The arctic ices are melting and so are the glaciers, the result global warming. Global warming is the increase in the average temperatures of the Earth's near-surface air and oceans in recent decades and its projected continuation. Global average air temperature near the Earth's surface rose alarmingly during the past century. The Intergovernmental Panel on Climate Change (IPCC) concludes, "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," which leads to warming of the surface and lower atmosphere by increasing the greenhouse effect. Natural phenomena such as solar variation combined with volcanoes have probably had a small warming effect from pre-industrial times to 1950, with only a a small cooling effect since 1950. This warming phenomena and sea level rise are expected to continue for more than a millennium even if greenhouse gas levels are stabilized. This reflects the large heat capacity of the oceans. An increase in global temperatures can in turn cause other changes, including sea level rise,can result in floods and drought. There may also be changes in the frequency and intensity of extreme weather events, where such changes will vary from region to region around the globe.