Climate Change: The State of the Science : Hearing Before the Committee on Science, House of Representatives, One Hundred Seventh Congress, First Session, March 14, 2001, Volume 4

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U.S. Government Printing Office, 2001 - 163 pages

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Page 152 - the balance of evidence suggests a discernible human influence on global climate' [5], and was sufficiently confident by the time of the Third Assessment Report to conclude that 'there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities...
Page 140 - To describe and understand the interactive physical, chemical and biological processes that regulate the total Earth system, the unique environment that it provides for life, the changes that are occurring in this system, and the manner in which they are influenced by human activities.
Page 54 - Hemisphere indicate that the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1000 years. It is also likely that, in the Northern Hemisphere, the 1990s was the warmest decade and 1998 the warmest year.
Page 154 - Based on recent global model simulations, it is very likely7 that nearly all land areas will warm more rapidly than the global average, particularly those at northern high latitudes in the cold season.
Page 55 - In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.
Page 64 - The size of this warming is broadly consistent with predictions of climate models, but it is also of the same magnitude as natural climate variability. Thus the observed increase could be largely due to this natural variability; alternatively this variability and other human factors could have offset a still larger human-induced greenhouse warming...
Page 55 - ... about 10% in the extent of snow cover since the late 1960s, and ground-based observations show that there is very likely to have been a reduction of about two weeks in the annual duration of lake and river ice cover in the mid- and high latitudes of the northern hemisphere, over the 20th century.
Page 158 - ... urbanisation over the land. Over both the last 140 years and 100 years, the best estimate is that the global average surface temperature has increased by 0.6 0.2C. (b) Additionally, the year by year (blue curve) and 50 year average (black curve) variations of the average surface temperature of the Northern Hemisphere for the past 1000 years have been reconstructed from "proxy" data calibrated against thermometer data (see list of the main proxy data in the diagram).
Page 148 - Hence, it is physically plausible to expect that over a short time period (eg, 20 years) there may be differences in temperature trends. In addition, spatial sampling techniques can also explain some of the differences in trends, but these differences are not fully resolved.
Page 99 - US House of Representatives Suite 2320, Rayburn House Office Building \ Washington, DC 20515 ^ Dear Mr.

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