Global warming is the increase in the average temperature of the Earth's near-surface air and oceans; with air pollution and water pollution it seems that it has been increasing in recent decades and is projected to continue.

An increase in global temperatures may in turn cause other changes, including sea level rise, and changes in the amount and pattern of precipitation resulting in floods and drought. There may also be changes in the frequency and intensity of extreme weather events, though it is difficult to connect specific events to global warming. Other effects may include changes in agricultural yields, glacier retreat, reduced summer streamflows, species extinctions and increases in the ranges of disease vectors.

Remaining scientific uncertainties include the exact degree of climate change expected in the future, and how changes will vary from region to region around the globe. There is ongoing political and public debate regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences. Most national governments have signed and ratified the Kyoto Protocol aimed at combating greenhouse gas emissions.