海角大神

Europe鈥檚 climate change commissioner is smiling, but some scientists have worry lines.

As nations prepare for a global conference on climate change, an 鈥渁stounding鈥� to cut down on carbon emissions, Miguel Arias Ca帽ete said Tuesday, something he wouldn鈥檛 have thought possible just six months ago.

鈥淭here are many, many reasons to be cheerful,鈥� Commissioner Ca帽ete told the BBC. 鈥淭he fact that 149 countries to date have presented the United Nations their commitments to fight global warming is astonishing.鈥�

These new policies would limit the predicted rise in global temperature from between 3.8 degrees and 4.7 degrees Celsius to about 鈥�3 [degrees] C maximum,鈥� Ca帽ete said. 聽

鈥淭hat's a big step, although clearly it's not enough,鈥� he added. The temperature increase needs to be brought down to about 2 degrees C to be deemed safe for most countries, according to the Intergovernmental Panel on Climate Change.

But even as nations around the world take steps to protect humans from carbon emissions, scientists are investigating their impact on underwater life聽鈥� and the picture is sobering.

If emissions keep climbing, say marine ecologists at the University of Adelaide,聽ocean ecosystems will be severely threatened by 2100.

Many scientists have studied various, scattered effects of climate change and聽ocean acidification, but now those studies are building into one comprehensive look at the oceanic effects of聽climate change, published Tuesday in the .

鈥淯ntil now, there has been almost total reliance on qualitative reviews and perspectives of potential global change,鈥� 聽marine ecologist Sean Connell, co-author of the study, in a statement. 鈥淲here quantitative assessments exist, they typically focus on single stressors, single ecosystems, or single species.鈥�

Professors Connell and Ivan Nagelkerken analyzed more than 630 published experiments, ranging from the bleaching of coral reefs to the competitive strengths of seaweeds to the effects of global warming on sharks鈥� hunting behavior.

They found that 鈥渕ore than half of the world鈥檚 ocean has experienced an increase in cumulative human impact over a 5[-year] time span, predominantly driven by increasing climate stressors such as sea surface temperature, ocean acidification, and UV radiation.鈥�

Sea creatures' abilities to adapt to the warming ocean聽will be 鈥渓imited,鈥� warned the scientists. They predict shrinking sea populations and widespread extinctions if climate change is not curbed.

Some plankton species will flourish in warmer waters, reports聽海角大神, but on the whole, 鈥渢here will be a species collapse from the top of the food chain down,鈥� predicts Professor Nagelkerken.

鈥淲ith higher metabolic rates in the warmer water, and therefore a greater demand for food, there is a mismatch with less food available for carnivores 鈥撀爐he bigger fish that fisheries industries are based around,鈥� he added.

For now, the climate change pact is a step in the right direction. The world鈥檚 biggest economies are leading the way, Jacquie McGlade, chief scientist of the UN environment programme, told the BBC.聽

"When [smaller] countries saw the big players 鈥撀爐he EU, the USA 鈥撀爌ut their figures on the table, there's a bit of copycat 鈥撀爓hich is a good thing,鈥� she said. 鈥淭his is going to be a race to the top, not the bottom.鈥�