Mar. 19, 2007 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.
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