Many natural systems, on all continents and in some oceans, are being affected by regional climate changes, particularly temperature increases.
Some of theses effects are described below:
- Global extent of snow and ice cover has declined, especially since 1980 and at a greater rate during the past decade, contributing to the rise in sea-level. Mountain glaciers are
getting smaller, snow cover is retreating earlier in the spring and sea ice in the Arctic is shrinking in all seasons, most dramatically in summer.
- Reductions are reported in permafrost, seasonally frozen ground and river and lake ice,leading to changes in Arctic and Antarctic ecosystems. Parts of the ice sheets on Greenland and West Antarctica, and the glaciers of the Antarctic Peninsula, are thinning and contributing to sea level rise.
- Hydrological systems have been affected resulting in enhanced run-off and warming of lakes and rivers in some regions.
- Warmer and drier conditions in the Sahel in Africa have led to a reduced length of growing season, with detrimental effects on crops, and severe implications for food
security, malnutrition and starvation.
- Terrestrial ecosystems have been affected, with observations of earlier timing of spring events, such as leaf-unfolding, bird migration and egg-laying, and of poleward and
higher elevation shifts in the distribution of plant and animal species.
- Marine and freshwater ecosystems have been affected by rising water temperatures, with observations of shifting species ranges and earlier fish migrations in rivers.
- There have been widespread increases in the number of heat waves and warm nights since 1950. There has been an increase in the extent of regions affected by drought, as well as an increase in the frequency of heavy rainfall events that have led to flooding in some regions. Tropical storm and hurricane frequencies vary considerably from year to year, but evidence suggests substantial increases in intensity and duration since the 1970s.
These changes in natural systems have been linked to many disaster type events experienced by
many countries.These events have had massive human and environmental implications.