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Horizon reveals potential huge increase in global warming

Category: Factual & Arts TV

Date: 13.01.2005
Printable version

BBC TWO's Horizon - broadcast today at 9.00pm - reveals for the first time the devastating affects of a phenomenon that scientists are calling 'global dimming'.


It may already have led to the terrible famine in Ethiopia in the Eighties and, perhaps even more worryingly, it may have masked the full effects of global warming.


According to work revealed exclusively on the programme by Dr Peter Cox of the Met Office's Hadley Centre - Britain's leading institute for climate research - in the next hundred years temperatures worldwide could rise by as much as ten degrees Celsius, twice as quickly as previously thought and enough to turn tracts of Britain into a desert.


Furthermore Dr Cox fears that unless action is taken swiftly, an unstoppable chain of climatic disasters may be set in motion in just 20 years.


The story of the unmasking of global dimming is as good as any thriller.


Two years ago climatologists noticed that the heat of the sun had been dropping dramatically for several decades – for example by up to 10% in the USA and 16% in parts of Britain.


No-one had noticed because the loss of heat from the sun had been offset by global warming.


The dimming is a bizarre by-product of the fossil fuels that cause global warming. It is caused by tiny airborne particles of soot, ash and sulphur dioxide reflecting back the heat of the sun.


But it is the effects of dimming that have really alarmed scientists. The heat of the sun is vital for seasonal rains like monsoons.


Recent work shows a direct link between dimming and the failure of the rains in Sub-Saharan Africa in the Eighties – the terrible droughts that afflicted Ethiopia, and led to the creation of Band Aid.


In other words, that African catastrophe may have been partly caused by western air pollution from cars and power stations.


Professor Veerabhadran Ramanathan of the University of California now believes that the same thing could affect areas populated by billions of people, eg India, where in recent years the monsoon has been coming later and later.


The worry is that one day it won't come at all.


Fortunately, the cure for the problem is relatively straightforward: simply clean up our emissions.


Scrubbers in power stations and catalytic converters in cars – things many people are doing anyway – cut particle pollution and remove the cause of global dimming.


But there is a catch: as we tackle the dimming, the full power of global warming will be revealed. This was the discovery of Dr David Travis of the University of Wisconsin.


In the days immediately after 9/11 the entire United States commercial airfleet was grounded for three days.


Dr Travis believed that aircraft vapour trails were themselves a significant contributor to solar dimming, and he found that their three day absence alone resulted in a massive jump in the daily temperature range – the difference between the highest daytime temperature and the lowest night time temperature.


This important climatic variable increased by more than one degree Celsius over the three days of the grounding.


The unforeseen climatic effects of 9/11 suggest that if we remove other causes of dimming, the impact on global temperatures could be huge.


Dr Cox now believes the cooling effects of dimming may be the reason that, so far, global warming has been relatively muted, despite the rapid rise in greenhouse gases.


In effect, two different forms of pollution – the airborne particles that cause visible air pollution, and invisible greenhouse gases like carbon dioxide - have been cancelling each other out, leading scientists to underestimate the power of global warming.


Dr Cox has now factored global dimming into the models for global warming and the effect is dramatic.


If nothing is done to tackle global warming then in just 20 years, Dr Cox believes, the globe could see a two degree increase – enough to begin the irreversible melting of the Greenland ice sheet and start the flooding of our cities.


Within 40 years, temperatures could be four degrees higher – enough to ignite the rainforests.


And, by the end of the century, if Britain does nothing about greenhouse gases, it will have a climate like that of North Africa, and our green and pleasant land will have become a desert.


Horizon: Global Dimming is a DOX production for BBC TWO.


The producer is David Sington and editor is Matthew Barrett.




Category: Factual & Arts TV

Date: 13.01.2005
Printable version


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