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A Take on Earth's Temperature, Post-Bali

A round-up of research taken in the wake of the Bali summit on climate change finds little to warm the heart with the one exception that Atlantic hurricanes may grow more numerous but less fierce.
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Flooded homes are shown near Lake Houston following Hurricane Harvey on August 30th, 2017, in Houston, Texas.

Flooded homes are shown near Lake Houston following Hurricane Harvey on August 30th, 2017, in Houston, Texas.

Arctic ice is going the way of the Wicked Witch of the West, and we should prepare for more of the severe storms that blew Dorothy into Oz. Those are among the conclusions of a series of new academic studies, which indicate that, as the world's nations debate the best way to deal with climate change, global warming appears to be accelerating.

According to newly published research, the Greenland ice sheet is melting more quickly than expected, and surface waters in the Arctic are at record temperature levels. Such reports suggest our earlier estimates of global temperature increases may have been too conservative.

As to what this portends, several reports predict Americans can expect fewer but wetter storms as the Earth heats up. And in a bit of potential good news, the link between global warming and intensifying hurricanes may not be as clear-cut as first believed.

First, the news from up north. The melting of the ice mass in western Greenland in 2007 was the largest on record, and the process continues to accelerate, according to University of Colorado geography professor Konrad Steffen, director of the Cooperative Institute for Research in Environmental Sciences. He presented his findings at the fall meeting of the American Geophysical Union, held December 10th through 14th in San Francisco.

Studying data from his network of 22 stations on the Greenland ice sheet, Steffen estimates the melting has increased by about 30 percent between 1979 (when satellite measurements were first taken) and 2006. Given that Greenland is home to about 5 percent of the world's ice, we're talking about a lot of cold water.

Steffen estimates that, at the current rate, the Greenland ice melt is producing a rise in global sea levels of about a half-millimeter per year. Or to look at it from a mountaintop perspective: "The amount of ice lost by Greenland over the last year is the equivalent of two times all the ice in the Alps."

Scientists observing the Greenland ice sheet by helicopter have noted an increase in moulins—cylindrical, vertical shafts in the ice that take melt water from the surface and deposit it down in the bedrock. "These melt-water drains seem to allow the ice sheet to respond more rapidly than expected to temperature spikes at the beginning of the annual warm season," Steffen says. "In recent years, the melting has begun earlier than usual."

One reason this concerns climate scientists so much is that melting ice creates its own self-perpetuating loop, in which more open water leads to greater temperature increases. This effect is so pronounced that, at one location in the Arctic this year, sea surface temperatures rose to five degrees Celsius (nine degrees Fahrenheit) above the 100-year historical average—a level never before observed by scientists.

That disquieting news comes from a new study by Michael Steele, an oceanographer with the University of Washington's Applied Physics Laboratory. He is lead author of the paper, "Arctic Ocean Surface Warming Trends Over the Past 100 Years," accepted for publication in AGU's GeophysicalResearchLetters. In it, he and his co-authors write: "Warming is particularly pronounced since 1995, and especially since 2000."

Steele notes that hard, white ice serves as a sort of sunscreen for the water below, reflecting the sunlight back into the atmosphere. Open water, on the other hand, absorbs the sun's rays. This can create a self-sustaining spiral, with less ice leading to warmer temperatures, which produce more melting and still less ice.

It's a phenomenon human beings helped set off, but are probably unable to stop.

The National Oceanic and Atmospheric Administration concluded in September that the Arctic ice cap will shrink 40 percent in most regions by the year 2050. At the fall meeting of the American Geophysical Union in San Francisco, Wieslaw Maslowski, a research associate professor in the Department of Oceanography at the Naval Postgraduate School in Monterey, California, concluded that, if current trends persist, the Arctic will be ice-free during the summer months by the year 2013.

So, in practical terms, what does this all mean for humans? That's the area of a new hybrid field of study that factors in both the effects of climate change and the socioeconomic conditions of the nations grappling with this problem. A research team from Purdue University in Indiana and the Abdus Salam International Centre for Theoretical Physics in Italy is analyzing the "socioclimactic" risk various nations face.

"Climate change is only half of the story," says Leigh Raymond, associate director of Purdue's Climate Change Research Center. "We need to consider how different societies are threatened by these physical changes in unique ways. Impoverished areas have fewer resources to deal with environmental stress, while wealthy areas have a greater amount of infrastructure that could be lost, and areas with larger populations have more lives at stake."

The team's first study, which Raymond calls "an important first step to get people thinking about the issues from this new perspective," finds that China—a major producer of greenhouse gases—is at particularly high risk as the climate changes. It is available online in the Proceedings of the National Academy of Sciences.

"China has a relatively moderate expected climate change," says Noah Diffenbaugh, an assistant professor of earth and atmospheric sciences at Purdue who led the study. "However, when you combine that with the fact it has the second largest economy in the world, a substantial poverty rate, and a large population, it creates one of the largest combined exposures on the planet."

Two new studies indicate global warming will have a pronounced effect on the weather of the United States, producing fewer but wetter storms. The reports, by researchers at the University of Colorado's Cooperative Institute in Environmental Sciences, will be published December 28th in a special edition of the Journal of Geophysical Research-Biogeosciences.

"We're likely to see fewer storms carrying more water," says Joel Finnis, a doctoral student at the university and the lead author of one of the studies. "This could mean an increased chance that individual events will produce severe weather, but a decrease in overall water resources."

Another new study by six scientists from various institutions—including Purdue's Diffenbaugh—comes to a similar conclusion. Published in the Proceedings of the National Academy of Sciences (posted December 4th), it predicts "a net increase during the late 21st century in the number of days in which severe thunderstorm environmental conditions occur." This increased probability of severe storms will be most pronounced in the Eastern and Southeastern U.S., which can expect turbulent summers, according to the report.

And on the subject of storms, new research refines earlier warnings that warmer ocean temperatures will result in fiercer hurricanes. Gabriel A. Vecchi of the National Oceanic and Atmospheric Administration and Brian J. Soden of the University of Miami's Rosensteil School of Marine and Atmospheric Science explored the relationship between changes in sea-surface temperatures and the upper limit of cyclone intensity.

Their reports, published in Nature magazine, find that the overall rise in ocean temperatures isn't as important as the relative temperature increases experienced by different regions of the tropical seas. Only those regions that are experiencing above-average warming can expect storms of greater intensity.

"A surprising result is that the current potential intensity for Atlantic hurricanes is about average, despite the record high temperatures of the Atlantic Ocean over the past decade," Soden says. "This is due to the (even greater increases in) warmth in other ocean basins."

"If the Atlantic warms more slowly than the rest of the tropical oceans, we would expect a decrease in the upper limit on hurricane intensity," Vecchi adds. "This is an interesting piece of the puzzle."

And a rare piece of encouraging environmental news.