Scientists: Area's days of extreme heat will spike in coming years

Ohio among states poised to see spike in dangerously high temperatures.

By Tom Henry / The Blade
Wed, 17 Jul 2019 23:06:05 GMT

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Killer heat is nothing new.

But the number of days people will be subjected to potentially deadly heat waves such as the one being endured by two-thirds of the country this weekend will more than triple in Ohio and quadruple in Michigan if a new report sounding an alarm about climate change comes true.

The 52-page report, issued this week by the Cambridge, Mass.-based Union of Concerned Scientists, said Ohio’s current trajectory — assuming there is no significantly greater effort to combat climate change — will bring 60 days a year with a heat index of 90 degrees or higher by mid-century, more than three times the state’s historical average of 17 days a year. The heat index measures the discomfort the average person is thought to experience as a result of temperature and humidity.

Michigan would have 34 days a year with a heat index of 90 degrees or higher by mid-century, four times its historical average of eight days a year, according to the data.

Drilling down more locally, the Toledo area can expect to have 58 days a year with a heat index of 90 degrees or higher by mid-century, more than three times its historical average of 18 days a year.

The new report comes as Toledo, like much of the country, is suffering through one of the hottest stretches of the summer to date. Meteorologists at The Blade’s media partner, 13abc WTVG, anticipated heat indexes of 108 to 113 on Friday and Saturday. The National Weather Service has issued an excessive heat warning for the region through Saturday evening.

The report, which can be seen online, allows viewers to filter by hotter temperature categories, such as the average and projected number of days in excess of 100 and 105-degree heat indexes, plus a category labeled “off the charts” for heat index. The forecasts call for more of each if nothing more is done to curb the effects of climate change.

Look up heat projections for specific cities and counties

The study projects out to the end of the century, and estimates the number of days that could be reigned in if “bold action” is taken soon.

In Toledo, for example, it claims the number of above-90 degree heat index days could be limited to 52 days instead of 89 by the end of the century with more aggressive action aimed at curbing greenhouse gases. The data also claims Toledo is headed for 11 days a year with a heat index of 105 degrees or more by mid-century, and 32 days a year by the end of the century.

Historically, Toledo has had none.

The Midwest in general will be hit hard, as will most other parts of the country, with the Southeast and the Southern Great Plains taking the biggest brunt.

“Few places would be unaffected by extreme heat conditions by mid-century and only a few mountainous regions would remain heat refuges by century’s end,” according to the group.

One of the report’s 10 co-authors, Kristina Dahl, a UCS senior climate scientist, said the group’s analysis “shows a hotter future that’s hard to imagine today.”

Five months of the year in parts of Florida and Texas could have heat indexes of 100 degrees or higher later this century without more aggressive action taken to combat greenhouse gases worldwide, many of those days with heat indexes surpassing 105 degrees.

“On some days, conditions would be so extreme that they exceed the upper limit of the National Weather Service heat-index scale and a heat index would be incalculable,” Ms. Dahl said. “Such conditions could pose unprecedented health risks.”

So-called “off-the-charts” days — typically those with a heat index of 127 degrees or more — occur now only in the Sonoran Desert on the southern California-Arizona border. Fewer than 2,000 people have historically lived there and have been exposed to the equivalent of a week or more of those extreme conditions per year on average.

But by mid-century, more than 6 million people could feel the effects of such temperatures for a week or more as the heat spreads to other areas. By late century, that figure could rise to more than 118 million people, more than a third of the current U.S. population.

Another one of the report’s co-authors, Erika Spanger-Siegfried, lead UCS climate analyst, noted that most of the country now has “little to no experience” with such extreme conditions.

“Exposure to conditions in that range makes it difficult for human bodies to cool themselves and could be deadly.” 

UCS said its methodology uses a set of 18 climate models, with the aggregate statistically downsized. Emission modeling was run with two future scenarios, one in which no substantial reductions in greenhouse gases are pursued through the latter part of the century, and one which considers the possibility of emissions starting to decline around mid-century.

Daily maximum temperature and daily minimum relative humidity output from downsized models was used to calculate the maximum heat index for each day in the warm season between 2006 and 2099. The mid-century estimates were based over a nearly 30-year period, from 2036-2065, as were the late century projections, from 2070 to 2099.

“Finally, we averaged the results from all the models for each time period,” the report said.

Variations in clothing thickness, height, weight, age, health, and physical activity were not taken into consideration. Neither were wind speed, cloudiness, shade levels, or any other factors known to worsen or improve heat-related impacts.

The National Oceanic and Atmospheric Administration in its latest monthly report on global climate issued Thursday stopped short of predicting that 2019 will become another record year for heat worldwide, but only because it doesn’t make such predictions. The administration did note that 2019 is “virtually certain” to at least become one of the world’s top five hottest years on record.

“We don't attempt to forecast whether there will be records broken,” Dan Collins, a meteorologist in NOAA’s Climate Prediction Center, said.

But he and others told reporters on a national conference call that combined global land and ocean temperatures for this June were the warmest on record, and that much of Europe — especially France — experienced a short, but record-breaking heat wave.

NOAA’s climate data goes back to 1880.

South America, Africa, and Alaska also had record or near-record June heat, while much of the continental United States was average or slightly cooler than normal, Karin Gleason, a climate scientist at NOAA’s National Centers for Environmental Information, said.

Nine of the 10 warmest Junes have occurred since 2010. The only one outside of that group was June, 1998, That month is currently ranked as the eighth warmest June on record, NOAA said.

NOAA’s three-month forecast shows at least a 70 percent chance of above-average heat in Alaska, the Southwest, the Eastern seaboard from Maine to North Carolina, and in Florida during the months of August through October. 

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