The Climate Science Special Report, released by the U.S. Global Change Research Program, Volume I of the Fourth National Climate Assessment, was released Friday afternoon. This authoritative assessment has a focus on the United States, and as mandated by the Global Change Research Act of 1990, it is part of the first of two volumes and, as stated on the report, “issue to serve as the foundation for efforts to assess climate-related risks and inform decision-making about responses. In accordance with this purpose, it does not include an assessment of literature on climate change mitigation, adaptation, economic valuation, or societal responses, nor does it include policy recommendations.”
The third assessment report was released on May 2014. This report undergoes six rounds of reviews by hundreds of scientists from different fields and organizations, and it is administered by NOAA. The next report is scheduled to be released late 2018.
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.
Here are the top 10 findings of the report:
- 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.
- 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.
- 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.
- 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.
- 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.
- Northern Hemisphere spring snow cover, North American maximum snow depth and Western snow water equivalent have all declined.
- Global mean sea level has risen about 7-8 inches since 1900, with about 3 of those inches occurring since 1993.
- 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.
- 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.
- For Atlantic hurricanes, increases are projected in precipitation rates and intensity.
Conclusions for the Southeast U.S.
Globally, in the last 115 years, air temperature has increased by 1.8 degrees Fahrenheit (1 degrees Celsius) – this is between 1901-2016. It is the warmest period in the history of modern civilization.
In Florida, there has been a notable increase in record high low temperatures, meaning that the nights are becoming warmer on average. This is extremely harmful for our health. The less time our bodies have to recoup from the day’s heating, the harder our bodies have to work.
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Higher temperatures also allow mosquito-borne and airborne diseases to spread rapidly or continue to spread well out of the regular season.
The last three years have biieen the warmest three years on record globally; 2017 will likely become the second warmest year on record, while 2016 currently holds the first spot.
Sea level rise
Sea levels on average globally have risen between 7-8 inches since 1900, with half of that amount, about 3 inches, occurring since 1993. The rate of rise is greater than during any preceding century in the last 2,800 years. Sea level rise is already affecting the U.S. More than 25 Atlantic and Gulf Coast cities have experienced acceleration in the incidence of daily tidal flooding.
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Sea levels are expected to continue to rise by several inches in the next 15 years and by up to 4 feet by the 2100. Scientific reports by NOAA in early 2017 stated that some projections were underestimated and that a higher rise of sea level cannot be ruled out. The report stated that a rise of as much as 8 feet by 2100 can’t be dismissed. Also, considering the bathymetry of the East and Gulf Coasts of the U.S., sea level rise will be higher that the global average.
Extreme weather events
Extreme events compound rainfall, drought, temperatures, snowpack, etc., which also ties to hurricanes.
As the atmosphere holds more water vapor due to an increase in global temperatures, the atmosphere also becomes more unstable, so by the time it reaches the tipping point where it can’t hold any more, all that water vapor must be released, resulting in heavier downpour.
For the southeast, this means that rainfall events are becoming more extreme, either by stronger atmospheric seasonal events such as stronger hurricanes, or even by typical afternoon storms dumping more rainfall on average.
The largest observed changes in rainfall and its intensity have happened in the Northeastern U.S.
On the other side of the spectrum, whenever drought events kick in, there will be extreme droughts that could perhaps last longer than in the past.
The magnitude of climate change beyond the next few decades will mainly depend on the amount of greenhouse gasses, especially carbon dioxide, emitted globally. If CO2 is not reduced significantly, the increase in average yearly global temperature will surpass 3.6 degrees Fahrenheit (2 degrees Celsius), which will lead to the extreme catastrophic impacts, scientists warned.
Humanity's safety is highly dependent on extreme weather events. Infrastructure, agriculture, water quality and quantity and natural ecosystems are all affected by extreme events.
The greatest uncertainty comes when considering future generations. Depending on how people react, the outcome might change for good or worse, according to the report.
Click here for the complete report.
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