Are human activities or natural variations in climate responsible for the climate changes observed today?
Question: Are human activities or natural variations in climate responsible for the climate changes observed today?
The Earth does go through natural cycles of warming and cooling, caused by factors such as changes in the sun or volcanic activity. This has been closely examined, and the warming we have seen in the past 50 years cannot be explained by natural factors alone. 1 This figure illustrates one piece of evidence that shows that recent global warming is primarily a result of greenhouse gas emissions from human activities.
» Learn more about the causes of climate change.
1. USGCRP (2009). Global Climate Change Impacts in the United States . Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson (eds.). United States Global Change Research Program. Cambridge University Press, New York, NY, USA.
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