The defining issue of 21st century: global climate

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To the teenage hoopsters he is said to have run ragged on the basketball court, he became known as Dr. J.

His friends acknowledge that Jerry Mahlman comes by the nickname honestly. He plays an intense game of basketball. His first name starts with J. And he holds a PhD in atmospheric science.

On Oct. 1, Jerry Mahlman, retires as head of one of the world's leading climate-modeling centers, the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Lab (GFDL). During his tenure, the lab has been credited with developing new, more accurate hurricane-forecasting tools, as well as models to forecast El Nio outbreaks up to a year in advance.

Recommended: Think you know the odd effects of global climate change? Take our quiz.

But the rise of climate change as a global issue also has placed the lab and its director at the center of what he calls "potentially the defining problem of the 21st century."

In an interview conducted during a two-day symposium earlier this month honoring his contributions to climate science, Mahlman summarized recent signs that he says boost his confidence that human-induced climate change is underway.

These signs range from Earth posting its warmest year on record and perhaps the warmest year in the past 1,000 years to recent paleoclimate research that tracks temperatures since AD 1000, using several natural "thermometers." At the start of the period, he says, the data show "very, very slow cooling - with lots of uncertainty in the data. Then about 1760, warming takes off. You can take different parts of the data set and get basically the same answer. It's an extraordinarily careful piece of research." Temperatures are warming the fastest in high, northern latitudes, the part of the world models point to as the regions of most pronounced change, he adds.

He acknowledges that uncertainties remain in computer simulations of climate, fueled by gaps in researchers' understanding about key aspects of climate - most notably the role clouds play. The problem, he notes, lies in a poor grasp of cloud physics as well as in the fact that clouds act on much smaller scales than computer models can now capture.

"Some people say that the fundamental uncertainties haven't changed in 20 years," he continues. This assertion, he says, is based in part on global temperature-increase estimates that have hovered for 20 years at a range of 1.5 to 4.5 degrees Celsius.

Yet, what has changed, he adds, is the confidence many researchers have in the temperature range. What was once a 66 percent chance that temperature increases would lie within that range has grown to a 90 to 95 percent chance as understanding of earth's climate system has improved.

Questions of certainty versus uncertainty continue to bedevil efforts to come up with a new consensus report on the science of climate change.

With nations meeting in The Hague in November to continue climate negotiations, the International Panel on Climate Change (IPCC) is preparing a new scientific assessment. In draft form, it reportedly carried a strong statement that humans are responsible for global warming. This stands in stark contrast to what Mahlman observes was a "triple wimpy" statement in the 1995 scientific assessment.

Yet the new draft, he adds, errs in the opposite direction. "I critiqued the new statement because I thought it was too strong," he says. "It was basically uncaveated, as in: Go home, baby - it's outta here. I suggested an alternative wording: 'Our confidence has increased.' "

He says he also is concerned that politics is pushing the IPCC into promising more dramatic improvements in regional climate-change forecasts than science will be able to deliver by the time the next set of reports are due in 2005-2006.

"I'm a little concerned that we'll rush to judgment rather than say: This is a problem for the 21st century, it's going to keep growing slowly, and we're gong to get various kinds of surprises," he says.

While acknowledging progress in climate science, Mahlman expresses a frustration at the lack of interest in Congress to adequately fund federal climate-change research projects and set up an infrastructure to coordinate them - a situation he terms "a national disgrace." When money is spent, he says, it tends to be on computers and satellites to the exclusion of more researchers to analyze the results.

"I call it the out-of-control hardware-brainware issue," he says. "We've had very nice success in getting funding for new supercomputers at GFDL. We can't get any money for people to empower our investment in supercomputers. That's just dumb."

Meanwhile, he says, demand for climate-change information is growing at a rate comparable to tech stocks on Wall Street in the 1990s. Water resource managers, agricultural interests, and others are thirsty for data.

"How do you build for a 100-year flood when you don't have a clue about what the hydrology is going to be like in 100 years?" Mahlman asks.

He sees the media's education role as critical, since informal surveys he conducts at universities suggest that much of the information students and faculty get on the issue comes from the media.

Still, Mahlman sees hopeful signs. "Governments all over the world" are "taking the issue very seriously," Mahlman says.

(c) Copyright 2000. The Christian Science Publishing Society

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