When it comes to battling global warming, it's a matter of degrees at the Group of Eight summit in L'Aquila, Italy.

President Barack Obama has joined other leaders of the industrialized world in backing new targets. White House officials confirm that Obama agreed to language supporting a goal of keeping the world's average temperature from rising more than 2 degrees Celsius, or 3.6 degrees Fahrenheit.

However, the G-8 nations were unable to persuade leaders of developing countries, such as China and India, to commit to reductions of their own. Their cooperation is viewed as critical to avoid the worst effects of climate change.

Climate change experts say the 2-degree threshold wouldn't eliminate the risk of runaway climate change but would reduce it. Scientists say even a slight increase in average temperatures could wreak havoc on farmers around the globe, as seasons shift, crops fail and storms and droughts ravage fields.

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