Scientists use observations from the ground, air, and space, along with computer models, to monitor and study past, present, and future climate change. Natural processes, which have been overwhelmed by human activities, can also contribute to climate change, including internal variability (e.g., cyclical ocean patterns like El Niño, La Niña and the Pacific Decadal Oscillation) and external forcings (e.g., volcanic activity, changes in the Sun’s energy output, variations in Earth’s orbit). These changes have a broad range of observed effects that are synonymous with the term.Ĭhanges observed in Earth’s climate since the mid-20th century are driven by human activities, particularly fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth’s atmosphere, raising Earth’s average surface temperature.

The current warming trend is unequivocally the result of human activity since the 1950s and is proceeding at an unprecedented rate over millennia.Ĭlimate change is a long-term change in the average weather patterns that have come to define Earth’s local, regional and global climates. Since the pre-industrial period, human activities are estimated to have increased Earth’s global average temperature by about 1 degree Celsius (1.8 degrees Fahrenheit), a number that is currently increasing by more than 0.2 degrees Celsius (0.36 degrees Fahrenheit) per decade. This term is not interchangeable with the term 'climate change.' Global warming is the long-term heating of Earth’s surface observed since the pre-industrial period (between 18) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth’s atmosphere. Learn more about global surface temperature here. This graph illustrates the change in global surface temperature relative to 1951-1980 average temperatures, with the year 2020 statistically tying with 2016 for hottest on record (Source: NASA's Goddard Institute for Space Studies).

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