When I began writing about global warming climate change, public outcry was tremendous. Amid a sea of media stories about the sins of our wasteful lifestyle, no one wanted to hear about contradictory research, conflicting data, or skeptical scientists.
Now, over two years later, a funny thing has happened. The roles have shifted. My stories are the staid and ordinary ones. It's the fellows predicting flood, famine, and disaster who are generating all the controversy.
I don't know whether to laugh or cry. What happened?
2008 was the year predicted to be the "hottest in a century". Instead it became the coldest of the decade. It was the year the North Pole would "melt entirely, allowing you to swim to it". Instead, nuclear-powered icebreakers became trapped in unseasonably thick ice. It was a year of record-breaking cold and snow, everywhere from Baghdad to the beaches of Malibu. It was the year the "Gore Effect" entered the public vocabulary, as whenever global warming protestors got together to march, they were met with blizzards and ice storms. Let's hope schadenfroh isn't a sin.
Polls are clear. Despite the media's increasingly shrill tone and ever-more unrealistic predictions, the public has lost all faith in global warming. After all, how many times can you say that this time the science is now finally proven, without being laughed at?
In some respects, that's good. It means less chance of implementing incredibly damaging policies, policies that will have disastrous impacts on standards of living, especially among the poor.
In other ways, it's bad. The overselling of inconclusive conjectures as "proven science" is leading some to distrust science itself. Given that, I think the year should conclude with a reminder of just what the scientific debate -- minus its alarmist media trappings-- is really all about.
As a moderately well known skeptic, I sometimes surprise people when I say I believe in global warming. If we define the term as, "man is having some impact on global temperatures", then the evidence is fairly clear. That statement in itself, though, means nothing. Are we impacting it enough to matter? Can CO2 cause catastrophic climate change?
That debate revolves around a single number, one so important we have a special name for it.
How much will the earth warm if we double the amount of atmospheric CO2, or its equivalent in other greenhouse gases? That value is called climate sensitivity. If all else remains equal, it’s fairly easy to calculate: about half a degree C, a figure accepted by most proponents and skeptics of AGW alike. It's also a value far too small for concern. With that sensitivity, the planet would warm by maybe a quarter of a degree by the year 2100. Yawn.
But there's a wrinkle in that simple calculation. As greenhouse gases rise, other things change as well. Some are positive feedbacks, which lead to more warming. Some are negative feedbacks, which counteract the warming. Scientists in the modeling community tend to believe positive effects predominate; they bandy about sensitivity values from 2C all the way up to 6C or more. Observational earth scientists (primarily geologists, meteorologists, and some atmospheric physicists) tend to believe negative effects dominate, and that the actual value may be even smaller than 0.5C.
The problem is that no real evidence exists for strong positive feedbacks. Worse, they seem contradicted by the paleoclimatic history of the planet, which has never experienced runaway warming even when CO2 levels were ten or more times higher than they are today. Over geologic time, CO2 correlates very poorly with temperature, leading one to conclude that it's a very weak greenhouse gas.
There is other evidence against a high sensitivity. But the real point is this. Whichever side is right, the media (and a few researchers) have forgotten one of the basic rules of science. Until a theory can predict the unexpected, it should always be viewed critically. The ancient Greeks knew the stars moved, and they had a thousand theories to predict why it would keep happening. Until we can explain past climate shifts and successfully predict future trends, global models are educational toys. Not indisputable evidence.
Some pundits are calling 2008 the year global warming was disproven. I prefer to call it the year science triumphed over alarmism.
quote: You've misread the article. My statement was that the base sensitivity is about 0.5C. The IPCC assumes the actual sensitivity, including positive feedbacks, is much higher.
quote: The most-cited IPCC emissions scenario is that of the doubling of atmospheric CO2 by 2100. However, that doubling uses a baseline of 280ppm (preindustrial levels). At the current level of 380ppm, that equates to an additional 50% increase.
quote: "Given it forces a rise of only 1/4 a degree over the next 90 years -- a value smaller and less rapid than the natural climate shifts we've already experienced in the past 100 years -- the conclusion is self-obvious."
quote: Booker, the U.K. Telegraph, for one: