It is a major aspect of current climate change, and has been demonstrated by direct temperature measurements and by measurements of various effects of the warming.
The Intergovernmental Panel on Climate Change Fifth Assessment Report concluded, “It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.” The largest human influence has been the emission of greenhouse gases such as carbon dioxide, methane, and nitrous oxide. Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to 1.7 C in a moderate scenario, or as much as 2.6 to 4.8 C in an extreme scenario, depending on the rate of future greenhouse gas emissions and on climate feedback effects.
The effects of global warming include rising sea levels, regional changes in precipitation, more frequent extreme weather events such as heat waves, and expansion of deserts. Surface temperature increases are greatest in the Arctic, which has contributed to the retreat of glaciers, permafrost, and sea ice.
Globally, a majority of people consider global warming a serious or very serious issue. Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, and maybe climate engineering. Every country in the world is a party to the United Nations Framework Convention on Climate Change , and that global warming should be limited to well below 2 C Some scientists call into question whether it is possible to limit temperature rise to 2 C ,
