Climate Science Special Report released; key findings of Earth's health

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By Irene Sans

The main take away from this assessment is that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of observed warming since the mid-20th century.

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  1. The global average temperature has increased 8 degrees Fahrenheit (1 degrees Celsius) from 1901 to 2016, and is rising faster that at any time in the last 1,700 years.
  2. The average annual temperature over the contiguous U.S. has increased 1.8 degrees Fahrenheit from 1901 to 2016. Surface and satellite data are consistent in their depiction of rapid warming since 1979. With no change in the rate of greenhouse gas emissions, an additional 5.8- to 11.9-degree Fahrenheit increase is projected by 2100.
  3. There have been marked changes in temperature extremes across the contiguous U.S. The number of high temperature records far exceeds the number of low temperature records. This trend is projected to continue.
  4. The global influence of natural variability is limited to a small fraction of observed climate trends. Solar output changes and internal natural variability can only contribute marginally to the observed changes in climate over the last century, and there is no convincing evidence for natural cycles in the observational record that could explain the observed changes in climate.
  5. Heavy precipitation events in most parts of the U.S. have increased in frequency and intensity since 1901, with the largest increase is in the Northeast and the second largest increase in the Midwest.
  6. Northern Hemisphere spring snow cover, North American maximum snow depth and Western snow water equivalent have all declined.
  7. Global mean sea level has risen about 7-8 inches since 1900, with about 3 of those inches occurring since 1993.
  8. The world's oceans have absorbed 93 percent of the excess heat caused by global warming since the mid-20th century. Oceans are warming, rising and getting more acidic.
  9. The Arctic is warming at a rate approximately twice as fast as the global average and, if it continues to warm at the same rate, Septembers will be nearly ice-free in the Arctic Ocean by the 2040s.
  10. For Atlantic hurricanes, increases are projected in precipitation rates and intensity.

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