# Archive for September, 2012

## New research from last week 38/2012

Posted by Ari Jokimäki on September 24, 2012

This time we have papers relating to oceans: acidification, temperatures in past oceans, AMOC variability, and intermediate Atlantic water in Arctic Ocean. Other studies are about temperatures in Canada, clouds and precipitation of North America, small mammal ranges, nitrogen compounds, Arctic climate change, and there’s a separate section on other other studies.

### Amount of ocean acidification and climate sensitivity don’t go hand in hand

Decoupled response of ocean acidification to variations in climate sensitivity – Matsumoto & McNeil (2012)

Abstract: “It is now well understood that the global surface ocean, whose pH has been reduced by ~0.1 in response to rising atmospheric CO2 since industrialization, will continue to become more acidic as fossil fuel CO2 emissions escalate.  However, it is unclear how uncertainties in climate sensitivity to future CO2 emissions will alter the manifestation of ocean acidification.  Using an earth system model of intermediate complexity, we perform a set of simulations that varies equilibrium climate sensitivity by 1.0 to 4.5°C for a given CO2 emissions scenario and find two unexpected and decoupled responses.  Firstly, the greater the climate sensitivity, the larger the surface mixed layer acidification signal but the smaller the subsurface acidification. However, taken throughout the ocean, highest climate sensitivity will paradoxically cause greater global warming while buffering whole-ocean pH by up to 24% on centennial time-scales. Secondly, we find a large decoupling between pH and carbonate ion concentration in surface waters whereby these chemical properties show opposite effects under variable climate sensitivity.  For every 1°C increase in climate sensitivity, the surface ocean pH reduction grows by 4%, while surface ocean carbonate ion reduction shrinks by 2%. The chemical and spatial decoupling found here highlights the importance of distinguishing the biological impacts of pH and aragonite saturation and understanding the spatial extent of important calcifying biomes so as to truly understand the long-term impacts of ocean acidification.”

Citation: Katsumi Matsumoto, Ben McNeil, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00290.1.

A second generation of homogenized Canadian monthly surface air temperature for climate trend analysis – Vincent et al. (2012)

Abstract: “This study presents a second generation of homogenized monthly mean surface air temperature data set for Canadian climate trend analysis. Monthly means of daily maximum and of daily minimum temperatures were examined at 338 Canadian locations. Data from co-located observing sites were sometimes combined to create longer time series for use in trend analysis. Time series of observations were then adjusted to account for nation-wide change in observing time in July 1961, affecting daily minimum temperatures recorded at 120 synoptic stations; these were adjusted using hourly temperatures at the same sites. Next, homogeneity testing was performed to detect and adjust for other discontinuities. Two techniques were used to detect non-climatic shifts in de-seasonalized monthly mean temperatures: a multiple linear regression based test and a penalized maximal t test. These discontinuities were adjusted using a recently developed quantile-matching algorithm: the adjustments were estimated with the use of a reference series. Based on this new homogenized temperature data set, annual and seasonal temperature trends were estimated for Canada for 1950–2010 and Southern Canada for 1900–2010. Overall, temperature has increased at most locations. For 1950–2010, the annual mean temperature averaged over the country shows a positive trend of 1.5°C for the past 61 years. This warming is slightly more pronounced in the minimum temperature than in the maximum temperature; seasonally, the greatest warming occurs in winter and spring. The results are similar for Southern Canada although the warming is considerably greater in the minimum temperature compared to the maximum temperature over the period 1900–2010.”

Citation: Vincent, L. A., X. L. Wang, E. J. Milewska, H. Wan, F. Yang, and V. Swail (2012), A second generation of homogenized Canadian monthly surface air temperature for climate trend analysis, J. Geophys. Res., 117, D18110, doi:10.1029/2012JD017859.

### Reconstruction of vertical temperature gradients in past oceans

Reconstruction of vertical temperature gradients in past oceans – proxy data from the Hauterivian – early Barremian (Early Cretaceous) of the Boreal Realm – Mutterlose et al. (2012)

Abstract: “A total of 25 mudstone samples from two sections in northwest Germany and northeast England (palaeolatitude ~ 40°N), respectively, of Hauterivian and early Barremian age were analyzed using TEX86 palaeothermometry. In addition, the stable isotope ratio (δ18O, δ13C) and trace element content (Mg, Sr, Fe, and Mn) of 138 belemnite guards from the same two outcrops were determined to reconstruct past sea water temperatures. The TEX86 based sea surface temperatures were constantly warm (24–26 °C) throughout the entire Hauterivian for both sections and even warmer for the early Barremian (27-30 °C). Stable water temperatures prevailed over a period of ~ 6.4 Ma in the southernmost part of the Boreal Realm. These findings clearly support the view of warm equable conditions for the Hauterivian at least for mid latitudinal settings. A constant off-set between higher TEX86-derived temperatures and lower δ18OBel-derived temperatures was observed. This may be explained by either increased sea water salinities, a deep dwelling habitat of belemnites or a combination of both. A by 3‰ higher salinity of the sea water below the thermocline, which would at least partly explain the by ~ 2‰ too positive δ18OBel values, can not be ruled out in these epicontinental settings. A habitat of the belemnites below the thermocline in perhaps 50 – 100 m water depth may have contributed to the positive δ18OBel data as well. The temperature difference between the TEX86 and the δ18OBel findings might therefore reflect a vertical temperature gradient of the water column of 4-5 °C and a salinity of the subsurface waters of 38‰.”

Citation: Jörg Mutterlose, Matthias Malkoc, Stefan Schouten, Jaap S. Sinninghe Damsté, Palaeogeography, Palaeoclimatology, Palaeoecology, http://dx.doi.org/10.1016/j.palaeo.2012.09.006.

### Volcanic eruptions might be a pacemaker for variability of Atlantic Meridional Overturning Circulation

Initialisation and predictability of the AMOC over the last 50 years in a climate model – Swingedouw et al. (2012)

Abstract: “The mechanisms involved in Atlantic meridional overturning circulation (AMOC) decadal variability and predictability over the last 50 years are analysed in the IPSL–CM5A–LR model using historical and initialised simulations. The initialisation procedure only uses nudging towards sea surface temperature anomalies with a physically based restoring coefficient. When compared to two independent AMOC reconstructions, both the historical and nudged ensemble simulations exhibit skill at reproducing AMOC variations from 1977 onwards, and in particular two maxima occurring respectively around 1978 and 1997. We argue that one source of skill is related to the large Mount Agung volcanic eruption starting in 1963, which reset an internal 20-year variability cycle in the North Atlantic in the model. This cycle involves the East Greenland Current intensity, and advection of active tracers along the subpolar gyre, which leads to an AMOC maximum around 15 years after the Mount Agung eruption. The 1997 maximum occurs approximately 20 years after the former one. The nudged simulations better reproduce this second maximum than the historical simulations. This is due to the initialisation of a cooling of the convection sites in the 1980s under the effect of a persistent North Atlantic oscillation (NAO) positive phase, a feature not captured in the historical simulations. Hence we argue that the 20-year cycle excited by the 1963 Mount Agung eruption together with the NAO forcing both contributed to the 1990s AMOC maximum. These results support the existence of a 20-year cycle in the North Atlantic in the observations. Hindcasts following the CMIP5 protocol are launched from a nudged simulation every 5 years for the 1960–2005 period. They exhibit significant correlation skill score as compared to an independent reconstruction of the AMOC from 4-year lead-time average. This encouraging result is accompanied by increased correlation skills in reproducing the observed 2-m air temperature in the bordering regions of the North Atlantic as compared to non-initialized simulations. To a lesser extent, predicted precipitation tends to correlate with the nudged simulation in the tropical Atlantic. We argue that this skill is due to the initialisation and predictability of the AMOC in the present prediction system. The mechanisms evidenced here support the idea of volcanic eruptions as a pacemaker for internal variability of the AMOC. Together with the existence of a 20-year cycle in the North Atlantic they propose a novel and complementary explanation for the AMOC variations over the last 50 years.”

Citation: Didier Swingedouw, Juliette Mignot, Sonia Labetoulle, Eric Guilyardi and Gurvan Madec, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1516-8.

### Identifying uncertainties in Arctic climate change projections

Abstract: “Wide ranging climate changes are expected in the Arctic by the end of the 21st century, but projections of the size of these changes vary widely across current global climate models. This variation represents a large source of uncertainty in our understanding of the evolution of Arctic climate. Here we systematically quantify and assess the model uncertainty in Arctic climate changes in two CO2 doubling experiments: a multimodel ensemble (CMIP3) and an ensemble constructed using a single model (HadCM3) with multiple parameter perturbations (THC-QUMP). These two ensembles allow us to assess the contribution that both structural and parameter variations across models make to the total uncertainty and to begin to attribute sources of uncertainty in projected changes. We find that parameter uncertainty is an major source of uncertainty in certain aspects of Arctic climate. But also that uncertainties in the mean climate state in the 20th century, most notably in the northward Atlantic ocean heat transport and Arctic sea ice volume, are a significant source of uncertainty for projections of future Arctic change. We suggest that better observational constraints on these quantities will lead to significant improvements in the precision of projections of future Arctic climate change.”

Citation: Daniel L. R. Hodson, Sarah P. E. Keeley, Alex West, Jeff Ridley, Ed Hawkins and Helene T. Hewitt, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1512-z.

### Variation of NO2 and NOx concentrations between and within 36 European study areas

Variation of NO2 and NOx concentrations between and within 36 European study areas: Results from the ESCAPE study – Cyrys et al. (2012)

Abstract: “The ESCAPE study (European Study of Cohorts for Air Pollution Effects) investigates long-term effects of exposure to air pollution on human health in Europe. This paper documents the spatial variation of measured NO2 and NOx concentrations between and within 36 ESCAPE study areas across Europe. In all study areas NO2 and NOx were measured using standardized methods between October 2008 and April 2011. On average, 41 sites were selected per study area, including regional and urban background as well as street sites. The measurements were conducted in three different seasons, using Ogawa badges. Average concentrations for each site were calculated after adjustment for temporal variation using data obtained from a routine monitor background site. Substantial spatial variability was found in NO2 and NOx concentrations between and within study areas; 40% of the overall NO2 variance was attributable to the variability between study areas and 60% to variability within study areas. The corresponding values for NOx were 30% and 70%. The within-area spatial variability was mostly determined by differences between street and urban background concentrations. The street/urban background concentration ratio for NO2 varied between 1.09 and 3.16 across areas. The highest median concentrations were observed in Southern Europe, the lowest in Northern Europe. In conclusion, we found significant contrasts in annual average NO2 and NOx concentrations between and especially within 36 study areas across Europe. Epidemiological long-term studies should therefore consider different approaches for better characterization of the intra-urban contrasts, either by increasing of the number of monitors or by modelling.”

Citation: Josef Cyrys et al., Atmospheric Environment
Volume 62, December 2012, Pages 374–390, http://dx.doi.org/10.1016/j.atmosenv.2012.07.080.

### Ranges of small mammals extended northwards during Paleocene-Eocene Thermal Maximum

Northward range extension of a diminutive-sized mammal (Ectocion parvus) and the implication of body size change during the Paleocene-Eocene Thermal Maximum – Burger (2012)

Abstract: “An abrupt global warming event marks the Paleocene-Eocene boundary, known as the Paleocene-Eocene Thermal Maximum (PETM). The event is distinguished in the strata globally by a significant negative excursion of δ13C ratio values. The response of the terrestrial biota to the abrupt climatic change has been well studied in northern Wyoming in the Bighorn Basin, where it has been observed that the mammalian fauna during the global warming event is represented by smaller, but morphologically similar species to those found later in the Eocene. Various hypotheses have been proposed to explain the observation smaller body sizes during the global warming event. In this article, evidence is presented to support the hypothesis that the observed body size decrease during the PETM was influenced by the appearance of smaller southern species who extended their geographic range northward during the abnormal global warming event. Using disperse organic carbon isotopic ratios of bulk sediment, the negative excursion of δ13C was located in the Piceance Creek Basin of western Colorado, 400 kilometers to the south of the Bighorn Basin. Below the stratigraphic level marking the negative carbon excursion in the Piceance Creek Basin are five specimens of the phenacodontid mammal (Ectocion parvus), a diminutive species of the genus Ectocion restricted to the basal Eocene (Wa-0 Biozone) in northern Wyoming. The five specimens of Ectocion parvus are associated with a late Paleocene (Clarkforkian) mammalian fauna in Colorado, implying that the diminutive species extended its geographic range northward during the global warming event. This evidence supports biogeographic models that assume poleward biogeographic shifts during global warming events, and will have modern day implications for the conservation of species as global temperatures rise in the near future.”

Citation: Benjamin John Burger, Palaeogeography, Palaeoclimatology, Palaeoecology, http://dx.doi.org/10.1016/j.palaeo.2012.09.008.

### Intermediate Atlantic water in Arctic Ocean was exceptionally warm during 2000s

Warming of the intermediate Atlantic Water of the Arctic Ocean in the 2000s – Polyakov et al. (2012)

Abstract: “This analysis evaluates the thermal state of the intermediate (depth range: 150–900m) Atlantic Water (AW) of the Arctic Ocean, beginning in the 1950s and with particular focus on the transition from the 1990s to the 2000s and on changes during the 2000s. Using an extensive array of observations, we document AW warming trends across various time scales and demonstrate that the 2000s were exceptionally warm, with no analogy since the 1950s nor probably in the history of instrumental observations in the Arctic Ocean. Warming in the recent decade was dominated by a warm AW pulse in addition to the underlying trend. Since 1997, the Canadian Basin experienced faster warming rate compared with the Eurasian Basin. The relative role of the AW warmth in setting the net energy flux to, and mass balance of the Arctic sea ice is still under debate. Additional carefully orchestrated field experiments are required in order to address this question of on-going Arctic climate change.”

Citation: Igor V. Polyakov, Andrey V. Pnyushkov, and Leonid A. Timokhov, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00266.1.

### How clouds and precipitation affect North America summer temperature?

Changes in cloud cover, precipitation, and summer temperature in North America from 1982 to 2009 – Tang & Leng (2012)

Abstract: “In North America (NA), trends in summer surface air temperatures vary on decadal time scales, and some regions have temperature trends that exhibit a lack of warming in 1982-2009. From a surface energy balance perspective, the summer mean daily maximum temperature change can be affected by changes in solar heating that is associated with cloud cover change, and changes in surface evaporative cooling due to different precipitation and land surface wetness, but little is known about regional cloud cover and precipitation feedbacks to decadal temperature trends. Changes in cloudiness and precipitation and their connections with summer mean daily maximum temperature variations in NA were investigated using observation-based products of temperature and precipitation and satellite-derived cloud cover and radiation products. Results show that summer mean daily maximum temperature variance is largely explained by changes in cloud cover and precipitation. Cloud cover effect dominates at the high and middle latitudes of NA and precipitation is a more dominant factor in the southern United States. The results indicate that cloud cover is either the major indicator of the summer mean daily maximum temperature changes (the effect) or the important local factor influencing the changes (the cause). Cloud cover is negatively correlated with mean daily maximum temperature variation in spring and autumn at the middle latitudes of NA, but not at the high latitudes.”

Citation: Qiuhong Tang, Guoyong Leng, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00225.1.

### Some other studies from last week

Last Millennium Climate and Its Variability in CCSM4 – Landrum et al. (2012)

A simulated climatology of spectrally decomposed atmospheric infrared radiation – Huang (2012)

Effect of cloud cover and atmospheric circulation patterns on the observed surface solar radiation in Europe – Chiacchio & Vitolo (2012)

Continuous rice cropping has been sequestering carbon in soils in Java and South Korea for the past 30 years – Minasny et al. (2012)

Evolution of the global wind wave climate in CMIP5 experiments – Dobrynin et al. (2012)

Is there a 60-year oscillation in global mean sea level? – Chambers et al. (2012)

Linking the 8.2 ka event and its freshwater forcing in the Labrador Sea – Hoffman et al. (2012)

Tree-ring derived Little Ice Age temperature trends from the central British Columbia Coast Mountains, Canada – Pitman & Smith (2012)

Changes in African temperature and precipitation associated with degrees of global warming – James & Washington (2012)

### CLASSIC OF THE WEEK: Langley & Abbot (1900)

Abstract: No abstract. Among other things, gives historical view on solar spectrum research.

Citation: Langley, S., Abbot, C., Annals of the Astrophysical Observatory of the Smithsonian Institution, vol. 1, pp.7-21.

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 »

## New research from last week 37/2012

Posted by Ari Jokimäki on September 17, 2012

Arctic sea ice is on the news and shows up in new research papers quite often. This week’s batch has 3 papers on Arctic sea ice and a few others were also published on the subject last week. There is lot of climate research coming from China. Couple of papers here and couple of others got published last week. What else we have? Two papers on permafrost, two on growing season, and some others. Papers are presented below, check them out if you need your weekly climate science fix.

### How well regional climate model reproduces observed Arctic sea ice retreat?

Abstract: “The effects of internal model variability on the simulation of Arctic sea-ice extent and volume have been examined with the aid of a seven-member ensemble with a coupled regional climate model for the period 1948–2008. Beyond general weaknesses related to insufficient representation of feedback processes, it is found that the model’s ability to reproduce observed summer sea-ice retreat depends mainly on two factors: the correct simulation of the atmospheric circulation during the summer months and the sea-ice volume at the beginning of the melting period. Since internal model variability shows its maximum during the summer months, the ability to reproduce the observed atmospheric summer circulation is limited. In addition, the atmospheric circulation during summer also significantly affects the sea-ice volume over the years leading to a limited ability to start with reasonable sea-ice volume into the melting period. Furthermore, the sea-ice volume pathway shows notable decadal variability that varies in amplitude among the ensemble members. The scatter is particularly large in periods when the ice volume increases, indicating limited skill in reproducing high-ice years.”

Citation: Dorn, W., Dethloff, K., and Rinke, A.: Limitations of a coupled regional climate model in the reproduction of the observed Arctic sea-ice retreat, The Cryosphere, 6, 985-998, doi:10.5194/tc-6-985-2012, 2012.

### Local growing season length has increased globally almost a day per decade since 1901

Abstract: “Global warming exerts a lengthening effect on the growing season, with observational evidences emerging from different regions over the world. However, the difficulty for a global overview of this effect for the last century arises from limited availability of the long-term daily observations. In this study, we find a good linear relationship between the start (end) date of local growing season (LGS) and the monthly mean temperature in April (October) using the global gridded daily temperature dataset for 1960–1999. Using homogenized daily temperature records from nine stations where the time series go back to the beginning of the twentieth century, we find that the rate of change in the start (end) date of the LGS for per degree warming in April (October) mean temperature keeps nearly constant throughout the time. This enables us to study LGS changes during the last century using global gridded monthly mean temperature data. The results show that during the period 1901–2009, averaged over the observation areas, the LGS length has increased by a rate of 0.89 days decade−1, mainly due to an earlier start (−0.58 days decade−1). This is smaller than those estimates for the late half of the twentieth century, because of multidecadal climate variability (MDV). A MDV component of the LGS index series is extracted by using Ensemble Empirical Mode Decomposition method. The MDV exhibits significant positive correlation with the Atlantic Multi–decadal Oscillation (AMO) over most of the Northern Hemisphere lands, but negative in parts of North America and Western Asia for start date of LGS. These are explained by analyzing differences in atmospheric circulation expressed by sea level pressure departures between the warm and cool phases of AMO. It is suggested that MDV in association with AMO accelerates the lengthening of LGS in Northern Hemisphere by 53 % for the period 1980–2009.”

Citation: Jiangjiang Xia, Zhongwei Yan and Peili Wu, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1438-5.

### Later autumn freeze-up causes decline in spring snow depth on Arctic sea ice

Projected decline in spring snow depth on Arctic sea ice caused by progressively later autumn open ocean freeze-up this century – Hezel et al. (2012)

Abstract: “We present the first analysis of snow depths on Arctic sea ice in the Coupled Model Intercomparison Project 5 (CMIP5) because of its importance for sea ice thermodynamics and ringed seal ({\it Phoca hispida}) habitat. Snow depths in April on Arctic sea ice decrease over the 21st century in RCP2.6, RCP4.5, and RCP8.5 scenarios. The chief cause is loss of sea ice area in autumn and, to a lesser extent, winter. By the end of the 21st century in the RCP8.5 scenario, snowfall accumulation is delayed by about three months compared to the late 20th century in the multi-model mean. Mean April snow depth north of 70$^\circ$N declines from about 28 cm to 16 cm. Precipitation increases as expected in a warmer climate, but much of this increase in the Arctic occurs as rainfall. The seasonality of snowfall rate grows, with increasing rates in winter and decreasing rates in summer and autumn, but the cumulative snowfall from September to April does not change. Ringed seals depend on spring snow cover on Arctic sea ice to create subnivean birth lairs. The area with snow depths above 20 cm — a threshold needed for ringed seals to build snow caves — declines by 70\%.”

Citation: Hezel, P. J. J., X. Zhang, C. M. M. Bitz, B. P. Kelly, and F. Massonnet (2012), Projected decline in spring snow depth on Arctic sea ice caused by progressively later autumn open ocean freeze-up this century, Geophys. Res. Lett., doi:10.1029/2012GL052794.

### WMO rejects old record – highest ever recorded temperature is now from Death Valley, USA, 1913

Abstract: “On 13 September 1922, a temperature of 58°C (136.4°F) was purportedly recorded at El Azizia (approximately 40 kilometers south-southwest of Tripoli) in what is now modern-day Libya. That temperature record of 58°C has been cited by numerous world record sources as the highest recorded temperature for the planet. During 2010–2011, a World Meteorological Organization (WMO) Commission of Climatology (CCl) special international panel of meteorological experts conducted an in-depth investigation of this record temperature for the WMO World Archive of Weather and Climate Extremes (Cerveny et al., 2007a; Cerveny et al., 2007; Quetelard et al. 2009) (http://wmo.asu.edu/). This committee identified five major concerns with the 1922 El Azizia temperature extreme record, specifically (a) potentially problematical instrumentation, (b) a probable new and inexperienced observer at time of observation, (c) unrepresentative microclimate of the observation site, (d) poor correspondence of the extreme to other locations and (e) poor comparison to subsequent temperature values recorded at the site. Based on these concerns, the WMO World Archive of Weather and Climate Extremes has rejected this temperature extreme of 58°C as the highest temperature officially recorded on the planet. The WMO assessment is that the highest recorded surface temperature of 56.7°C (134°F) was measured on 10 July 1913 at Greenland Ranch (Death Valley) CA USA.”

Citation: Khalid Ibrahim El Fadli, Randall S. Cerveny, Christopher C. Burt, Philip Eden, David Parker, Manola Brunet, Thomas C. Peterson, Gianpaolo Mordacchini, Vinicio Pelino, Pierre Bessemoulin, José Luis Stella, Fatima Driouech, M.M Abdel wahab, Matthew B. Pace, Bulletin of the American Meteorological Society 2012, doi: http://dx.doi.org/10.1175/BAMS-D-12-00093.1.

### Heavy precipitation increase and light precipitation decrease are expected globally suggesting more floods and droughts

How much do precipitation extremes change in a warming climate? – Shiu et al. (2012)

Abstract: “Daily data from reanalyses of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) are analyzed to study changes in precipitation intensity with respect to global mean temperature. The results are in good agreement with those derived from the Global Precipitation Climatology Project (GPCP) data by Liu et al., [2009], providing an independent verification for large changes in the precipitation extremes: about 100% increase for the annual top 10% heavy precipitation and about 20% decrease for the light and moderate precipitation for one degree warming in the global temperature. These changes can substantially increase the risk of floods as well as droughts, thus severely affecting the global ecosystems. Atmospheric models used in the reanalysis mode, with the benefit of observed wind and moisture fields, appear to be capable of realistically simulating the change of precipitation intensity with global temperature. In comparison, coupled climate models are capable of simulating the shape of the change in precipitation intensity, but underestimate the magnitude of the change by about one order of magnitude. The most likely reason of the underestimation is that the typical spatial resolution of climate models is too coarse to resolve atmospheric convection.”

Citation: Shiu, C.-J., S. C. Liu, C. Fu, A. Dai, and Y. Sun (2012), How much do precipitation extremes change in a warming climate?, Geophys. Res. Lett., doi:10.1029/2012GL052762.

### Uncertainties in the evolution of tropical lower stratospheric ozone

Uncertainties in the evolution of stratospheric ozone and implications for recent temperature changes in the tropical lower stratosphere – Solomon et al. (2012)

Abstract: “Observations from satellites and balloons suggest that ozone abundances have decreased in the tropical lower stratosphere since the late 1970s, but this long-term change is occurring in a region of large interannual variability. Three different ozone databases provide regression fits to the ozone observations, and are available for use in model studies of the influence of ozone changes on stratospheric and tropospheric temperatures. Differences between these ozone databases suggest that the estimated decreases of tropical lower stratospheric ozone in recent decades are uncertain by about a factor of two to three. The uncertainties in ozone decreases lead to similar uncertainties in cooling of the tropical lower stratosphere, a key area of focus in climate change studies.”

Citation: Solomon, S., P. J. Young, and B. Hassler (2012), Uncertainties in the evolution of stratospheric ozone and implications for recent temperature changes in the tropical lower stratosphere, Geophys. Res. Lett., doi:10.1029/2012GL052723.

### Permafrost thawing reconstruction during last 170 years in east Siberia

A reconstruction of the thawing of the permafrost during the last 170 years on the Taimyr Peninsula (East Siberia, Russia) – Fedotov et al. (2012)

Abstract: “Reconstructing the temporal and spatial changes in climate on a seasonal basis during the past few centuries may help us better understand the modern-day interplay between natural and anthropogenic climate variability. The objective of this paper is to reconstruct the thawing of the permafrost at 71°N in Arctic Siberia during the termination of the Little Ice Age and the subsequent Recent Warming period. Sediment samples from two lakes on the Taimyr Peninsula were analysed by high-resolution X-ray fluorescence spectroscopy at a scan resolution of 1 mm, and pollen analyses were conducted. The depth-age models of the cores were constructed using 210Pb and 137Cs activity according to the constant rate of supply (CRS) model. The lake sediment cover of these lakes began to form ca. 1840. We defined three periods of increased permafrost thawing during the last 170 years. The first maximum of permafrost melting occurred from 1870 to 1880, the second episode was from 1900 to 1930 and the third began between 1960 and 1965. During these periods, the maxima of permafrost melting occurred with a specific time lag following.”

Citation: A.P. Fedotov, M.A. Phedorin, I.V. Enushchenko, K.E. Vershinin, M.S. Melgunov, T.V. Khodzher, A reconstruction of the thawing of the permafrost during the last 170 years on the Taimyr Peninsula (East Siberia, Russia), Global and Planetary Change, DOI: 10.1016/j.gloplacha.2012.09.002.

### Tropical cyclones might contribute to Arctic sea ice variability

Tropical cyclone effects on Arctic Sea ice variability – Scoccimarro et al. (2012)

Abstract: “In recent years increasing interest has been put on the role that intense Tropical Cyclones can play in the climate system. The following study is aimed at highlighting the effects of strong Tropical Cyclones over the Tropical Atlantic on the mean climate. Their composite effect on the surface winds is made apparent by a wide cyclonic perturbation that affects a large portion of the Atlantic tropical Ocean. Teleconnection patterns, which are visible in the Sea Level Pressure anomalies associated with this Tropical Composite Cyclone, appear to link the activity of the hurricanes to the Arctic Ocean. A significant negative correlation between the energy dissipated by hurricanes in the Tropical atmosphere and the sea ice cover along the Transpolar Drift Stream path, has also been found.”

Citation: Scoccimarro, E., S. Gualdi, and A. Navarra (2012), Tropical cyclone effects on Arctic Sea ice variability, Geophys. Res. Lett., 39, L17704, doi:10.1029/2012GL052987.

### Urban heat island has affected thermal growing season trends in east China

Thermal growing season trends in east China, with emphasis on urbanization effects – Yang et al. (2012)

Abstract: “Dense meteorological station network-derived data on daily surface air temperatures over the period 1961–2007 were used to investigate the changes in the thermal growing season (GS) indicators for east China. The 394 stations are classified into six categories: metropolises, large cities, medium-sized cities, small cities, suburbs, and rural area using satellite-measured night-time light imagery and census data. Only the temperature data on 258 small cities and rural stations were used to calculate the GS indicators to reflect more ‘natural’ changes in thermal GS parameters. During the studied period, the regional mean length of the GS significantly extended by 3.05 and 2.61 d decade−1 for base temperatures of 5 and 10 °C, respectively. This extension is attributed primarily to the GS initiating at an earlier time (2.49 and 2.10 d decade−1 for base temperatures of 5 and 10 °C, respectively), rather than to the delayed end of the GS (0.55 and 0.51 d decade−1 for base temperatures of 5 and 10 °C, respectively). The mean growing degree days (GDD) has increased by 51.84 and 35.89 degree days decade−1 on average at temperatures higher than 5 and 10 °C. When the temperature data from all the 394 stations(including metropolis, large city, medium city, and suburban) were used to calculate the GS indicators, urban heat island (UHI) effects were evident, especially in highly urbanized Yangtze River Delta. The GS extension and GDD increase in metropolises increased by more than onefold over those observed for rural areas. This result indicates significant UHI effects on climatic GS changes. On the basis of the GDD changes, we find that UHI effects contributed to more than 10% in the GDD increase at temperatures higher than 10 °C. Therefore, excluding the urbanization effects from station observational data in evaluating changes in GS indices is necessary, especially for regions characterized by rapid urbanization.”

Citation: Dr Xuchao Yang, Zhan Tian, Baode Chen, International Journal of Climatology, DOI: 10.1002/joc.3590.

### Climate might have contributed to the collapse of ancient Chinese city

The possible climate impact on the collapse of an ancient urban city in Mu Us Desert, China – Cui & Chang (2012)

Abstract: “Tongwan City is one of the most famous and best-researched archaeological sites in China. By using palaeoclimatology proxy records from China over the last 2,000 years and archaeological/historical documents, we analyse the possible effect of climate on the collapse of Tongwan City, an ancient urban city of the Daxia state (AD 407–427). During Tongwan City’s existence (AD 413–994), two severe cold and drought stages were recorded by both natural proxy data and the synthesis compiled from the historical documents. The first cold and drought stage occurred at about AD 420–550, with the lowest point centred at about AD 500. The second cold and drought stage occurred at about AD 780–950. These periods correspond to the times of climate deterioration, especially weak summer monsoons, which eventually resulted in the intensive desertification and collapse of Tongwan City.”

Citation: Jianxin Cui and Hong Chang, Regional Environmental Change, 2012, DOI: 10.1007/s10113-012-0345-y.

### Permafrost carbon release could lead to significant warming even under less intensive emissions trajectories

Significant contribution to climate warming from the permafrost carbon feedback – MacDougall et al. (2012)

Abstract: “Permafrost soils contain an estimated 1,700 Pg of carbon, almost twice the present atmospheric carbon pool. As permafrost soils thaw owing to climate warming, respiration of organic matter within these soils will transfer carbon to the atmosphere, potentially leading to a positive feedback. Models in which the carbon cycle is uncoupled from the atmosphere, together with one-dimensional models, suggest that permafrost soils could release 7–138 Pg carbon by 2100 (refs 3, 4). Here, we use a coupled global climate model to quantify the magnitude of the warming generated by the feedback between permafrost carbon release and climate. According to our simulations, permafrost soils will release between 68 and 508 Pg carbon by 2100. We show that the additional surface warming generated by the feedback between permafrost carbon and climate is independent of the pathway of anthropogenic emissions followed in the twenty-first century. We estimate that this feedback could result in an additional warming of 0.13–1.69 °C by 2300. We further show that the upper bound for the strength of the feedback is reached under the less intensive emissions pathways. We suggest that permafrost carbon release could lead to significant warming, even under less intensive emissions trajectories.”

Citation: Andrew H. MacDougall, Christopher A. Avis & Andrew J. Weaver, Nature Geoscience, 2012, doi:10.1038/ngeo1573.

### Global phenological response to climate change in crop areas

Global phenological response to climate change in crop areas using satellite remote sensing of vegetation, humidity and temperature over 26 years – Brown et al. (2012)

Abstract: “The recent increase in food prices has revealed that climate, combined with an expanding population and a widespread change in diet, may result in an end to an era of predictable abundance of global cereal crops. The objective of this paper is to estimate changes of agriculturally-relevant growing season parameters, including the start of the season, length of the growing period and the position of the height or peak of the season, in the primary regions with rainfed agriculture during the past 26 years. Our analysis found that globally, 27% of cereal crop areas have experienced changes in the length of the growing season since 1981, the majority of which had seasons that were at least 2.3 days per year longer on average. We also found both negative and positive trends in the start of season globally, with different effects of changing temperature and humidity being isolated depending on the country and region. We investigated the correlation between the peak timing of the growing season and agricultural production statistics for rain fed agriculture. We found that two thirds of the countries investigated had at least 25% of pixels with crop production that behaved differently than expected from the null hypothesis of no correlation. The results show that variations in the peak of the growing season have a strong effect on global food production in these countries. We show that northern hemisphere countries and states appear to have improved model fit when using phenological models based on humidity while southern hemisphere countries and states have improved model fit by phenological models based on accumulated growing degree days, showing the impact of climate variability during the past two and a half decades.”

Citation: M.E. Brown, K.M. de Beurs, M. Marshall, Remote Sensing of Environment, Volume 126, November 2012, Pages 174–183, http://dx.doi.org/10.1016/j.rse.2012.08.009.

### CLASSIC OF THE WEEK: Tolman (1899)

Abstract: No abstract.

Citation: Cyrus F. Tolman Jr., The Journal of Geology, Vol. 7, No. 6 (Sep. – Oct., 1899) (pp. 585-618).

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 »

## New research from last week 36/2012

Posted by Ari Jokimäki on September 10, 2012

I spent most of the last week cataloging all the surveys that didn’t send me an e-mail, but I did also have a peek on new research papers published last week. Some of them are presented below.

### Exceptionally hot summer frequency has increased in Central and Eastern Europe

Abstract: “The paper focuses on exceptionally hot summers (EHS) as a manifestation of contemporary climate warming. The study identifies EHS occurrences in Central and Eastern Europe and describes the characteristic features of the region’s thermal conditions. Average air temperatures in June, July and August were considered, as well as the number of days with maximum temperatures exceeding 25, 30 and 35 °C, and with a minimum temperature greater than >20 °C, as recorded at 59 weather stations in 1951–2010. Extremely hot summers are defined as having an average temperature equal to or greater than the long-term average plus 2 SD. A calendar of EHSs was compiled and their spatial extent identified. The region experienced 12 EHSs, which occurred in a given year at 5 % or more stations (1972, 1981, 1988, 1992, 1997, 1998, 1999, 2002, 2003, 2006, 2007 and 2010). The EHS frequency of occurrence was found to be clearly on an increase. Indeed, only one EHS occurred during the first 30 years, but these occurred five times during the last 10 years of the study period. Their geographical extent varied both in terms of location and size. EHSs were observed at 57 out of the total of 59 weather stations in the study (the exceptions were Pecora and Cluj). The average air temperature of EHSs tended to exceed the relevant long-term average by 2–4 °C. The summer of 2010 was among the hottest (temperature anomaly 5.5–6 °C) and spatially largest.”

Citation: Robert Twardosz and Urszula Kossowska-Cezak, Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0757-0.

### Inorganic carbon content of the top layer of soil in China’s grasslands has decreased

Widespread decreases in topsoil inorganic carbon stocks across China’s grasslands during 1980s-2000s – Yang et al. (2012)

Abstract: “Soil carbon (C) stocks consist of inorganic and organic components, ~ 1.7 times larger than the total of the C stored in vegetation and the atmosphere together. Significant soil C losses could thus offset any C sink in vegetation, creating a positive feedback to climate change. However, compared with the susceptible sensitivity of organic matter decay to climate warming, soil inorganic carbon (SIC) stocks are often assumed to be relatively stable. Here we evaluated SIC changes across China’s grasslands over the last two decades using data from a recent regional soil survey during 2001-2005 and historical national soil inventory during the 1980s. Our results showed that SIC stocks in the top 10 cm decreased significantly between the two sampling periods, with a mean rate of 26.8 (95%CI: 15.8-41.7) g C m-2 yr-1. The larger decreases in SIC stocks were observed in those regions with stronger soil acidification and richer soil carbonates. The lost SIC could be released to the atmosphere as carbon dioxide, redistributed to the deeper soil layer, and transferred to the nearby regions. The fraction of soil carbonates entering into the atmosphere may diminish the strength of terrestrial C sequestration and amplify the positive C-climate feedback.”

Citation: Yuanhe Yang, Jingyun Fang, Chengjun Ji, Wenhong Ma, Anwar Mohammat, Shifeng Wang, Shaopeng Wang, Arindam Datta, David Robinson, Pete Smith, Global Change Biology, DOI: 10.1111/gcb.12025.

### Watching the tropics grow

Abstract: “Historical radiosonde data are analyzed using the tropopause height frequency method to investigate the variation of the Southern Hemisphere tropical edge from 1979/80–2010/11, independently of reanalysis-derived data. Averaged across the hemisphere we identify a tropical expansion trend of 0.41 ± 0.37 deg dec−1, significant at the 90% level. A comparison with four reanalyses shows generally consistent results between radiosondes and reanalyses. Estimated rates of tropical expansion in the SH are broadly similar, as is the interannual variability. However, notable differences remain. Some of these differences are related to the methodology used to identify the height of the tropopause in the reanalyses, which produces inconsistent results in the subtropics. Differences between radiosondes and reanalyses are also more manifest in data-poor regions. In these regions, the reanalyses are not fully constrained, allowing the internal model dynamics to drive the variability. The performance of the reanalyses varies temporally compared to the radiosonde data. These differences are particularly apparent from 1979 to 1985 and from 2001 to 2010. In the latter period, we hypothesize that the increased availability and quality of satellite-based data improves the results from the ERA Interim reanalysis, creating an inconsistency with earlier data. This apparent inhomogeneity results in a tropical expansion trend in that product that is inconsistent with the radiosonde-based observations. These results confirm the need for careful evaluation of reanalysis-based data for use in studies of long-term climate variability.”

Citation: Lucas, C., H. Nguyen, and B. Timbal (2012), An observational analysis of Southern Hemisphere tropical expansion, J. Geophys. Res., 117, D17112, doi:10.1029/2011JD017033.

### Species abundances and distributions have changed in response to post-LIA and late twentieth century climate warming

Faunal (Chironomidae, Cladocera) responses to post-Little Ice Age climate warming in the high Austrian Alps – Nevalainen & Luoto (2012)

Abstract: “Present climate warming strongly affects limnological and ecological properties of lakes and may cause regime shifts that alter structure and function in the water bodies. Such effects are especially pronounced in climatologically extreme areas, e.g. at high altitudes. We examined a sediment core from Lake Oberer Landschitzsee, Austrian Alps, which spans the period from the Little Ice Age (LIA) to present. We investigated whether post-LIA climate warming altered aquatic invertebrate communities and limnological status in this sensitive high Alpine lake. Fossil Cladocera (Crustacea) and Chironomidae (Diptera) and organic matter in the core were analyzed. Chironomids were used to assess the lake’s benthic quality (i.e. oxygen availability). An instrumental Alpine temperature record was used to assess whether changes in the biotic assemblages correspond to post-LIA temperature trends. The planktonic and macro- and microbenthic invertebrate communities exhibit almost complete and simultaneous species turnover after the LIA, from about AD 1850 onward, when Sergentia coracina-type replaced oxyphilous Micropsectra contracta-type as the dominant macrobenthic taxon, and phytophilous Acroperus harpae outcompeted Alona affinis and Alona quadrangularis in the microbenthos. These directional community shifts corresponded with a period of reduced benthic quality, higher sediment organic content, and progressive climate warming, superimposed on Alpine land-use changes, until the early twentieth century. Detected changes suggest increased productivity and lower benthic oxygen availability. Faunal shifts were even more pronounced during the late twentieth century, simultaneous with enhanced warming. A new planktonic Cladocera species, Bosmina longirostris, typically absent from high Alpine lakes, colonized the lake and gradually became dominant toward the core top. Results show that post-LIA climate warming, coupled with increasing benthic and planktonic production, substantially altered the limnological and ecological status of this remote Alpine lake. Observed faunal turnovers provide evidence that temperature-driven ecological thresholds, whether associated directly or indirectly with greater human activity, have been crossed. Species abundances and distributions have changed in response to post-LIA and late twentieth century climate warming.”

Citation: Liisa Nevalainen and Tomi P. Luoto, Journal of Paleolimnology, 2012, DOI: 10.1007/s10933-012-9640-3.

### How much carbon has accumulated in long-lived products such as buildings and furniture?

Abstract: “A better understanding of the global carbon cycle as well as of climate change mitigation options such as carbon sequestration requires the quantification of natural and socioeconomic stocks and flows of carbon. A so-far under-researched aspect of the global carbon budget is the accumulation of carbon in long-lived products such as buildings and furniture. We present a comprehensive assessment of global socioeconomic carbon stocks and the corresponding in- and outflows during the period 1900–2008. These data allowed calculation of the annual carbon sink in socioeconomic stocks during this period. The study covers the most important socioeconomic carbon fractions, i.e. wood, bitumen, plastic and cereals. Our assessment was mainly based on production and consumption data for plastic, bitumen and wood products and the respective fractions remaining in stocks in any given year. Global socioeconomic carbon stocks were 2.3 GtC in 1900 and increased to 11.5 GtC in 2008. The share of wood in total C stocks fell from 97% in 1900 to 60% in 2008, while the shares of plastic and bitumen increased to 16% and 22%, respectively. The rate of gross carbon sequestration in socioeconomic stocks increased from 17 MtC yr−1 in 1900 to a maximum of 247 MtC yr−1 in 2007, corresponding to 2.2%–3.4% of global fossil-fuel-related carbon emissions. We conclude that while socioeconomic carbon stocks are not negligible, their growth over time is not a major climate change mitigation option and there is an only modest potential to mitigate climate change by the increase of socioeconomic carbon stocks.”

Citation: Christian Lauk et al 2012 Environ. Res. Lett. 7 034023 doi:10.1088/1748-9326/7/3/034023.

### Natural variability and mankind warmed sea surface which played vital role in extreme climate events of 2010

Climate extremes and climate change: The Russian heat wave and other climate extremes of 2010 – Trenberth & Fasullo (2012)

Abstract: “A global perspective is developed on a number of high impact climate extremes in 2010 through diagnostic studies of the anomalies, diabatic heating, and global energy and water cycles that demonstrate relationships among variables and across events. Natural variability, especially ENSO, and global warming from human influences together resulted in very high sea surface temperatures (SSTs) in several places that played a vital role in subsequent developments. Record high SSTs in the Northern Indian Ocean in May 2010, the Gulf of Mexico in August 2010, the Caribbean in September 2010, and north of Australia in December 2010 provided a source of unusually abundant atmospheric moisture for nearby monsoon rains and flooding in Pakistan, Colombia, and Queensland. The resulting anomalous diabatic heating in the northern Indian and tropical Atlantic Oceans altered the atmospheric circulation by forcing quasi-stationary Rossby waves and altering monsoons. The anomalous monsoonal circulations had direct links to higher latitudes: from Southeast Asia to southern Russia, and from Colombia to Brazil. Strong convection in the tropical Atlantic in northern summer 2010 was associated with a Rossby wave train that extended into Europe creating anomalous cyclonic conditions over the Mediterranean area while normal anticyclonic conditions shifted downstream where they likely interacted with an anomalously strong monsoon circulation, helping to support the persistent atmospheric anticyclonic regime over Russia. This set the stage for the “blocking” anticyclone and associated Russian heat wave and wild fires. Attribution is limited by shortcomings in models in replicating monsoons, teleconnections and blocking.”

Citation: Trenberth, K. E., and J. T. Fasullo (2012), Climate extremes and climate change: The Russian heat wave and other climate extremes of 2010, J. Geophys. Res., 117, D17103, doi:10.1029/2012JD018020.

### You can measure also other things from tree rings than width to estimate temperature

Secular temperature trends for the southern Rocky Mountains over the last five centuries – Berkelhammer & Stott (2012)

Abstract: “Pre-instrumental surface temperature variability in the Southwestern United States has traditionally been reconstructed using variations in the annual ring widths of high altitude trees that live near a growth-limiting isotherm. A number of studies have suggested that the response of some trees to temperature variations is non-stationary, warranting the development of alternative approaches towards reconstructing past regional temperature variability. Here we present a five-century temperature reconstruction for a high-altitude site in the Rocky Mountains derived from the oxygen isotopic composition of cellulose (δ18Oc) from Bristlecone Pine trees. The record is independent of the co-located growth-based reconstruction while providing the same temporal resolution and absolute age constraints. The empirical correlation between δ18Oc and instrumental temperatures is used to produce a temperature transfer function. A forward-model for cellulose isotope variations, driven by meteorological data and output from an isotope-enabled General Circulation Model, is used to evaluate the processes that propagate the temperature signal to the proxy. The cellulose record documents persistent multidecadal variations in δ18Oc that are attributable to temperature shifts on the order of 1°C but no sustained monotonic rise in temperature or a step-like increase since the late 19th century. The isotope-based temperature history is consistent with both regional wood density-based temperature estimates and some sparse early instrumental records.”

Citation: Berkelhammer, M. and L. D. Stott (2012), Secular temperature trends for the southern Rocky Mountains over the last five centuries, Geophys. Res. Lett., 39, L17701, doi:10.1029/2012GL052447.

### Negative climate change effects on Arctic thecosomes might show up well before ocean acidification effects

Synergistic effects of ocean acidification and warming on overwintering pteropods in the Arctic – Lischka & Riebesell (2012)

Abstract: “Ocean acidification and warming will be most pronounced in the Arctic Ocean. Aragonite shell-bearing pteropods in the Arctic are expected to be among the first species to suffer from ocean acidification. Carbonate undersaturation in the Arctic will first occur in winter and because this period is also characterized by low food availability, the overwintering stages of polar pteropods may develop into a bottleneck in their life cycle. The impacts of ocean acidification and warming on growth, shell degradation (dissolution), and mortality of two thecosome pteropods, the polar Limacina helicina and the boreal L. retroversa, were studied for the first time during the Arctic winter in the Kongsfjord (Svalbard). The abundance of L. helicina and L. retroversa varied from 23.5 to 120 ind m−2 and 12 to 38 ind m−2, and the mean shell size ranged from 920 to 981 μm and 810 to 823 μm, respectively. Seawater was aragonite-undersaturated at the overwintering depths of pteropods on two out of ten days of our observations. A seven-day experiment (temperature levels: 2 and 7°C, pCO2 levels: 350, 650 (only for L. helicina) and 880 μatm) revealed a significant pCO2 effect on shell degradation in both species, and synergistic effects between temperature and pCO2 for L. helicina. A comparison of live and dead specimens kept under the same experimental conditions indicated that both species were capable of actively reducing the impacts of acidification on shell dissolution. A higher vulnerability to increasing pCO2 and temperature during the winter season is indicated compared with a similar study from fall 2009. Considering the species winter phenology and the seasonal changes in carbonate chemistry in Arctic waters, negative climate change effects on Arctic thecosomes are likely to show up first during winter, possibly well before ocean acidification effects become detectable during the summer season.”

Citation: Silke Lischka, Ulf Riebesell, Global Change Biology, DOI: 10.1111/gcb.12020.

### Ozone depletion is important factor in lower stratospheric cooling

Abstract: “The effect of ozone depletion on temperature trends in the tropical lower stratosphere is explored with an atmospheric general circulation model, and directly contrasted to the effect of increased greenhouse gases and warmer sea surface temperatures. Confirming and extending earlier studies we find that, over the second half of the 20th Century, the model’s lower-stratospheric cooling caused by ozone depletion is several times larger than that induced by increasing greenhouse gases. Moreover, our model suggests that the response to different forcings is highly additive. Finally we demonstrate that when ozone depletion alone is prescribed in the model, the seasonal cycle of the resultant cooling trends in the lower stratosphere is quite similar to that recently reported in satellite and radiosonde observations: this constitutes strong, new evidence for the key role of ozone depletion on tropical lower-stratospheric temperature trends.”

Citation: Polvani, L. M., and S. Solomon (2012), The signature of ozone depletion on tropical temperature trends, as revealed by their seasonal cycle in model integrations with single forcings, J. Geophys. Res., 117, D17102, doi:10.1029/2012JD017719.

### Causal decoupling between total solar irradiance and global temperature has appeared since 1960s

Abstract: “The Sun has surely been a major external forcing to the climate system throughout the Holocene. Nevertheless, opposite trends in solar radiation and temperatures have been empirically identified in the last few decades. Here, by means of an inferential method—the Granger causality analysis—we analyze this situation and, for the first time, show that an evident causal decoupling between total solar irradiance and global temperature has appeared since the 1960s.”

Citation: Antonello Pasini et al 2012 Environ. Res. Lett. 7 034020, doi:10.1088/1748-9326/7/3/034020.

### Ice winter severity index in western Baltic region is modulated by solar activity

Solar forcing on the ice winter severity index in the western Baltic region – Leal-Silv & Velasco Herrera (2012)

Abstract: “The Sun is the fundamental energy sources of the Earth’s climate and therefore its variations can contribute to natural climate variations. In the present work we study the variability of ice winter severity index in the Baltic Sea since the 15th century and its possible connection with solar activity, based in a new method for finding and measuring amplitude-phase cross-frequency coupling in time series with a low signal/noise ratio, we suggests that the ice winter severity index in the Baltic Sea is modulated by solar activity and solar motion in several frequency bands during the last 500 yrs. According to our model a strong coupling between the decadal periodicity in the ice winter severity index time series and the secular periodicity of solar activity is present. We found that the ice winter severity index is strongly modulated by solar activity at the decadal periodicity. We also found that the 180 year periodicity of the Barycentre motion modulates the amplitudes of the decadal periodicity of solar activity and the Ice winter severity index. This method represents a useful tool for study the solar-terrestrial relationships.”

Citation: M.C. Leal-Silv, V.M. Velasco Herrera, Journal of Atmospheric and Solar-Terrestrial Physics, http://dx.doi.org/10.1016/j.jastp.2012.08.010.

### Transition to shrub-dominated Arctic may lead to net C loss if soil temperatures rise

Interactions among shrub cover and the soil microclimate may determine future Arctic carbon budgets – Cahoon et al. (2012)

Abstract: “Arctic and Boreal terrestrial ecosystems are important components of the climate system because they contain vast amounts of soil carbon (C). Evidence suggests that deciduous shrubs are increasing in abundance, but the implications for ecosystem C budgets remain uncertain. Using midsummer CO2 flux data from 21 sites spanning 16° of latitude in the Arctic and Boreal biomes, we show that air temperature explains c. one-half of the variation in ecosystem respiration (ER) and that ER drives the pattern in net ecosystem CO2 exchange across ecosystems. Woody sites were slightly stronger C sinks compared with herbaceous communities. However, woody sites with warm soils (> 10 °C) were net sources of CO2, whereas woody sites with cold soils (< 10 °C) were strong sinks. Our results indicate that transition to a shrub-dominated Arctic will increase the rate of C cycling, and may lead to net C loss if soil temperatures rise.”

Citation: Sean M. P. Cahoon, Patrick F. Sullivan, Gaius R. Shaver, Jeffrey M. Welker, Eric Post, Ecology Letters, DOI: 10.1111/j.1461-0248.2012.01865.x.

### Open access database of grape harvest dates for climate research

Abstract: “We present an open-access dataset of grape harvest dates (GHD) series that has been compiled from international, French and Spanish literature and from unpublished documentary sources from public organizations and from wine-growers. As of June 2011, this GHD dataset comprises 380 series mainly from France (93% of the data) as well as series from Switzerland, Italy, Spain and Luxemburg. The series have variable length (from 1 to 479 data, mean length of 45 data) and contain gaps of variable sizes (mean ratio of observations/series length of 0.74). The longest and most complete ones are from Burgundy, Switzerland, Southern Rhône valley, Jura and Ile-de-France. The most ancient harvest date of the dataset is in 1354 in Burgundy. The GHD series were grouped into 27 regions according to their location, to geomorphological and geological criteria, and to past and present grape varieties. The GHD regional composite series (GHD-RCS) were calculated and compared pairwise to assess their reliability assuming that series close to one another are highly correlated. Most of the pairwise correlations are significant (p-value < 0.001) and strong (mean pairwise correlation coefficient of 0.58). As expected, the correlations tend to be higher when the vineyards are closer. The highest correlation (R = 0.91) is obtained between the High Loire Valley and the Ile-de-France GHD-RCS. The strong dependence of the vine cycle on temperature and, therefore, the strong link between the harvest dates and the temperature of the growing season was also used to test the quality of the GHD series. The strongest correlations are obtained between the GHD-RCS and the temperature series of the nearest weather stations. Moreover, the GHD-RCS/temperature correlation maps show spatial patterns similar to temperature correlation maps. The stability of the correlations over time is explored. The most striking feature is their generalised deterioration at the late 19th–early 20th century. The possible effects on GHD of the phylloxera crisis, which took place at this time, are discussed. The median of all the standardized GHD-RCS was calculated. The distribution of the extreme years of this general series is not homogenous. Extremely late years all occur during a two-century long time window from the early 17th to the early 19th century, while extremely early years are frequent during the 16th and since the mid-19th century.”

Citation: Daux, V., Garcia de Cortazar-Atauri, I., Yiou, P., Chuine, I., Garnier, E., Le Roy Ladurie, E., Mestre, O., and Tardaguila, J.: An open-access database of grape harvest dates for climate research: data description and quality assessment, Clim. Past, 8, 1403-1418, doi:10.5194/cp-8-1403-2012, 2012.

### CLASSIC OF THE WEEK: Ross (1854)

Abstract: No abstract.

Citation: James Clark Ross, Philosophical Transactions of the Royal Society of London, Vol. 144, (1854) (pp. 285-296).

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 »

## New research from last week 35/2012

Posted by Ari Jokimäki on September 3, 2012

Cities are doing experiments and citizens are experiencing it. They deflate Polar cell and see what happens to Siperian High. Then they think about what to do next. Someone says, “I know, let’s inflate Hadley cell”. Everyone thinks it’s a good idea, and so they do it. They watch grassland grow and wonder what happens in Amazon area. They are bored with lab rats so they pour acid to oceans and watch what happens to corals. They change climate and see if spring damage increases enough to have an effect on woody plants. They use heaters on sea surface and watch ocean circulation to stop. They manipulate clouds with their aerosols.

Cool experiments, huh?

### Climate change mitigation experiments are going on in cities all over the world

A survey of urban climate change experiments in 100 cities – Broto & Bulkeley (2012)

Abstract: “Cities are key sites where climate change is being addressed. Previous research has largely overlooked the multiplicity of climate change responses emerging outside formal contexts of decision-making and led by actors other than municipal governments. Moreover, existing research has largely focused on case studies of climate change mitigation in developed economies. The objective of this paper is to uncover the heterogeneous mix of actors, settings, governance arrangements and technologies involved in the governance of climate change in cities in different parts of the world. The paper focuses on urban climate change governance as a process of experimentation. Climate change experiments are presented here as interventions to try out new ideas and methods in the context of future uncertainties. They serve to understand how interventions work in practice, in new contexts where they are thought of as innovative. To study experimentation, the paper presents evidence from the analysis of a database of 627 urban climate change experiments in a sample of 100 global cities. The analysis suggests that, since 2005, experimentation is a feature of urban responses to climate change across different world regions and multiple sectors. Although experimentation does not appear to be related to particular kinds of urban economic and social conditions, some of its core features are visible. For example, experimentation tends to focus on energy. Also, both social and technical forms of experimentation are visible, but technical experimentation is more common in urban infrastructure systems. While municipal governments have a critical role in climate change experimentation, they often act alongside other actors and in a variety of forms of partnership. These findings point at experimentation as a key tool to open up new political spaces for governing climate change in the city.”

Citation: Vanesa Castán Broto, Harriet Bulkeley, Global Environmental Change, http://dx.doi.org/10.1016/j.gloenvcha.2012.07.005.

### Qinghai-Tibetan grassland net primary production has increased significantly since 1961

Impacts of climate and CO2 changes on the vegetation growth and carbon balance of Qinghai-Tibetan grasslands over the past five decades – Piao et al. (2012)

Abstract: “Climate change has significantly influenced global and regional terrestrial carbon balances. After being systematically calibrated against eddy-covariance measurements, meteorological observation, soil inventory data and satellite observed LAI (Leaf Area Index) in the Qinghai-Tibetan plateau (Tan et al., 2010), the process-based ecosystem model called ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms) was used in this study to investigate climate change and rising atmospheric CO2 concentration driven spatio-temporal changes in vegetation net primary production (NPP) and net ecosystem production (NEP) of Qinghai-Tibetan grasslands from 1961 to 2009. Overall, our simulation suggests that Qinghai-Tibetan grassland NPP significantly increased with a rate of 1.9 Tg C yr– 2 (1 Tg = 1012 g) since 1961. At the regional scale, change in precipitation, temperature, and atmospheric CO2 concentration accounts for 52%, 34%, 39% of the increase in NPP, respectively, but their relative roles are not constant across the study area. Increase in NPP over central and southwestern Qinghai-Tibetan plateau is primarily attributed to precipitation changes, while rising atmospheric CO2 concentration is the main cause of NPP increase in eastern plateau. The model simulation also suggests that Qinghai-Tibetan grassland NEP increased from a net carbon source of − 0.5 Tg C yr– 1 in the 1960s to a net carbon sink of 21.8 Tg C yr– 1 in the 2000s, mainly due to the rising atmospheric CO2 concentration and precipitation change. Although recent climate warming benefited vegetation growth, rising temperature did not significantly accelerate net carbon uptake from Qinghai-Tibetan grassland ecosystems due to enhanced soil carbon decomposition accompanying increase in temperature.”

Citation: Shilong Piao, Kun Tan, Huijuan Nan, Philippe Ciais, Jingyun Fang, Tao Wang, Nicolas Vuichard, Biao Zhue, Global and Planetary Change, http://dx.doi.org/10.1016/j.gloplacha.2012.08.009.

### Amazon is more vulnerable to climate change due to actions of mankind

Amazon’s vulnerability to climate change heightened by deforestation and man-made dispersal barriers – Feeley & Rehm (2012)

Abstract: “Species migrations in response to climate change have already been observed in many taxonomic groups worldwide. However, it remains uncertain if species will be able to keep pace with future climate change. Keeping pace will be especially challenging for tropical lowland rainforests due to their high velocities of climate change combined with high rates of deforestation, which may eliminate potential climate analogs and/or increase the effective distances between analogs by blocking species movements. Here we calculate the distances between current and future climate analogs under various climate change and deforestation scenarios. Under even the most sanguine of climate change models (IPSL_CM4, A1b emissions scenario), we find that the median distance between areas in the Amazon rainforest and their closest future (2050) climate analog as predicted based on just temperature changes alone is nearly 300 km. If we include precipitation, the median distance increases by over 50% to >475 km. Since deforestation is generally concentrated in the hottest and driest portions of the Amazon, we predict that habitat loss will have little direct impact on distances between climate analogs. If, however, deforested areas also act as a barrier to species movements, nearly 30 or 55% of the Amazon will effectively have no climate analogs anywhere in tropical South America under projections of reduced or Business-As-Usual deforestation, respectively. These “disappearing climates” will be concentrated primarily in the southeastern Amazon. Consequently, we predict that several Amazonian ecoregions will have no areas with future climate analogs, greatly increasing the vulnerability of any populations or species specialized on these conditions. These results highlight the importance of including multiple climatic factors and human land-use in predicting the effects of climate change, as well as the daunting challenges that Amazonian diversity faces in the near future.”

Citation: Kenneth J. Feeley, Evan M. Rehm, Global Change Biology, DOI: 10.1111/gcb.12012.

### Area of Hadley cell has increased and area of Polar cell has decreased

Abstract: “Previous studies have shown that the mean latitude of the sub-tropical jet streams in both hemispheres have shifted toward the poles over the last few decades. This paper presents a study of the movement of both the subtropical and Polar fronts, the location of the respective jet streams, between 1979 and 2010 at mid-latitudes, using total ozone measurements to identify the sharp horizontal boundary that occurs at the position of the fronts. Previous studies have shown that the two fronts are the boundaries of three distinct regimes in the stratosphere, corresponding to the Hadley, Ferrel, and polar meridionally overturning circulation cells in the troposphere. Over the period of study the horizontal area of the Hadley cell has increased at latitudes between 20 and 60 degrees while the area of the Polar cell has decreased. A linear regression analysis was performed to identify the major factors associated with the movement of the subtropical jet streams. These were: (1) changes in the Tropical land plus ocean temperature, (2) direct radiative forcing from greenhouse gases in the troposphere, (3) changes in the temperature of the lower tropical stratosphere, (4) the Quasi-Biennial Oscillation, and (5) volcanic eruptions. The dominant mechanism was the direct radiative forcing from greenhouse gases. Between 1979 and 2010 the poleward movement of the subtropical jet streams was 3.7 ± 0.3 degrees in the Northern Hemisphere and 6.5 ± 0.2 degrees in the Southern Hemisphere. Previous studies have shown that weather systems tend to follow the jet streams. The observed poleward movement in both hemispheres over the past thirty years represents a significant change in the position of the sub-tropical jet streams, which should lead to significant latitudinal shifts in the global weather patterns and the hydrologic cycle.”

Citation: Hudson, R. D.: Measurements of the movement of the jet streams at mid-latitudes, in the Northern and Southern Hemispheres, 1979 to 2010, Atmos. Chem. Phys., 12, 7797-7808, doi:10.5194/acp-12-7797-2012, 2012.

### Ocean acidification reduces induction of coral settlement by crustose coraline algae

Ocean acidification reduces induction of coral settlement by crustose coraline algae – Webster et al. (2012)

Abstract: “Crustose coralline algae (CCA) are a critical component of coral reefs as they accrete carbonate for reef structure and act as settlement substrata for many invertebrates including corals. CCA host a diversity of microorganisms that can also play a role in coral settlement and metamorphosis processes. While the sensitivity of CCA to ocean acidification (OA) is well established, the response of their associated microbial communities to reduced pH and increased CO2 was previously unknown. Here we investigate the sensitivity of CCA-associated microbial biofilms to OA and determine whether OA adversely affects the ability of CCA to induce coral larval metamorphosis. We experimentally exposed the CCA Hydrolithon onkodes to four pH/pCO2 conditions consistent with current IPCC predictions for the next few centuries (pH: 8.1, 7.9, 7.7, 7.5, pCO2: 464, 822, 1187, 1638 μatm). Settlement and metamorphosis of coral larvae was reduced on CCA pre-exposed to pH 7.7 (pCO2 = 1187 μatm) and below over a six week period. Additional experiments demonstrated that low pH treatments did not directly affect the ability of larvae to settle, but instead most likely altered the biochemistry of the CCA or its microbial associates. Detailed microbial community analysis of the CCA revealed diverse bacterial assemblages that altered significantly between pH 8.1 (pCO2 = 464 μatm) and pH 7.9 (pCO2 = 822 μatm) with this trend continuing at lower pH/higher pCO2 treatments. The shift in microbial community composition primarily comprised changes in the abundance of the dominant microbes between the different pH treatments and the appearance of new (but rare) microbes at pH 7.5. Microbial shifts and the concomitant reduced ability of CCA to induce coral settlement under OA conditions projected to occur by 2100 is a significant concern for the development, maintenance and recovery of reefs globally.”

Citation: N.S. Webster, S. Uthicke, E. Botté, F. Flores, A.P. Negri, Global Change Biology, DOI: 10.1111/gcb.12008.

### Belief in experiencing global warming significantly predicts local risk perception

Do people “personally experience” global warming, and if so how, and does it matter? – Akerlof et al. (2012)

Abstract: “For most people, the direct and personally observable signals of climate change should be difficult to detect amid the variability of everyday weather. Yet, previous research has shown that some people believe they have personally experienced global warming. Through four related studies, our paper sheds light on what signals of global warming some people believe they are detecting, why, and whether or not it matters. These studies were conducted using population survey and climatic data from a single county in Michigan. Study 1 found that 27% of the county’s adult residents felt that they had personally experienced global warming. Study 2 – based on content analysis of people’s open-ended responses – found that the most frequently described personal experiences of global warming were changes in seasons (36%), weather (25%), lake levels (24%), animals and plants (20%), and snowfall (19%). Study 3 – based on NOAA climatic data – found that most, but not all, of these detected signals are borne out in the climatic record. Study 4 – using the survey data – found that personal experience of global warming matters in that it predicts perceptions of local risk of global warming, controlling for demographics, political affiliation, and cultural beliefs about national policy outcomes. We conclude that perceived personal experience of global warming appears to heighten people’s perception of the risks, likely through some combination of direct experience, vicarious experience (e.g., news media stories), and social construction.”

Citation: Karen Akerlof, Edward W. Maibach, Dennis Fitzgerald, Andrew Y. Cedeno, Amanda Neuman, Global Environmental Change, http://dx.doi.org/10.1016/j.gloenvcha.2012.07.006.

### Holocene climate variability in northern Italy was influenced by solar activity and NAO

Abstract: “Here we present high-resolution stable isotope and lamina thickness profiles as well as radiocarbon data for the Holocene stalagmite ER 76 from Grotta di Ernesto (north-eastern Italy), which was dated by combined U-series dating and lamina counting. ER 76 grew between 8 ka (thousands of years before 2000 AD) and today, with a hiatus from 2.6 to 0.4 ka. Data from nine meteorological stations in Trentino show a significant influence of the North Atlantic Oscillation (NAO) on winter temperature and precipitation in the cave region. Spectral analysis of the stable isotope signals of ER 76 reveals significant peaks at periods of 110, 60–70, 40–50, 32–37 and around 25 a. Except for the cycle between 32 and 37 a all periodicities have corresponding peaks in power spectra of solar variability, and the 25-a cycle may correspond to NAO variability. This suggests that climate variability in northern Italy was influenced by both solar activity and the NAO during the Holocene. Six periods of warm winter climate in the cave region were identified. These are centred at 7.9, 7.4, 6.5, 5.5, 4.9 and 3.7 ka, and their duration ranges from 100 to 400 a. The two oldest warm phases coincide with the deposition of sapropel S1 in the Mediterranean Sea indicating that the climate in the cave region was influenced by this prominent pluvial phase in the Mediterranean area. For the younger warm phases it is difficult to establish a supra-regional climate pattern, and some of them may, thus, reflect regional climate variability. This highlights the complexity of regional and supra-regional scale Holocene climate patterns.”

Citation: Scholz, D., Frisia, S., Borsato, A., Spötl, C., Fohlmeister, J., Mudelsee, M., Miorandi, R., and Mangini, A.: Holocene climate variability in north-eastern Italy: potential influence of the NAO and solar activity recorded by speleothem data, Clim. Past, 8, 1367-1383, doi:10.5194/cp-8-1367-2012, 2012.

### Sea surface has warmed and upper-layer circulation has weakened during winters in South China Sea

Trends of upper-layer circulation in the South China Sea during 1959–2008 – Yang & Wu (2012)

Abstract: “In this paper, the trend of upper-layer circulation in the South China Sea (SCS) is studied based on the Simple Ocean Data Assimilation product for 1959–2008. It is found that the basin-averaged SST in winter displays a warming rate close to the global mean value while it does not have significant trend in summer. The upper-layer circulation in the SCS has been weakened in winter by 10% over this period, while in summer it tends to be more energetic. Further analyses suggest that the weakening of the winter SCS ocean circulation in winter is associated with weakening of the East Asian monsoon over recent decades. Moreover, an eastward retreat of the anti-cyclonic “Kuroshio loop” from the SCS is found, which may be due to an intensification of the Kuroshio transport in the past 50 years.”

Citation: Yang, H., and L. Wu (2012), Trends of upper-layer circulation in the South China Sea during 1959–2008, J. Geophys. Res., 117, C08037, doi:10.1029/2012JC008068.

### Spring damage risk for woody plants is increasing due to climate change in Illinois, USA

Reconstructing patterns of temperature, phenology, and frost damage over 124 years – spring damage risk is increasing – Augspurger (2012)

Abstract: “Climate change with both warmer spring temperatures and greater temperature fluctuations has altered phenologies, possibly leading to greater risk of spring frost damage to temperate deciduous woody plants. Phenological observations of 20 woody species from 1993-2012 in Trelease Woods, Champaign Co., Illinois, USA were used to identify years with frost damage to vegetative and reproductive phases. Local temperature records were used in combination with the phenological observations to determine what combinations of the two were associated with damage. Finally, a long-term temperature record (1889-1992) was evaluated to determine if the frequency of frost damage has risen in recent decades. Frost {less than or equal to} -1.7 ºC occurred after bud-break in 14 of the 20 years of observation. Frost damage occurred in five years in the interior and in three additional years at only the forest edge. The degree of damage varied with species, life stage, tissue (vegetative or reproductive), and phenological phase. Common features associated with the occurrence of damage to interior plants were (1) a period of unusual warm temperatures in March, followed by (2) a frost event in April with a minimum temperature {less than or equal to} -6.1˚C with (3) a period of 16 – 33 days between the extremes. In the long-term record, 10 of 124 years met these conditions, but the yearly probability of frost damage increased significantly, from 0.03 from 1889-1979 to 0.21 from 1980-2012. When the criteria were ‘softened’ to {less than or equal to} -1.7 ˚C in April and an interval of 16 – 37 days, 31 of 124 years met the conditions, and the yearly damage probability increased significantly to 0.19 from 1889-1979 to 0.42 from 1980-2012. In this forest, the combination of warming trends and temperature variability (extremes) associated with climate change is having ecologically important effects, making previously rare frost damage events more common.”

Citation: LiAugspurger, Carol K. Reconstructing patterns of temperature, phenology, and frost damage over 124 years – spring damage risk is increasing. Ecology. http://dx.doi.org/10.1890/12-0200.1.

### Siberian High makes temperature of arid region of northwest China rise faster

Why does the temperature rise faster in the arid region of northwest China? – Li et al. (2012)

Abstract: “During 1960–2010, the air temperature in the arid region of northwest China had a significant rising trend (P < 0.001), at a rate of 0.343°C/decade, higher than the average of China (0.25°C/decade) and that of the entire globe (0.13°C/decade) for the same period. Based on the analysis of the data from 74 meteorological stations in the region for 1960–2010, we found that among the four seasons the temperature change of winter has been playing the most important role in the yearly change in this region. We also found that the winter temperature in this region has a strong association with the Siberian High (correlation coefficient: R = −0.715) and the greenhouse gas emission (R = 0.51), and between the two the former is stronger. We thus suggest that the weakening of the Siberian High during the 1980s to 1990s on top of the steady increasing of the greenhouse emission is the main reason for the higher rate of the temperature rise in the arid region of the northwest China.”

Citation: Li, B., Y. Chen, and X. Shi (2012), Why does the temperature rise faster in the arid region of northwest China?, J. Geophys. Res., 117, D16115, doi:10.1029/2012JD017953.

### Indirect aerosol forcing – mankind affects climate also through clouds

Anthropogenic radiative forcing of marine stratocumulus clouds under different thermodynamic conditions—An LES model study – Song & Yum (2012)

Abstract: “A LES model with bin microphysics was used to investigate the aerosol indirect effects of marine stratocumulus clouds that develop under different thermodynamic conditions. The diurnal contrasts of cloud development were also examined in detail. Three observed CCN spectra that represent maritime, continental and polluted air masses were used as input CCN spectra. Two observed thermodynamic soundings and two derived ones from the observed soundings to vary the inversion altitude were used as initial thermodynamic conditions. With these initial conditions the model was run for the daytime and nocturnal conditions to make the total number of model runs to be 24. For both daytime and nocturnal conditions, the cloud depth and liquid water path (LWP) varied with the thermodynamic soundings. For a given thermodynamic sounding, LWP tended to be similar or slightly smaller for polluted. However, cloud top radiative cooling is stronger for polluted due to smaller sizes of cloud droplets and therefore turbulent mixing is stronger for polluted. However, there were significant differences in LWP between the daytime and nocturnal clouds. For the daytime condition, the cloud became decoupled from the surface layer and moisture supply was limited for all soundings. In contrast, with the absence of solar radiation, cloud top radiative cooling was much stronger, turbulent mixing was also much stronger and therefore no decoupling occurred and clouds were thicker with greater LWP in the nocturnal runs. To note is the derived thermodynamic sounding (named MH) that produced the thickest clouds: the clouds were too thick to be maintained as a single layer cloud and became multi-layered for the daytime condition while the maritime stratocumulus cloud broke up into a cumuliform cloud due to heavy drizzle for the nocturnal condition. From the daytime run results, the anthropogenic cloud radiative forcing was calculated by subtracting the net cloud radiative forcing for maritime from that for polluted. It amounted to be − 21.6 W m− 2 for MH but was more than a factor of two larger for all three other soundings, − 56.4, − 55.4 and − 55.7 W m− 2. For the MH sounding, the LWP was noticeably smaller for polluted than for maritime, the relative difference of the effective radii between maritime and polluted was small and therefore albedo difference between the two was also small, compared to those for the other three soundings. Notable is the similar magnitude of the anthropogenic cloud radiative forcing for these three soundings despite the significant differences in cloud depths among the clouds produced by these soundings. This may imply that there may be an optimal range of cloud depth that can produce a strong anthropogenic cloud radiative forcing. The cloud depths were smaller than 150 m for the thermodynamic sounding that produced the shallowest clouds but it seemed to be within the optimal range.”

Citation: Keunyong Song, Seong Soo Yum, Atmospheric Research, Volume 118, 15 November 2012, Pages 370–389, http://dx.doi.org/10.1016/j.atmosres.2012.07.018.

### Deep Arctic Ocean was warmer than today during the last glacial cycle due to ocean circulation conditions

Deep Arctic Ocean warming during the last glacial cycle – Cronin et al. (2012)

Abstract: “In the Arctic Ocean, the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier Atlantic Layer by a halocline. Ongoing sea ice loss and warming in the Arctic Ocean have demonstrated the instability of the halocline, with implications for further sea ice loss. The stability of the halocline through past climate variations is unclear. Here we estimate intermediate water temperatures over the past 50,000 years from the Mg/Ca and Sr/Ca values of ostracods from 31 Arctic sediment cores. From about 50 to 11 kyr ago, the central Arctic Basin from 1,000 to 2,500 m was occupied by a water mass we call Glacial Arctic Intermediate Water. This water mass was 1–2 °C warmer than modern Arctic Intermediate Water, with temperatures peaking during or just before millennial-scale Heinrich cold events and the Younger Dryas cold interval. We use numerical modelling to show that the intermediate depth warming could result from the expected decrease in the flux of fresh water to the Arctic Ocean during glacial conditions, which would cause the halocline to deepen and push the warm Atlantic Layer into intermediate depths. Although not modelled, the reduced formation of cold, deep waters due to the exposure of the Arctic continental shelf could also contribute to the intermediate depth warming.”

Citation: T. M. Cronin, G. S. Dwyer, J. Farmer, H. A. Bauch, R. F. Spielhagen, M. Jakobsson, J. Nilsson, W. M. Briggs Jr & A. Stepanova, Nature Geoscience, 2012, doi:10.1038/ngeo1557.

### CLASSIC OF THE WEEK: Ångström (1949)

Abstract: No abstract. Like the name says, paper goes through Swedish meteorological research. Also climate research is included.

Citation: Anders Ångström, Tellus, Volume 1, Issue 1, pages 60–64, February 1949, DOI: 10.1111/j.2153-3490.1949.tb01930.x.

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