Global warming
GLOBAL WARMING
The term "global warming" is a specific example of global climate change. The term "climate change" can also refer to other periods of overall temperature change such as global warming. In common usage, the term "global warming" refers to the warming in recent decades and its projected continuation, and implies a human influence.
The average global air temperature near the Earth's surface increased 0.740.18 °c (1.33 ± 0.32 °F) during the hundred years ending in 2005. "most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations" via the greenhouse effect. Natural phenomena such as solar variation combined with
volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.
Climate projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century.The range of values results from the use of differing scenarios of future greenhouse gases emissions as well as models with differingclimate sensetivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.
Increasing global temperature will cause sea level to rise, and is expected to increase the intensity ofextreme weather events and to change the amount and pattern of precipitation. Other effects of global warming include changes in agric yields, trade routes, glacier retreat, species extinctions and increases in the ranges of disease vectors.
CAUSESThe Earth's climate changes in response to external forcing, including variations in its orbit around the Sun (orbital forcing),eruptions of volcanoes, and greenhouse gas atmospheric concentrations. The detailed causes of the recent remain an active field of research, but scientific consensus is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the industrial era
RECENT INFORMATION ON THIS...
LAND
Global temperatures on both land and sea have increased by 0.75 °C (1.35 °F) relative to the period 1860–1900, according to the instrumental temperature record. This measured temperature increase is not significantly affected by the urban heat island effect. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade). Temperatures in the lower trophosphere have increased between 0.12 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979. Temperature is believed to have been relatively stable over one or two years thousands before 1850, with possibly regional fluctuations such as the Little ice age.
SEA
Sea temperatures increase more slowly than those on land both because of the larger effective heat capacity of the oceans and because the ocean can lose heat by evaporation more readily than the land. The NORTHERN HEMISPHERE has more land than the SOUTHERN HEMISPHERE, so it warms faster. The Northern Hemisphere also has extensive areas of seasonal snow and sea-ice cover subject to the ice-albedo feedback. More greenhouse gases are emitted in the Northern than Southern Hemisphere, but this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres.
: http://en.wikipedia.org
