[Image:3 examples of internal climate variability (1950-2012), the El Niño – Southern Oscillation, the Arctic Oscillation, and the North Atlantic Oscillation (NOAA).png|thumb |right |alt=Refer to caption |This image shows three examples of internal climate variability measured between 1950 and 2012: the El Niño–Southern oscillation, the Arctic oscillation, and the North Atlantic oscillation.]] Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent changes observed in the Earth's climate, commonly known as 'global warming'. The effort has focused on changes observed during the period of instrumental temperature record, when records are most reliable; particularly in 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.

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.