New research from last week 48/2012
Posted on 3 December 2012 by Ari Jokimäki
Sometimes in the past western Greenland was warmer than today! There has been increasingly warm summers in Euro-Mediterranean region - is this due to increasing solar radiation observed in Spain? There's an increasing need of dusting in Tibetan Plateau due to warming, which by the way is proceeding globally just as expected from GHG-cause. We also look at Fijian corals, vegetation response to climate, and an example of climate caused collapse of prehistoric human society. Check out also the 25 other studies if you want to know some other things, such as the impact of precipitation on vehicle speeds on UK motorways, or storm of November 1724.
Peak Holocene warmth was 2-3K warmer than today in western Greenland
Highlights:► This paper presents five Holocene lake records from west Greenland. ► Chironomids provide quantitative estimates of summer air temperature anomalies. ► Peak Holocene warmth occurred from 6 to 4 ka, with temperatures 2–3° warmer than today. ► A transient climate change is recorded at all five study sites ∼4.2 ka. ► The inferred paleotemperature history agrees well with local glacial geologic records.
Abstract:"Predicting the response of the Greenland Ice Sheet to future climate change presents a major challenge to climate science. Paleoclimate data from Greenland can provide empirical constraints on past cryospheric responses to climate change, complementing insights from contemporary observations and from modeling. Here we examine sedimentary records from five lakes near Jakobshavn Isbræ in central West Greenland to investigate the timing and magnitude of major Holocene climate changes, for comparison with glacial geologic reconstructions from the region. A primary objective of this study is to constrain the timing and magnitude of maximum warmth during the early to middle Holocene positive anomaly in summer insolation. Temperature reconstructions from subfossil insect (chironomid) assemblages suggest that summer temperatures were warmer than present by at least 7.1 ka (the beginning of the North Lake record; ka = thousands of years before present), and that the warmest millennia of the Holocene occurred in the study area between 6 and 4 ka. Previous studies in the Jakobshavn region have found that the local Greenland Ice Sheet margin was most retracted behind its present position between 6 and 5 ka, and here we use chironomids to estimate that local summer temperatures were 2–3 °C warmer than present during that time of minimum ice sheet extent. As summer insolation declined through the late Holocene, summer temperatures cooled and the local ice sheet margin expanded. Gradual, insolation-driven millennial-scale temperature trends in the study area were punctuated by several abrupt climate changes, including a major transient event recorded in all five lakes between 4.3 and 3.2 ka, which overlaps in timing with abrupt climate changes previously documented around the North Atlantic region and farther afield at ∼4.2 ka."
Citation: Yarrow Axford, Shanna Losee, Jason P. Briner, Donna R. Francis, Peter G. Langdon, Ian R. Walker, Quaternary Science Reviews, Volume 59, 3 January 2013, Pages 87–100, http://dx.doi.org/10.1016/j.quascirev.2012.10.024.
Warming seems make Tibetan Plateau dustier
Highlights:► We provide the Tanggula ice core record during 1850–2004 A.D. ► The 1860–1874 and 1930–1954 are two high dust flux periods. ► Dust flux increased since 1960 within warming perspective. ► High dust is correlated with strengthened westerlies over the Tibetan Plateau and low pressure in the source regions. ► Warming seems make Tibetan Plateau dustier.
Abstract:"The dustiness on the remote Tibetan Plateau and its trend within the ongoing global warming perspective are not well understood. In this study, we present the detailed dust history from 1850 to 2004 AD on an annual timescale from a shallow ice core from Tanggula, central Tibetan Plateau. Two periods of strong dustiness, one at the end of the Little Ice Age (1860–1874) and the other during the period 1930–1954, occurred during low oxygen isotope stage, which is correlated with temperature on multi-year and decadal timescales. The extremely high level of dust flux between 1860 and 1874 was unique – this level has not occurred again during the past century, and the 1930s' dustiness was characterized more by strong wind and dust storms rather than drought, as shown by great grain size but low dust flux. We have used the composite analysis of modern meteorological data to study the possible dustiness mechanism and found that strengthened high-level westerlies over the Tibetan Plateau and intensified low pressure activities in the upward potential source regions, such as Tarim Basin, are the possible causes for high dust flux in Tanggula. Those results have revealed that although the dustiness on the Tibetan Plateau normally occurs in cold conditions, pronounced warming since the 1960s can change the dust pattern and strengthen the dustiness in this remote and high-altitude region, and can thus induce associated environmental issues by creating dustier conditions."
Citation: Guangjian Wu, Chenglong Zhang, Baiqing Xu, Rui Mao, Daniel Joswiak, Ninglian Wang, Tandong Yao, Quaternary Science Reviews, Volume 59, 3 January 2013, Pages 57–66, http://dx.doi.org/10.1016/j.quascirev.2012.10.003.
Increasing solar radiation in Spain suggests decrease of clouds and/or aerosols
Highlights:► We develop a new dataset of surface solar radiation records in Spain. ► The global and diffuse solar radiation series have been homogenized. ► The global solar radiation shows a significant increase over the 1985-2010 period. ► The diffuse component shows a significant decrease during the same period. ► These results point towards a recent decrease of clouds and/or aerosols.
Abstract: "There is a growing interest in the study of decadal variations in surface solar radiation during the last decades, although the analyses of long-term time series in some areas with major gaps in observations, such as in Spain, is still pending. This work describes for the first time the development of a new dataset of surface solar radiation in Spain based on the longest series with records of global solar radiation (G), most of them starting in the early 1980s. Additional records of diffuse solar radiation (D), which is a component of G much less studied due to the general scarcity of long-term series, are available for some of these series. Particular emphasis is placed upon the homogenization of this data set in order to ensure the reliability of the trends, which can be affected by non-natural factors such as relocations or changes of instruments. The mean annual G series over Spain shows a tendency to increase during the 1985-2010 period, with a significant linear trend of + 3.9 Wm- 2 per decade. Similar significant increases are observed in the mean seasonal series, with the highest rate of change during summer (+ 6.5 Wm- 2 per decade) and secondly in autumn (+ 4.1 W m- 2 per decade) and spring (+ 3.2 Wm- 2 per decade). These results are in line with the widespread increase of G, also known as brightening period, reported at many worldwide observation sites. Furthermore, the annual mean D series starts without relevant variations during the second half of the 1980s, but it is disturbed by a strong increase in 1991 and 1992, which might reflect the signal of the Pinatubo volcanic eruption. Afterwards, the mean series shows a tendency to decrease up to the mid-2000s, with a significant linear trend of -2.1 Wm- 2per decade during the 1985-2010 period. All these results point towards a diminution of clouds and/or aerosols over the area."
Citation: A. Sanchez-Lorenzo, J. Calbó, M. Wild, Global and Planetary Change, http://dx.doi.org/10.1016/j.gloplacha.2012.11.010.
Increasingly warm summers in the Euro–Mediterranean zone
Abstract:"The recent increase in European temperatures led to a strong enhancement in the occurrence of extremely warm events, with relevant consequences for environment and everyday life. Here, we investigate the evolution of very intense warm and cold events in a south-western European zone during 1961–2007 at a seasonal level. Special attention is given to summertime when warming is the most pronounced. Using a previously developed theoretical model, we discuss how the average properties and long-term trends observed in probability density functions of daily temperatures can explain changes in the frequency of severe, isolated events. In this perspective, the recent intensification of extremely warm events, especially experienced by the Mediterranean zone, is proved to be well consistent with a pure shift of seasonal mean temperatures. On the other hand, any change in the second and higher distributional moments of daily temperatures is ruled out by the data, whereas the average values of these properties, that is, variability and asymmetry, do play a role by shaping the temporal behavior of very intense events."
Citation: Claudia Simolo, Michele Brunetti, Maurizio Maugeri, Teresa Nanni, Regional Environmental Change, November 2012, DOI: 10.1007/s10113-012-0373-7.
Atmospheric carbon-13 Suess Effect shows in Fijian corals
Highlights: ► Long-term decreasing trend in coral δ13C is due to the atmospheric 13C Suess Effect. ► Fiji Porites corals growing at deeper water depths have lower mean δ13C. ► Fiji Porites corals growing at deeper water depths have lower skeletal extension rate rate. ► The growth of corals into shallower water with time dampens the δ13C trend. ► The trend in coral δ13C lags the trend in atmospheric CO2 δ13C by ~ 10 years.
Abstract: "In the context of increasing anthropogenic CO2 emissions, determing the rate of oceanic CO2 uptake is of high interest. Centennial-scale changes in δ13C of the surface water dissolved inorganic carbon (DIC) reservoir have been shown to be influenced by the carbon isotopic composition of atmospheric CO2. However, the avalability of direct oceanic δ13C measurments is limited and methods for reconstructing past δ13C variability of the oceanic DIC are needed. Geochemical reconstructions of DIC variability can help in understanding how the ocean has reacted to historical changes in the carbon cycle. This study explores the potential of using temporal variations in δ13C measured in five Fijian Porites corals for reconstructing oceanic δ13C variability. A centennial-scale decreasing δ13C trend is observed in these Fiji corals. Other studies have linked similar decreasing δ13C trends to anthropogenic changes in the atmospheric carbon reservoir (the “13C Suess Effect”). In the Fiji corals, whereas we conclude that solar irradiance is the factor influencing the δ13C cycle on seasonal scale, it is not responsible for the centennial scale δ13C decreasing trend. In addition, variations in skeletal extension rate are not found to account for centennial-scale δ13C variability in these corals. Rather, we found that water depth at which a Fijian Porites colony calcifies influences both δ13C and extension rate mean values. The water depth-δ13C relationship induces a dampening effect on the centennial-scale decreasing δ13C trend. We removed this water depth effect from the δ13C composite, resulting in a truer representation of δ13C variability of the Fiji surface water DIC (δ13C Fiji-DIC). The centennial trend in this Fiji coral composite δ13C Fiji-DIC time-serie, shares similarities with atmospheric δ13CCO2, implicating the 13C Suess effect as the source of the this coral δ13C trend. Additionaly, our study found that the δ13C variability between the atmosphere and the ocean in this region is not synchronous; the coral δ13C response is delayed by ~ 10 years. This agrees with the model of the isotopic disequilibrium between atmospheric δ13CCO2and oceanic surface water DIC."
Citation: Emilie P. Dassié, Gavin M. Lemley, Braddock K. Linsley, Palaeogeography, Palaeoclimatology, Palaeoecology, http://dx.doi.org/10.1016/j.palaeo.2012.11.012.
Phenology is important factor in vegetation feedbacks to climate system
Highlights:► The sensitivity of vegetation phenology to climate change varies among biomes. ► Key weaknesses in our current understanding of phenology drivers are identified. ► Phenology controls many feedbacks of vegetation to the climate system. ► The size and seasonality of these feedbacks will shift as phenology shifts. ► Models that couple the land surface to the climate system need better phenology.
Abstract: "Vegetation phenology is highly sensitive to climate change. Phenology also controls many feedbacks of vegetation to the climate system by influencing the seasonality of albedo, surface roughness length, canopy conductance, and fluxes of water, energy, CO2 and biogenic volatile organic compounds. In this review, we first discuss the environmental drivers of phenology, and the impacts of climate change on phenology, in different biomes. We then examine the vegetation-climate feedbacks that are mediated by phenology, and assess the potential impact on these feedbacks of shifts in phenology driven by climate change. We finish with an overview of phenological modeling and we suggest ways in which models might be improved using existing data sets. Several key weaknesses in our current understanding emerge from this analysis. First, we need a better understanding of the drivers of phenology, particularly in under-studied biomes (e.g. tropical forests). We do not have a mechanistic understanding of the role of photoperiod, even in well-studied biomes. In all biomes, the factors controlling senescence and dormancy are not well-documented. Second, for the most part (i.e. with the exception of phenology impacts on CO2exchange) we have only a qualitative understanding of the feedbacks between vegetation and climate that are mediated by phenology. We need to quantify the magnitude of these feedbacks, and ensure that they are accurately reproduced by models. Third, we need to work towards a new understanding of phenological processes that enables progress beyond the modeling paradigms currently in use. Accurate representation of phenological processes in models that couple the land surface to the climate system is particularly important, especially when such models are being used to predict future climate."
Citation: Andrew D. Richardson, Trevor F. Keenan, Mirco Migliavacca, Youngryel Ryu, c, Oliver Sonnentag, Michael Toomey, Agricultural and Forest Meteorology, Volume 169, 15 February 2013, Pages 156–173, http://dx.doi.org/10.1016/j.agrformet.2012.09.012.
ENSO mega-drought triggered collapse of prehistoric Aboriginal society in northwest Australia
Highlights:•Millennial scale failure of the Australian monsoon, •ENSO mega-drought, •Climate forced rapid change of Aboriginal cultures.
Abstract:"The Kimberley region of northwest Australia contains one of the World's largest collections of rock art characterised by two distinct art forms; the fine featured anthropomorphic figures of the Gwion Gwion or Bradshaw paintings, and broad stroke Wandjina figures. Luminescence dating of mud wasp nests overlying Gwion Gwion paintings has confirmed an age of at least 17,000 yrs B.P. with the most recent dates for these paintings from around the mid-Holocene (5000 to 7000 yrs B.P.). Radiocarbon dating indicates that the Wandjina rock art then emerged around 3800 to 4000 yrs B.P. following a hiatus of at least 1200 yrs. Here we show that a mid-Holocene ENSO forced collapse of the Australian summer monsoon and ensuing mega-drought spanning approximately 1500 yrs was the likely catalyst of this change in rock art. The severity of the drought we believe was enhanced through positive feedbacks triggered by change in land surface condition and increased aerosol loading of the atmosphere leading to a weakening or failure of monsoon rains. This confirms that pre-historic aboriginal cultures experienced catastrophic upheaval due to rapid natural climate variability and that current abundant seasonal water supplies may fail again if significant change in ENSO occurs."
Citation: McGowan, H., S. Marx, P. Moss, and A. Hammond (2012), Evidence of ENSO mega-drought triggered collapse of prehistory Aboriginal society in northwest Australia, Geophys. Res. Lett., 39, L22702, doi:10.1029/2012GL053916.
Global temperature continues to increase in good agreement with best estimates of IPCC
Abstract:"We analyse global temperature and sea-level data for the past few decades and compare them to projections published in the third and fourth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). The results show that global temperature continues to increase in good agreement with the best estimates of the IPCC, especially if we account for the effects of short-term variability due to the El Niño/Southern Oscillation, volcanic activity and solar variability. The rate of sea-level rise of the past few decades, on the other hand, is greater than projected by the IPCC models. This suggests that IPCC sea-level projections for the future may also be biased low."
Citation: Stefan Rahmstorf et al 2012 Environ. Res. Lett. 7 044035 doi:10.1088/1748-9326/7/4/044035.
Climate warming and vegetation response after Heinrich event 1 in southern Europe
Abstract:"Chironomids preserved in a sediment core from Lago di Origlio (416 m a.s.l.), a lake in the foreland of the Southern Swiss Alps, allowed quantitative reconstruction of Late Glacial and Early Holocene summer temperatures using a combined Swiss–Norwegian temperature inference model based on chironomid assemblages from 274 lakes. We reconstruct July air temperatures of ca. 10 °C between 17 300 and 16 000 cal yr BP, a rather abrupt warming to ca. 12.0 °C at ca. 16 500–16 000 cal yr BP, and a strong temperature increase at the transition to the Bølling/Allerød interstadial with average temperatures of about 14 °C. During the Younger Dryas and earliest Holocene similar temperatures are reconstructed as for the interstadial. The rather abrupt warming at 16 500–16 000 cal yr BP is consistent with sea-surface temperature as well as speleothem records, which indicate a warming after the end of Heinrich event 1 (sensu stricto) and before the Bølling/Allerød interstadial in southern Europe and the Mediterranean Sea. Pollen records from Origlio and other sites in southern Switzerland and northern Italy indicate an early reforestation of the lowlands 2000–1500 yr prior to the large-scale afforestation of Central Europe at the onset of the Bølling/Allerød period at ca. 14 700–14 600 cal yr BP. Our results suggest that these early afforestation processes in the formerly glaciated areas of northern Italy and southern Switzerland have been promoted by increasing temperatures."
Citation: Samartin, S., Heiri, O., Lotter, A. F., and Tinner, W.: Climate warming and vegetation response after Heinrich event 1 (16 700–16 000 cal yr BP) in Europe south of the Alps, Clim. Past, 8, 1913-1927, doi:10.5194/cp-8-1913-2012, 2012.
Other studies from last week
CLASSIC OF THE WEEK: Barker (1800)
Abstract:No abstract. This is the last of Thomas Barker's annual climate reports. He made continuous weather observations through many decades in 18th century and reported about them annually in Royal Society's Philosophical Transactions.
Citation: Thomas Barker, Esq., Phil. Trans. R. Soc. Lond. January 1, 1800 90 46-48; doi:10.1098/rstl.1800.0004.
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