8/3/2019 Global Warming Refers to the Rising Average Temperature of Earth

http://slidepdf.com/reader/full/global-warming-refers-to-the-rising-average-temperature-of-earth 1/1

Global warming refers to the rising average temperature of Earth's atmosphere and oceans andits projected continuation. In the last 100 years, Earth's average surface temperature increased by

about 0.8 °C (1.4 °F) with about two thirds of the increase occurring over just the last threedecades.

[2]Warming of the climate system is unequivocal, and scientists are more than 90%

certain most of it is caused by increasing concentrations of greenhouse gases produced by human

activities such as deforestation and burning fossil fuels.

[3][4][5][6]

These findings are recognized bythe national science academies of all the major industrialized countries.[7][A]

 

Climate model projections are summarized in the 2007 Fourth Assessment Report (AR4) by theIntergovernmental Panel on Climate Change (IPCC). They indicate that during the 21st century

the global surface temperature is likely to rise a further 1.1 to 2.9 °C (2 to 5.2 °F) for their lowestemissions 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 gasconcentrations.

[9][10] 

An increase in global temperature will cause sea levels to rise and will change the amount and

 pattern of  precipitation, and a probable expansion of subtropical deserts.

[11]

Warming is expectedto 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 including heat waves, droughts and heavy rainfall events, species

extinctions due to shifting temperature regimes, and changes in crop yields. Warming and relatedchanges will vary from region to region around the globe, with projections being more robust in

some areas than others.[12]

In a 4 °C world[clarification needed ]

, the limits for human adaptation arelikely 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 uponwhich human livelihoods depend would not be preserved.

[13] 

Most countries are parties to the United Nations Framework Convention on Climate Change (UNFCCC),[14]

whose ultimate objective is to prevent "dangerous" anthropogenic (i.e., human-

induced) climate change.[15]

Parties to the UNFCCC have adopted a range of policies designed toreduce greenhouse gas emissions[16]:10[17][18][19]:9 and to assist in adaptation to global

warming.[16]:13[19]:10[20][21]

Parties to the UNFCCC have agreed that deep cuts in emissions arerequired,

[22]and that future global warming should be limited to below 2.0 °C (3.6 °F) relative to

the pre-industrial level.[22][B] 2011 analyses by the United Nations Environment Programme[23] and International Energy Agency

[24]suggest that current efforts to reduce emissions may be

inadequately stringent to meet the UNFCC