention is then focused on assessing the statistical significance of the derived slope parameter, but the adequacy of the linear model itself, and the inherent assumption of a deterministic linear trend, is seldom tested. Here, a parametric statistical test is applied to test the hypothesis of a linear deterministic trend in global sea surface temperature. The results show that a linear slope is not adequate for describing the long-term variability of sea surface temperature over most of the earth’s surface. This does not mean that sea surface temperature is not increasing, rather that the increase should not be characterized by the slope from a linear fit. Therefore, describing the long-term variability of sea surface temperature by implicitly assuming a deterministic linear trend can give misleading results, particularly in terms of uncertainty, since the actual increase could be considerably larger than the one predicted by a deterministic linear model.” Barbosa, Susana M., 2011: Testing for Deterministic Trends in Global Sea Surface Temperature. J. Climate, 24, 2516–2522. doi:

1963: The break point of the Northern Hemisphere temperature trend during the twentieth century – Ivanov & Evtimov (2010) “Besides gradually, climate can also change abruptly. The global surface temperature series is a major indicator of such changes. Using rigorous statistical tools, we show that during the twentieth century the time series of annual Northern Hemisphere surface temperature is well described by a trend-stationary process, but the trend line breaks in 1963. After six transitory years, in 1970, the temperature course locks up into a new regime with a triple linear warming rate. For the emergence and abruptness of the break we reveal the key roles of the Mount Agung eruption and the interannual to interdecadal changes of the major modes and patterns of climate variability. We offer an abrupt climate shift scenario based on the adaptivity of climatic regimes against instant external forcings.” Martin A. Ivanov, Stilian N. Evtimov, International Journal of Climatology, Volume 30, Issue 11, pages 1738–1746, September 2010, DOI: 10.1002/joc.2002.

Warming Break Trends and Fractional Integration in the Northern, Southern, and Global Temperature Anomaly Series – Gil-Alana (2008) “This paper deals with the estimation of time trends in temperature anomaly series. However, instead of imposing that the estimated residuals from the time trends are covariance stationary processes with spectral density that is positive and finite at the zero frequency [I(0)], the author allows them to be fractionally integrated. In this context, a new procedure for testing fractional integration with segmented trends is applied to the northern, southern, and global temperature anomaly series. The results show that the three series are fractionally integrated, and the warming effects are substantially higher after the break in all cases.” Gil-Alana, Luis A., 2008: Warming Break Trends and Fractional Integration in the Northern, Southern, and Global Temperature Anomaly Series. J. Atmos. Oceanic Technol., 25, 570–578. doi: [Full text]

Semiparametric estimation and testing of the trend of temperature series – Gao & Hawthorne (2006) “The application of a partially linear model to global and hemispheric temperature series is proposed. Partially linear modelling allows the trend to take a very general form rather than imposing the restriction of linearity seen in existing studies. The removal of the linearity restriction is based on the fact that it is well accepted that a significant trend is present in global temperature series. The model will allow for the data to ‘speak for themselves’ with regard to the form of the trend. The results initially reveal that a linear trend does not approximate well the behaviour of global or hemispheric temperature series. This is further confirmed through a formal testing procedure. The results suggest that little faith should be instilled in long-term forecasts of temperatures in which the trend of global and hemispheric series is assumed to be linear. All the current evidence suggest that temperatures will continue to rise in an unknown and probably nonlinear fashion.” Jiti Gao, Kim Hawthorne, The Econometrics Journal, Volume 9, Issue 2, pages 332–355, July 2006, DOI: 10.1111/j.1368-423X.2006.00188.x.

Are winters getting warmer? – Vogelsang & Franses (2006) “We examine whether any trends in monthly temperatures are the same through-out the year for various lengthy series. The data concern the world, the northern and southern hemispheres, and about three centuries of data for the United Kingdom and the Netherlands. For the empirical exercise, we rely on new and accurate tests which have been recently developed. These tests do not have standard distributions, so that critical values have to be tabulated. The empirical findings include significant worldwide temperature increases, differences across months for the northern hemisphere, and warming winters for the UK and the Netherlands.” Timothy J. Vogelsang, Philip Hans Franses, Environmental Modelling & Software, Volume 20, Issue 11, November 2005, Pages 1449–1455,

Tests of common deterministic trend slopes applied to quarterly global temperature data – Fomby & Vogelsang (2003) “We examine the global warming temperature data sets of Jones et al. (1999) and Vinnikov et al. (1994) in the context of the multivariate deterministic trend-testing framework of Franses and Vogelsang (2002). We find that, across all seasons, global warming seems to be present for the globe and for the northern and southern hemispheres. Globally and within hemispheres, it appears that seasons are not warming equally fast. In particular, winters appear to be warming faster than summers. Across hemispheres, it appears that the winters in the northern and southern hemispheres are warming equally fast whereas the remaining seasons appear to have unequal warming rates. The results obtained here seem to coincide with the findings of Kaufmann and Stern (2002) who use cointegration analysis and find that the hemispheres are warming at different rates.” Thomas B. Fomby, Timothy J. Vogelsang, (2003) “TESTS OF COMMON DETERMINISTIC TREND SLOPES APPLIED TO QUARTERLY GLOBAL TEMPERATURE DATA”, , Vol. Iss: 17, pp.29 – 43, doi: 10.1016/S0731-9053(03)17002-8.

The Application of Size-Robust Trend Statistics to Global-Warming Temperature Series – Fomby & Vogelsang (2002) “In this note, new evidence is provided confirming that global temperature series spanning back to the mid-1800s have statistically significant positive trends. Although there is a growing consensus that global temperatures are on the rise systematically, some recent studies have pointed out that strong serial correlation (or a unit root) in global temperature data could, in theory, generate spurious evidence of a significant positive trend. In other words, strong serially correlated data can mimic trending behavior over fixed periods of time. A serial-correlation–robust trend test recently was proposed that controls for the possibility of spurious evidence due to strong serial correlation. This new test is valid whether the errors are stationary or have a unit root (strong serial correlation). This test also has the attractive feature that it does not require estimates of serial correlation nuisance parameters. The test is applied to six annual global temperature series, and it provides strong evidence that global temperature series have positive trends that are statistically significant even when controlling for the possibility of strong serial correlation. The point estimates of the rate of increase in the trend suggest that temperatures have risen about 0.5°C (1.0°F) 100 yr−1. If the analysis is restricted to twentieth-century data, many of the point estimates are closer to 0.6°C.” Fomby, Thomas B., Timothy J. Vogelsang, 2002: The Application of Size-Robust Trend Statistics to Global-Warming Temperature Series. J. Climate, 15, 117–123, doi:;2. [Full text]

Structural Time Series Models and Trend Detection in Global and Regional Temperature Series – Zheng & Basher (1999) “A unified statistical approach to identify suitable structural time series models for annual mean temperature is proposed. This includes a generalized model that can represent all the commonly used structural time series models for trend detection, the use of differenced series (successive year-to-year differences), and explicit methods for comparing the validity of no-trend nonstationary residuals models relative to trend models. Its application to Intergovernmental Panel on Climate Change global and latitude-belt temperature series reveals that a linear trend model (starting in 1890, with Southern Oscillation index signal removal and a red noise residuals process) is the optimal model for much of the globe, from the Northern Hemisphere Tropics to the Southern Hemisphere midlatitudes, but that a random stationary increment process (with no deterministic trend) is preferred for the northern part of the Northern Hemisphere. The result for the higher northern latitudes appears to be related to the greater climate variability there and does not exclude the possibility of a trend being present. The hemispheric and global series will contain a mixture of the two processes but are dominated by and best represented by the linear trend model. The latitudinal detectability of trends is oppositely matched to where GCMs indicate greatest anthropogenic trend, that is, it is best for the Tropics rather than for the high latitudes. The results reinforce the view that the global temperatures are affected by a long-term trend that is not of natural origin.” Zheng, Xiaogu, Reid E. Basher, 1999: Structural Time Series Models and Trend Detection in Global and Regional Temperature Series. J. Climate, 12, 2347–2358, doi:;2. [Full text]

Trend Estimation and Regression Analysis in Climatological Time Series: An Application of Structural Time Series Models and the Kalman Filter – Visser & Molenaar (1995) “The detection of trends in climatological data has become central to the discussion on climate change due to the enhanced greenhouse effect. To prove detection, a method is needed (i) to make inferences on significant rises or declines in trends, (ii) to take into account natural variability in climate series, and (iii) to compare output from GCMs with the trends in observed climate data. To meet these requirements, flexible mathematical tools are needed. A structural time series model is proposed with which a stochastic trend, a deterministic trend, and regression coefficients can be estimated simultaneously. The stochastic trend component is described using the class of ARIMA models. The regression component is assumed to be linear. However, the regression coefficients corresponding with the explanatory variables may be time dependent to validate this assumption. The mathematical technique used to estimate this trend-regression model is the Kaiman filter. The main features of the filter are discussed. Examples of trend estimation are given using annual mean temperatures at a single station in the Netherlands (1706–1990) and annual mean temperatures at Northern Hemisphere land stations (1851–1990). The inclusion of explanatory variables is shown by regressing the latter temperature series on four variables: Southern Oscillation index (SOI), volcanic dust index (VDI), sunspot numbers (SSN), and a simulated temperature signal, induced by increasing greenhouse gases (GHG). In all analyses, the influence of SSN on global temperatures is found to be negligible. The correlations between temperatures and SOI and VDI appear to be negative. For SOI, this correlation is significant, but for VDI it is not, probably because of a lack of volcanic eruptions during the sample period. The relation between temperatures and GHG is positive, which is in agreement with the hypothesis of a warming climate because of increasing levels of greenhouse gases. The prediction performance of the model is rather poor, and possible explanations are discussed.” Visser, H., J. Molenaar, 1995: Trend Estimation and Regression Analysis in Climatological Time Series: An Application of Structural Time Series Models and the Kalman Filter. J. Climate, 8, 969–979, doi:;2. [Full text]

Selecting a Model for Detecting the Presence of a Trend – Woodward & Gray (1995) “The authors consider the problem of determining whether the upward trending behavior in the global temperature anomaly series should be forecast to continue. To address this question, the generic problem of determining whether an observed trend in a time series realization is a random (i.e., short-term) trend or a deterministic (i.e., permanent) trend is considered. The importance of making this determination is that forecasts based on these two scenarios are dramatically different. Forecasts based on a series with random trends will not predict the observed trend to continue, while forecasts based on a model with deterministic trend will forecast the trend to continue into the future. In this paper, the authors consider an autoregressive integrated moving average (ARIMA) model and a “deterministic forcing function + autoregressive (AR) noise” model as possible random trend and deterministic trend models, respectively, for realizations displaying trending behavior. A bootstrap-based classification procedure for classifying an observed time series realization as ARIMA or “function + AR” using linear and quadratic forcing functions is introduced. A simulation study demonstrates that the procedure is useful in distinguishing between realizations from these two models. A unit-root test is also examined in an effort to distinguish between these two types of models. Using the techniques developed here, the temperature anomaly series are classified as ARIMA (i.e., having random trends).” Woodward, Wayne A., H. L. Gray, 1995: Selecting a Model for Detecting the Presence of a Trend. J. Climate, 8, 1929–1937, doi:;2. [Full text]

Global Warming and the Problem of Testing for Trend in Time Series Data – Woodward & Gray (1993)“In recent years a number of statistical tests have been proposed for testing the hypothesis that global warming is occurring. The standard approach is to examine one or two of the more prominent global temperature datasets by letting Yt = a + bt + Et, where Yt represents the temperature at time t and Et represents error from the trend line, and to test the hypothesis that b = 0. Several authors have applied these tests for trend to determine whether or not a significant long-term or deterministic trend exists, and have generally concluded that there is a significant deterministic trend in the data. However, we show that certain autoregressive-moving average (ARMA) models may also be very reasonable models for these data due to the random trends present in their realizations. In this paper, we provide simulation evidence to show that the tests for trend detect a deterministic trend in a relatively high percentage of realizations from a wide range of ARMA models, including those obtained for the temperature series, for which it is improper to forecast a trend to continue over more than a very short time period. Thus, we demonstrate that trend tests based on models such as Yt = a + bt + Et, where Yt for the purpose of prediction or inference concerning future behavior should be used with caution. Of course, the projections that the warming trend will extend into the future are largely based on such factors as the buildup of atmospheric greenhouse gases. We have shown here, however, that based solely on the available temperature anomaly series, it is difficult to conclude that the trend will continue over any extended length of time.” Woodward, Wayne A., H. L. Gray, 1993: Global Warming and the Problem of Testing for Trend in Time Series Data. J. Climate, 6, 953–962, doi:;2. [Full text]

Climate spectra and detecting climate change – Bloomfield & Nychka (1992) “Part of the debate over possible climate changes centers on the possibility that the changes observed over the previous century are natural in origin. This raises the question of how large a change could be expected as a result of natural variability. If the climate measurement of interest is modelled as a stationary (or related) Gaussian time series, this question can be answered in terms of (a) the way in which change is estimated, and (b) the spectrum of the time series. These computations are illustrated for 128 years of global temperature data using some simple measures of change and for a variety of possible temperature spectra. The results highlight the time scales on which it is important to know the magnitude of natural variability. The uncertainties in estimates of trend are most sensitive to fluctuations in the temperature series with periods from approximately 50 to 500 years. For some of the temperature spectra, it was found that the standard error of the least squares trend estimate was 3 times the standard error derived under the naïve assumption that the temperature series was uncorrelated. The observed trend differs from zero by more than 3 times the largest of the calculated standard errors, however, and is therefore highly significant.” Peter Bloomfield and Douglas Nychka, Climatic Change, Volume 21, Number 3 (1992), 275-287, DOI: 10.1007/BF00139727.

Trends in global temperature – Bloomfield (1992) “Statistical models consisting of a trend plus serially correlated noise may be fitted to observed climate data such as global surface temperature, the trend and noise representing systematic change and other variations, respectively. When such a model is fitted, the estimated character of the noise determines the precision of the estimated trend, and hence the precision of the estimate of the magnitude of the systematic change in the variable considered. The results of fitting such models to global temperature imply that there is uncertainty in the amount of temperature change over the past century of up to ± 0.2 °C, but that the change of around one half of a degree Celsius is significantly different from zero. The statistical models for climate variability also imply that the observed temperature data provide only imprecise information about the climate sensitivity. This is defined here as the equilibrium response of global temperature to a doubling of the atmospheric concentration of carbon dioxide. The temperature changes observed to date are compatible with a wide range of climate sensitivities, from 0.7 °C to 2.2 °C. When data uncertainties are taken into account, the interval widens even further.” Peter Bloomfield, Climatic Change, Volume 21, Number 1 (1992), 1-16, DOI: 10.1007/BF00143250.

Inference about trends in global temperature data – Galbraith & Green (1992) “Interpretation of the effects of increasing atmospheric carbon dioxide on temperature is made more difficult by the fact that it is unclear whether sufficient global warming has taken place to allow a statistically significant finding of any upward trend in the temperature series. We add to the few existing statistical results by reporting tests for both deterministic and stochastic non-stationarity (trends) in time series of global average temperature. We conclude that the statistical evidence is sufficient to reject the hypothesis of a stochastic trend; however, there is evidence of a trend which could be approximated by a deterministic linear model.” John W. Galbraith and Christopher Green, Climatic Change, Volume 22, Number 3 (1992), 209-221, DOI: 10.1007/BF00143028.

Interdecadal oscillations and the warming trend in global temperature time series – Ghil & Vautard (1991) “THE ability to distinguish a warming trend from natural variability is critical for an understanding of the climatic response to increasing greenhouse-gas concentrations. Here we use singular spectrum analysis1 to analyse the time series of global surface air tem-peratures for the past 135 years, allowing a secular warming trend and a small number of oscillatory modes to be separated from the noise. The trend is flat until 1910, with an increase of 0.4 °C since then. The oscillations exhibit interdecadal periods of 21 and 16 years, and interannual periods of 6 and 5 years. The interannual oscillations are probably related to global aspects of the El Niño-Southern Oscillation (ENSO) phenomenon. The interdecadal oscillations could be associated with changes in the extratropical ocean circulation. The oscillatory components have combined (peak-to-peak) amplitudes of >0.2 °C, and therefore limit our ability to predict whether the inferred secular warming trend of 0.005 °Cyr−1 will continue. This could postpone incontrovertible detection of the greenhouse warming signal for one or two decades.” M. Ghil & R. Vautard, Nature 350, 324 – 327 (28 March 1991); doi:10.1038/350324a0. [Full text]

Global Warming as a Manifestation of a Random Walk – Gordon (1991) “Global and hemispheric series of surface temperature anomalies are examined in an attempt to isolate any specific features of the structure of the series that might contribute to the global warming of about 0.5°C which has been observed over the past 100 years. It is found that there are no significant differences between the means of the positive and negative values of the changes in temperature from one year to the next; neither do the relative frequencies of the positive and negative values differ from the frequencies that would be expected by chance with a probability near 0.5. If the interannual changes are regarded as changes of unit magnitude and plotted in a Cartesian frame of reference with time measured along the x axis and yearly temperature differences along the y axis, the resulting path closely resembles the kind of random walk that occurs during a coin-tossing game. We hypothesize that the global and hemispheric temperature series are the result of a Markov process. The climate system is subjected to various forms of random impulses. It is argued that the system fails to return to its former state after reacting to an impulse but tends to adjust to a new state of equilibrium as prescribed by the shock. This happens because a net positive feedback accompanies each shock and slightly alters the environmental state.” Gordon, A. H., 1991: Global Warming as a Manifestation of a Random Walk. J. Climate, 4, 589–597, doi:;2. [Full text]

Detecting CO2-induced climatic change – Wigley & Jones (1981) “Although it is widely believed that increasing atmospheric CO2 levels will cause noticeable global warming, the effects are not yet detectable, possibly because of the ‘noise’ of natural climatic variability. An examination of the spatial and seasonal distribution of signal-to-noise ratio shows that the highest values occur in summer and annual mean surface temperatures averaged over the Northern Hemisphere or over mid-latitudes. The spatial and seasonal characteristics of the early twentieth century warming were similar to those expected from increasing CO2 based on an equilibrium response model. This similarity may hinder the early detection of CO2 effects on climate.” T. M. L. Wigley & P. D. Jones, Nature 292, 205 – 208 (16 July 1981); doi:10.1038/292205a0.

Posted in AGW evidence, Climate science | 2 Comments »

New research from last week 20/2012

Posted by Ari Jokimäki on May 21, 2012

This week I have some bad news for you. Late 20th century warming was not natural event in Australasia, but it seems that we did it with our fossil fuels. When we started warming up the Earth with carbon dioxide from fossil fuels, I guess we just didn’t realize that climate sensitivity is bigger for that than for solar forcing. We see that for example in tropospheric water vapor increase and in oceanic warming. Summer monsoon is also weakening and making air pollution situation even worse. Humans might be affected too, as has happened during past climate changes.

So what do we do? We start using biofuels, but that then seems to destroy stratospheric ozone, which protects us from solar UV radiation. El Niño is of no help, because it just mixes up the carbon dioxide in the atmosphere. We could try to see if we can identify tree rings in Ethiopia, but that might be just fun recreational activity and might not actually help. Perhaps we should just hope that climate sensitivity is not that bad. After all, there is uncertainty in cloud feedback, so it might be that we only get 2+ Kelvins of warming. Perhaps best thing to do is to sit back, read some more studies next week, and hope they come up with a plan for us, right?

Transition from fossil fuels to biofuels might be bad idea from ozone layer perspective

Impacts of the production and consumption of biofuels on stratospheric ozone – Revell et al. (2012)

Abstract: “Biofuels are becoming increasingly popular sources of renewable energy as economic pressures and environmental consequences encourage the use of alternatives to fossil fuels. However, growing crops destined for use as biofuels incurs large N2O emissions associated with the use of nitrogen-based fertilizers. Besides being a greenhouse gas, N2O is also the primary source of stratospheric NOx (NO + NO2) which leads to stratospheric ozone depletion. In this paper, the potential effects on the ozone layer of a large-scale shift away from fossil fuel use to biofuels consumption over the 21st century are examined. Under such a scenario, global-mean column ozone decreases by 2.6 DU between 2010 and 2100 in contrast to a 0.7 DU decrease under a control simulation (the IPCC SRES B1 scenario for greenhouse gases) and a 9.1 DU increase under the more commonly used SRES A1B scenario. Two factors cause the decrease in ozone in the biofuels simulation: 1) large N2O emissions lead to faster rates of the ozone-depleting NOx cycles and; 2) reduced CO2 emissions (due to less fossil fuel burning) lead to relatively less stratospheric cooling over the 21st century, which decreases ozone abundances. Reducing CO2 emissions while neglecting to reduce N2O emissions could therefore be damaging to the ozone layer.”

Citation: Revell, L. E., G. E. Bodeker, P. E. Huck, and B. E. Williamson (2012), Impacts of the production and consumption of biofuels on stratospheric ozone, Geophys. Res. Lett., 39, L10804, doi:10.1029/2012GL051546.

Late 20th century warming was unusual and outside natural variability in Australasia during last millenium

Evidence of unusual late 20th century warming from an Australasian temperature reconstruction spanning the last millennium – Gergis et al. (2012) [FULL TEXT]

Abstract: “This study presents the first multi-proxy warm season (September-February) temperature reconstruction for the combined land and oceanic region of Australasia (0°S-50°S, 110°E-180°E). We perform a 3000-member ensemble Principal Component Reconstruction (PCR) using 27 temperature proxies from the region. The proxy network explained 69% of the inter-annual variance in the HadCRUT3v SONDJF spatial mean temperature over the 1921-1990 calibration period. Applying eight stringent reconstruction ‘reliability’ metrics identified post A.D. 1430 as the highest quality section of the reconstruction, but also revealed a skilful reconstruction is possible over the full A.D. 1000-2001 period. The average reconstructed temperature anomaly in Australasia during A.D. 1238-1267, the warmest 30-year pre-instrumental period, is 0.09°C (±0.19°C) below 1961-1990 levels. Following peak pre-industrial warmth, a cooling trend culminates in a temperature anomaly of 0.44°C (±0.18°C) below 1961-1990 levels between A.D. 1830-1859. A preliminary assessment of the roles of solar, volcanic, and anthropogenic forcings and natural ocean-atmosphere variability is performed using CSIRO Mk3L model simulations and independent palaeoclimate records. Solar and volcanic forcing does not have a marked influence on reconstructed Australasian temperature variations, which appear to be masked by internal variability. In 94.5% of the 3000-member reconstruction ensemble, there are no other warm periods in the past 1,000 years that match or exceed post-1950 warming observed in Australasia. The unusual 20th century warming cannot be explained by natural variability alone, suggesting a strong influence of anthropogenic forcing in the Australasian region.”

Citation: Joëlle Gergis, Raphael Neukom, Steven J. Phipps, Ailie J. E. Gallant, David J. Karoly, and PAGES Aus2K Project Members, Journal of Climate 2012, doi:

Is climate sensitivity less for solar forcing than for carbon dioxide forcing?

Sensitivity of an Earth system climate model to idealized radiative forcing – Andrews et al. (2012)

Abstract: “We diagnose forcing and climate feedbacks in benchmark sensitivity experiments with the new Met Office Hadley Centre Earth system climate model HadGEM2-ES. To identify the impact of newly-included biogeophysical and chemical processes, results are compared to a parallel set of experiments performed with these processes switched off, and different couplings with the biogeochemistry. In abrupt carbon dioxide quadrupling experiments we find that the inclusion of these processes does not alter the global climate sensitivity of the model. However, when the change in carbon dioxide is uncoupled from the vegetation, or when the model is forced with a non-carbon dioxide forcing – an increase in solar constant – new feedbacks emerge that make the climate system less sensitive to external perturbations. We identify a strong negative dust-vegetation feedback on climate change that is small in standard carbon dioxide sensitivity experiments due to the physiological/fertilization effects of carbon dioxide on plants in this model.”

Citation: Andrews, T., M. A. Ringer, M. Doutriaux-Boucher, M. J. Webb, and W. J. Collins (2012), Sensitivity of an Earth system climate model to idealized radiative forcing, Geophys. Res. Lett., 39, L10702, doi:10.1029/2012GL051942.

Updated estimates of world ocean heat content and sea level change

World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010 – Levitus et al. (2012)

Abstract: “We provide updated estimates of the change of ocean heat content and the thermosteric component of sea level change of the 0–700 and 0–2000 m layers of the World Ocean for 1955–2010. Our estimates are based on historical data not previously available, additional modern data, and bathythermograph data corrected for instrumental biases. We have also used Argo data corrected by the Argo DAC if available and used uncorrected Argo data if no corrections were available at the time we downloaded the Argo data. The heat content of the World Ocean for the 0–2000 m layer increased by 24.0 ± 1.9 × 1022 J (±2S.E.) corresponding to a rate of 0.39 W m−2 (per unit area of the World Ocean) and a volume mean warming of 0.09°C. This warming corresponds to a rate of 0.27 W m−2 per unit area of earth’s surface. The heat content of the World Ocean for the 0–700 m layer increased by 16.7 ± 1.6 × 1022 J corresponding to a rate of 0.27 W m−2 (per unit area of the World Ocean) and a volume mean warming of 0.18°C. The World Ocean accounts for approximately 93% of the warming of the earth system that has occurred since 1955. The 700–2000 m ocean layer accounted for approximately one-third of the warming of the 0–2000 m layer of the World Ocean. The thermosteric component of sea level trend was 0.54 ± .05 mm yr−1 for the 0–2000 m layer and 0.41 ± .04 mm yr−1 for the 0–700 m layer of the World Ocean for 1955–2010.”

Citation: Levitus, S., et al. (2012), World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010, Geophys. Res. Lett., 39, L10603, doi:10.1029/2012GL051106.

Radiosondes and reanalyses see positive trends in tropospheric water vapor over parts of Arctic

Recent changes in tropospheric water vapor over the Arctic as assessed from radiosondes and atmospheric reanalyses – Serreze et al. (2012) [Presentation material]

Abstract: “Changes in tropospheric water vapor over the Arctic are examined for the period 1979 to 2010 using humidity and temperature data from nine high latitude radiosonde stations north of 70°N with nearly complete records, and from six atmospheric reanalyses, emphasizing the three most modern efforts, MERRA, CFSR and ERA-Interim. Based on comparisons with the radiosonde profiles, the reanalyses as a group have positive cold-season humidity and temperature biases below the 850 hPa level and consequently do not capture observed low-level humidity and temperature inversions. MERRA has the smallest biases. Trends in column-integrated (surface to 500 hPa) water vapor (precipitable water) computed using data from the radiosondes and from the three modern reanalyses at the radiosonde locations are mostly positive, but magnitudes and statistical significance vary widely between sites and seasons. Positive trends in precipitable water from MERRA, CFSR and ERA-Interim, largest in summer and early autumn, dominate the northern North Atlantic, including the Greenland, Norwegian and Barents seas, the Canadian Arctic Archipelago and (on the Pacific side) the Beaufort and Chukchi seas. This pattern is linked to positive anomalies in air and sea surface temperature and negative anomalies in end-of-summer sea ice extent. Trends from ERA-Interim are weaker than those from either MERRA or CFSR. As assessed for polar cap averages (the region north of 70°N), MERRA, CFSR and ERA-Interim all show increasing surface-500 hPa precipitable over the analysis period encompassing most months, consistent with increases in 850 hPa air temperature and 850 hPa specific humidity. Data from all of the reanalyses point to strong interannual and decadal variability. The MERRA record in particular shows evidence of artifacts likely introduced by changes in assimilation data streams. A focus on the most recent decade (2001–2010) reveals large differences between the three reanalyses in the vertical structure of specific humidity and temperature anomalies.”

Citation: Serreze, M. C., A. P. Barrett, and J. Stroeve (2012), Recent changes in tropospheric water vapor over the Arctic as assessed from radiosondes and atmospheric reanalyses, J. Geophys. Res., 117, D10104, doi:10.1029/2011JD017421.

El Niño has an influence to atmospheric carbon dioxide distribution

Influence of El Niño on Mid-tropospheric CO2 from Atmospheric Infrared Sounder and Model – Jiang et al. (2012)

Abstract: “We investigate the influence of El Niño on the mid-tropospheric CO2 from the Atmospheric Infrared Sounder (AIRS) and Model of Ozone and Related Chemical Tracers version 2 (MOZART-2). AIRS mid-tropospheric CO2 data are used to study the temporal and spatial variability of CO2 in response to El Niño. CO2 difference between the Central Pacific and Western Pacific correlates well with the Southern Oscillation Index. To reveal the temporal and spatial variability of El Niño signal in the AIRS mid-tropospheric CO2, a multiple regression method is applied to the CO2 data from September 2002 to February 2011. There is more (less) mid-tropospheric CO2 in the Central Pacific and less (more) mid-tropospheric CO2 in the Western Pacific during El Niño (La Niña) events. Similar results are seen in the MOZART-2 convolved mid-tropospheric CO2, although the El Niño signal in the MOZART-2 is weaker than that in the AIRS data.”

Citation: Xun Jiang, Jingqian Wang, Edward T. Olsen, Maochang Liang, Thomas S. Pagano, Luke L. Chen, Stephen J. Licata, and Yuk L. Yung, Journal of the Atmospheric Sciences 2012, doi:

Were historical population crises in China related to climate?

A tale of two population crises in recent Chinese history – Lee & Zhang (2012) [FULL TEXT]

Abstract: “The fall of the Ming dynasty in the first half of the 17th century and the Taiping Rebellion from 1851–1864 were two of the most chaotic periods in Chinese history, and each was accompanied by large-scale population collapses. The ‘Kang-Qian Golden Age’ (also known as ‘High Qing’), during which population size expanded rapidly, falls in between the two. Scholars remain divided in their opinions concerning the above alternation of population growth and decline as to whether variations in population size or climate change should be identified as the root cause. In either case, the synergistic impact of population growth and climate change upon population growth dynamics is overlooked. In the present study, we utilized high-resolution empirical data, qualitative survey, statistical comparison and time-series analysis to investigate how the two factors worked synergistically to drive population cycles in 1600–1899. To facilitate our research, we posited a set of simplified pathways for population growth in historical agrarian China. Our results confirm that the interrelation between population growth, climate change and population crises in recent Chinese history basically followed our posited pathways. The recurrences of population crises were largely determined by the combination of population growth and climate change. Our results challenge classic Malthusian/post-Malthusian interpretations and historians’ views of historical Chinese population cycles.”

Citation: Harry F. Lee and David D. Zhang, Climatic Change, 2012, DOI: 10.1007/s10584-012-0490-9.

Trying to see annual tree-rings in permanent growing readiness trees of Ethiopia

Growth dynamics and potential for cross-dating and multi-century climate reconstruction of Podocarpus falcatus in Ethiopia – Krepkowski et al. (2012)

Abstract: “Podocarpus falcatus is an indigenous evergreen conifer species of tropical mountain forests in southeastern Ethiopia, showing potential tree ages of around 500 years. To study the influence of seasonal climate on the growth pattern of P. falcatus, we combined high-resolution electronic dendrometer measurements with wood anatomical investigations of microcores from the outermost stem parts collected in monthly intervals. At any time of the year sufficient rain events are able to cause cambial activity in P. falcatus. This permanent growing readiness leads to irregular wood formation with the formation of intra-annual density fluctuations and missing rings. Wood anatomical studies of microcores collected around the circumference of a mature P. falcatus revealed locally different activity status of the cambium on different lobes of the stem. Tree-ring width measurements of stem disks resulted in tentative tree ages that were confirmed by radiocarbon dating of selected wood samples. Although our efforts to cross-date ring-width series from several stem disks were not successful, further sampling in areas with different rainfall regimes, additional radiocarbon dating and measurements of stable isotopes hopefully would enable the establishment of a multi-century-long tree-ring series for climate reconstruction.”

Citation: Julia Krepkowski, Achim Bräuning, Aster Gebrekirstos, Dendrochronologia,

Weakening of summer monsoon has increased aerosol concentrations over eastern China

Increases in aerosol concentrations over eastern China due to the decadal-scale weakening of the East Asian summer monsoon – Zhu et al. (2012) [FULL TEXT]

Abstract: “China has been experiencing increased concentrations of aerosols, commonly attributed to the large increases in emissions associated with the rapid economic development. We show by using a chemical transport model driven by the assimilated meteorological fields that the observed decadal-scale weakening of the East Asian summer monsoon also contributed to the increases in aerosols in China. We find that the simulated aerosol concentrations have strong negative correlations with the strength of the East Asian Summer monsoon. Accounting for sulfate, nitrate, ammonium, black carbon, and organic carbon aerosols, the summer surface-layer PM2.5 concentration averaged over eastern China (110°–125°E, 20°–45°N) can be 17.7% higher in the weakest monsoon years than in the strongest monsoon years. The weakening of the East Asian Summer monsoon increases aerosol concentrations mainly by the changes in atmospheric circulation (the convergence of air pollutants) in eastern China.”

Citation: Zhu, J., H. Liao, and J. Li (2012), Increases in aerosol concentrations over eastern China due to the decadal-scale weakening of the East Asian summer monsoon, Geophys. Res. Lett., 39, L09809, doi:10.1029/2012GL051428.

Differences in cloud feedbacks continue to be important contributors to 2.1–4.7 K range of equilibrium climate sensitivity

Forcing, feedbacks and climate sensitivity in CMIP5 coupled atmosphere-ocean climate models – Andrews et al. (2012)

Abstract: “We quantify forcing and feedbacks across available CMIP5 coupled atmosphere-ocean general circulation models (AOGCMs) by analysing simulations forced by an abrupt quadrupling of atmospheric carbon dioxide concentration. This is the first application of the linear forcing-feedback regression analysis of Gregory et al. (2004) to an ensemble of AOGCMs. The range of equilibrium climate sensitivity is 2.1–4.7 K. Differences in cloud feedbacks continue to be important contributors to this range. Some models show small deviations from a linear dependence of top-of-atmosphere radiative fluxes on global surface temperature change. We show that this phenomenon largely arises from shortwave cloud radiative effects over the ocean and is consistent with independent estimates of forcing using fixed sea-surface temperature methods. We suggest that future research should focus more on understanding transient climate change, including any time-scale dependence of the forcing and/or feedback, rather than on the equilibrium response to large instantaneous forcing.”

Citation: Andrews, T., J. M. Gregory, M. J. Webb, and K. E. Taylor (2012), Forcing, feedbacks and climate sensitivity in CMIP5 coupled atmosphere-ocean climate models, Geophys. Res. Lett., 39, L09712, doi:10.1029/2012GL051607.

Observed tropical tropopause cooling might not be statistically significant

How well do we know recent climate trends at the tropical tropopause? – Wang et al. (2012)

Abstract: “The tropical tropopause is a transition layer between the troposphere and stratosphere that influences global climate and atmospheric chemistry. Several studies have reported multidecadal tropical tropopause cooling and have suggested a correlation between observed tropopause temperature and stratospheric water vapor. Our more rigorous examination of the observations shows tropopause trends have greater uncertainty than previously suggested and the cooling may not be statistically significant. We used two approaches to remove time-varying bias effects from cold-point tropopause trends estimated from radiosonde observations. Our results are consistent with expectations from a conceptual model of tropopause changes and could resolve discrepancies between complex climate models and observations.”

Citation: Wang, J. S., D. J. Seidel, and M. Free (2012), How well do we know recent climate trends at the tropical tropopause?, J. Geophys. Res., 117, D09118, doi:10.1029/2012JD017444.

CLASSIC OF THE WEEK: Dobson (1923)

Measurements of the Sun’s Ultra-Violet Radiation and Its Absorption in the Earth’s Atmosphere – Dobson et al. (1923) [FULL TEXT]

Abstract: No abstract. Quote from the paper: “The object of the present work was to obtain, if possible, a long series of measurements of the ultra-violet light radiated by the sun, the atmospheric transmission coefficient for this light and also the amount of ozone in the atmosphere.”

Citation: G. M. B. Dobson, Proc. R. Soc. Lond. A September 1, 1923 104 725 252-271; doi:10.1098/rspa.1923.0107 .

When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Posted in Climate science | 2 Comments »

New research from last week 19/2012

Posted by Ari Jokimäki on May 14, 2012

Wouldn’t it be nice to see something like following headlines in popular news media:

“Growth change of oak and beech are related to climate time series and N deposition trends!”

“Atmospheric lifetime of methane only 9.1 ± 0.9 years!”

“WAIS Divide was colder than the last 1000-year average from 1300 to 1800 C.E.!”

“Concentrations of rBC in the ice cores displayed significant variability at annual to decadal time scales!”

I bet papers with these in their frontpage would be sold out in minutes.

Contrary to expectations, British butterflies don’t utilise an increased range of habitat types with global warming

Habitat associations of thermophilous butterflies are reduced despite climatic warming – Oliver et al. (2012)

Abstract: “Climate warming threatens the survival of species at their warm, trailing-edge range boundaries, but also provides opportunities for the ecological release of populations at the cool, leading edges of their distributions. Thus, as the climate warms, leading-edge populations are expected to utilise an increased range of habitat types, leading to larger population sizes and range expansion. Here, we test the hypothesis that the habitat associations of British butterflies have expanded over three decades of climate warming. We characterise the habitat breadth of 27 southerly-distributed species from 77 monitoring transects between 1977 and 2007 by considering changes in densities of butterflies across 11 habitat types. Contrary to expectation, we find that 20 out of 27 (74%) butterfly species showed long term contractions in their habitat associations, despite some short-term expansions in habitat breadth in warmer-than-usual years. Thus, we conclude that climatic warming has ameliorated habitat contractions caused by other environmental drivers to some extent, but that habitat degradation continues to be a major driver of reductions in habitat breadth and population density of butterflies.”

Citation: Tom H. Oliver, Chris D. Thomas, Jane K. Hill, Tom Brereton, David B. Roy, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02737.x.

Droughts have become more intense and last longer in Urmia Lake Basin, Iran

Observed climate variability and change in Urmia Lake Basin, Iran – Delju et al. (2012)

Abstract: “This paper analyzes climate variability and change in the Urmia Lake Basin, northwest of Iran. Annual average of the following data time series has been analyzed by statistical methods: dry bulb temperature, maximum and minimum temperature, precipitation, and number of rainy and snowy days. We have also used mean monthly temperature and precipitation data for analysis of drought spells for the period 1964–2005 to find out whether fluctuations in the lake level are attributable to natural drought. Our results indicate that mean precipitation has decreased by 9.2 % and the average maximum temperature has increased by 0.8°C over these four decades. The seasonal changes are particularly visible in winter and spring. Results of the Palmer Drought Severity Index show that on average, drought episodes have hit the Urmia Lake Basin every 5 years and most of them reached severe levels, but recent droughts have become more intense and last longer.”

Citation: A. H. Delju, A. Ceylan, E. Piguet and M. Rebetez, Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0651-9.

Asian summer monsoon intensity has decreased with global warming

Decreasing Asian summer monsoon intensity after 1860 AD in the global warming epoch – Xu et al. (2012)

Abstract: “The trend of the Indian summer monsoon (ISM) intensity and its nature during the past 100 and 200 years still remain unclear. In this study we reconstructed the ISM intensity during the past 270 years from tree ring δ18O at Hongyuan, eastern edge of the Tibet Plateau. The monsoon failures inferred from δ18Otree ring correlate well with those recorded in ice cores, speleothem, and historical literature sources. 22.6, 59.0, and 110.9-years frequency components in the Hongyuan δ18Otree ring series, which may be the responses to solar activities, synchronize well with those recorded in other ISM indices. A notable feature of the reconstructed ISM intensity is the gradually decreasing trend from about 1860 to the present, which is inversely related to the increasing temperature trend contemporaneously. Such “decreasing ISM intensity–increasing temperature” tendency can also be supported by ice core records and meteorological records over a wide geographic extension. The decrease in sea surface temperature gradient between tropical and north Indian Ocean, and the decrease in land-sea thermal contrast between tropical Indian Ocean and “Indian sub-continent–western Himalaya” are possibly responsible for the observed decreasing ISM trend.”

Citation: Hai Xu, Yetang Hong and Bin Hong, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1378-0.

Sunshine hour decline in China since 1960’s due to air pollution

The magnitude of the effect of air pollution on sunshine hours in China – Wang et al. (2012)

Abstract: “This study investigates the changes in sunshine hours in relation to API (Air Pollution Index) across China. Data were collected from a total of 38 cities over the period of 1960–2009. Sunshine hours in over 84% of the cities significantly (p < 0.05) decline with an average of 16.7% for the 1960s–2000s. This decline is mainly prevalent over Sichuan Basin (22.4%), North China Plain (18.8%), and Yangtze River Delta (18.2%). While the sunshine hour decline is largely in the 20th century (with the strongest drop in the 1980s and the least in the 1990s), it rebounds by 0.3% after 2000. For especially in winter seasons and the North China region, API is negatively related with sunshine hours. For days with API > 80, sunshine hours are on the average 0.7 h d−1 (8.4%) shorter than for days with API ≤ 80 under clear-sky condition for 2001–2005. In cities with average daily API ≤ 80 and >80 for the 2000s, sunshine hour decline for the 1960s–2000s is 0.8 h d−1 (13.4%) and 1.0 h d−1 (15.9%) respectively. Winter seasons with high API (90) exhibit the highest sunshine hour decline (21.5%). The study shows that spatiotemporal changes in sunshine hours in China could largely be explained in terms of API.”

Citation: Wang, Y., Y. Yang, N. Zhao, C. Liu, and Q. Wang (2012), The magnitude of the effect of air pollution on sunshine hours in China, J. Geophys. Res., 117, D00V14, doi:10.1029/2011JD016753.

In 2007 there were lot of melt ponds on Arctic sea ice and in 2011 there were even more

Exceptional melt pond occurrence in the years 2007 and 2011 on the Arctic sea ice revealed from MODIS satellite data – Rösel & Kaleschke (2012)

Abstract: “Melt ponds contribute to the ice-albedo feedback as they reduce the surface albedo of sea ice, and hence accelerate the decay of Arctic sea ice. Here, we analyze the melt pond fraction, retrieved from the MODIS sensor for the years 2000–2011 to characterize the spatial and temporal evolution. A significant anomaly of the relative melt pond fraction at the beginning of the melt season in June 2007 is documented. This is followed by above-average values throughout the entire summer. In contrast, the increase of the relative melt pond fraction at the beginning of June 2011 is within average values, but from mid-June, relative melt pond fraction exhibits values up to two standard deviations above the mean values of 30 ± 1.2% which are even higher than in Summer 2007.”

Citation: Rösel, A., and L. Kaleschke (2012), Exceptional melt pond occurrence in the years 2007 and 2011 on the Arctic sea ice revealed from MODIS satellite data, J. Geophys. Res., 117, C05018, doi:10.1029/2011JC007869.

Signal of human influence on climate has strengthened over the first decade of the 21st century

Observed 21st century temperatures further constrain likely rates of future warming – Stott & Jones (2012)

Abstract: “We carry out a detection and attribution analysis of observed near-surface temperatures to 2010 and demonstrate that the signal of human influence on climate has strengthened over the first decade of the 21st century. As a result, we show that global warming is set to continue, with the second decade of the 21st century predicted to be very likely warmer than the first. Estimates of future warming rates consistent with observations of past climate change are now better constrained than they were a decade ago. The highest rates of warming previously consistent with past warming now appear to be unlikely.”

Citation: Peter A. Stott, Gareth S. Jones, Atmospheric Science Letters, DOI: 10.1002/asl.383.

Antactic ice core records of black carbon deposition since 1850

Changes in black carbon deposition to Antarctica from two high-resolution ice core records, 1850–2000 AD – Bisiaux et al. (2012) [FULL TEXT]

Abstract: “Refractory black carbon aerosols (rBC) emitted by biomass burning (fires) and fossil fuel combustion, affect global climate and atmospheric chemistry. In the Southern Hemisphere (SH), rBC is transported in the atmosphere from low- and mid-latitudes to Antarctica and deposited to the polar ice sheet preserving a history of emissions and atmospheric transport. Here, we present two high-resolution Antarctic rBC ice core records drilled from the West Antarctic Ice Sheet divide and Law Dome on the periphery of the East Antarctic ice sheet. Separated by ~3500 km, the records span calendar years 1850–2001 and reflect the rBC distribution over the Indian and Pacific ocean sectors of the Southern Ocean. Concentrations of rBC in the ice cores displayed significant variability at annual to decadal time scales, notably in ENSO-QBO and AAO frequency bands. The delay observed between rBC and ENSO variability suggested that ENSO does not directly affect rBC transport, but rather continental hydrology, subsequent fire regimes, and aerosol emissions. From 1850 to 1950, the two ice core records were uncorrelated but were highly correlated from 1950 to 2002 (cross-correlation coefficient at annual resolution: r = 0.54, p < 0.01) due to a common decrease in rBC variability. The decrease in ice-core rBC from the 1950s to late 1980s displays similarities with inventories of SH rBC grass fires and biofuel emissions, which show reduced emission estimates over that period.”

Citation: Bisiaux, M. M., Edwards, R., McConnell, J. R., Curran, M. A. J., Van Ommen, T. D., Smith, A. M., Neumann, T. A., Pasteris, D. R., Penner, J. E., and Taylor, K.: Changes in black carbon deposition to Antarctica from two high-resolution ice core records, 1850–2000 AD, Atmos. Chem. Phys., 12, 4107-4115, doi:10.5194/acp-12-4107-2012, 2012.

Most temperature proxies really are linear functions of annual mean temperature

A test for non-linearity in temperature proxy records – Støve et al. (2012)

Abstract: “Are temperature proxy records linear recorders of past temperature conditions? We apply a statistical test for linearity to 15 millennial-long proxy records with annual resolution that where shown to significantly respond to Northern Hemisphere annual mean temperature selected from a collection of 30 proxies. The test, based on generalized additive modeling, shows that most of the proxies can indeed be shown to be linear functions of annual mean temperature, but two proxy records do not appear to have a linear relationship with temperature — this supports the assumption of linearity in most climate reconstruction work. The method tests for non-linearity in a proxy relative to the group of proxies it is being used together with. We test robustness of the results and find that the results are stable to choice of proxies. The linearity-testing method is quite general and could in the future be used for larger and more extensive sets of proxies.”

Citation: Bård Støve, Fredrik Charpentier Ljungqvist, Peter Thejll, Journal of Climate 2012, doi:

New technique for measuring past methane mixing ratios from ice cores

Continuous measurements of methane mixing ratios from ice cores – Stowasser et al. (2012) [FULL TEXT]

Abstract: “This work presents a new, field-deployable technique for continuous, high-resolution measurements of methane mixing ratios from ice cores. The technique is based on a continuous flow analysis system, where ice core samples cut along the long axis of an ice core are melted continuously. The past atmospheric air contained in the ice is separated from the melt water stream via a system for continuous gas extraction. The extracted gas is dehumidified and then analyzed by a Wavelength Scanned-Cavity Ring Down Spectrometer for methane mixing ratios. We assess the performance of the new measurement technique in terms of precision (±0.8 ppbv, 1σ), accuracy (±8 ppbv), temporal (ca. 100 s), and spatial resolution (ca. 5 cm). Using a firn air transport model, we compare the resolution of the measurement technique to the resolution of the atmospheric methane signal as preserved in ice cores in Greenland. We conclude that our measurement technique can resolve all climatically relevant variations as preserved in the ice down to an ice depth of at least 1980 m (66 000 yr before present) in the North Greenland Eemian Ice Drilling ice core. Furthermore, we describe the modifications, which are necessary to make a commercially available spectrometer suitable for continuous methane mixing ratio measurements from ice cores.”

Citation: Stowasser, C., Buizert, C., Gkinis, V., Chappellaz, J., Schüpbach, S., Bigler, M., Faïn, X., Sperlich, P., Baumgartner, M., Schilt, A., and Blunier, T.: Continuous measurements of methane mixing ratios from ice cores, Atmos. Meas. Tech., 5, 999-1013, doi:10.5194/amt-5-999-2012, 2012.

Evidence for global Little Ice Age from West Antarctic borehole temperatures

Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide – Orsi et al. (2012)

Abstract: “The largest climate anomaly of the last 1000 years in the Northern Hemisphere was the Little Ice Age (LIA) from 1400–1850 C.E., but little is known about the signature of this event in the Southern Hemisphere, especially in Antarctica. We present temperature data from a 300 m borehole at the West Antarctic Ice Sheet (WAIS) Divide. Results show that WAIS Divide was colder than the last 1000-year average from 1300 to 1800 C.E. The temperature in the time period 1400–1800 C.E. was on average 0.52 ± 0.28°C colder than the last 100-year average. This amplitude is about half of that seen at Greenland Summit (GRIP). This result is consistent with the idea that the LIA was a global event, probably caused by a change in solar and volcanic forcing, and was not simply a seesaw-type redistribution of heat between the hemispheres as would be predicted by some ocean-circulation hypotheses. The difference in the magnitude of the LIA between Greenland and West Antarctica suggests that the feedbacks amplifying the radiative forcing may not operate in the same way in both regions.”

Citation: Orsi, A. J., B. D. Cornuelle, and J. P. Severinghaus (2012), Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide, Geophys. Res. Lett., 39, L09710, doi:10.1029/2012GL051260.

Yet another analysis suggests that greenhouse gases and aerosols controlled temperature after 1950

A fractal climate response function can simulate global average temperature trends of the modern era and the past millennium – van Hateren (2012) [FULL TEXT]

Abstract: “A climate response function is introduced that consists of six exponential (low-pass) filters with weights depending as a power law on their e-folding times. The response of this two-parameter function to the combined forcings of solar irradiance, greenhouse gases, and SO2-related aerosols is fitted simultaneously to reconstructed temperatures of the past millennium, the response to solar cycles, the response to the 1991 Pinatubo volcanic eruption, and the modern 1850–2010 temperature trend. Assuming strong long-term modulation of solar irradiance, the quite adequate fit produces a climate response function with a millennium-scale response to doubled CO2 concentration of 2.0 ± 0.3 °C (mean ± standard error), of which about 50 % is realized with e-folding times of 0.5 and 2 years, about 30 % with e-folding times of 8 and 32 years, and about 20 % with e-folding times of 128 and 512 years. The transient climate response (response after 70 years of 1 % yearly rise of CO2 concentration) is 1.5 ± 0.2 °C. The temperature rise from 1820 to 1950 can be attributed for about 70 % to increased solar irradiance, while the temperature changes after 1950 are almost completely produced by the interplay of anthropogenic greenhouse gases and aerosols. The SO2-related forcing produces a small temperature drop in the years 1950–1970 and an inflection of the temperature curve around the year 2000. Fitting with a tenfold smaller modulation of solar irradiance produces a less adequate fit with millennium-scale and transient climate responses of 2.5 ± 0.4 and 1.9 ± 0.3 °C, respectively.”

Citation: J. H. van Hateren, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1375-3.

New derivations for atmospheric lifetimes of some GHG’s

Reactive greenhouse gas scenarios: Systematic exploration of uncertainties and the role of atmospheric chemistry – Prather et al. (2012)

Abstract: “Knowledge of the atmospheric chemistry of reactive greenhouse gases is needed to accurately quantify the relationship between human activities and climate, and to incorporate uncertainty in our projections of greenhouse gas abundances. We present a method for estimating the fraction of greenhouse gases attributable to human activities, both currently and for future scenarios. Key variables used to calculate the atmospheric chemistry and budgets of major non-CO2 greenhouse gases are codified along with their uncertainties, and then used to project budgets and abundances under the new climate-change scenarios. This new approach uses our knowledge of changing abundances and lifetimes to estimate current total anthropogenic emissions, independently and possibly more accurately than inventory-based scenarios. We derive a present-day atmospheric lifetime for methane (CH4) of 9.1 ± 0.9 y and anthropogenic emissions of 352 ± 45 Tg/y (64% of total emissions). For N2O, corresponding values are 131 ± 10 y and 6.5 ± 1.3 TgN/y (41% of total); and for HFC-134a, the lifetime is 14.2 ± 1.5 y.”

Citation: Prather, M. J., C. D. Holmes, and J. Hsu (2012), Reactive greenhouse gas scenarios: Systematic exploration of uncertainties and the role of atmospheric chemistry, Geophys. Res. Lett., 39, L09803, doi:10.1029/2012GL051440.

Causes and differences of temperature response of tree species radial growth

Radial growth change of temperate tree species in response to altered regional climate and air quality in the period 1901–2008 – Kint et al. (2012)

Abstract: “Both increasing and decreasing 20th century growth trends have been reported in forests throughout Europe, but only for few species and areas suitable modelling techniques have been used to distinguish individual tree growth (operating on a local scale) from growth change due to exogenous factors (operating on a broad geographical scale). This study relates for the first time observed growth changes, in terms of basal area increment (BAI) of dominant trees of pedunculate oak, common beech and Scots pine, in north-west European temperate lowland forests (Flanders) to climate, atmospheric CO2 and tropospheric O3 concentrations, N deposition, site quality and forest structure for more than a century (the period 1901–2008), applying mixed models. Growth change during the 20th century is observed for oak (increasing growth) and beech (increasing growth until the 1960s, growth decline afterwards), but not for pine. It was possible to relate growth change of oak and beech to climate time series and N deposition trends. Adding time series for CO2 and O3 concentration did not significantly improve model results. For oak and beech a switch from positive to negative growth response with increasing nitrogen deposition throughout time is observed. Growth increase for oak is mainly determined by the interaction between growing season temperature and soil water recharge. It is reasonable to assume that the observed growth trend for oak will continue for as long as early season water availability is not compromised. The decreasing trend in summer relative air humidity observed since the 1960s in the study area can be a main cause of recent beech BAI decrease. A further growth decline of beech can be expected, independent of site quality.”

Citation: Vincent Kint, Wim Aertsen, Matteo Campioli, Dries Vansteenkiste and Andy Delcloo, et al., Climatic Change, 2012, DOI: 10.1007/s10584-012-0465-x.

CLASSIC OF THE WEEK: Lord Kelvin (1864)

On the secular cooling of the earth – Lord Kelvin (1864) [FULL TEXT (partial)]

Abstract: No abstract. Quote from the beginning of the paper: “For eighteen years it has pressed on my mind, that essential principles of Thermo-dynamics have been overlooked by those geologists who uncompromisingly oppose all paroxysmal hypostheses, and maintain not only that we have examples now before us, on the earth, of all the different actions by which its crust has been modified in geological history, but that these actions have never, or have not on the whole, been more violent in the past time than they are at present.”

Citation: Lord Kelvin (William Thomson), Transactions of the Royal Society of Edinburgh, Vol. XXIII, pp. 167169, 1864. Read April 28, 1862.

When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Posted in Climate science | 1 Comment »

Rules of discussion

Posted by Ari Jokimäki on May 9, 2012

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New research from last week 18/2012

Posted by Ari Jokimäki on May 7, 2012

Last week scientists moved the borders of unknown little further in following subjects (among others): astronomical climate forcing, NAO-snow cover relation, global temperature analysis, daily mean temperature, hurricane activity, ocean acidification, mass extinction, AMO, insect ice toleration, lake ice, sea ice, climate system annual cycle, growing season, 18th century meteorology, bark beetle outbreaks, summer monsoon, and iceberg distribution.

Astronomical forcing as a pacemaker of climate

Is the astronomical forcing a reliable and unique pacemaker for climate? A conceptual model study – De Saedeleer et al. (2012) [FULL TEXT]

Abstract: “There is evidence that ice age cycles are paced by astronomical forcing, suggesting some kind of synchronisation phenomenon. Here, we identify the type of such synchronisation and explore systematically its uniqueness and robustness using a simple paleoclimate model akin to the van der Pol relaxation oscillator and dynamical system theory. As the insolation is quite a complex quasiperiodic signal involving different frequencies, the traditional concepts used to define synchronisation to periodic forcing are no longer applicable. Instead, we explore a different concept of generalised synchronisation in terms of (coexisting) synchronised solutions for the forced system, their basins of attraction and instabilities. We propose a clustering technique to compute the number of synchronised solutions, each of which corresponds to a different paleoclimate history. In this way, we uncover multistable synchronisation (reminiscent of phase- or frequency-locking to individual periodic components of astronomical forcing) at low forcing strength, and monostable or unique synchronisation at stronger forcing. In the multistable regime, different initial conditions may lead to different paleoclimate histories. To study their robustness, we analyse Lyapunov exponents that quantify the rate of convergence towards each synchronised solution (local stability), and basins of attraction that indicate critical levels of external perturbations (global stability). We find that even though synchronised solutions are stable on a long term, there exist short episodes of desynchronisation where nearby climate trajectories diverge temporarily (for about 50 kyr). As the attracting trajectory can sometimes lie close to the boundary of its basin of attraction, a small perturbation could quite easily make climate to jump between different histories, reducing the predictability. Our study brings new insight into paleoclimate dynamics and reveals a possibility for the climate system to wander throughout different climatic histories related to preferential synchronisation regimes on obliquity, precession or combinations of both, all over the history of the Pleistocene.”

Citation: Bernard De Saedeleer, Michel Crucifix and Sebastian Wieczorek, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1316-1.

North Atlantic Oscillation is related to European snow cover, particularly in January and February

Physical mechanisms of European winter snow cover variability and its relationship to the NAO – Kim et al. (2012)

Abstract: “Annual snow cover in the Northern Hemisphere has decreased in the past two decades, an effect associated with global warming. The regional scale changes of snow cover during winter, however, vary significantly from one region to another. In the present study, snow cover variability over Europe and its connection to other atmospheric variables was investigated using Cyclostationary Empirical Orthogonal Function (CSEOF) analysis. The evolution of atmospheric variables related to each CSEOF mode of snow cover variability was derived via regression analysis in CSEOF space. CSEOF analysis clearly shows that the North Atlantic Oscillation (NAO) is related to European snow cover, particularly in January and February. A negative NAO phase tends to result in a snow cover increases, whereas a positive NAO phase results in snow cover decreases. The temporal changes in the connection between the NAO and European snow cover are explained by time-dependent NAO-related temperature anomalies. If the NAO phase is negative, the temperature is lower in Europe and snow cover increases; by contrast, when the NAO phase is positive, the temperature is higher and snow cover decreases. Temperature and snow cover variations in Europe are associated with the thermal advection by anomalous wind by NAO. CSEOF analysis also shows an abrupt increase of snow cover in December and January and a decrease in February and March since the year 2000, approximately. This abrupt change is associated with sub-seasonal variations of atmospheric circulation in the study region.”

Citation: Yoojin Kim, Kwang-Yul Kim and Baek-Min Kim, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1365-5.

NOAA introduces improvements to Merged Land-Ocean Surface Temperature analysis

NOAA’s Merged Land-Ocean Surface Temperature Analysis – Vose et al. (2012)

Abstract: “This paper describes the new release of the Merged Land-Ocean Surface Temperature analysis (MLOST version 3.5), which is used in operational monitoring and climate assessment activities by the NOAA National Climatic Data Center. The primary motivation for the latest version is the inclusion of a new land dataset that has several major improvements, including a more elaborate approach for addressing changes in station location, instrumentation, and siting conditions. The new version is broadly consistent with previous global analyses, exhibiting a trend of 0.076 °C dec−1 since 1901, 0.162 °C dec−1 since 1979, and widespread warming in both time periods. In general, the new release exhibits only modest differences with its predecessor, the most obvious being very slightly more warming at the global scale (0.004 °C dec−1 since 1901) and slightly different trend patterns over the terrestrial surface.”

Citation: Russell S. Vose, Derek Arndt, Viva F. Banzon, David R. Easterling, Byron Gleason, Boyin Huang, Ed Kearns, Jay H. Lawrimore, Matthew J. Menne, Thomas C. Peterson, Richard W. Reynolds, Thomas M. Smith, Claude N. Williams, Jr., David L. Wuertz, Bulletin of the American Meteorological Society 2012, doi:

So, how do we determine daily mean temperature then?

Estimating daily mean temperature from synoptic climate observations – Ma & Guttorp (2012) [FULL TEXT]

Abstract: “We compare some different approaches to estimating daily mean temperature (DMT). In many countries, the routine approach is to calculate the average of the directly measured minimum and maximum daily temperature. In some, the maximum and minimum are obtained from hourly measurements. In other countries, temperature readings at specific times throughout the day are taken into account. For example, the Swedish approach uses a linear combination of five temperature readings, including the minimum and the maximum, with coefficients that depend on longitude and month. We first look at data with very high temporal resolution, and compare some different approaches to estimating DMT. Then, we compare the Swedish formula to various averages of the daily minimum and maximum, finding the latter method being substantially less precise. We finally compare the Swedish formula to hourly averages, and find that a recalibrated linear combination improves estimation accuracy.”

Citation: Yuting Ma, Peter Guttorp, International Journal of Climatology, DOI: 10.1002/joc.3510.

Eastern North Pacific hurricane season 2010 was one of the least active seasons on record

Eastern North Pacific Hurricane Season of 2010 – Stewart & Cangialosi (2012)

Abstract: “The 2010 eastern North Pacific hurricane season was one of the least active seasons on record. Only seven named storms developed, which is the lowest number observed at least since routine satellite coverage of that basin began in 1966. Furthermore, only three of those storms reached hurricane status, which is also the lowest number of hurricanes ever observed in the satellite era season. However, two tropical storms made landfall – Agatha in Guatemala and Georgette in Mexico, with Agatha directly causing 190 deaths and moderate to severe property damage as a result of rain-induced floods and mud slides. On average, the National Hurricane Center track forecasts in the eastern North Pacific for 2010 were quite skillful.”

Citation: Stacy R. Stewart and John P. Cangialosi, Monthly Weather Review 2012, doi:

Expected ocean acidification from human actions seems to be unprecedented in the geologic past

History of Seawater Carbonate Chemistry, Atmospheric CO2, and Ocean Acidification – Zeebe (2012) [FULL TEXT]

Abstract: “Humans are continuing to add vast amounts of carbon dioxide (CO2) to the atmosphere through fossil fuel burning and other activities. A large fraction of the CO2 is taken up by the oceans in a process that lowers ocean pH and carbonate mineral saturation state. This effect has potentially serious consequences for marine life, which are, however, difficult to predict. One approach to address the issue is to study the geologic record, which may provide clues about what the future holds for ocean chemistry and marine organisms. This article reviews basic controls on ocean carbonate chemistry on different timescales and examines past ocean chemistry changes and ocean acidification events during various geologic eras. The results allow evaluation of the current anthropogenic perturbation in the context of Earth’s history. It appears that the ocean acidification event that humans are expected to cause is unprecedented in the geologic past, for which sufficiently well-preserved records are available.”

Citation: Richard E. Zeebe, Annual Review of Earth and Planetary Sciences, Vol. 40: 141-165 (Volume publication date May 2012), DOI: 10.1146/annurev-earth-042711-105521.

End-Permian mass extinction may be important ancient analog for 21st century oceans

End-Permian Mass Extinction in the Oceans: An Ancient Analog for the Twenty-First Century? – Payne & Clapham (2012)

Abstract: “The greatest loss of biodiversity in the history of animal life occurred at the end of the Permian Period (~252 million years ago). This biotic catastrophe coincided with an interval of widespread ocean anoxia and the eruption of one of Earth’s largest continental flood basalt provinces, the Siberian Traps. Volatile release from basaltic magma and sedimentary strata during emplacement of the Siberian Traps can account for most end-Permian paleontological and geochemical observations. Climate change and, perhaps, destruction of the ozone layer can explain extinctions on land, whereas changes in ocean oxygen levels, CO2, pH, and temperature can account for extinction selectivity across marine animals. These emerging insights from geology, geochemistry, and paleobiology suggest that the end-Permian extinction may serve as an important ancient analog for twenty-first century oceans.”

Citation: Jonathan L. Payne and Matthew E. Clapham, Annual Review of Earth and Planetary Sciences, Vol. 40: 89-111 (Volume publication date May 2012), DOI: 10.1146/annurev-earth-042711-105329.

Greenland ice cores show highly variable Atlantic Multidecadal Oscillation

Greenland ice core evidence for spatial and temporal variability of the Atlantic Multidecadal Oscillation – Chylek et al. (2012)

Abstract: “The Greenland δ18O ice core record is used as a proxy for Greenland surface air temperatures and to interpret Atlantic Multidecadal Oscillation (AMO) variability. An analysis of annual δ18O data from six Arctic ice cores (five from Greenland and one from Canada’s Ellesmere Island) suggests a significant AMO spatial and temporal variability within a recent period of 660 years. A dominant AMO periodicity near 20 years is clearly observed in the southern (Dye3 site) and the central (GISP2, Crete and Milcent) regions of Greenland. This 20-year variability is, however, significantly reduced in the northern (Camp Century and Agassiz Ice Cap) region, likely due to a larger distance from the Atlantic Ocean, and a much lower snow accumulation. A longer time scale AMO component of 45–65 years, which has been seen clearly in the 20th century SST data, is detected only in central Greenland ice cores. We find a significant difference between the AMO cycles during the Little Ice Age (LIA) and the Medieval Warm Period (MWP). The LIA was dominated by a ∼20 year AMO cycle with no other decadal or multidecadal scale variability above the noise level. However, during the preceding MWP the 20 year cycle was replaced by a longer scale cycle centered near a period of 43 years with a further 11.5 year periodicity. An analysis of two coupled atmosphere-ocean general circulation models control runs (UK Met Office HadCM3 and NOAA GFDL CM2.1) agree with the shorter and longer time-scales of Atlantic Meridional Overturning Circulation (AMOC) and temperature fluctuations with periodicities close to those observed. However, the geographic variability of these periodicities indicated by ice core data is not captured in model simulations.”

Citation: Chylek, P., C. Folland, L. Frankcombe, H. Dijkstra, G. Lesins, and M. Dubey (2012), Greenland ice core evidence for spatial and temporal variability of the Atlantic Multidecadal Oscillation, Geophys. Res. Lett., 39, L09705, doi:10.1029/2012GL051241.

Did some insects survive in Greenland during last glacial stage?

Interglacial insects and their possible survival in Greenland during the last glacial stage – Böcher (2012)

Abstract: “Sediments from the last interglacial (Eemian) in Jameson Land, East Greenland, and the Thule area, NW Greenland, have revealed a number of insect fragments of both arctic and more or less warmth-demanding species. Altogether, the interglacial fauna of Coleoptera (beetles) indicates boreal conditions. Undoubtedly, a large fraction of the insect fauna succumbed when the mild Eemian climate cooled drastically during the last glacial stage. However, a group of hardy species now found far north into the High Arctic might be glacial survivors. It is, however, still puzzling why well-adapted arctic beetle species such as Amara alpina and Isochnus arcticus did not survive the last glacial stage in Greenland. Two factors that have not been sufficiently considered when discussing survival contra extinction are the importance of microclimate and the number of sun-hours during the Arctic summer. Even among the Coleoptera, which as a group fares quite badly in the Arctic, there might be survivors, at least among those found both during the interglacial and as fossils during the early Holocene. First of all, glacial survival applies to the seed bug Nysius groenlandicus, which was widespread during the Eemian, was found soon after the last deglaciation, and is now almost omnipresent in Greenland.”

Citation: Jens Böcher, Boreas, DOI: 10.1111/j.1502-3885.2012.00251.x.

Lakes in eastern North America already have up to 21 day longer ice free season

Local climatic drivers of changes in phenology at a boreal-temperate ecotone in eastern North America – Beier et al. (2012)

Abstract: “Ecosystems in biogeographical transition zones, or ecotones, tend to be highly sensitive to climate and can provide early indications of future change. To evaluate recent climatic changes and their impacts in a boreal-temperate ecotone in eastern North America, we analyzed ice phenology records (1975–2007) for five lakes in the Adirondack Mountains of northern New York State. We observed rapidly decreasing trends of up to 21 days less ice cover, mostly due to later freeze-up and partially due to earlier break-up. To evaluate the local drivers of these lake ice changes, we modeled ice phenology based on local climate data, derived climatic predictors from the models, and evaluated trends in those predictors to determine which were responsible for observed changes in lake ice. November and December temperature and snow depth consistently predicted ice-in, and recent trends of warming and decreasing snow during these months were consistent with later ice formation. March and April temperature and snow depth consistently predicted ice-out, but the absence of trends in snow depth during these months, despite concurrent warming, resulted in much weaker trends for ice-out. Recent rates of warming in the Adirondacks are among the highest regionally, although with a different seasonality of changes (early winter > late winter) that is consistent with other lake ice records in the surrounding area. Projected future declines in snow cover could create positive feedbacks and accelerate current rates of ice loss due to warming. Climate sensitivity was greatest for the larger lakes in our study, including Wolf Lake, considered one of the most ecologically intact ‘wilderness lakes’ in eastern North America. Our study provides further evidence of climate sensitivity of the boreal-temperate ecotone of eastern North America and points to emergent conservation challenges posed by climate change in legally protected yet vulnerable landscapes like the Adirondack Park.”

Citation: Colin M. Beier, John C. Stella, Martin Dovčiak and Stacy A. McNulty, Climatic Change, 2012, DOI: 10.1007/s10584-012-0455-z.

With 2007 wind, 2010 and 2011 would have reached record lows in Arctic summer sea ice extent

The role of summer surface wind anomalies in the summer Arctic sea ice extent in 2010 and 2011 – Ogi & Wallace (2012)

Abstract: “Strong summertime anticyclonic wind anomalies over the Arctic Ocean, with anomalous flow toward the Fram Strait, during summer months of 2007 contributed to the record-low the Arctic sea-ice extent observed in September of that year. Had the summer winds over the Arctic during the summers of 2010 and 2011 been the same as those in 2007, September sea ice extent would have reached new record lows in those years as well. By regulating the flow of ice toward and through the Fram Strait, variations in low-level winds over the Arctic have contributed to the month-to-month, year-to-year, and decade-to-decade variability of sea ice extent.”

Citation: Ogi, M. and J. M. Wallace (2012), The role of summer surface wind anomalies in the summer Arctic sea ice extent in 2010 and 2011, Geophys. Res. Lett., 39, L09704, doi:10.1029/2012GL051330.

Global warming is accompanied by amplification of the annual cycle of the climate system

What drives the global summer monsoon over the past millennium? – Liu et al. (2012) [FULL TEXT]

Abstract: “The global summer monsoon precipitation (GSMP) provides a fundamental measure for changes in the annual cycle of the climate system and hydroclimate. We investigate mechanisms governing decadal-centennial variations of the GSMP over the past millennium with a coupled climate model’s (ECHO-G) simulation forced by solar-volcanic (SV) radiative forcing and greenhouse gases (GHG) forcing. We show that the leading mode of GSMP is a forced response to external forcing on centennial time scale with a globally uniform change of precipitation across all monsoon regions, whereas the second mode represents internal variability on multi-decadal time scale with regional characteristics. The total amount of GSMP varies in phase with the global mean temperature, indicating that global warming is accompanied by amplification of the annual cycle of the climate system. The northern hemisphere summer monsoon precipitation (NHSMP) responds to GHG forcing more sensitively, while the southern hemisphere summer monsoon precipitation (SHSMP) responds to the SV radiative forcing more sensitively. The NHSMP is enhanced by increased NH land–ocean thermal contrast and NH-minus-SH thermal contrast. On the other hand, the SHSMP is strengthened by enhanced SH subtropical highs and the east–west mass contrast between Southeast Pacific and tropical Indian Ocean. The strength of the GSMP is determined by the factors controlling both the NHSMP and SHSMP. Intensification of GSMP is associated with (a) increased global land–ocean thermal contrast, (b) reinforced east–west mass contrast between Southeast Pacific and tropical Indian Ocean, and (c) enhanced circumglobal SH subtropical highs. The physical mechanisms revealed here will add understanding of future change of the global monsoon.”

Citation: Jian Liu, Bin Wang, So-Young Yim, June-Yi Lee, Jong-Ghap Jhun and Kyung-Ja Ha, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1360-x.

Growing season and freeze-free period are getting longer in Colorado at high elevation

Growing season expansion and related changes in monthly temperature and growing degree days in the Inter-Montane Desert of the San Luis Valley, Colorado – Mix et al. (2012)

Abstract: “Most climate change studies on high elevation ecosystems identify changes in biota, while several report abiotic factors. However, very few report expansion of the freeze-free period, or discuss monthly changes of temperature and growing degree days (GDD) during the growing season. This study provides initial data on agriculturally-related aspects of climate change during the growing season (M-J-J-A-S) in the inter-montane desert of the San Luis Valley (SLV), Colorado. Temperature data were gathered from 7 climate stations within the SLV. Based on ordinal days, the last vernal freeze is occurring (p < 0.05) earlier at 3 stations than in prior years, ranging between 5.52 and 11.86 days during 1981–2007. Significantly-later autumnal freezes are occurring at 5 stations by 5.95–18.10 days, while expansion of the freeze-free period was significantly longer at all stations by 7.20–24.21 days. The freeze-free period averaged about 93 days prior to the 1980s, but now averages about 107 days. Increases (p < 0.05) in daily mean, maximum, minimum temperature occurred at nearly all stations for each month. Increases in GDD10, GDD4.4 (potato) and GDD5.5 (alfalfa) also occurred at nearly all stations for all months during 1994–2007. Higher temperatures increase the number of GDD, quickening crop growth and maturity, and potentially reducing yield and quality unless varieties are adapted to changes and water is available for the season extension and increased evapotranspiration.”

Citation: Ken Mix, Vicente L. Lopes and Walter Rast, Climatic Change, 2012, DOI: 10.1007/s10584-012-0448-y.

Meteorological observations from 18th century Brazil

The meteorological observations of Bento Sanches Dorta, Rio de Janeiro, Brazil: 1781–1788 – Farrona et al. (2012)

Abstract: “Bento Sanches Dorta was an astronomer and geographer in the Portuguese colony of Rio de Janeiro in Brazil from 1781 to 1788. He recorded daily readings of meteorological and geomagnetic variables during that period. This dataset provides, to the best of our knowledge, the earliest known continuous 8-year-long instrumental meteorological observations for any South American site. His data show that the winters in this period were relatively cool, and that 1785 was the rainiest and hottest year, and 1787 the driest and coolest. The records display a distinct seasonal cycle and a variability that are comparable with the modern data.”

Citation: A. M. M. Farrona, R. M. Trigo, M. C. Gallego and J. M. Vaquero, Climatic Change, 2012, DOI: 10.1007/s10584-012-0467-8.

Spruce forest damaging bark beetle outbreaks are more severe in warmer climate

Climate affects severity and altitudinal distribution of outbreaks in an eruptive bark beetle – Marini et al. (2012)

Abstract: “Temperature warming and the increased frequency of climatic anomalies are expected to trigger bark beetle outbreaks with potential severe consequences on forest ecosystems. We characterized the combined effects of climatic factors and density-dependent feedbacks on forest damage caused by Ips typographus (L.), one of the most destructive pests of European spruce forests, and tested whether climate modified the interannual variation in the altitudinal outbreak range of the species. We analyzed a 16-year time-series from the European Alps of timber loss in Picea abies Karsten forests due to I. typographus attacks and used a discrete population model and an information theoretic approach to compare multiple competing hypotheses. The occurrence of dry summers combined with warm temperatures appeared as the main abiotic triggers of severity of outbreaks. We also found an endogenous negative feedback with a 2-year lag suggesting a potential important role of natural enemies. Forest damage per hectare averaged 7-fold higher where spruce was planted in sites warmer than those within its historical climatic range. Dry summers, but not temperature, was related to upward shifts in the altitudinal outbreak range. Considering the potential increased susceptibility of spruce forests to insect outbreaks due to climate change, there is growing value in mitigating these effects through sustainable forest management, which includes avoiding the promotion of spruce outside its historical climatic range.”

Citation: Lorenzo Marini, Matthew P. Ayres, Andrea Battisti and Massimo Faccoli, Climatic Change, DOI: 10.1007/s10584-012-0463-z.

Global warming might be responsible for recent weakening of East Asian summer monsoon

Recent weakening of northern East Asian summer monsoon: A possible response to global warming – Zhu et al. (2012)

Abstract: “We investigate the possible causes of the weakening of northern East Asian summer monsoon (EASM) from 1954 to 2010. We found that the decreased intensity of northern EASM as measured by a circulation index (EASMI) is significantly correlated with the increase of the surface air temperature (SAT) averaged over the Lake Baikal region (45°–65°N, 80°–130°E) defined as SATI. Corresponding to increasing SATI, an anomalous low-level anticyclone occurs with northeasterly prevailing over northern East Asia (30°–50°N,100°–130°E), resulting in a weakened southwesterly monsoon winds and drier climate in this region. Numerical experiments with the community atmosphere model version 3 (CAM3) show that the joint forcing induced by greenhouse gases (GHG), sea surface temperature (SST), solar radiance (SR), and volcano activity (VC) can replicate the observed trend of SATI and its related circulation anomalies, but without GHG forcing the model failed to simulate the warming trend of SATI after 1970s. This implies that the global warming is likely responsible for the local warming around the Lake Baikal, which in turn weakens the northern EASM in recent decades.”

Citation: Zhu, C., B. Wang, W. Qian, and B. Zhang (2012), Recent weakening of northern East Asian summer monsoon: A possible response to global warming, Geophys. Res. Lett., 39, L09701, doi:10.1029/2012GL051155.

Increased accuracy for mapping Antarctic iceberg distribution

Antarctic icebergs distributions, 2002–2010 – Tournadre et al. (2012)

Abstract: “Interest for icebergs and their possible impact on southern ocean circulation and biology has increased during the recent years. While large tabular icebergs are routinely tracked and monitored using scatterometer data, the distribution of smaller icebergs (less than some km) is still largely unknown as they are difficult to detect operationally using conventional satellite data. In a recent study, Tournadre et al. (2008) showed that small icebergs can be detected, at least in open water, using high resolution (20 Hz) altimeter waveforms. In the present paper, we present an improvement of their method that allows, assuming a constant iceberg freeboard elevation and constant ice backscatter coefficient, to estimate the top-down iceberg surface area and therefore the distribution of the volume of ice on a monthly basis. The complete Jason-1 reprocessed (version C) archive covering the 2002–2010 period has been processed using this method. The small iceberg data base for the southern ocean gives an unprecedented description of the small iceberg (100 m–2800 m) distribution at unprecedented time and space resolutions. The iceberg size, which follows a lognormal distribution with an overall mean length of 630 m, has a strong seasonal cycle reflecting the melting of icebergs during the austral summer estimated at 1.5 m/day. The total volume of ice in the southern ocean has an annual mean value of about 400 Gt, i.e., about 35% of the mean yearly volume of large tabular icebergs estimated from the National Ice Center database of 1979–2003 iceberg tracks and a model of iceberg thermodynamics. They can thus play a significant role in the injection of meltwater in the ocean. The distribution of ice volume which has strong seasonal cycle presents a very high spatial and temporal variability which is much contrasted in the three ocean basins (South Atlantic, Indian and Pacific oceans). The analysis of the relationship between small and large (>5 km) icebergs shows that a majority of small icebergs are directly associated with the large ones but that there are vast regions, such as the eastern branch of the Wedell Gyre, where the transport of ice is made only through the smaller ones.”

Citation: Tournadre, J., F. Girard-Ardhuin, and B. Legrésy (2012), Antarctic icebergs distributions, 2002–2010, J. Geophys. Res., 117, C05004, doi:10.1029/2011JC007441.

CLASSIC OF THE WEEK: Walker (1937)

World weather, VI – Walker (1937) [FULL TEXT]

Abstract: “The fluctuations of pressure, temperature, and rainfall in winter in the region of the North Atlantic had been studied as a connected system in the last paper of this series; and a similar system is now shown to hold in the spring, summer, and autumn. But the amount of persistence is small, so that the results are of little value for foreshadowing weather; nor does a consideration of the trade wind region lead to success in this respect. Similarly the Southern Oscillation which was found active in the summer and winter seasons over a large part of the globe is now shown to function in the two remaining seasons: and while that of March to May has little control over the following quarter, the Southern Oscillation of September to November has a correlation coefficient of .90 with the Oscillation of December to February. Thus there are a number of relationships of between .60 and .82 available for foreshadowing weather.”

Citation: Sir Gilbert T. Walker, 1937, Memoirs of the Royal Meteorological Society, Vol. IV, No. 39.

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