COLUMBUS, Ohio (WCMH) – It’s not the heat or the humidity. It’s the combination of the two that will turn Columbus summers stifling, dangerous and unrecognizable as our planet heats up in the coming decades.

With the heat index topping 100 degrees Fahrenheit last week, this is about the hottest Columbus gets. The city currently sees about three weeks year with a heat index of 90, when the National Weather Service calls for “extreme caution.”

But extreme heat’s occasional nuisance – currently limited to the capital city’s dog days of summer – are predicted to dramatically increase in years to come, according to a major report from the Union of Concerned Scientists, a nonprofit science advocacy organization based in Massachusetts.

The report, published in 2019, projects that Columbus’ 19 days per year of a 90+ heat index will increase to 65 days by midcentury and 97 days by late century.

“This is what scientists have been talking about all this time, and it’s heartbreaking,” said UCS senior climate scientist Rachel Licker, an author of the report based in Wisconsin. “This is not stuff that we’re used to in the Midwest.”

The heat index measures what outside conditions feel like by factoring in temperature and humidity. Our bodies sweat to combat hot temperatures, but humidity can stop sweat from evaporating.

According to the NWS’s heat index chart above, a 90-degree day feels like 100 degrees at 60% humidity, and a 100-degree day would feel like 129 degrees at the same humidity.

“When it’s more humid, it’s more difficult for your body to efficiently cool itself,” Licker said. And heat illness comes quicker to children, the elderly and people with respiratory and heart conditions.

Extreme heat days to increase exponentially without action

While heat indexes in the 90s are mostly bearable for Ohioans, extremely hot days will skyrocket. Columbus currently sees 1 day a year where the heat index hits 100 degrees. By midcentury (2036-2065), UCS projects that to increase to 24 days and by late century (2070-2099) to 52 days.

A similar future is forecast statewide. If current emissions trends continue to late century, Cleveland will see 35 days a year with a heat index over 100; Toledo will see 49 days; Dayton 57 days; and Cincinnati 66 days.

“We’re talking about basically Ohio spending the entire summer in conditions with the heat index above 100 degrees Fahrenheit, or a couple of weeks,” Licker said. “So, there’s just so much benefit to reducing greenhouse gas emissions.”

For perspective, the projected rise in Ohio’s average temperatures will make summer feel more like the hot and humid areas inland of the Gulf of Mexico if current carbon emissions continue.

“What’s the climate of Central Ohio going to be 60, 70 years from now? Something much more along the line of central Louisiana, central Mississippi or central Alabama,” said Sean Sublette, a meteorologist with climate change research group Climate Central.

His organization projected a worst-case scenario in 2014 in which Columbus’ average summer temperature of just over 83 degrees will increase to nearly 95 degrees by 2100, comparable to what summer feels like now on Texas’ southern border.

But with coal use starting to decline in the U.S., that forecast has moved slightly to conditions felt in the Deep South. Still sweltering, but better.

“There are inklings of progress,” Sublette said, noting that wind and solar are now the cheapest forms of energy in America.

Summer in Ohio’s capital city, however, is already heating up. Climate Central research shows Columbus’ average longest streak in a year of 85-plus-degree days more than doubled from 1970 to 2020.

“Think about Columbus ultimately turning into Lexington, ultimately turning into Nashville, then ultimately turning down to Huntsville,” Sublette explained. “And then, oh my heavens, next thing you know, it’s just like Birmingham.”

Hope exists despite the heat

UCS’s forecast assumes the U.S. and the world stay on their current emissions trajectories through the end of the century, one where transportation and power generation largely rely on fossil fuels like petroleum, coal and natural gas.

But the report also lays out two scenarios that show Ohio is not yet doomed to face insufferable summers.

With “slow action” on climate change, carbon emissions start to decline midcentury and the planet warms to just 2.4 degrees Celsius by 2100, compared with 4.3 degrees under no action.

And with “rapid action,” the most hopeful scenario, global warming is limited to the Paris Climate Agreement’s goal of 2 degrees Celsius, although humans have already heated the earth by 1.1 degrees Celsius (2 degrees Fahrenheit), according to the United Nations’ latest climate report.

“There already is some climate change because of the decisions that we’ve made,” Licker said, which are seen in the stronger heat waves and wildfires of recent summers. “But it’s about trying to preserve a climate that’s at least somewhat recognizable to the climate that we currently have and to give ourselves a fair shot of actually adapting.”

“And when we’re talking about a place like Columbus having 52 days above 100 versus one,” she continued, “that would require such an enormous level of adaptation, investments and lifestyle change.”

How to fight climate change

Faced with the possibility that Ohio’s mild summers could resemble that of the Deep South by 2070, what can be done?

Climate Central does not advocate for specific policies, but Sublette put humanity’s objective simply: “We need to find a way to generate electricity that doesn’t involve setting carbon on fire.”

Broadly, that includes generating electricity from solar, wind, hydroelectric and other renewable resources, plus transitioning to electric vehicles for public and private transportation.

The U.S. House of Representatives is currently considering a $1 trillion, bipartisan infrastructure bill that would make some progress. It includes $15 billion for electric vehicle infrastructure, $40 billion to make public transportation more environmentally friendly, and more than $70 billion for upgrading the nation’s electricity grid.

But no matter how carbon emissions are reduced, Sublette said, the sooner the better.

“How much warmer we get really is going to be determined about how we generate energy these next 10, 20 or 30 years,” he said. “That’s going to go a long way in determining what it’s going to be like at the end of the century.”

And that includes, Licker said, holding leaders accountable by voting and demanding action.

“We need systemic change,” she said.

As for individual action on climate change, Sublette said, “Do the little things.” That includes planting trees, composting food waste, limiting plastic use and – if you have the means – installing solar panels or driving a hybrid or electric car.

“It’s not that we’re going to hit a point where it doesn’t matter anymore in terms of taking action,” Licker said. “Every fraction of a degree does matter. That said, the more we let the earth warm, the worse it’s going to get.”