Global warming is not just a 'blanket' trapping heat on Earth - it's more like tanning oil, scientists claim

The long-held belief that carbon dioxide is wrapping the planet in a ‘blanket’ that traps more heat, causing global warming, is not quite right, scientists say.

They claim that the story is more complex, although the potentially catastrophic consequences will likely be the same.

Experts say that in the long term, global warming is more like tanning oil letting the Earth absorb more of the sun's incoming rays.

A team from the University of Washington and the Massachusetts Institute of Technology (MIT) explained that broadly speaking, carbon dioxide being belched out by factories and vehicles acts as a blanket, trapping long-wave infrared energy coming off the Earth.

The atmosphere then emits less of this long-wave radiation to space because the upper atmosphere is cooler than the Earth's surface.

But the Earth gradually heats up under this ‘blanket’ and hotter objects emit more long-wave radiation, according to the Pnas study. 

Without icecaps to reflect back the suns rays and increased humidity, Earth will begin to absorb more shortwave radiation - the high-energy rays coming directly from the sun (stock image shown)

UN REPORT WARNS FOSSIL FUELS MUST BE PHASED OUT BY 2100

The use of fossil fuels must be phased out by the end of the century, UN scientists have warned despite growing concerns over energy supplies.

The UN's Intergovernmental Panel on Climate Change issued stark predictions that continued greenhouse gas emissions will cause 'severe, pervasive and irreversible' impacts around the world.

In its latest assessment of global warming, which was published last week, it urged governments to cut carbon dioxide emissions by up to 70 per cent by 2050.

The authors said fossil fuels would need to be phased out completely from electricity production by 2100 unless new technology could safely bury carbon dioxide from power stations underground to prevent it from being released into the atmosphere.

Rajendra Pachauri, chair of the IPCC, warned that the cost of delaying action to tackle climate change would be 'proportionally higher'.

He said: 'The world needs a combination of adaptation and mitigation.

'We will not be able to adapt to the impacts of climate change if we don't to anything to tackle the root of the problem. The impacts will exceed our capacity to cope with them.

'In the absence of carbon capture and storage then power generation from fossil fuels would need to be phased out by the end of this century if we want to limit temperature increases to 2°C.'

More than two thirds of the Britain's electricity comes from fossil fuels and cutting down on coal, oil and gas use is seen as a major challenge.

So within about a decade the effect of adding the thicker ‘blanket’ has been cancelled by the warmer body emitting more energy, the experts explained.

In the longer term, the study and its computer models show that the Earth will begin to absorb more shortwave radiation - the high-energy rays coming directly from the sun. 

Experts have previously shied away from talking about shortwave radiation because clouds can reflect this visible light back to space and clouds remain one of the big unknowns under climate change.

The researchers warn that the planet is likely to have less ice and the air will become more humid under climate change, both of which will act to absorb more shortwave radiation from the sun.

Those effects will be like putting tanning oil on the planet, letting it absorb more of the sun's incoming rays, they explained.

Melting ice creates darker surfaces that can absorb more heat, and the more melting, the more heat it can absorb. Likewise, warmer air holds more water vapour, causing it to absorb solar radiation that might otherwise bounce back off clouds, ice or snow.

‘While greenhouse gases trap one type of radiation, it's the other type - visible, shortwave radiation - that is really sustaining global warming over the long term,’ said co-author Kyle Armour, a postdoctoral researcher at MIT. 

The computer models should help scientists better detect climate change in satellite data, which can measure both shortwave radiation reflected by the Earth and long-wave radiation emitted by the Earth.

Most of the study's simulations involved a one-time addition of carbon dioxide into the atmosphere.

Yet one scenario simulated continuously increasing carbon dioxide, as is happening now, and found the long-wave radiation effect lasted about 20 years before the shortwave effect took over.

Professor of atmospheric sciences David Battisti at Washington University said: 'Our results do not change our overall expectation that the planet will continue to warm due to the burning of fossil fuels, but they do change our fundamental understanding of how that warming comes about.' 

Source: Dailymail