No Sun link' to climate change

[Guest guest]

'No Sun link' to climate change

By Richard Black

Environment correspondent, BBC News website

Scientists have produced further compelling evidence showing that

modern-day climate change is not caused by changes in the Sun's activity.

 

The research contradicts a favoured theory of climate

" sceptics " , that changes in cosmic rays coming to Earth

determine cloudiness and temperature.

The idea is that variations in solar activity affect cosmic ray

intensity.

But Lancaster University scientists found there has been no significant

link between them in the last 20 years.

Presenting their findings in the Institute of Physics journal,

Environmental Research Letters, the UK team explain that they used three

different ways to search for a correlation, and found virtually none.

 

 

This is the latest piece of evidence which at the very least puts the

cosmic ray theory, developed by Danish scientist Henrik Svensmark at the

Danish National Space Center (DNSC), under very heavy pressure.

Dr Svensmark's idea formed a centrepiece of the controversial documentary

The Great Global Warming Swindle.

Wrong path

" We started on this game because of Svensmark's work, " said

Terry Sloan from Lancaster University.

" If he is right, then we are going down the wrong path of taking all

these expensive measures to cut carbon emissions; if he is right, we

could carry on with carbon emissions as normal. "

Cosmic rays are deflected away from Earth by our planet's magnetic field,

and by the solar wind - streams of electrically charged particles coming

from the Sun.

The Svensmark hypothesis is that when the solar wind is weak, more cosmic

rays penetrate to Earth.

That creates more charged particles in the atmosphere, which in turn

induces more clouds to form, cooling the climate.

The planet warms up when the Sun's output is strong.

Professor Sloan's team investigated the link by looking for periods in

time and for places on the Earth which had documented weak or strong

cosmic ray arrivals, and seeing if that affected the cloudiness observed

in those locations or at those times.

" For example; sometimes the Sun 'burps' - it throws out a huge burst

of charged particles, " he explained to BBC News.

" So we looked to see whether cloud cover increased after one of

these bursts of rays from the Sun; we saw nothing. "

Over the course of one of the Sun's natural 11-year cycles, there was a

weak correlation between cosmic ray intensity and cloud cover - but

cosmic ray variability could at the very most explain only a quarter of

the changes in cloudiness.

And for the following cycle, no correlation was found.

Limited effect

Dr Svensmark himself was unimpressed by the findings.

" Terry Sloan has simply failed to understand how cosmic rays work on

clouds, " he told BBC News.

" He predicts much bigger effects than we would do, as between the

equator and the poles, and after solar eruptions; then, because he

doesn't see those big effects, he says our story is wrong, when in fact

we have plenty of evidence to support it. "

But another researcher who has worked on the issue, Giles Harrison from

Reading University, said the work was important " as it provides an

upper limit on the cosmic ray-cloud effect in global satellite cloud

data " .

 

Dr Harrison's own research, looking at the UK only, has also suggested

that cosmic rays make only a very weak contribution to cloud formation.

 

The Svensmark hypothesis has also been attacked in recent months by Mike

Lockwood from the UK's Rutherford-Appleton Laboratory.

He showed that over the last 20 years, solar activity has been slowly

declining, which should have led to a drop in global temperatures if the

theory was correct.

The Intergovernmental Panel on Climate Change (IPCC), in its vast

assessment of climate science last year, concluded that since

temperatures began rising rapidly in the 1970s, the contribution of

humankind's greenhouse gas emissions has outweighed that of solar

variability by a factor of about 13 to one.

According to Terry Sloan, the message coming from his research is simple.

 

" We tried to corroborate Svensmark's hypothesis, but we could not;

as far as we can see, he has no reason to challenge the IPCC - the IPCC

has got it right.

" So we had better carry on trying to cut carbon emissions. "

 

 

Richard.Black-INTERNET

Story from BBC NEWS:

 

http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/7327393.stm

Published: 2008/04/03 13:04:23 GMT