Global warming and climate change are terms for the observed century-scale rise in the average temperature of the Earth's climate system and its related effects.
Climate is the statistics of weather, usually over a 30-year interval.
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Multiple lines of scientific evidence show that the climate system is warming.
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In 2014, the Intergovernmental Panel on Climate Change Fifth Assessment Report concluded that "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century."
The Intergovernmental Panel on Climate Change is a scientific and intergovernmental body under the auspices of the United Nations, set up at the request of member governments, dedicated to the task of providing the world with an objective, scientific view of climate change and its political and economic impacts.
The largest human influence has been emission of greenhouse gases such as carbon dioxide, methane and nitrous oxide; human activities have led to carbon dioxide concentrations above levels not seen in hundreds of thousands of years.
Nitrous oxide, commonly known as laughing gas, nitrous, nitro, or NOS is a chemical compound with the formula N
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range.
Carbon dioxide is a colorless and odorless gas vital to life on Earth.
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 for their lowest emissions scenario and 2.6 to 4.8 °C for the highest emissions scenario.
Climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice.
These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing.
Anticipated effects include warming global temperature, rising sea levels, changing precipitation, and expansion of deserts in the subtropics.
The subtropics are geographic and climate zones located roughly between the tropic circle of latitude at 23.5 latitude and temperate latitudes.
A desert is a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life.
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity.
Warming is expected to be greater over land than over the oceans and greatest in the Arctic, with the continuing retreat of glaciers, permafrost and sea ice.
A glacier is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds its ablation over many years, often centuries.
In geology, permafrost is ground, including rock or soil, at or below the freezing point of water 0 °C for two or more years.
Sea ice arises as seawater freezes.
Other likely changes include more frequent extreme weather events including heat waves, droughts, heavy rainfall with floods and heavy snowfall; ocean acidification; and species extinctions due to shifting temperature regimes.
Snow pertains to frozen crystalline water throughout its life cycle, starting when it precipitates from clouds and accumulates on surfaces, then metamorphoses in place, and ultimately melts, slides or sublimates away.
Extreme weather includes unexpectable, unusual, unpredictable severe or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past.
A drought is a period of below-average precipitation in a given region, resulting in prolonged shortages in its water supply, whether atmospheric, surface water or ground water.
Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels.
Because the climate system has a large "inertia" and greenhouse gases will stay in the atmosphere for a long time, many of these effects will not only exist for decades or centuries, but will persist for tens of thousands of years.
Inertia is the resistance of any physical object to any change in its state of motion; this includes changes to its speed, direction, or state of rest.
An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body.
Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, building systems resilient to its effects, and possible future climate engineering.
Climate engineering, commonly referred to as geoengineering, also known as climate intervention, is the deliberate and large-scale intervention in the Earth’s climatic system with the aim of limiting adverse climate change.
Most countries are parties to the United Nations Framework Convention on Climate Change, whose ultimate objective is to prevent dangerous anthropogenic climate change.
The United Nations Framework Convention on Climate Change is an international environmental treaty negotiated at the Earth Summit in Rio de Janeiro from 3 to 14 June 1992, then entered into force on 21 March 1994.
Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 °C relative to pre-industrial levels, with efforts made to limit warming to 1.5 °C.
Public reactions to global warming and concern about its effects are also increasing.
A global 2015 Pew Research Center report showed a median of 54% consider it "a very serious problem".
The Pew Research Center is a nonpartisan American "fact tank" which is based in Washington, D.C. It provides information on social issues, public opinion, and demographic trends shaping the United States and the world.
The median is the value separating the higher half of a data sample, a population, or a probability distribution, from the lower half.
There are significant regional differences, with Americans and Chinese among the least concerned.