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There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause. |
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# Glaciers Are Retreating Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska, and Africa.
#Snow Cover Is Decreasing Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and the snow is melting earlier.
# Sea Level Is Rising Global sea level rose about 8 inches (20 centimeters) in the last century. The rate in the last two decades, however, is nearly double that of the last century and accelerating slightly every year.
# Arctic Sea Ice Is Declining
Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades.
# Extreme Events Are Increasing in Frequency
The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events.
# Ocean Acidification Is Increasing
Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30%.This increase is due to humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the ocean. The ocean has absorbed between 20% and 30% of total anthropogenic carbon dioxide emissions in recent decades (7.2 to 10.8 billion metric tons per year).
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