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Global Effects of Climate Change
Warming of the climate system is evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level. Some notable observations include -
| (a) |
the amounts of carbon dioxide, methane and nitrous oxide now in the atmosphere far exceed the pre-industrial levels. |
| (b) |
the world’s average surface temperature has increased by 0.6°C in the 20th century. Eleven of the last 12 years rank among the 12 warmest years since instrumented temperature measurement began around 1850. |
| (c) |
the best estimate is that global temperatures would increase by 1.8 to 4.0°C at the end of the 21st century (compared to 1980-1999 levels). |
| (d) |
as a result of thermal expansion of the oceans and melting of ice sheets and glaciers on land, global average sea level rose at an average rate of 1.8 mm per year between 1961 and 2003. It is projected to rise by 18 to 59 cm by the end of the 21st century (compared to 1980-1999 levels). |
| (e) |
widespread changes in extreme temperatures have been observed over the last 50 years. Cold days, cold nights and frost have become less frequent; while hot days, hot nights, and heat waves have become more frequent. It is very likely that the upward trend of having high temperatures and heat waves will continue in this century. |
| (f) |
the frequency of heavy precipitation events has increased over most land areas. In this century, heavy precipitation events will become more frequent. Precipitation is likely to increase at high latitudes and decrease over most subtropical land regions. |
The key conclusions from the United Nations Intergovernmental Panel on Climate Change Fourth Assessment Report indicate that -
| (a) |
most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations, |
| (b) |
observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases, and |
| (c) |
a wide variety of policies and instruments are available to governments to create the incentives for mitigation action, but the applicability depends on national circumstances and sectoral context. |
Further information
See Also:
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