Scientists debate reasons behind warming of bay

August 11, 1991|By Liz Bowie

Scientists say a six-year warming trend in the Chesapeake Bay's water could be due to local weather patterns rather than global warming and should not determine the bay cleanup plans.

"We have had several warm years; it is inevitable that we have short-term variation in climate," said Christopher D'Elia, a Chesapeake Biological Laboratory scientist.

"People want to worry about global warming. I don't see any technical justification for raising that concern. It is a several-degree increase," Dr. D'Elia said. "It is out of left field. I don't see why they are making such a big deal out of this."

The U.S. Environmental Protection Agency released information last week that proved the bay waters warmed on average 2.6 degrees Fahrenheit over the past six years. The warming appeared in winter rather than summer.

One EPA official speculated the rising temperatures could have been caused by global warming, although he said it was premature to draw any conclusions.

The global-warming theory says that gases from industry and agriculture are trapping heat within the atmosphere and warming the Earth. While the theory is widely accepted, there is sharp disagreement about how fast it may occur.

EPA administrator William K. Reilly suggested at an interstate meeting on the bay that its cleanup might be hampered by the bay's higher temperatures, which make it more difficult to raise the level of oxygen in the water.

But several scientists said it is too early to worry, based on six years of data.

"I would not want to link this trend to global warming in any way, at this time," said Hugh Ducklow, a professor at the University of Maryland's Horn Point Environmental Laboratory in Cambridge, who is involved in studying how global warming might affect oceans.

The rate of estimated global warming of air temperatures over the past century, which is about 1 degree, is far less than the rate of warming seen in the bay in the past six years, Dr. Ducklow said.

Why the bay is heating up is difficult to say, the scientists said. But the possibilities include a reduction in the fresh, cold water flowing off the land from snowmelt or a natural cycle that has not been recognized before.

Whatever the cause, the trend does not justify major changes in bay cleanup plans, several scientists said.

Michael Haire, Chesapeake Bay Program manager for the Maryland Department of the Environment, said the bay-warming issue will be considered when officials meet next year to review the goal of reducing nutrients by 40 percent by the year 2000.

A computer model designed to estimate how much nitrogen and phosphorus pouring into the bay needs to be reduced takes into account the higher temperatures, Mr. Haire said.

But he said the model does not factor in further temperature increases. To do so, and use the data to help decide on major cleanup strategies -- such as how much money to spend on cutting back on farm field fertilizers or sewage plant renovations -- would be folly, he said.

"The preliminary data is not significant enough to project 30 or 40 years in the future," he said.

The Chesapeake Bay Foundation wants a more conservative approach.

"We can't guarantee that it [bay warming] will reverse itself," said Ann Powers, a senior attorney at the foundation, an environmental group based in Annapolis. "I think we have to act conservatively and assume it is a long-term trend."

Focusing attention on the rising temperature may hurt the Chesapeake Bay cleanup movement, Dr. D'Elia believes, because it draws the focus away from the bay's proven problems.

People who live around the bay should ask why state officials have not acted to control development, which is causing far more problems.

"Given the various other insults we are heaping upon the flora and fauna of Chesapeake Bay, I doubt that we will be able to detect any effect, unless this change continues for a decade or more," Dr. Ducklow said.

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