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M. P. Calef, A. D. McGuire, and F. S. Chapin III

nontrivial impact on area burned over recent decades” ( Cumming 2005 ). The extent of human impact on natural fires varies among regions in interior Alaska ( DeWilde 2003 ). Human influence on fire can be measured by the number of human fire starts and the total area burned by both human- and lightning-caused fires. Therefore, we analyzed the geographic relationships (nearest distance) between fire locations, both in terms of ignitions and area burned, and settlements, major highways, and major rivers in

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Yan Li, Lijuan Zhu, Xinyi Zhao, Shuangcheng Li, and Yan Yan

better characterize the urbanization process and to develop a more suitable station classification scheme, researchers should concentrate on the mechanisms of urbanization influence on temperature change. In general, the urbanization impact on temperature depends on two main aspects including changes in land surface properties, such as changes in surface albedo, roughness, and heat capacity, and human activity within a city, which releases anthropogenic heat and other pollutants. Land cover change

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Maria M. Kvalevåg and Gunnar Myhre

1. Introduction A decline in solar radiation has been observed at the surface ( Liepert 2002 ; Stanhill and Cohen 2001 ). Called global dimming, this decline is presumed to be a consequence of an increased amount of scattering and absorbing aerosols and gases in the atmosphere from human activity and is likely to be linked to the reduced pan evaporation ( Roderick and Farquhar 2002 ). Alpert et al. (2005) pointed out that the larger the population the stronger the decline in surface solar

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Kirk Zmijewski and Richard Becker

water now supports large irrigated agricultural regions and also Uzbekistan’s cotton industry, which is the fifth largest exporter in the world ( CIA 2012 ). Additionally, human population since 1960 in the Aral Sea watershed has grown from 15 million to over 65 million increasing the demand for both food and water ( Vörösmarty et al. 2000 ). Figure 1. Location map: The location and extent of the Aral Sea watershed. Lakes and reservoirs are shown in gray outline and the reservoir and dam locations

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Roland J. Viger, Lauren E. Hay, Steven L. Markstrom, John W. Jones, and Gary R. Buell

because it is one of only 40 rivers within the conterminous United States that flows unimpeded for more than 320 km ( Morris 2009 ). It contains many water-storing surface depressions, including officially designated wetland areas such as the Great Swamp and the Chickasawatchee Swamp, and supports a diversity of plant and animal life. The Flint River is also important to human populations because it is a major water supply for the states of Georgia and Florida and because it has flooded several cities

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Friederike E. L. Otto, Luke J. Harrington, David Frame, Emily Boyd, Kristian Cedervall Lauta, Michael Wehner, Ben Clarke, Emmanuel Raju, Chad Boda, Mathias Hauser, Rachel A. James, and Richard G. Jones

climate change to be quantified, while at the same time others inquire as to whether current measures and efforts are commensurate with the challenges of climate change. As the climate is evolving quickly into the future, alongside other socioeconomic factors relevant to human and natural systems, it is not sufficient to assess impacts in climate sensitive systems without identifying the specific role of climate change. Currently there is a gap between what is perceived or assumed by many, and what

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Kristen Guirguis, Alexander Gershunov, Alexander Tardy, and Rupa Basu

–health relationships. Such information would be highly beneficial for making informed decisions about when to issue a warning, which could prevent heat-related illnesses and save lives. There have been many studies investigating the impacts of extreme heat on human health (e.g., Basu and Samet 2002 ; Martiello and Giacchi 2010 ). Most of this work has focused on health impacts that are related to daily ambient apparent temperatures observed throughout the summer (e.g., Basu 2009 ; Basu et al. 2008 , 2012

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Chuanguo Yang, Zhaohui Lin, Zhongbo Yu, Zhenchun Hao, and Shaofeng Liu

values, respectively. A better water balance is obtained with a WBI of 0.948 when the withdrawal is included. The WBI fell below 1.0 for the first time in this study, which indicates the probable existence of return flow in the withdrawal, for example, irrigation. d. Simulation of human activities’ impacts An alternative way to represent the effect of human activity is to integrate a new module in the coupled model system. In a river basin, parts of surface runoff and channel flow are usually dammed

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Jose A. Marengo, Luiz E.O.C. Aragão, Peter M. Cox, Richard Betts, Duarte Costa, Neil Kaye, Lauren T. Smith, Lincoln M. Alves, and Vera Reis

MOTIVATION. Amazonia has experienced “droughts and floods of the century” during the last 10 years, and this has affected humans and natural systems through direct impacts from the events as well as increased forest fires and an increased risk of diseases. There is more data than ever before to monitor and understand the impact of such climatic extremes. However, the quantity of long-term multitemporal and multisource information increases the complexity of data management and limits the

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Kenneth E. Kunkel, Roger A. Pielke Jr., and Stanley A. Changnon

This paper reviews recent work on trends during this century in societal impacts (direct economic losses and fatalities) in the United States from extreme weather conditions and compares those with trends of associated atmospheric phenomena. Most measures of the economic impacts of weather and climate extremes over the past several decades reveal increasing losses. But trends in most related weather and climate extremes do not show comparable increases with time. This suggests that increasing losses are primarily due to increasing vulnerability arising from a variety of societal changes, including a growing population in higher risk coastal areas and large cities, more property subject to damage, and lifestyle and demographic changes subjecting lives and property to greater exposure.

Flood damages and fatalities have generally increased in the last 25 years. While some have speculated that this may be due in part to a corresponding increase in the frequency of heavy rain events, the climate contribution to the observed impacts trends remains to be quantified. There has been a steady increase in hurricane losses. However, when changes in population, inflation, and wealth are considered, there is instead a downward trend. This is consistent with observations of trends in hurricane frequency and intensity. Increasing property losses due to thunderstorm-related phenomena (winds, hail, tornadoes) are explained entirely by changes in societal factors, consistent with the observed trends in the thunderstorm phenomena. Winter storm damages have increased in the last 10–15 years and this appears to be partially due to increases in the frequency of intense nor'easters. There is no evidence of changes in drought-related losses (although data are poor) and no apparent trend in climatic drought frequency. There is also no evidence of changes in the frequency of intense heat or cold waves.

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