Statistical Analysis Debunks Climate Change Naysayers

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Despite the findings of hundreds of scientists and reviewers on the Intergovernmental Panel on Climate Change, some governments and policymakers may continue to justify inaction on global warming. Some assert global climate change can be attributed to the proportion of cosmic rays in our atmosphere, while others contend the issue still requires further study.


“These arguments are moot,” says Peter Tsigaris, PhD, an economist at Thompson Rivers University in British Columbia, Canada. “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, Dr. Tsigaris has concluded that regardless of whether climate change can be wholly attributed to human factors, it makes strong economic and environmental sense to take action as though global warming is human-caused.

Dr. Tsigaris arrived at this conclusion after creating the solution for a question he posed to his statistics students. He 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 evidence indicates he’s 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,” Dr. Tsigaris explains. “In statistical terms, the observed test statistics from the evidence pass beyond a reasonable doubt.”

If a scientist rejects the null, based on strong evidence in favor 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,” Dr. Tsigaris 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 Dr. Tsigaris, who cautions that the cost of a Type II error could be as high as humankind destroying 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. 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 behavior and taking action now is estimated at 1% of global GDP,” he continues, “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.”

The IPCC report concluded global warming was very likely (90%) to have been caused by humans. The Stern Review states “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% 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% 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% of global GDP each year.”

Book Pick of the Day:The Economics of Climate Change: The Stern Review publishes science news so organic consumers have access to the latest information on climate change and threats to our environment. You can view more posts by visiting the Environment Section of our blog.

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