Ecosystems
During the 20 th century , the global climate has warmed by about 0.6°C, or about 0.06°C per decade. Computer models which simulate the effects on climate of increasing atmospheric greenhouse gas concentrations project that global average surface temperatures will rise by a further 3°C by the end of the 21 st century , or 0.3°C per decade. It is currently believed that most ecosystems can withstand at most a 0.1°C global temperature change per decade, before experiencing severe ecological stresses, leading in some cases to species extinction. A warming of even 2°C over the next 100 years would shift current climate zones in temperate regions of the world about 300 km towards higher latitudes, and vertically by 300 m. The composition and geographical distribution of unmanaged ecosystems will change as individual species respond to new conditions. At the same time, habitats will be degraded and fragmented by the combination of climate change, deforestation , desertification and ot...