GLOUCESTER POINT, Va. (AP) — For years, computer simulations have predicted that climate change will cause East Coast sea levels to rise at an increasingly rapid rate.
In a 2010 study, Virginia Institute of Marine Science oceanographer John Boon looked at decades of tide-gauge readings for evidence of this ever-faster-rising water.
Boon didn't find the accelerating sea levels, and he was skeptical that they existed.
But using a more sophisticated statistical method, Boon looked at the tide-gauge readings again in a 2012 study. This time, he found that sea levels are indeed rising at an increasing rate from Norfolk to Nova Scotia.
To a layman, this might look like a flip-flop. But to scientists, this is how the job is done.
"A skeptic is basically a normal scientist at work," said Boon, 73. "You look at the evidence and say, 'I need to be convinced.'"
Boon added that he was a skeptic — not a denier.
Two other studies last year, by Old Dominion University and the U.S. Geological Survey, also found rising sea-level rates along much of the East Coast. Using differing methodologies, the three studies in effect validated one another.
The studies portend a major threat to cities such as Norfolk, New York and Boston. Sea levels there aren't going up in a straight line but are climbing increasingly fast, the way a debt can soar with compound interest.
In low-lying Norfolk, neighborhoods are flooding more frequently during storms. Rising seas mean more flooding, more property damage and the prospect of people having to find new homes.
Using 1992 as a starting point, Boon projects that the sea level at Norfolk could rise about 2 feet by 2050.
That follows thousands of years in which the sea level went up only about a foot a century.
Boon said that if present trends continue, 2 feet could go up to nearly 6 feet by 2100. That would be devastating for coastal Virginia, but Boon said he is much less confident in projections that far off.
Some people who don't believe in climate change seized on Boon's first study as proof that they were right, said Carl Hershner, a Virginia Institute of Marine Science professor who relies heavily on Boon's work to relate sea-level issues to the public.
"There were people who were only too happy to say, 'Aha, your own scientists don't see this in the data,'" Hershner said, declining to name names.
Hershner praised Boon's approach. "Having drawn a conclusion and reported it, he did not feel like his reputation depended on always having that particular perspective."
Boon is an emeritus professor, retired from teaching but still conducting research. A tall, friendly man with wispy gray hair, he discussed his work by telephone and in an interview in the Virginia Institute of Marine Science library, where east-facing windows afforded a handsome view of the York River.
Boon found that the rate of sea-level rise was accelerating from Norfolk to Halifax, Nova Scotia, making that region a global hot spot for rising waters.
While water in a bathtub rises evenly, sea levels don't work that way. Water temperature, currents, coastal geography and other factors can make sea levels go up faster in some places than others. In coastal Virginia, sinking land contributes to the problem.
"Sea-level change is happening regionally," Boon said. "It's like politics. All politics is local. All sea-level change is kind of local, too."
Climate scientists say the planet is warming largely because people are burning fossil fuels, such as coal and oil, that release heat-trapping gases in the atmosphere.
Global sea levels go up in part because ice that melts on land adds to the oceans' waters and because warming water expands.
But why is sea-level rise accelerating along much of the East Coast?
A major factor could be a change in the Gulf Stream, the current that brings warm water north from the tropics.
When Gulf Stream waters reach the cold North Atlantic Ocean, they cool. Cold water is denser than warm water, so it sinks. That cold water then moves south to replace the water that rose in the tropics. The system works like a big watery conveyor belt.
But climate change may be making those North Atlantic waters too warm to sink properly. That, among other things, could be slowing the conveyor belt.
Tal Ezer is an Old Dominion oceanographer who led that university's 2012 study of rising seas. In February, he published a study finding evidence that the Gulf Stream has indeed slowed.
The ocean is not flat. For example, the water level is lower on the side of the Gulf Stream nearest the East Coast and higher on the other side. So the Gulf Stream resembles a wall keeping a lot of water from moving to the coast.
If the Gulf Stream slows, computer simulations suggest, that wall would lower, allowing water to drop on the far side of the stream and rise along the coast, adding to already-rising coastal sea levels.
Ezer said his study indicating a slowing Gulf Stream, plus the three 2012 studies of rising seas, appear to show this is happening.
For his part, Boon said the rising rates of sea-level rise that he documented are likely caused by climate change, but he isn't 100 percent convinced.
After all, he's a skeptic.
Information from: Richmond Times-Dispatch, http://www.timesdispatch.com