Tag: lake levels

Transcript

Some scientists in the great lakes basin are looking at how global warming
Might be affecting the region, both today and long into the future. The
Great lakes radio consortium’s Lester graham reports.

Many researchers in a number of different fields are coming to the same basic conclusion: the earth is warming and it’s affecting the Great Lakes. So far, the effects have been difficult to track, unlike watching the day-to-day changes in the weather. Measuring climate change requires measurements over many decades, or better yet over centuries. There are only a few places where weather measurements have been taken over that long of a period. But, where they have, researchers are finding weather is becoming more chaotic and indications are that the long-term climate is warming.
Many climatologists believe that warming is due at least in part to greenhouse gases, that is, pollution in the upper atmosphere trapping more of the sun’s heat, much in the same way a greenhouse works.

Taylor Jarnigan is a research ecologist with the U-S Environmental Protection agency who’s been looking at one aspect of climate change. He’s been studying whether increasing amounts of lake effect snow from Lake Superior over the past century, especially the past 50 years, is evidence of a change in the temperature of the lake. Preliminary study suggests that the lake’s surface temperature is warming, and that causes more snow when cold air passes over it. But he says the amount of snow has varied widely from year to year.

“Some of this variability is certainly due –in my opinion– to an increasing volatile climate system itself. El niño and la niña are becoming more intense, so you have an increasing oscillation between, say, an usually warm summer followed by an unusually cold winter which tends to produce an unusually large amount of snow.”

The surface temperature of the lake has only been monitored for a few decades, while snowfall depths have been recorded for much longer. Jarnigan says, since there seems to be a direct correlation between the surface temperature of the lake and snowfall, he can calculate the temperature of the lake going back more than a century, and finds that Lake Superior is getting warmer.

When researchers find direct measurements that have been taken for more than a century, they feel fortunate. For example, John Magnuson with the University of Wisconsin has been reviewing the conclusions from the Intergovernmental Panel on Climate Change. That’s the international organization established by the United Nations to study global warming. As a part of that review, Magnuson has been looking over shipping and harbor records that date back 150 years or more to see if there’s evidence of global warming. One thing he’s learned is that lakes and streams aren’t iced over for as long as they once were.

“And in the last hundred-and-fifty years we’ve seen significant changes in lakes around the entire– lakes and streams around the entire northern hemisphere. The date of freezing on the average and the date of break up is changing by about six days per century.”

And Magnuson says that six day change on both ends of the freeze-thaw cycle mean that there’s nearly two weeks less ice coverage than a century ago.

That seems to bolster research at the National Oceanic and Atmospheric Administration’s Great Lakes Ecological Research Laboratory. Studies there indicate that over the last several years Great Lakes ice coverage on average is not as far ranging and doesn’t last as long as it did historically.

There’s no certain way to tell what might happen to the Great Lakes if the apparent warming trend continues.

But there are some ways to speculate. There are at least two computer models that try to estimate how much warmer the climate in the Great Lakes region might become by the year 2090. Based on those models, researchers have tried to figure out what that might mean for the area. Peter Sousounis was working at the University of Michigan at the time of that research. He says using either computer model it looks as though crops would produce more. Soybean yields could double. But other predictions are not as beneficial. It looks as though Great Lakes water levels would drop, probably about three feet more than they’ve already dropped, causing some problems for shipping. The study also found algae production would decrease by 10 to 20 percent. That’s important because algae provide the base for the Great Lakes’ food chain. Pine trees might also be all but eliminated from the region, and Sousounis says dangerously high ozone days might occur twice as often.

“Our findings indicate there are some potentially serious consequences in terms of reduced lake levels impacting shipping across the region, some serious economic impacts that if we don’t learn how to deal with these, there are going to be some serious changes in our lifestyles.”

Critics say the models can’t represent all of the variability in nature, so it’s difficult to be sure about any of the predictions. An adjustment here or there can lead to all kinds of alternative scenarios. Sousounis concedes more work needs to be done and more variables plugged into the models, but he’s convinced change will come; the degree of change is the only question.

These days, very few scientists argue against the studies that suggest the earth is warming. John Magnuson with the University of Wisconsin says a few DO argue that the change might merely be natural climate variability – that is, Mother Nature taking an interesting twist– and not necessarily a warm-up caused by manmade greenhouse gases.

“The skeptics, or the more cautious people, what they do when they look at that range of variation over the last thousand years, what they see is there is a signal in the warming that’s coming above the historic variation of climate. And, the climatologists of the world collectively feel there’s very strong evidence that warming is occurring, that greenhouse gases are a very significant part of that warming.”

Magnuson says most mainstream scientists agree climate change is happening, and even dramatic reductions in greenhouse gases won’t prevent some continued global warming over this century. But most say reducing pollution would slow the rise in temperatures and curtail the warming sooner. Only time will tell how that warming will change the Great Lakes region, and all of the researchers we talked to say in the meantime we’ll likely see more chaotic roller coaster type weather patterns as never before in recorded history.

For the Great Lakes Radio Consortium, this is Lester Graham.