global warming

Global warming refers to the rising average temperature of Earth's atmosphere and Oceans, the which started to increase of in the late 19th century and is projected to keep going up. Since the early 20th century, Earth's average surface temperature has Increased by about 0.8 ° C (1.4 ° F), with about two thirds of the increase of occurring since 1980.Warming of the climate system is unequivocal, and Scientists are more than 90% Certain That most of it is Caused by Increasing concentrations of greenhouse gases produced by human activities as deforestation and burning Such fossil fuels.These Findings are Recognized by the National Science Academies of all the major industrialized nations.Climate model projections are summarized in the 2007 Fourth Assessment Report (AR4) by the Intergovernmental Panel on Climate Change (IPCC). They indicate during the 21st century That the global surface temperature is Likely to rise a further 1.1 to 2.9 ° C (2 to 5.2 ° F) for Their lowest emissions scenario and 2.4 to 6.4 ° C (4.3 to 11.5 ° F) for Their highest . [8] The ranges of these estimates Arise from the use of models with differing sensitivity to greenhouse gas concentrations.An increase of temperature will cause in global sea levels to rise and will change the amount and pattern of precipitation, and a probable expansion of subtropical deserts.Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers , permafrost and sea ice. Other Likely effects of the warming include more frequent occurrence of extreme weather events-heat waves Including, droughts and heavy rainfall, species extinctions due to shifting temperature regimes, and changes in crop yields. Warming and related changes will Vary from region to region around the globe, with projections being more robust in some areas than others.If the global mean temperature increases to 4 ° C above preindustrial levels, the limits for human adaptation are Likely to be exceeded in many parts of the world, while the limits for adaptation for natural systems would largely be exceeded throughout the world. Hence, the ecosystem services upon the which human livelihoods depend would not be preserved.Most countries are parties to the United Nations Framework Convention on Climate Change (UNFCCC), Whose ultimate objective is to Prevent "dangerous" anthropogenic (ie, human-induced) climate change. Parties to the UNFCCC have adopted a range of policies designed toReduced 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 'global future warming should be limited to below 2.0 ° C (3.6 ° F) relative to the pre-industrial levels.2011 report of analyzes by the United Nations Environment Programme and the International Energy Agency suggest Efforts That as of the early 21st century to Reduced emissions may be inadequately stringent to meet the UNFCCC's 2 ° C target.