# AGW Observer

## 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.