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China has experienced rapid urbanization and dramatic economic growth since its reform process started in late 1978. In this article, we present evidence for a significant urbanization effect on climate based on analysis of impacts of land-use changes on surface temperature in southeast China, where rapid urbanization has occurred. Our estimated warming of mean surface temperature of 0.05°C per decade attributable to urbanization is much larger than previous estimates for other periods and locations. The spatial pattern and magnitude of our estimate are consistent with those of urbanization characterized by changes in the percentage of urban population and in satellite-measured greenness. Land-use changes from urbanization, creating an urban heat island (UHI), have been suspected as partially being responsible for the observed warming over land during the last few decades because of (i) the observed decrease in the diurnal temperature range (DTR) resulting from a larger increase or a smaller decrease in minimum temperature relative to maximum temperature and (ii) a lower rate of warming observed over the past 20 years in the lower troposphere compared with the surface (1). The area-weighted average warming effect of UHI over land during the 20th century has been estimated to be Ͻ0.06°C per century (1-4) globally and approximately 0.06ϳ0.15°C per century (5, 6) in the U.S. based on differences in temperature trends between rural and urban stations. A much larger estimate of 0.27°C per century in the U.S. has been reported recently (7) by comparing trends in observed and reanalysis surface temperatures over the period from 1950 to 1999.China has experienced rapid urbanization and dramatic economic growth since its reform process started in late 1978. From 1978 to 2000, China's gross domestic product grew at an average annual rate of 9.5%, compared with 2.5% for developed countries and 5% for developing countries; the number of small towns soared from 2,176 to 20,312, nearly double that of the world average during this period; the number of cities increased from 190 to 663; and the proportion of urban population rose from 18% to 39% (see the Peopledaily article at http:͞͞english. peopledaily.com.cn͞200111͞27͞eng2001112785410.shtml and the State Family Planning Commission of China web site at www.sfpc.gov.cn͞EN͞enews20030320-1.htm). In this article, we present evidence for a significant urbanization effect on climate based on analysis of impacts of land-use changes on surface temperature in southeast China, where most of China's urbanization has occurred. Data and MethodsThe UHI effect has been estimated by comparing observed temperatures in urban stations with those in their surrounding rural stations, but such results largely depend on how rural versus urban stations are classified and whether the data are homogeneous (7-9). Population data often are used to identify a station as urban and rural, but such information generally is out-of-date, and thus satellite measurements of night lights have been substituted re...

The terrestrial carbon sink, as of yet unidentified, represents 15-30% of annual global emissions of carbon from fossil fuels and industrial activities. Some of the missing carbon is sequestered in vegetation biomass and, under the Kyoto Protocol of the United Nations Framework Convention on Climate Change, industrialized nations can use certain forest biomass sinks to meet their greenhouse gas emissions reduction commitments. Therefore, we analyzed 19 years of data from remote-sensing spacecraft and forest inventories to identify the size and location of such sinks. The results, which cover the years 1981-1999, reveal a picture of biomass carbon gains in Eurasian boreal and North American temperate forests and losses in some Canadian boreal forests. For the 1.42 billion hectares of Northern forests, roughly above the 30th parallel, we estimate the biomass sink to be 0.68 ؎ 0.34 billion tons carbon per year, of which nearly 70% is in Eurasia, in proportion to its forest area and in disproportion to its biomass carbon pool. The relatively high spatial resolution of these estimates permits direct validation with ground data and contributes to a monitoring program of forest biomass sinks under the Kyoto protocol.