Abstracts on Global Climate Change

Dec 2006

Water in the Earth’s atmosphere

Quante, M Matthias, V


Water is the key to our existence on this planet and it is involved in nearly all biological, geological, and chemical processes. Life on Earth depends very much on the remarkable properties of water. The availability of freshwater is for many regions one of the key concerns in connection with global climate change. The atmosphere contains only about 0.001% of the water available on our planet. Despite this small amount its horizontal and vertical distribution plays a key role in the global water cycle and the Earth’s climate. The atmosphere has direct connections to most of the other reservoirs and steers the redistribution of water between them with an average turnover time of about 10 days. Evaporation over the oceans exceeds precipitation and over land evapotranspiration amounts only to 2/3 of the precipitation reaching the ground. Consequently, there is a net flux of water from the oceans towards the continents, of course via the atmosphere, which has the largest overall volume of fluxes. Water is present in the atmosphere as solid, liquid, or gas. Water vapour is the most important greenhouse gas in the atmosphere and, in addition, changes of water phase and cloud-radiation interaction contribute strongly to the global energy cycle. Water is also a physically and chemically integral part of other biogeochemical cycles. Although there have been large efforts and improvements in recent years, uncertainties in quantifying the components of the atmospheric water cycle still exist. Observational capabilities on the global scale are not satisfactory at present, but the advent of new satellites devoted to the global observation of precipitation and cloud systems along with dedicated modelling projects certainly will improve the situation. Progress is urgently needed to adequately contribute to the answer of one of the central questions in the context of global warming: Is the hydrological cycle accelerating?.

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Evaluating long-term trends in annual and seasonal precipitation in Taiwan

Yu, PS Yang, TC Kuo, CC


This work studies long-term rainfall variations in Taiwan and provides local climate change analyses to global climate change. Around a century of rainfall data from 33 rain-gauges populate the database used herein. Statistical tests, such as cumulative deviations, Mann-Whitney-Pettitt statistics and the Kruskal-Wallis test, were first employed to determine whether annual rainfall series exhibit any regular trend. Analytical results indicate that the annual rainfall has increased in northern Taiwan, declined in central and southern Taiwan, and exhibited no clear tendency in Eastern Taiwan. Almost all of these rainfall series changed significantly around 1960, which date divides historical rainfall series into two sample groups. This change in the seasonal rainfall was further investigated.

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A land surface model incorporated with soil freeze/thaw and its application in GAME/Tibet

Hu, HP Ye, BS Zhou, YH Tian, FQ


Land surface process is of great importance in global climate change, moisture and heat exchange in the interface of the earth and atmosphere, human impacts on the environment and ecosystem, etc. Soil freeze/thaw plays an important role in cold land surface processes. In this work the diurnal freeze/thaw effects on energy partition in the context of GAME/Tibet are studied. A sophisticated land surface model is developed, the particular aspect of which is its physical consideration of soil freeze/thaw and vapor flux. The simultaneous water and heat transfer soil sub-model not only reflects the water flow from unfrozen zone to frozen fringe in freezing/thawing soil, but also demonstrates the change of moisture and temperature field induced by vapor flux from high temperature zone to low temperature zone, which makes the model applicable for various circumstances. The modified Picard numerical method is employed to help with the water balance and convergence of the numerical scheme. Finally, the model is applied to analyze the diurnal energy and water cycle characteristics over the Tibetan Plateau using the Game/Tibet datasets observed in May and July of 1998. Heat and energy transfer simulation shows that: (i) There exists a negative feedback mechanism between soil freeze/thaw and soil temperature/ground heat flux; (ii) during freezing period all three heat fluxes do not vary apparently, in spite of the fact that the negative soil temperature is higher than that not considering soil freeze; (iii) during thawing period, ground heat flux increases, and sensible heat flux decreases, but latent heat flux does not change much; and (iv) during freezing period, soil temperature decreases, though ground heat flux increases.

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Personal values, beliefs, and ecological risk perception

Slimak, MW Dietz, T

RISK ANALYSIS 26:6 1689-1705

A mail survey on ecological risk perception was administered in the summer of 2002 to a randomized sample of the lay public and to selected risk professionals at the U.S. Environmental Protection Agency (US EPA). The ranking of 24 ecological risk items, from global climate change to commercial fishing, reveals that the lay public is more concerned about low-probability, high-consequence risks whereas the risk professionals are more concerned about risks that pose long-term, ecosystem-level impacts. To test the explanatory power of the value-belief-norm (VBN) theory for risk perception, respondents were questioned about their personal values, spiritual beliefs, and worldviews. The most consistent predictors of the risk rankings are belief in the new ecological paradigm (NEP) and Schwartz’s altruism. The NEP and Schwartz’s altruism explain from 19% to 46% of the variance in the risk rankings. Religious beliefs account for less than 6% of the variance and do not show a consistent pattern in predicting risk perception although religious fundamentalists are generally less concerned about the risk items. While not exerting as strong an impact, social-structural variables do have some influence on risk perception. Ethnicities show no effect on the risk scales but the more educated and financially well-off are less concerned about the risk items. Political leanings have no direct influence on risk rankings, but indirectly affect rankings through the NEP. These results reveal that the VBN theory is a plausible explanation for the differences measured in the respondents’ perception of ecological risk.

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Predicting woodrat (Neotoma) responses to anthropogenic warming from studies of the palaeomidden record

Smith, FA Betancourt, JL


Aim The influence of anthropogenic climate change on organisms is an area of great scientific concern. Increasingly there is recognition that abrupt climate transitions have occurred over the late Quaternary; studies of these shifts may yield insights into likely biotic responses to contemporary warming. Here, we review research undertaken over the past decade investigating the response of Neotoma (woodrats) body size and distribution to climate change over the late Quaternary (the last 40,000 years). By integrating information from woodrat palaeomiddens, historical museum specimens and field studies of modern populations, we identify potential evolutionary responses to climate change occurring over a variety of temporal and spatial scales. Specifically, we characterize climatic thresholds in the past that led to local species extirpation and/or range alterations rather than in situ adaptation, and apply them to anticipate potential biotic responses to anthropogenic climate change. Location Middens were collected at about 55 sites scattered across the western United States, ranging from about 34 to 46 degrees N and about 104 to 116 degrees W, respectively. Data for modern populations were drawn from studies conducted in Death Valley, California, Missoula, Montana and the Sevilleta LTER site in central New Mexico. Methods We analysed faecal pellets from midden series collected at numerous cave sites across the western United States. From these we estimated body mass using techniques validated in earlier studies. We compared body size fluctuations at different elevations in different regions and integrated these results with studies investigating temperature-body size tradeoffs in modern animals. We also quantify the rapidity of the size changes over the late Quaternary to estimate the evolutionary capacity of woodrats to deal with predicted rates of anthropogenic climate change over the next century. Results We find remarkable similarities across the geographical range to late Quaternary climate change. In the middle of the geographical range woodrats respond in accordance to Bergmann’s rule: colder climatic conditions select for larger body size and warmer conditions select for smaller body size. Patterns are more complicated at range boundaries, and local environmental conditions influence the observed response. In general, woodrat body size fluctuates with approximately the same amplitude and frequency as climate; there is a significant and positive correlation between woodrat body size and generalized climate proxies (such as ice core records). Woodrats have achieved evolutionary rates of change equal to or greater than those needed to adapt in situ to anthropogenic climate change. Main conclusions In situ body size evolution is a likely outcome of climate change, and such shifts are part of a normal spectrum of adaptation. Woodrats appear to be subject to ongoing body size selection in response to fluctuating environmental conditions. Allometric considerations suggest that these shifts in body size lead to substantial changes in the physiology, life history and ecology of woodrats, and on their direct and indirect interactions with other organisms in the ecosystem. Our work highlights the importance of a finely resolved and long-term record in understanding biotic responses to climatic shifts.

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Interhemispheric anti-phasing of rainfall during the last glacial period

Wang, XF Auler, AS Edwards, RL Cheng, H Ito, E Solheid, M


We have obtained a high-resolution oxygen isotopic record of cave calcite from Caverna Botuvera (27 degrees 13’S, 49 degrees 09’W), southern Brazil, which covers most of the last 36 thousand years (ka), with an average resolution of a few to several decades. The chronology was determined with 46 U/Th ages from two stalagmites. Tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change. We interpret our record in terms of meteoric precipitation changes, hence the variability of South American Monsoon (SAM) intensity. The oxygen isotopic profile broadly follows local insolation changes and shows clear millennial-scale variations during the last glacial period with amplitudes as large as 3 parts per thousand but with smaller centennial-scale shifts (< 1 parts per thousand) during the Holocene. The overall record is strikingly similar to, but strongly anti-correlated with, a number of records from the Northern Hemisphere. We compared our record to other precisely dated contemporaneous records from Hulu Cave eastern China. Minima in 6180 (wet periods, intense SAM) at our site are synchronous with maxima in delta O-18 (dry periods, weak East Asian Monsoon, EAM) in eastern China (within precise dating errors) and vice versa. This anti-phased precipitation relationship between two low-latitude locations may be interhemispheric in extent, based on comparison with records from other sites. Precipitation anti-phasing may be related to north-south shifts in the mean position of the intertropical convergence zone (ITCZ) and asymmetry in Hadley circulation in two hemispheres, associated not with seasonal changes as observed today, but with millennial-scale climate shifts. The millennial-scale atmospheric see-saw patterns that we observe could have important controls and feedbacks on climate within hemispheres because of water vapor’s greenhouse properties. (c) 2006 Elsevier Ltd. All rights reserved.

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Frequency of debris flows and rockfall along the Mendoza river valley (Central Andes), Argentina: Associated risk and future scenario

Moreiras, SM


The frequency of debris flows and rockfalls was estimated by temporal distribution of these events during the last 50 years. This parameter was expressed by annual probability of occurrence and mean interval of recurrence of historical events. More recurrent events in this sector of the Central Andes are associated with the Guido locality and tunnels situated along International road No. 7. Furthermore, these events are more frequent in Cordillera Frontal where the mean recurrence interval was lower than in Precordillera. The maximum interval of recurrence is rarely greater than 20 years, showing the activity of these events on human lives and infrastructure in this region. The accuracy of the determined recurrence frequency is discussed. A future scenario indicates that landslides will be probably more frequent under global climate change. As a consequence, those most vulnerable elements in the region, the international access routes, may be severely damaged in the future, implying an adverse impact in our regional economy. (c) 2006 Elsevier Ltd and INQUA. All rights reserved.

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Seasonal-to-decadal predictability and prediction of South American climate

Nobre, P Marengo, JA Cavalcanti, IFA Obregon, G Barros, V Camilloni, I Campos, N Ferreira, AG

JOURNAL OF CLIMATE 19:23 5988-6004

The dynamical basis for seasonal to decadal climate predictions and predictability over South America is reviewed. It is shown that, while global tropical SSTs affect both predictability and predictions over South America, the current lack of SST predictability over the tropical Atlantic represents a limiting factor to seasonal climate predictions over some parts of the continent. The model’s skill varies with the continental region: the highest skill is found in the “Nordeste” region and the lowest skill over southeastern Brazil. It is also suggested that current two-tier approaches to predict seasonal climate variations might represent a major limitation to forecast coupled ocean-atmosphere phenomena like the South Atlantic convergence zone. Also discussed are the possible effects of global climate change on regional predictability of seasonal climate.

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Comparative risk assessment of the burden of disease from climate change

Campbell-Lendrum, D Woodruff, R


The World Health Organization has developed standardized comparative risk assessment methods for estimating aggregate disease burdens attributable to different risk factors. These have been applied to existing and new models for a range of climate-sensitive diseases in order to estimate the effect of global climate change on current disease burdens and likely proportional changes in the future. The comparative risk assessment approach has been used to assess the health consequences of climate change worldwide, to inform decisions on mitigating greenhouse gas emissions, and in a regional assessment of the Oceania region in the Pacific Ocean to provide more location-specific information relevant to local mitigation and adaptation decisions. The approach places climate change within the same criteria for epidemiologic assessment as other health risks and accounts for the size of the burden of climate-sensitive diseases rather than just proportional change, which highlights the importance of small proportional changes in diseases such as diarrhea and malnutrition that cause a large burden. These exercises help clarify important knowledge gaps such as a relatively poor understanding of the role of nonclimatic factors (socioeconomic and other) that may modify future climatic influences and a lack of empiric evidence and methods for quantifying more complex climate-health relationships, which consequently are often excluded from consideration. These exercises highlight the need for risk assessment frameworks that make the best use of traditional epidemiologic methods and that also fully consider the specific characteristics of climate change. These include the long-term and uncertain nature of the exposure and the effects on multiple physical and biotic systems that have the potential for diverse and widespread effects, including high-impact events.

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Growth and physiological responses of canola (Brassica napus) to three components of global climate change: temperature, carbon dioxide and drought

Qaderi, MM Kurepin, LV Reid, DM


Elevated CO2 appears to be a significant factor in global warming, which will likely lead to drought conditions in many areas. Few studies have considered the interactive effects of higher CO2, temperature and drought on plant growth and physiology. We grew canola (Brassica napus cv. 45H72) plants under lower (22/18 degrees C) and higher (28/24 degrees C) temperature regimes in controlled environment chambers at ambient (370 mu mol mol(-1)) and elevated (740 mu mol mol(-1)) CO2 levels. One half of the plants were watered to field capacity and the other half at wilting point. In three separate experiments, we determined growth, various physiological parameters and content of abscisic acid (ABA), indole-3-acetic acid and ethylene. Drought-stressed plants grown under higher temperature at ambient CO2 had decreased stem height and diameter, leaf number and area, dry matter, leaf area ratio, shoot/root weight ratio, net CO2 assimilation and chlorophyll fluorescence. However, these plants had increased specific leaf weight, leaf weight ratio and chlorophyll concentration. Elevated CO2 generally had the opposite effect, and partially reversed the inhibitory effects of higher temperature and drought on leaf dry weight accumulation. This study showed that higher temperature and drought inhibit many processes but elevated CO2 partially mitigate some adverse effects. As expected, drought stress increased ABA but higher temperature inhibited the ability of plants to produce ABA in response to drought.

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