World News: Earth to get hotter despite global warming slowdown (13 March 2014)

Earth to get hotter despite global warming slowdown

WASHINGTON: Earth's climate would continue to warm during this century on track with previous estimates, despite the recent slowdown in the rate of global warming, a new Nasa study has warned.

The research hinges on a new and more detailed calculation of the sensitivity of Earth's climate to the factors that cause it to change, such as greenhouse gas emissions.

Drew Shindell, a climatologist at Nasa's Goddard Institute for Space Studies in New York, found Earth is likely to experience roughly 20 per cent more warming than estimates that were largely based on surface temperature observations during the past 150 years.

Global temperatures have increased at a rate of 0.12 degrees celsius per decade since 1951, researchers said.

But since 1998, the rate of warming has been only 0.05 degrees celsius per decade - even as atmospheric carbon dioxide continues to rise at a rate similar to previous decades, they said.

Recent research suggested Earth may be less sensitive to greenhouse gas increases than previously thought.

The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), issued in 2013, also reduced the lower range of Earth's potential for global warming, said researchers.

To put a number to climate change, researchers calculate what is called Earth's "transient climate response."

This calculation determines how much global temperatures will change as atmospheric carbon dioxide continues to increase — at about one per cent per year — until the total amount of atmospheric carbon dioxide has doubled.

The estimates for transient climate response range from near 1.4 degrees celsius offered by recent research, to the IPCC's estimate of 1.0 degrees celsius.

Shindell's study estimates a transient climate response of 1.7 degrees celsius, and determined it is unlikely values will be below 1.3 degrees celsius.

In order to understand the role played by carbon dioxide emissions in global warming, it is necessary to account for the effects of atmospheric aerosols, researchers said.

While multiple studies have shown the Northern Hemisphere plays a stronger role than the Southern Hemisphere in transient climate change, this had not been included in calculations of the effect of atmospheric aerosols on climate sensitivity.

When corrected, the range of likely warming based on surface temperature observations is in line with earlier estimates, despite the recent slowdown, researchers said.

The research was published in the journal Nature Climate Change.


soure from: http://timesofindia.indiatimes.com/home/environment/global-warming/Earth-to-get-hotter-despite-global-warming-slowdown/articleshow/31940484.cms