A NASA temperature graph shows the long-term trend.
New study suggests that 70 to 80 percent of the Earth’s land surface will see summer temps that exceed historical extremes
By Summit Voice
SUMMIT COUNTY — Even if efforts to cap average global temperature increases at 3.5 degrees are realized, about 70 to 80 percent of the Earth’s land surface could experience summer temperatures far above today’s norms, according a new research paper published last week in the journal Climatic Change Letters.
“We wanted to determine the impact such a temperature increase might have upon the frequency of seasonal-mean temperature extremes in various regions of the world.” said Bruce Anderson, and associate professor of geography at Boston University. “In particular, we wanted to determine if preventing the global-mean temperature increase from reaching this threshold would prevent extreme temperature values from becoming a normal occurrence in these regions.”
Anderson’s research indicates that if the 3.5 degree increase comes to pass 70 to 80 percent of the land surface will experience summertime temperature values that exceed observed historical extremes (equivalent to the top 5 percent of summertime temperatures experienced during the second half of the 20th century) in at least half of all years. In other words, even if an increase in the global mean temperature is limited to 3.5 degrees, current historical extreme values will still effectively become the norm for most of the earth’s land surface.
“Many regions of the globe—including much of Africa, the southeastern and central portions of Asia, Indonesia, and the Amazon — are already committed to reaching this point, given current amounts of heat-trapping gases in the atmosphere” Anderson said. Global-mean temperatures are expected to increase an additional 1degree during the coming decades — even if no more carbon dioxide, methane, or other heat-trapping gases are added to the atmosphere.
In the United States, the impacts are expected to be most severe over the western third of the country
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“In these regions, if the 3.5 degree threshold is passed, it is more likely than not that every summer will be an extreme summer compared with today,” said Anderson. Further, the region is expected to follow soon after Africa, Asia, and the Amazon as one in which summertime temperature extremes will become the norm. “While the western third of the U.S. is not committed to reaching such a situation, it is certainly on the brink,” said Anderson.
“While previous work, including our own and that of researchers at Stanford, has highlighted that summertime temperature extremes, and how frequently they occur, will change significantly even in response to relatively small increases in global-mean temperatures, the extent and immediacy of the results really caught us off guard,” said Anderson.
“Because these results are referenced to increases in global-mean temperatures, and not some particular time or change in amount of heat-trapping gases, they hold whether we reach this global-mean temperature increase in the next 40-50 years as currently projected, or the next century. They really are telling us that this is a temperature threshold that poses significant risks to our lives and livelihoods.”
Extreme summertime temperatures killed tens of thousands in Europe in 2003 and Russia in 2010 and produced over $50 billion in agriculture losses across the central and eastern U.S. in 1988. In addition, at least 18 states, including much of the southern and south-eastern U.S., suffered through these types of extreme conditions this past summer.
