By 2080, the city of cheesesteaks and brotherly love could feel as hot as the land of Elvis and barbecue, according to new research.

The peer-reviewed article, published last week in Nature Communications, projected many eastern U.S. cities could see radically different climates in future decades. An interactive map showed Philadelphia will become as hot as current day Memphis if nothing is done to decrease global carbon dioxide emissions.

Lead author Matthew Fitzpatrick, an associate professor at the University of Maryland Center for Environmental Science, said his goal was to reach the general public about the impact of human-caused climate change.

“We hear all the time about the Paris climate accord and how we want to hold global warming to a 1.5 degree celsius mean. But none of us experience mean global temperature on a daily basis," Fitzpatrick said. "So the idea was to translate this into something with more resonance with people.”

Fitzpatrick is an ecologist by training, not a climate scientist. His article shows that most of the big cities of the eastern U.S., including Boston, New York and Philadelphia, will take on climates of areas hundreds of miles to the south and southwest. He co-wrote the paper with another ecologist, Robert Dunn, of North Carolina State University.

The authors used various data sets — including U.S. Census geographic files and historical climate data from 1960 to 1990, and projections for 2070-2099 from the Consultative Group for International Agricultural Research — to derive and map their findings. They ran 54 projections based on higher or lower amounts of climate change, but all showed significant increases in temperature. They chose two scenarios for their map: one where steps are taken to reduce carbon dioxide emissions and one where nothing is done.

Fitzpatrick and Dunn found that if major steps are taken to reduce carbon, the climate in Philly could feel more like California, Md., a town near the Chesapeake Bay where a typical summer is 5.6 degrees warmer than here.

However, if greenhouse gases aren’t reduced from current levels, summers in Philly could become more like those in Memphis, Tenn., which is now an average of 6.5 degrees Fahrenheit warmer. A typical winter in Memphis is currently 9.1 degrees Fahrenheit warmer than in Philadelphia. Summers in Atlantic City, N.J., would more resemble Elizabeth City, N.C., which is currently 3.4 degrees Fahrenheit warmer in summer.

And Allentown, Pa., could feel more like Jonesboro, Ark. — bad news for Lehigh Valley ski resorts. The typical winter in Jonesboro is 10.6 degrees Fahrenheit warmer than in Allentown.

Sample of interactive map by University of Maryland Center for Environmental Science research showing how Philadelphia will become as warm as current day Memphis by 2080.
University of Maryland Center for Environmental Science
Sample of interactive map by University of Maryland Center for Environmental Science research showing how Philadelphia will become as warm as current day Memphis by 2080.

“What surprised me the most was putting the analysis together and seeing the results from where I live in Cumberland, Md., and to see that it’s going to become more like southern Kentucky,” said Fitzpatrick, who grew up in York, Pa. “I’m one of those rare people who like snow and cold. To think we might lose that here is discouraging.”

Fitzpatrick noted that the data could even be underplaying the potential impact. It does not, for example, take into account the heat island effect in urban areas with large, treeless swaths of concrete and steel.

That won’t be good news for tens of thousands of Philadelphia residents. Data show that temperatures can already get much higher in some neighborhoods than others here on a hot day. In fact, there can be as much as a 20-degree difference between Philly neighborhoods. In cities, heat gets trapped in areas with blocks of black-roofed rowhouses, strip shopping centers, and busy roads, but few trees or other sources of shade in between. These areas even stay warmer at night because heat is released so slowly from the structures.

Fitzpatrick cautioned that he sought to find the closest climate match for cities. So none of the matches are perfect for temperature and precipitation for all seasons, he said. For example, the data show Memphis is much drier now than Philly in summer, but it doesn’t suggest Philly will be that way in 2080. In fact, experts expect Philadelphia to become wetter as the climate changes.

Christine Knapp, director of Philadelphia’s Office of Sustainability, said she’s not familiar with the climate of Memphis, but her employer’s own projections agree that it is expected to get warmer as the decades progress because of human-caused climate change.

She said the city hasn’t updated that information in a few years, however.

“The bad news is that the projections always get worse with newer data,” Knapp said.