Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent changes observed in the Earth's climate. The effort has focused on changes observed during the period of instrumental temperature record, when records are most reliable; particularly on the last 50 years, when human activity has grown fastest and observations of the troposphere have become available. The dominant mechanisms (to which recent climate change has been attributed) are anthropogenic, i.e., the result of human activity. They are:
- increasing atmospheric concentrations of greenhouse gases
- global changes to land surface, such as deforestation
- increasing atmospheric concentrations of aerosols.
There are also natural mechanisms for variation including climate oscillations, changes in solar activity, variations in the Earth's orbit, and volcanic activity.
The Intergovernmental Panel on Climate Change (IPCC) has concluded that " of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations." The IPCC defines "very likely" as indicating a probability of greater than 90%, based on expert judgement.
Attribution of recent climate change to human activities is based on multiple lines of evidence:
- A basic physical understanding of the climate system: greenhouse gas concentrations have increased and their warming properties are well-established.
- Historical estimates of past climate changes suggest that the recent changes in global surface temperature are unusual.
- Computer-based climate models are unable to replicate the observed warming unless human greenhouse gas emissions are included.
- Natural forces alone (such as solar and volcanic activity) cannot explain the observed warming.
The IPCC's attribution of recent global warming to human activities is a view shared by most scientists, and is also supported by a number of scientific organizations (see scientific opinion on climate change).
Read more about Attribution Of Recent Climate Change: Background, Detection Vs. Attribution, Attribution of 20th Century Climate Change, Scientific Literature and Opinion, Difficulties in Attribution, Solar Activity, Earlier Climate Changes, Internal Climate Variability and Global Warming
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