The world’s oceans have warmed 50 percent faster over the last 40
years than previously thought due to climate change, Australian and US
climate researchers reported Wednesday. Higher ocean temperatures
expand the volume of water, contributing to a rise in sea levels that is
submerging small island nations and threatening to wreak havoc in
low-lying, densely-populated delta regions around the globe.
The study, published in the British journal Nature, adds to a growing
scientific chorus of warnings about the pace and consequences rising
oceans. It also serves as a corrective to a massive report issued last year
by the Nobel-winning UN Intergovernmental Panel on Climate Change
(IPCC), according to the authors.
Rising sea levels are driven by two things: the thermal expansion of
sea water, and additional water from melting sources of ice. Both
processes are caused by global warming. The ice sheet that sits atop
Greenland, for example, contains enough water to raise world ocean
levels by seven meters (23 feet), which would bury sea-level cities from
Dhaka to Shanghai.
Trying to figure out how much each of these factors contributes to
rising sea levels is critically important to understanding climate change,
and forecasting future temperature rises, scientists say. But up to now,
there has been a perplexing gap between the projections of
computer-based climate models, and the observations of scientists
gathering data from the oceans.
The new study, led by Catia Domingues of the Center for Australian
Weather and Climate Research, is the first to reconcile the models with
observed data. Using new techniques to assess ocean temperatures to a
depth of 700 meters (2,300 feet) from 1961 to 2003, it shows that thermal
warming contributed to a 0.53 millimeter-per-year rise in sea levels rather
than the 0.32 mm rise reported by the IPCC.