New
data suggests sea levels are rising faster than previously thought
From: ClickGreen Staff The acceleration in global sea level from the 20th century to the last two decades has been significantly larger than scientists previously thought, according to a new Harvard study.
The study, co-authored by Carling Hay, a post-doctoral
fellow in the Department of Earth and Planetary Sciences (EPS), and Eric
Morrow, a recent PhD graduate of EPS, shows that previous estimates of global
sea-level rise from 1900-1990 had been over-estimated by as much as 30 percent.
The report, however, confirms previous estimates of
sea-level change since 1990, suggesting that the rate of sea-level change is
increasing more quickly than previously believed.
"What this paper shows is that sea-level acceleration
over the past century has been greater than had been estimated by others,"
Morrow said. "It's a larger problem than we initially thought."
"Scientists now believe that most of the world's ice
sheets and mountain glaciers are melting in response to rising
temperatures." Hay added. "Melting ice sheets cause global mean sea
level to rise. Understanding this contribution is critical in a warming
world."
Hay and Morrow, however,
suggest that from 1901 until 1990, the figure was closer to 1.2 millimeters per
year. But everyone agrees that global sea level has risen by about 3
millimeters annually since that time, and so the new study points to a larger
acceleration in global sea level.
"Another concern with this is that many efforts to
project sea-level change into the future use estimates of sea level over the
time period from 1900 to 1990," Morrow said.
"If we've been
over-estimating the sea-level change during that period, it means that these
models are not calibrated appropriately, and that calls into question the
accuracy of projections out to the end of the 21st century."
To obtain their improved estimate of 20th century global
sea level, Hay and Morrow approached the challenge of estimating sea-level rise
from a completely new perspective.
Typically, Hay said, estimates of sea-level rise are
created by dividing the world's oceans into sub-regions, and gathering records
from tide gauges - essentially yard-sticks used to measure ocean tides - from
each area.
Using records that contain the most complete data, researchers
average them together to create estimates of sea level for each region, then
average those rates together to create a global estimate.
Continue reading at ENN affiliate, ClickGreen.
