Wednesday, December 7, 2005
The Economist today summarized the scientific results from the last year that have solidified our understanding of climate changes caused by human energy use and release of greenhouse gases. First, the Earth continues to warm. Surface temperature measurements show that the last decade was the warmest on record since reliable measurements began in the early 1800s. Ice core and tree ring estimates of earlier temperatures suggest the decade may have been the warmest in the last 1000 years. Second, the Arctic shows signs of rapid warming. Researchers have found that the amount of sea ice has fallen by 8% in the past 30 years, and also found signs that Greenland’s ice cap is melting more rapidly than in the past. Third, the surface temperature and tropospheric temperatures are now known to be rising in parallel, thus resolving a seeming inconsistency in the data. Fourth, the changes in the way the world’s oceans have warmed up at different depths over the past 65 years are best explained by warming induced by greenhouse gases, as opposed to changes in the sun's activity. That had been the main alternative hypothesis for what might be causing the climate to change. Fifth, recent severe storm events verify the predicted link between increased sea-surface temperatures and the frequency of the most intense categories of hurricane, typhoon and tropical storm. Sixth, ocean currents in the North Atlantic are faltering in ways that computer models of the climate previously suggested would happen in response to increased temperatures. Seventh, the cooling effect of aerosols counterbalancing warming appears to be diminishing as air pollution control measures take effect.
The question now, as the Economist notes, is what are we going to do about it.