Global warming appears to affect when Pennsylvania lakes freeze, thaw

University Park, Pa. -- Pennsylvania ice fishermen no longer know what to expect.

Before the last couple of years, ice-fishing aficionados around the state had been complaining that Keystone State lakes were freezing later and thawing earlier than in the good old days, cutting down on the “hardwater” fishing season. But the last two frigid winters have made an already confusing scenario even more confounding.

Results of an international study of lakes and rivers in the Northern Hemisphere released in 2001 -- led by a University of Wisconsin, Madison researcher who reviewed a 150-year record of freeze and ice breakup dates for lakes and rivers—confirmed the claims of Pennsylvania ice fishermen. A decades-long warming trend had delayed lake freezing an average of about 10 days and hastened thawing by an average of almost nine days. Combined, that’s an average of almost three fewer weeks of ice fishing a year than in the past.

Pennsylvania never did have the long, frigid ice-fishing seasons popularized by the movie classic “Grumpy Old Men” and enjoyed in places like Minnesota, but Pennsylvania old-timers will tell you it was common in the state through the 1950s, ‘60s, ‘70s and ‘80s to start ice fishing shortly after Thanksgiving and continue right through March. Seems like that is rarely the case anymore.

Now, as the holidays approach and the first thin ice appears on many waters across the state, ice fishermen don’t know whether to dig out their augers and tip-ups or just chill by the fire for another month or so, until safe ice forms on lakes across the state.

Surprisingly, weather and climate experts in Penn State’s College of Agricultural Sciences aren’t sure what to tell them.

“The difficulty in trying to determine a trend in weather is that there is naturally so much variability,” says Bryan Swistock, a Penn State Cooperative Extension water resources specialist who keeps track of precipitation and weather trends in Pennsylvania. “Despite the long-term warming trend and the results of that study, in the last few years we have heard reports of more winter kills of fish, thicker ice and ice covering lakes lasting longer—so go figure. I guess we could say that if it weren’t for global warming, the last few winters might have been worse.”

Swistock points out that an El Nino warm ocean current phenomenon has been identified this fall in the Pacific, and that normally would portend a warmer-than-usual winter in Pennsylvania. Scientists only recently have begun to understand the influence of El Nino and La Nina currents in the Pacific Ocean on weather in the eastern United States.

“Although a weak El Nino is developing, the current three-month projection for our state from the National Weather Service is for below-normal temperatures,” Swistock says. “I think the key here is that the El Nino appears to be quite weak. If it were stronger, there might be a better chance for us to have a warmer winter. Right now, it looks like a cooler than normal winter is in store, so that could be good news for ice fishermen.”

Jim Shortle, distinguished professor of agricultural and environmental economics, has been doing research funded by the U.S. Environmental Protection Agency over the last decade to learn how global climate change will affect Pennsylvania. He has focused much of his work on how global warming will impact Pennsylvania agriculture.

“Since most models suggest increases in winter temperatures in Pennsylvania, I can’t think global climate change will be good for ice fishing in Pennsylvania,” he says. “My interest is primarily in the societal adaptation and economic impact of climate change, and how it will affect water resources. A reduction in ice-fishing opportunities is one likely outcome, and it may be taking place already.”

Shortle believes evidence of climate change only continues to accumulate, and the study showing lakes freezing later and thawing earlier was just one more verification. He’s not surprised Pennsylvania ice fishermen have been aware of the trend.

“Even the more credible skeptics are being converted,” Shortle says. “I had colleagues who said this is not happening, but I have seen those opinions change. People are having a hard time maintaining their skepticism of global climate change. The large societal risks cannot be ignored—ice fishing may be the least of our worries.”

But what does all this mean for the 2004-05 ice-fishing season?

Will there be safe ice on Pennsylvania lakes through the winter?

“All the experts agree,” says Swistock with a chuckle, “that we just don’t know. It was an unusual year—the wettest on record for parts of the state. We had remnants from more hurricanes than usual move through. That could all point towards a nasty winter. But then again, it might not.”