Scientists have documented climate induced changes in some 100 physical and 450 biological processes. In the Russian Arctic, higher temperatures are melting the permafrost, causing the foundations of five story apartment buildings to slump. Worldwide, the rain, when it falls, is often more intense. Floods and storms are more severe and heat waves are becoming more extreme. Rivers freeze later in the winter and melt earlier. Trees flower earlier in spring insects emerge faster and birds lay eggs sooner. Glaciers are melting. The global mean sea level is rising.
Even if we reduce our greenhouse gas missions dramatically today, these trends will continue for decades or centuries to come. The rate of climate change expected over the next 100 years is unprecedented in human history. Throughout geologic time the average global temperature has usually varied by 50 Celsius over intervals of millions of years. Now scientists believe that the temperature of the Earth’s surface – which has already risen by 0. ICC since the late 8005 – is likely to increase by another 1. 4 to 5. Cuddling the course of the 21 SST century.
Such an unusually rapid rate of change would affect fundamental Earth systems upon which our very lives depend – including ocean circulation and the hydrological, carbon and nutrient cycles. It would disrupt the natural and managed ecosystems that provide us with water, food and fiber. It would add to existing environmental stresses such as desertification, declining water quality, stratospheric ozone depletion, urban air pollution and deforestation. Researchers have been investing a great deal of effort in analyzing how climate change will influence the natural environment and human society.