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Climate change affecting oceans faster: study

Marine biodiversity Climate change is having a more pronounced effect on animals and plants in the world's oceans than scientists had previously anticipated, a new analysis shows.

Scientists had expected that the effect of climate change would be slower in the oceans than on land, due to the amount of energy it takes to heat such large bodies of water.

But after studying the changes in temperature on land and in the oceans over 50 years, researchers led by Michael Burrows from the Scottish Marine Science Institute say this isn't the case.

Their calculations of the velocity of climate change and shifts in seasonal timing between 1960 and 2009 appear in today's issue of the journal Science .

"We were surprised by the findings," says Australian co-author Anthony Richardson from the CSIRO's Climate Adaptation Flagship.

"We expected things to not be responding as quickly in the ocean, but this work is telling us we should be expecting as great or greater change in the oceans."

Temperature shift is not the only way climate change affects the oceans, but it is one of the most important, says Richardson. Many marine species need their environment to be within a particular temperature range for vital growth and reproduction processes.

The faster the temperature changes, the harder it will be for those species to adapt.

"They need to respond in some way, and that could be by moving, or changing their behaviour," Richardson says.

The rate of warming seen by the scientists was greatest in equatorial oceans, which is also where biodiversity is currently highest, the analysis shows.

In contrast, some parts of the ocean were actually cooling because of factors such as melting ice, or higher winds triggered by climate change that led to greater mixing of deeper, cold water.

The combined effects of ocean temperature changes and other effects of climate change in the oceans, such as acidification caused by dissolved carbon dioxide, are likely to have significant impacts on marine ecosystems, Richardson says.

"You can imagine that ecosystems are going to look quite different in the future because we'll get a rearrangement of species in space and in time."

"Overall, we expect the impact of this is going to be negative, but there will be winners and losers," he says. "The trouble is, we don't know yet which species they will be."