Text 3780, 130 rader
Skriven 2007-03-20 16:16:06 av Alan Hess
Ärende: more on warming
=======================
Hollywood possibly has caused overblown fears of the effect of global warming,
but the earth does seem to be warming.  This article column a statistical
analysis from which the researcher concludes that, whether or not global
warming can be totally attributed to human factors, it makes sense to act as if
it is, and take action now.

*************

Web address: http://www.sciencedaily.com/releases/2007/03/070319110332.htm     

     
Source:   Thompson Rivers University
Date:     March 19, 2007
     More on:       
Global Warming, Environmental Issues, Climate, Geography, Environmental
Science, Earth Science
Statistical Analysis Debunks Climate Change Naysayers

Science Daily - In a thought-provoking statistical analysis, Dr. Peter Tsigaris
of Thompson Rivers University in Kamloops, BC, Canada, concludes that whether
or not climate change can be wholly attributed to human factors, it makes
strong economic and environmental sense to treat it as human-caused and take
action now.

Despite the fact that the hundreds of scientists and reviewers on the
Intergovernmental Panel on Climate Change announced Feb. 2 in Paris that global
warming is "very likely" caused by human activity, governments and other
policy-makers may still justify inaction because of naysayers like Danish
weather scientist Henrik Svensmark, who maintains that global climate change
can be attributed to the proportion of cosmic rays in our atmosphere, and
atmospheric physicist S. Fred Singer, who asserts that "The whole question of
anthropogenic, or human-caused, global warming is central to setting any policy
of climate mitigation and therefore warrants closer examination."

"These arguments are moot," says Peter Tsigaris, an economist at Thompson
Rivers University, in Kamloops, BC. He continues: "The important question is
the cost of these opinions being wrong relative to the cost of the IPCC report
being wrong in its assessment." In a thought-provoking statistical analysis,
Tsigaris has concluded that whether or not climate change can be wholly
attributed to human factors, it makes strong business and environmental sense
to take action and mitigate the effects of global warming beyond taking
measures to adopt.

He arrived at this conclusion as a result of creating the solution for a
question he posed to his statistics students.

Tsigaris asked, "A claim is made that global warming is caused by humans. Set
up the null and alternative hypothesis for this claim. As a scientist, you want
to test that the above claim is true beyond a reasonable doubt. Discuss in
terms of the type I and type II errors that are associated with the claim, and
discuss the implications of the errors in terms of their associated costs."

The null hypothesis, considered true unless the evidence brought forward throws
serious doubt on it, is that global warming is not caused by human activities;
the alternative hypothesis is the claim that it is. In the analogy of our
justice system, a person on trial is assumed to be innocent, the null, until
the evidence indicates that (s)he is guilty, the alternative, beyond a
reasonable doubt.

Now for the interesting part. "As a scientist, in order to reject the null and
thus accept the alternative, there has to be evidence that goes beyond a
reasonable doubt. In statistical terms, the observed test statistics from the
evidence pass beyond a reasonable doubt," explains Tsigaris.

If the scientist rejects the null, based on strong evidence in favour of the
rejection, there is still a small chance of making a type I error. In the same
way, acceptance of the null might be the wrong decision. The latter decision
would be associated with a type II error.

"A Type I error implies that you have accepted that global warming is caused by
humans when in fact it is not, while a Type II error implies the opposite," he
says.

"As one of my statistics students, Robert Guercio, wrote in his exam booklet,
'The cost of a type I error would mean spending a great amount of money and
time focusing on how we can stop humans from causing global warming when humans
are not the problem, but the cost of a type II error would mean spending a
great deal of money and time on finding what is causing global warming and then
continue to work on some factor of global warming, but not focusing on the real
factor, humans."

It's not just a lesson in numbers, explains Tsigaris, who cautions that the
cost of a type II error, stating that global climate change is not human-caused
when in fact it is, could be as high as humankind destroying itself. As
Lovelock points out in his Gaia theory, earth is self regulating and will look
after itself.

"It is obvious that a type II error, being unaware that global warming is
caused by humans and maintaining our current living styles, is much more
serious than a type I error which argues that humans are the cause when they
are not, in terms of the costs," he says.

"Rising sea levels, temperature and precipitation caused by human lifestyles
will have an impact on our health, agriculture, forestry, water, coastal areas,
as well as on other species and natural areas," he says, adding that "this
analysis also confirms the Stern Review on The Economics of Climate Change
which suggests that the cost of taking action today is way less than the cost
of continuing the current path we have chosen."

"The cost of changing behaviour and taking action now is estimated at one
percent of global GDP and this can be seen as an investment from a long-term
perspective: investing in cleaner technologies and also putting a price tag on
the use of our atmosphere. If we delay as we would do if we accepted that
climate change is not human-caused when this conclusion was false, we would be
faced with a huge cost," warns Tsigaris.

The recent 2007 IPCC report concluded that global warming was very likely (90
per cent) to have been caused by humans. The Stern Review states that "the
benefits of strong and early action far outweigh the economic costs of not
acting" and estimates that "if we don't act, the overall costs and risks of
climate change will be equivalent to losing at least 5 per cent  of global GDP
each year, now and forever. If a wider range of risks and impacts is taken into
account, the estimates of damage could rise to 20 per cent of GDP or more. In
contrast, the costs of action ? reducing greenhouse gas emissions to avoid the
worst impacts of climate change ? can be limited to around  1 per cent of
global GDP each year.

Note: This story has been adapted from a news release issued by Thompson Rivers
University.
 

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