Global Climate Change And Extreme Weather Events

FIGURE SA-18 Observed changes in (A) global average surface temperature; (B) global average sea level rise from tide gauge (blue) and satellite (red) data; and (C) Northern Hemisphere snow cover for March-April. All changes are relative to corresponding averages for the period 1961-1990. Smoothed curves represent decadal averaged values while circles show yearly values. The shaded areas are the uncertainty intervals estimated from a comprehensive analysis of known uncertainties (A and B) and from the time series (C). SOURCE: Figure SPM.3 in IPCC (2007).

Percent Change in Average Annual Precipitation, 1976-2005

Percent Change in Average Annual Precipitation, 1976-2005

FIGURE SA-19 Drought is seizing more territory in the wake of mounting temperatures. Drying trends in the last 30 years are evident in the rain forests of Africa and South America and in already dry regions such as southern Europe and western North America. In wet areas, precipitation increasingly arrives in heavy downpours, raising the risk of flooding. Winter rain is replacing snow, an ominous development for hundreds of millions of people who depend on spring snowmelt for their water supply.

SOURCE: Reprinted from National Geographic Society (2007) with permission from the National Geographic Society.

48 GLOBAL CLIMATE CHANGE AND EXTREME WEATHER EVENTS

with changes in wind patterns and decreases in snowpack and snow cover. Periods of heavy precipitation have occurred with greater frequency over most land areas in parallel with increases in atmospheric water vapor.

Over the next two decades, the Earth is expected to warm by an additional 0.2°C. Even if the concentrations of all greenhouse gases and aerosols (both of which cause the atmosphere to trap heat) could be kept the same levels as in 2000, warming would still be expected to proceed at about half the present rate. Continued greenhouse gas emissions at or above current rates are very likely to induce changes in the global climate system during the twenty-first century of even greater magnitude than has been observed during the late twentieth century.

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