Oceans, greenhouse gases rising faster: reports
By Susan Heavey
WASHINGTON (Reuters) – Ocean and so-called greenhouse gas
levels are rising faster than they have for thousands of years,
according to two reports published on Thursday that are likely
to fuel debate on global warming.
One study found the Earth’s ocean levels have risen twice
as fast in the past 150 years, signaling the impact of human
activity on temperatures worldwide, researchers said in the
Sea levels were rising by about 1 millimeter (0.04 inches)
every year about 200 years ago and as far back as 5,000 years,
geologists found from deep sediment samples from the New Jersey
coastline. Since then, levels have risen by about 2 millimeters
(0.08 inches) a year.
While the planet has been in a warmer period, driving cars
and other activities that create carbon dioxide are having a
clear impact, the Rutgers University-led team said.
“Half of the current rise … was going on anyway. But that
means half of what’s going on is not background. It’s human
induced,” said Kenneth Miller, a geology professor at the New
Jersey-based school who led the 15-year effort.
Carbon dioxide emissions come mainly from burning coal and
other fossil fuels in power plants, factories and automobiles.
Miller and his colleagues analyzed five 500-meter
(1,650-foot) deep samples to look for fossils, sediment types
and variations in chemical composition, giving them data on the
past 100 million years.
They also analyzed data from satellite, shoreline markers
and by gauging ocean tides, among other measures.
“It allows us to understand the mechanisms of sea level
change before humans intervened,” Miller said in an interview.
His team did not determine whether the rate is
The research, funded mostly by the National Science
Foundation, also found ocean levels were lower during the
dinosaur era than previously thought. They were about 100
meters (330 feet) higher than now, not 250 meters (820 feet) as
many geologists had thought, Miller said.
SAMPLES FROM ANTARCTIC DEPTHS
Measurements also showed that, while many scientists had
thought polar ice caps did not exist before 15 million years
ago, frozen water at the poles did form periodically.
“We believe the ice sheet was not around all the time. It
was only around during cool snaps of the climate,” Miller said.
In another report published in Science, European
researchers using three large samples of polar cap ice found
carbon dioxide levels were stable until 200 years ago.
“Today’s rise is about 200 times faster than any rise
recorded” in the samples, study author Thomas Stocker said in
an e-mail interview with Reuters.
The historic data “put the present rise of the last 200
years into a longer-term context,” he added.
Trapped gas bubbles in the ice, drilled out from Antarctica
depths of about 3,000 meters (9,900 feet), provided scientists
with information on the Earth’s air up to 650,000 years ago.
Researchers participating in The European Project for Ice
Coring in Antarctica measured levels of carbon dioxide as well
as methane and nitrous oxide — two other gases known to affect
the atmosphere’s protective ozone layer.
“The study does not directly address global warming. But
what we provide is an important new baseline for the climate
models with which we investigate global warming,” said Stocker,
a professor of climate and environmental physics at the
University of Bern in Switzerland.