Global warming is the unequivocal and continuing rise in the average temperature of Earth’s climate system. Since 1971, 90% of the warming has occurred in the oceans. “Global warming” is also used to refer to increases in average temperature of the air and sea at Earth’s surface.
The IPCC stated that the largest driver of global warming is carbon dioxide (CO2) emissions from fossil fuel combustion, cement production, and land-use changes such as deforestation.
Warming is expected to be strongest in the Arctic, with the continuing retreat of glaciers, permafrost, and sea ice. Other likely effects of the warming include more frequent extreme weather events including heat waves, droughts and heavy rainfall; ocean acidification; and species extinctions due to shifting temperature regimes. Effects significant to humans include the threat to food security from decreasing crop yields and the loss of habitat from inundation.
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Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes.
The United Nations Framework Convention on Climate Change (UNFCCC), whose ultimate objective is to prevent dangerous anthropogenic (human-induced) climate change. Parties to 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. Reports published in 2011 by the United Nations Environment Programme and the International Energy Agency suggest that efforts as of the early 21st century to reduce emissions may be inadequate to meet the UNFCCC’s 2 °C target.
Depletion of the ozone layer by chemical refrigerants has also resulted in a strong cooling effect in the stratosphere. If the sun were responsible for observed warming, warming of both the troposphere and the stratosphere would be expected. The main negative feedback is the energy which the Earth’s surface radiates into space as infrared radiation.
Climate change could result in global, large-scale changes in natural and social systems. Two examples are ocean acidification caused by increased atmospheric concentrations of carbon dioxide, and the long-term melting of ice sheets, which contributes to sea level rise.
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Global Warming Impacts
Rising Seas, Changes in rainfall patterns, The increased likelihood of extreme events, Melting of the ice caps, Widespread vanishing of animal populations, Spread of disease, Bleaching of Coral Reefs due to warming seas and acidification due to the carbonic acid formation, Loss of Plankton due to warming seas.