July 2017 Tied for Warmest Month on Record; Gives Further Support to Recently Released Climate Change Special Report

Following the release by the New York Times of a draft copy of a Climate Change Special Report (CSSR) prepared to provide the scientific basis of the upcoming 2018 Fourth National Climate Assessment—as if perfectly planned for maximum effect, according to an analysis released on August 15 by NASA’s Goddard Institute for Space Studies (GISS)— July 2017 was the warmest July on record (since 1880), and statistically tied with the warmest month on record of August 2016.  (GISTEMP Team, 2017: GISS Surface Temperature Analysis (GISTEMP).  What makes the July 2017 record so concerning, is that unlike 2016, 2017 is a non-El Nino year, and therefore, lacking the additional heat input into the atmosphere provided by the El Nino phenomena.

While this blog generally will address regulatory and legal issues surrounding climate change, it is good to look at the scientific consensus on just how the climate is changing globally, and therefore, why there is the regulatory and legal response we see developing both internationally and nationally.

One of the signatures of a warming atmosphere is a jet stream (an ‘atmospheric river’ that forms between warmer and cooler regions of the atmosphere and directs the motion of low and high pressure systems) that is “wavier.”  In other words, the jet stream will flow more “north/south” than “west/east.”  This pattern can be seen clearly in the GISS Surface Temperature Anomaly map for North America.  While the Eastern and Midwestern portions of the US experienced a relatively average or cooler than average July (the “cool side of the jet”), the western U.S. across western Canada through Alaska experienced an extremely warm July (the “warm side of the jet”).  As seen on the GISS map, other areas of extreme heat were found in the Middle East/Northeast Africa, across most of China into Mongolia, and generally off the coast of Antarctica near South America.

Moving away from the extremes of this past July, the CSSR presented the following conclusions regarding the overall state of the global climate.  These conclusions are given in terms of scientific “confidence” in their likelihood (based on statistical methods.)

  • Since the last Climate Assessment was published (in 2014), 2014 became the warmest year on record globally; 2015 surpassed 2014 by a wide margin; and 2016 surpassed 2015. Executive Summary (“ES”), pg. 13.
  • Sixteen of the last 17 years are the warmest years on record for the globe. ES, pg. 13;
  • Many lines of evidence demonstrate that it is extremely likely that human influence has been a dominant cause of the observed warming since the mid-20th Over the last century, there are no convincing alternative explanations supported by the extent of the observational evidence (very high confidence). ES, pg. 14;
  • Average annual temperatures over the contiguous United States are projected to rise (very high confidence). Increases of about 2.5°F, relative to the 1976-2005 average, are projected for the next few decades in all emissions scenarios, implying recent record-setting years may be “common” in the near future (high confidence). ES, pg. 17;
  • The frequency of cold waves has decreased since the early 1900s and the frequency of heat waves has increased since the mid-1960s. (very high confidence). ES, pg. 19;
  • The frequency and intensity of heavy precipitation events in the United States are projected to continue to increase over the 21st century (high confidence). ES, pg. 22;
  • The world’s oceans have absorbed about 93 percent of the excess heat caused by greenhouse gas warming since the mid-20th century, making them warmer and altering global and regional climate feedbacks (very high confidence). ES, pg. 26;
  • The world’s oceans are currently absorbing more than a quarter of the CO2 emitted to the atmosphere annually from human activities, making them more acidic with potential detrimental impacts to marine ecosystems (very high confidence). ES, pg. 29;
  • Annual average near-surface temperatures across Alaska and the Arctic have increased over the last 50 years at a rate more than twice as fast as the global average temperature (very high confidence). ES, pg. 30;
  • Since the early 1980s, annual average arctic sea ice has decreased in extent between 3.5 percent and 4.1 percent per decade, has become thinner by between 4.3 and 7.5 feet, and is melting at lease 15 more days each year. September sea ice extent has decreased between 10.7% and 15.9 percent per decade (very high confidence). ES, pg. 31.

The point of listing some of the conclusions in the CSSR is to show where scientific consensus regarding anthropogenic warming lies. These facts are not controversial in the scientific community.  How humanity responds to these conclusions will be the subject of future regulatory activity, legal developments, and politics.


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