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Fingerprints of climate change seen in Pa.’s hot summer days

Smoke and haze from the Canadian wildfires hang over Pittsburgh on June 28, 2023.
Oliver Morrison
90.5 WESA
Smoke and haze from the Canadian wildfires hang over Pittsburgh on June 28, 2023.

This summer was the hottest on record, globally.

Pennsylvania did not set records, but a new analysis shows it is still feeling the effects of climate change. And a separate analysis links the wildfire smoke that plagued Pennsylvania over the summer was also related to climate change.

The state is getting warmer and wetter with climate change. Hot days and warm nights have been trending up since the 1970s.

“You’re absolutely seeing spans of days across this summer where the temperature was clearly made warmer by the influence of climate change,” said Peter Girard, vice president of communications for the science and communication group Climate Central.

The group’s Climate Shift Index compares daily temperatures with a model showing likely temperatures in a world without the greenhouse gases that cause climate change.

Climate Central’s latest analysis using the CSI shows Harrisburg had eight days this summer with an index score of 2 or higher. That means the hot temperatures were twice as likely under climate change.

Philadelphia had nine days between June 1 and Aug. 31 touched by climate change, Pittsburgh had three, and State College had six.

In Allentown, there were seven days with a score of 2 or greater. Wilkes-Barre had five days and Erie had one.

The report says 97% of the U.S. population experienced at least one summer day with temperatures made at least twice more likely due to human-caused climate change.

The South, Southwest, and Southeast regions saw the strongest climate fingerprints on summer daily average temperatures.

An analysis from World Weather Attribution, a group that quantifies how climate change influences the intensity and likelihood of an extreme weather event, shows the record-breaking July heat waves in Arizona, New Mexico, and Texas would have been virtually impossible without human-caused climate change.

WWA also found climate change more than doubled the likelihood of extreme fire weather conditions in Canada in May and June that sent smoke into the U.S., causing unhealthy air quality in many places, including Pennsylvania.

This story is produced in partnership with StateImpact Pennsylvania, a collaboration among WESA, The Allegheny Front, WITF and WHYY.