More Research Builds Case for Global Warming, Rising Seas

By Charlene Porter
IIP Staff Writer
21 June 2011

Washington — Research published June 20 finds a steady rise in the sea level on the U.S. Atlantic coast, a faster rise now than at any time in the last 2,000 years.

The scientific team publishing in the Proceedings of the National Academy of Sciences included researchers from Yale University, the University of Pennsylvania, Woods Hole Oceanographic Institution and others, and was supported with funding from the National Science Foundation (NSF). Their findings represent the first continuous sea-level reconstruction for the past 2,000 years, comparing variations in global temperature to changes in sea level over the millennia, according to an NSF press release.

“It’s especially valuable for anticipating the evolution of coastal systems,” said Paul Cutler, the program director in NSF’s Division of Earth Sciences, “in which more than half the world’s population now lives.

The researchers found that sea level was relatively stable from 200 B.C. to A.D. 1000. The water started creeping higher in the 11th century and rose a half millimeter each year for 400 years. That was followed by another stable period of a few hundred years. In the 19th century, sea level began rising again and has been rising about 2 millimeters per year, the fastest pace in 2,200 years.

The scientific team calculated these alternating epochs of rising and steady sea levels by examining sediment cores extracted from coastal salt marshes in the state of North Carolina. Those sediments and the fossilized microorganisms within them were analyzed through radiocarbon testing and other techniques that allowed estimates of the samples’ ages and changes in sea level over time.

“Sea-level rise is a potentially disastrous outcome of climate change,” said Benjamin Horton of the University of Pennsylvania, “as rising temperatures melt land-based ice and warm ocean waters.”

Another study released in June touches upon one of the key controversies surrounding global warming data: What’s causing it? Human activities pumping greenhouse gases into the atmosphere? Or is it part of a natural cycle that the Earth undergoes through the millennia? Research by a scientist at the U.S. Geological Survey lessens the significance of one natural source cited by climate skeptics as a possible cause — volcanic emissions.

Human activities — anthropogenic causes, as scientists refer to them — are emitting much more greenhouse gases than volcanoes are. “Present-day volcanoes emit relatively modest amounts of CO2,” writes Terrence Gerlach in an article in Eos, the publication of the American Geophysical Union.

The global output of volcanoes annually is estimated to range from 0.15 billion to 0.26 billion metric tons, or gigatons. Human-generated CO2 emissions amount to 35 gigatons, reports Gerlach, which “clearly dwarf all estimates of the annual present-day global volcanic CO2 emission rate.”

Analysis of human emissions has been subdivided to specific sources. Gerlach wrote that they can individually outpace what volcanoes may spew: Light-duty vehicles like cars and trucks spew 3 gigatons a year and cement production emits 1.4 gigatons per year.