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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 oceantemperatures 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 theglobe.

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 massivereport 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 seawater, 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 oceanlevels by seven metres (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 importantto 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, andthe observations of scientists gathering data from the oceans.

The new study, led by Catia Domingues of the Centre for Australian Weather and Climate Research, is the first to reconcile the modelswith observed data. Using new techniques to assess ocean temperatures to a depth of 700 metres (2,300 feet) from 1961 to 2003, it shows that thermal warming contributed to a 0.53 millimetre-per-yearrise in sea levels rather than the 0.
STEP 2 - Answer these questions (choose the best answer):



Principio del formulario
1. What happens when the ocean's temperature rises?
  [pic]It causes...