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
0 comments :
Post a Comment