Research Points to Greenhouse Gases For Dlobal Warming

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By John Myers
Forum News Service
DULUTH, Minnesota. -- Research by a University of Minnesota Duluth professor that separates Earth's natural climate variability from outside factors points in particular to greenhouse gas-induced climate change as the likely cause of the warming planet.

The study found that natural climate variability probably has helped keep things cooler in recent years than they otherwise would have been due to the outside factors.

The research, published today in Science Magazine, was headed by the University of Minnesota Duluth's Byron Steinman, an assistant professor of geological sciences with the Large Lakes Observatory and the Department of Earth and Environmental Sciences.

By analyzing computer models that simulate Earth's climate over time, Steinman and his fellow researchers outlined an approach to pinpoint that internal variability.

The paper, "Atlantic and Pacific Multidecadal Oscillations and Northern Hemisphere Temperatures," is the latest in a line of peer-reviewed research that points to greenhouse gas as the driver of the changing climate.

The study looked at how weather patterns spurred by the northern Atlantic and northern Pacific oceans -- called oscillations -- affect climate trends.

The natural cooling trend in recent years hasn't been enough to offset global warming, but it likely has helped slow the pace of global warming in recent years, Steinman said

But when the current negative period of oscillation turns positive, and the naturally variable factors start increasing temperatures, "it's only going to accelerate'' the global warming trend, Steinman said.

With a model of that internal variability in place, the scientists were able to broaden the understanding of how outside forces such as greenhouse gases, solar fluctuations and volcanic eruptions affect climate events such as increased drought in Africa and an increase in Atlantic hurricanes.

"Are these trends being driven by natural, internal oscillations? Are they being driven by external forces?''' Steinman said. "Based on our research, it appears as though these changes are being strongly influenced by external forces and, in particular, the increase in greenhouse gases from fossil fuel burning."

Steinman, formerly of Penn State University, started with UMD's Swenson College of Science and Engineering last fall. Before coming to UMD he worked closely with renowned climate scientist Michael Mann, distinguished professor of meteorology at Penn State, and Sonya Miller, a Penn State meteorology coder and analyst.

Steinman said he expects the paper's findings to spur additional work.

"We're moving forward with some ideas, concepts and questions that people have been thinking about for years," he said. "Over the next few years, I would expect some of our findings to be challenged in the way that all good science is challenged. That's the way