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| | | Climate Variability and Climate Change |
Maintained by WMO |
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| | Natural or man-made? | | |  Human activities are increasing the atmospheric concentrations of greenhouse gases (which tend to warm the atmosphere) and, in some regions, aerosols (which tend to cool the atmosphere). These changes in greenhouse gases and aerosols, taken together, are projected to lead to regional and global changes in climate and climate-related parameters such as temperature, precipitation, soil moisture and sea level. Based on the range of sensitivities of climate to increases in greenhouse gas concentrations reported by the Intergovernmental Panel on Climate Change (IPCC) and plausible ranges of emissions and aerosol concentrations, climate models project an increase in global mean surface temperature of about 1-3.5°C by 2100 and an associated increase in sea level of about 15-95 cm. The reliability of regional-scale predictions is still low and the degree to which climate variability may change is uncertain. However, potentially serious changes have been identified, including an increase in some regions in the incidence of extreme high-temperature events, floods and droughts, with resultant consequences for fires, pest outbreaks, and ecosystem composition, structure and functioning, including primary productivity. [Figure: variation in global mean annual air temperature since 1860, by courtesy of the UK Met Office] | | | | Adapting to the consequences | | |  Policymakers will have to decide to what degree they want to take precautionary measures by mitigating greenhouse gas emissions and enhancing the resilience of vulnerable systems by means of adaptation. Uncertainty does not mean that a nation or the world community cannot position itself better to cope with the broad range of possible climate changes or protect against potentially costly future outcomes. Delaying such measures may leave a nation or the world poorly prepared to deal with adverse changes and may increase the possibility of irreversible or very costly consequences. Options for adapting to change or mitigating change that can be justified for other reasons today (e.g., abatement of air and water pollution) and make society more flexible or resilient to anticipated adverse effects of climate change appear particularly desirable. (Image courtesy of FAO/G Bizzarri.) | | | | |
 | | | | | CLIMATE CHANGE II: First US Assessment Shows Broad Impact
by UN Wire, UN Wire 01 June 2000 | |
| | UNWire, 12.6.2000 CLIMATE CHANGE II: First US Assessment Shows Broad Impact The first national assessment of the possible effects of global warming on the United States to be released today predicts a dramatic impact on the country's climate in the coming decades. The report, prepared by a panel of government officials, academics, industry representatives and nongovernmental organizations, predicts US temperatures will rise 5 to 10 degrees Fahrenheit over the next century. The predictions include an increase in droughts and floods; rising sea levels, which will shrink coastal wetlands and increase storm surges; disproportionately hotter cities; and more heat waves (CNN.com ). The report includes regional and national effects, including predictions that Pacific Northwest salmon are likely to be harmed by rising water temperatures; forests could replace deserts in the southwest; and Native Alaskans will have more difficulty hunting ice-dwelling seals, an effect they have already begun to experience. The report also includes some positive impacts of warming, such as increased agricultural yield and fewer ice-hindered shipping lanes in Alaska and the Great Lakes (Andrew Rifkin, New York Times ). Global warming skeptics pointed to discrepancies in the study's two computer models as evidence of inaccuracy. "Look at North Dakota. One [model] turns it into a desert, the other a swamp," said S. Fred Singer of the Science and Environmental Policy Project . "Neither will probably happen" (Curt Suplee, Washington Post ). Environmental groups applauded the draft report as a "balanced assessment" of the potential impacts of warming. "America's alarm bells should go off today," said World Wildlife Fund Climate Change Campaign Director Jennifer Morgan. "The national assessment shows that now more than ever the United States must act to protect its national treasures" (Union of Concerned Scientists release , 9 Jun). (All cites 12 June unless otherwise noted.) (Back to Contents) |
| Serge Garcia
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1076 Topics - 5135 Related Knowledge - 2534 Members - 34 Editors |
