Front Page

UK

World

Business

Sci/Tech

Sport

Despatches

World Summary


On Air

Cantonese

Talking Point

Feedback

Low Graphics

Help

Site Map

Friday, February 13, 1998 Published at 19:25 GMT



Sci/Tech

Scientists blame sun for global warming
image: [ The Sun is more active than it has ever been in the last 300 years ]
The Sun is more active than it has ever been in the last 300 years

Climate changes such as global warming may be due to changes in the sun rather than to the release of greenhouse gases on Earth.

Climatologists and astronomers speaking at the American Association for the Advancement of Science meeting in Philadelphia say the present warming may be unusual - but a mini ice age could soon follow.

The sun provides all the energy that drives our climate, but it is not the constant star it might seem.

Careful studies over the last 20 years show that its overall brightness and energy output increases slightly as sunspot activity rises to the peak of its 11-year cycle.

And individual cycles can be more or less active.

The sun is currently at its most active for 300 years.

That, say scientists in Philadelphia, could be a more significant cause of global warming than the emissions of greenhouse gases that are most often blamed.

The researchers point out that much of the half-a-degree rise in global temperature over the last 120 years occurred before 1940 - earlier than the biggest rise in greenhouse gas emissions.


[ image: Ancient trees reveal most warm spells are caused by the sun]
Ancient trees reveal most warm spells are caused by the sun
Using ancient tree rings, they show that 17 out of 19 warm spells in the last 10,000 years coincided with peaks in solar activity.

They have also studied other sun-like stars and found that they spend significant periods without sunspots at all, so perhaps cool spells should be feared more than global warming.

The scientists do not pretend they can explain everything, nor do they say that attempts to reduce greenhouse gas emissions should be abandoned. But they do feel that understanding of our nearest star must be increased if the climate is to be understood.
 





Back to top | BBC News Home | BBC Homepage

©

[an error occurred while processing this directive] [an error occurred while processing this directive]
  Relevant Stories

27 Jan 98 | Sci/Tech
'Blinkers' on the sun

10 Dec 97 | World
Deal to cut greenhouse gases

08 Dec 97 | World
Rising tides threaten Pacific islanders

08 Nov 97 | Sci/Tech
Solar flares threaten Earth

07 Nov 97 | Sci/Tech
El Nino here to stay

 
  Internet Links

American Association for the Advancement of Science

The Great Global Warming Debate


The BBC is not responsible for the content of external internet sites.