While a politician might be faulted for pushing a particular agenda that serves his own purposes, who can fault the impartial scientist who warns us of an imminent global-warming Armageddon? After all, the practice of science is an unbiased search for the truth, right? The scientists have spoken on global warming. There is no more debate. But let me play devil’s advocate. Just how good is the science underpinning the theory of manmade global warming? My answer might surprise you: it is 10 miles wide, but only 2 inches deep.

Contrary to what you have been led to believe, there is no solid published evidence that has ruled out a natural cause for most of our recent warmth – not one peer-reviewed paper. The reason: our measurements of global weather on decadal time scales are insufficient to reject such a possibility. For instance, the last 30 years of the strongest warming could have been caused by a very slight change in cloudiness. What might have caused such a change? Well, one possibility is the sudden shift to more frequent El Niño events (and fewer La Niña events) since the 1970s. That shift also coincided with a change in another climate index, the Pacific Decadal Oscillation.

The associated warming in Alaska was sudden, and at the same time we just happened to start satellite monitoring of Arctic sea ice. Coincidences do happen, you know…that’s why we have a word for them.

We make a big deal out of the “unprecedented” 2007 opening of the Northwest Passage as summertime sea ice in the Arctic Ocean gradually receded, yet the very warm 1930s in the Arctic also led to the Passage opening in the 1940s. Of course, we had no satellites to measure the sea ice back then.

So, since we cannot explore the possibility of a natural source for some of our warming, due to a lack of data, scientists instead explore what we have measured: manmade greenhouse gas emissions. And after making some important assumptions about how clouds and water vapor (the main greenhouse components of the atmosphere) respond to the extra carbon dioxide, scientists can explain all of the recent warming.

Never mind that there is some evidence indicating that it was just as warm during the Medieval Warm Period. While climate change used to be natural, apparently now it is entirely manmade. But a few of us out there in the climate research community are rattling our cages. In the August 2007 Geophysical Research Letters, my colleagues and I published some satellite evidence for a natural cooling mechanism in the tropics that was not thought to exist. Called the “Infrared Iris” effect, it was originally hypothesized by Prof. Richard Lindzen at the Massachusetts Institute of Technology.

By analyzing six years of data from a variety of satellites and satellite sensors, we found that when the tropical atmosphere heats up due to enhanced rainfall activity, the rain systems there produce less cirrus cloudiness, allowing more infrared energy to escape to space. The combination of enhanced solar reflection and infrared cooling by the rain systems was so strong that, if such a mechanism is acting upon the warming tendency from increasing carbon dioxide, it will reduce manmade global warming by the end of this century to a small fraction of a degree. Our results suggest a “low sensitivity” for the climate system.

What, you might wonder, has been the media and science community response to our work? Absolute silence. No doubt the few scientists who are aware of it consider it interesting, but not relevant to global warming. You see, only the evidence that supports the theory of manmade global warming is relevant these days.

The behavior we observed in the real climate system is exactly opposite to how computerized climate models that predict substantial global warming have been programmed to behave. We are still waiting to see if any of those models are adjusted to behave like the real climate system in this regard.

And our evidence against a “sensitive” climate system does not end there. In another study (conditionally accepted for publication in the Journal of Climate) we show that previously published evidence for a sensitive climate system is partly due to a misinterpretation of our observations of climate variability. For example, when low cloud cover is observed to decrease with warming, this has been interpreted as the clouds responding to the warming in such a way that then amplifies it. This is called “positive feedback,” which translates into high climate sensitivity.

But what if the decrease in low clouds were the cause, rather than the effect, of the warming? While this might sound like too simple a mistake to make, it is surprisingly difficult to separate cause and effect in the climate system. And it turns out that any such non-feedback process that causes a temperature change will always look like positive feedback. Something as simple as daily random cloud variations can cause long-term temperature variability that looks like positive feedback, even if in reality there is negative feedback operating.

The fact is that so much money and effort have gone into the theory that mankind is 100 percent responsible for climate change that it now seems too late to turn back. Entire careers (including my own) depend upon the threat of global warming. Politicians have also jumped aboard the Global Warming Express, and this train has no brakes.

While it takes only one scientific paper to disprove a theory, I fear that no amount of evidence will be able to counter what everyone now considers true. If tomorrow the theory of manmade global warming were proved to be a false alarm, one might reasonably expect a collective sigh of relief from everyone. But instead there would be cries of anguish from vested interests.

About the only thing that might cause global warming hysteria to end will be a prolonged period of cooling…or at least, very little warming. We have now had at least six years without warming, and no one really knows what the future will bring. And if warming does indeed end, I predict that there will be no announcement from the scientific community that they were wrong. There will simply be silence. The issue will slowly die away as Congress reduces funding for climate change research.

Oh, there will still be some diehards who will continue to claim that warming will resume at any time. And many will believe them. Some folks will always view our world as a fragile, precariously balanced system rather than a dynamic, resilient one. In such a world-view, any manmade disturbance is by definition bad. Forests can change our climate, but people aren’t allowed to.

It is unfortunate that our next generation of researchers and teachers is being taught to trust emotions over empirical evidence. Polar bears are much more exciting than the careful analysis of data. Social and political ends increasingly trump all other considerations. Science that is not politically correct is becoming increasingly difficult to publish. Even science reporting has become more sensationalist in recent years.

I am not claiming that all of our recent warming is natural. But the extreme reluctance for most scientists to even entertain the possibility that some of it might be natural suggests to me that climate research has become corrupted. I fear that the sloppy practice of climate change science will damage our discipline for a long time to come.

Roy W. Spencer is a principal research scientist at the University of Alabama in Huntsville. His book, Climate Confusion: How Global Warming Leads to Bad Science, Pandering Politicians and Misguided Policies that Hurt the Poor, will be published this month.