US National Weather Service Memphis Tennessee
The heat index for Memphis on July 8 was 107 degrees. Shelby Countians will need to get used to that if nothing is done about climate change, according to a new report.
Memphis summers could boil above a heat index of 127 degrees for 20 days of the year by the end of this century if nothing is done about climate change, according to a new report by the Union of Concerned Scientists (UCS).
Union of Concerned Scientists/Facebook
The Washington-D.C.-area group says it ”puts rigorous, independent science to work to solve our planet’s most pressing problems.” On Tuesday, the group issued dire warnings about the future if the country does not capture heat-trapping emissions, which cause climate change, in a report called “Killer Heat in the United States: Climate Choices and the Future of Dangerously Hot Days”
[pullquote-1] “The rise in days with extreme heat will change life as we know it nationwide, but with significant regional differences,” said Rachel Licker, senior climate scientist at UCS and report co-author. “For example, in some regions currently unaccustomed to extreme heat— those such as the upper Midwest, Northeast and Northwest — the ability of people and infrastructure to cope with it is woefully inadequate. At the same time, people in states 
already experiencing extreme heat — including in the Southeast, Southern Great Plains, and Southwest—have not seen heat like this.
“By late century, they may have to significantly alter ways of life to deal with the equivalent of up to five months a year with a heat index above — often way above — 105 degrees. We don’t know what people would be able and willing to endure, but such heat could certainly drive large-scale relocation of residents toward cooler regions.”
The report lays out several scenarios for the future — with action on climate change, slow action, and rapid action. Those scenarios are laid out into possibilities for the middle of this century and the end of the century.
Visit the UCS interactive map with all of the data here.
Union of Concerned Scientists
A screenshot of the UCS interactive map, which indicates that if nothing is done about climate change, Shelby County could have 83 days per year with a heat index over 105 degrees.
Shelby County hasn’t had days with a heat index above 127 degrees, according to the study. If nothing is done, the county could see four such days a year by mid-century. By the end of the 21st century, Shelby County is looking at 20 days per year with heat indices of more than 127 degrees.
With bold action on climate change, the USC report says Shelby County would have three days of 127-degree heat each year by midcentury. With that action, the county could cut those 20 days of “off the chart” heat to only four by the end of the century.
Here are the climate-change-related, heat index scenarios for Shelby County, according to the UCS:
Report: Much Hotter Days Ahead for Memphis If No Action on Climate Change
Here are some future scenarios the group outlined for Tennessee:
• Historically, there have been 51 days per year on average with a heat index above 90 degrees Fahrenheit, the worker safety threshold. This would increase to 100 days per year on average by midcentury and 128 by the century’s end.
• Historically, there have been eight days per year on average with a heat index above 100 degrees Fahrenheit. This would increase to 53 days per year on average by midcentury and 84 by the century’s end.
Of the cities with a population of 50,000 or more in the state, Clarksville, Jackson and Memphis would experience the highest frequency of these days. Limiting warming to 2 degrees Celsius above pre-industrial levels would cap the frequency of such days at an average of 40 per year.
[pullquote-2] • By the end of the century, an estimated 6.1 million people would be exposed to a heat index above 100 degrees Fahrenheit for the equivalent of two months or more per year. By limiting warming to 2 degrees Celsius, more than 4.9 million of those residents would avoid such days of extreme conditions.
• Historically, there has been an average of two days per year with a heat index above 105 degrees Fahrenheit. This would increase to 32 days per year on average by midcentury and 63 by the century’s end. Limiting warming to 2 degrees Celsius above pre-industrial levels would cap the frequency of such days at an average of 21 per year.
• By the end of the century, an estimated 6.3 million people would be exposed to a heat index above 105 degrees Fahrenheit for the equivalent of a month or more per year. By limiting warming to 2 degrees Celsius, nearly 4.6 million of those residents would avoid such days of extreme conditions.
Report: Much Hotter Days Ahead for Memphis If No Action on Climate Change (2)
• Historically, the state as a whole has experienced zero “off-the-charts” heat days in an average year. This would increase to two days per year on average by midcentury and 11 by the end of the century. Limiting warming to 2 degrees Celsius could cap the frequency of such days at an average of one per year.
• By the end of the century, an estimated 5 million people would endure “off-the-charts” heat days for the equivalent of a week or more per year.
“Our analysis shows a hotter future that’s hard to imagine today,” said Kristina Dahl, senior climate scientist at UCS and co-author of the report. “Nearly everywhere, people will experience more days of dangerous heat even in the next few decades.
“By the end of the century, with no action to reduce global emissions, parts of Florida and Texas would experience the equivalent of at least five months per year on average when the ‘feels like’ temperature exceeds 100 degrees Fahrenheit, with most of these days even surpassing 105 degrees.”
To review the data for yourself, visit the UCS report website.