by MaryTMartin » 25 Jan 2011, 01:22
Global warming describes an increase over time of the average global temperature at the surface of the Earth, which has risen by 0.6 ± 0.2°C since the late 19th century. Global warming theories attempt to account for the rise and assess the extent to which the effects are due to human causes. Most of the warming of the last 50 years is attributed to increases in the greenhouse effect caused by human-generated carbon dioxide (CO2); solar variability and other natural causes also play a role.
Climate models predict that temperatures will increase (with a range of 1.4°C to 5.8°C for change between 1990 and 2100). Much of this uncertainty results from not knowing future CO2 emissions, but there is also uncertainty about the accuracy of climate models. Climate commitment studies predict that even if levels of greenhouse gases and solar activity were to remain constant, the global climate is committed to 0.5°C of warming over the next one hundred years due to the lag in warming caused by the oceans.
Although the discussion of global warming often focuses on temperature, global warming or any climate change may cause changes in other things as well, including the sea level, precipitation, weather patterns, etc. These may affect human activity via floods, droughts, heat waves, changes to agricultural yields, etc