Fresh Ideas:Denying climate change: Irresponsible

When I wrote about Republican presidential candidates' ideas about climate change, I had intended to write more generally about the persistent denial of the reality of human-caused climate change on the part of American conservatives, an increasingly stubborn denial not shared by conservatives in the rest of the world.

But then I became interested in what the candidates had to say, and that became the article. In a letter to the Appeal, however, John S. Adams offered me a perfect example of climate-denial arguments, and an opportunity to refute some of those arguments.

Adams writes about the "hockey stick graph ... which was exposed as a hoax in 2009" and about the medieval warm period, apparently conflating two arguments commonly used by climate-change denialists.

It was not hard to find refutations of both these arguments. In Grist Magazine, Coby Beck took on both.

First, the "hockey stick." One climate study showed a hockey-stick-shaped graph of global temperatures over a period of years, with the blade part of the hockey stick representing the twentieth century when global temperatures took a steep upward curve. Adams points out that this study was challenged by two Canadians (neither of them climatologists), who said they had found errors in the published description of the data that prevented them from duplicating the study.

Beck explains that the Canadians' claims have been refuted by dozens of climatologists. Moreover, while climate denialists assert that the purportedly flawed study is the foundation of climate science, it isn't - it is only one of many studies. There are many other temperature reconstructions, and they all support the conclusion that late 20th century warming is anomalous for the last 2,000 years.

Next, the medieval warm period. This period of warmer temperatures across a part of the globe is used by climate-change denialists to challenge the steady upward trend in temperatures found by climatologists. Beck explains that there is no good evidence that the medieval warm period was a globally warm period comparable to today, although there may have been places that exhibited notable warmth. But all global proxy reconstructions of past climates agree that it is warmer now, and the temperature is rising faster now, than at any time in the last 1,000 years.

Adams asserts, "There is no scientific proof that CO2 and human activity cause climate change."

This is simply incorrect.

In science, what matters is the balance of evidence, and theories that can explain that evidence. In climate science, there is a theory of anthropogenic (human-caused) climate change, first presented over 100 years ago, that is based on well-established laws of physics, supported by observation and data, further backed by sophisticated climate models that can successfully reproduce the climate's behavior over the last century.

Adams asserts, "In the past 10 years, the Earth has not warmed. That is a fact."

Wrong again. NASA's Goddard Institute for Space Studies reports that "the last decade has been the warmest on record."

There are policy discussions and decisions that must be made regarding human-caused climate change and societal responses to it. It may be possible to craft a response to climate change that uses market forces to shift our economy from over-reliance on fossil fuels. By indulging in climate-change denial, American conservatives are simply shirking their responsibility to engage in this discussion.

• Anne Macquarie, a private-sector urban planner, is a longtime resident of Carson City.