Global warming and climate change both refer to the observed century-scale rise in the average temperature of the Earth'sclimate system and its related effects. Multiple lines of scientific evidence show that the climate system is warming.[2][3]More than 90% of the additional energy stored in the climate system since 1970 has gone into ocean warming; the remainder has melted ice, and warmed the continents and atmosphere.[4][a] The observed increases in global average surface temperature and atmospheric carbon dioxide have been much faster in recent decades than the natural changes of previous millennia, and levels are now higher than at any time for hundreds of thousands of years prior.[5] [6]
Scientific understanding of the cause of global warming has been increasing. In itsfourth assessment (AR4 2007) theIntergovernmental Panel on Climate Change (IPCC) reported that scientists were more than 90% certain that most of global warming was being caused by increasing concentrations of greenhouse gases produced by human activities(anthropogenic).[7][8][9] In 2010 that finding was recognized by the national science academies of all major industrialized nations.[10][b]
Climate model projections were summarized in the 2013 Fifth Assessment Report (AR5) by the IPCC. They indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to 1.7 °C (0.5 to 3.1 °F) for their lowestemissions scenario using stringent mitigation and 2.6 to 4.8 °C (4.7 to 8.6 °F) for their highest.[12]
Future climate change and associated impacts will vary from region to regionaround the globe.[13][14] The effects of an increase in global temperature include arise in sea levels and a change in the amount and pattern of precipitation, as well as a probable expansion of subtropicaldeserts.[15] Warming is expected to bestrongest in the Arctic, with the continuingretreat of glaciers, permafrost and sea ice. Other likely effects of the warming include more frequent extreme weather events including heat waves, droughts, heavyrainfall, and heavy snowfall;ocean acidification; and species extinctions due to shifting temperature regimes. Effects significant to humans include the threat tofood security from decreasing crop yields and the loss of habitat frominundation.
Possible responses to global warming include mitigation by emissions reduction,adaptation to its effects, building systemsresilient to its effects, and possible futureclimate engineering. Most countries are parties to the United Nations Framework Convention on Climate Change(UNFCCC),whose ultimate objective is to prevent dangerous anthropogenic climate change. The UNFCCC have adopted a range of policies designed to reduce greenhouse gas emissions and to assist in adaptation to global warming. Parties to the UNFCCC have agreed that deep cuts in emissions are required,[and that future global warming should be limited to below 2.0 °C (3.6 °F) relative to the pre-industrial level.[c]
No comments:
Post a Comment