After much whispering and pre-publicity, a group of 86 evangelical leaders has announced their support for what The New York Times calls “a major initiative to fight global warming.” As part of the “Evangelical Climate Initiative,” they are calling for “federal legislation that would require reductions in carbon dioxide emissions through ‘cost-effective, market-based mechanisms.'” (For a response from another group of evangelical leaders, go to the Interfaith Stewardship Alliance.)

I have great respect for the supporters of this initiative, and I don’t doubt their sincerity. And I’m glad to see a call for “market-based” solutions to a problem. Unfortunately, this looks to me like another example (alongside the fuzzy advocacy of the ONE Campaign) of Christians, evangelicals in this case, endorsing a hip cause without thinking through its economic logic.

I doubt any of these evangelical leaders has relevant expertise when es to global warming, especially since the scientific issues involved are plex and change from day to day. So presumably they are simply trusting the advertised “scientific consensus” on this issue and using that perceived consensus as a filter for interpreting mundane events, like ice melting in Antarctica. That’s a problem, not only because the consensus is more manufactured than real (that is, objectively decided), but also because a scientific consensus that the planet is warming still wouldn’t tell us what to do about it. That’s a prudential question that can only be answered by taking account not only of the intended consequences of a policy, but also its unintended consequences.

The issue is not whether we should see ourselves as stewards over creation. That’s a non-negotiable Christian principle. The issue is whether these evangelicals have done the obligatory serious thinking before advocating a specific public policy.

When es to global warming, there are at least four separate issues to keep in mind. You don’t need to be a climate expert to do this.

(1) Is the planet warming?

(2) If the planet is warming, is human activity (like CO2 emissions) causing it?

(3) If the planet is warming, and we’re causing it, is it bad overall?

(4) If the planet is warming, we’re causing it, and it’s bad, would the monly advocated (e.g., the Kyoto Protocol, restrictions on CO2 emissions) make any difference?

If I had to guess based on current evidence, to question (1) I would answer: “Probably.” That is, we’re probably in the middle of a slight warming trend. So in a trivial sense, the climate is “changing.” I say this is trivial, because we know from natural “data recorders” like ice cores that historically, Earth’s climate is always changing. In fact, the last several thousand years, corresponding to recorded human history, have been uncharacteristically mild.

What about (2)? Are CO2 emissions causing this warming? Notice that the question isn’t whether CO2 is a green house gas. That’s uncontroversial. The question is whether the increase in atmospheric CO2 from human activity is causing warming, or whether one of the many natural feedback mechanisms is mitigating its effects? For example, in some cases, increase in CO2 leads to more plant growth, which in turn sequesters CO2. This is one of many examples of a natural feedback process that makes long range climate prediction unimaginably difficult. So at the moment, in answer to (2), I would say: “We don’t know.”

What about (3)? Is it obvious that global warming would be bad, overall? No, it’s not. It might be a net gain. In fact, it’s possible that human CO2 emissions could be preventing an overdue ice age, as Guillermo Gonzalez and I mention briefly in The Privileged Planet.

More specifically, is it obvious that the world’s poor would be worse off, overall, than they would be if the global climate stayed exactly the same? No, it’s not obvious.

Finally, what about (4)? Is it obvious that a reduction in American CO2 emissions, for example, would make much difference? No, it’s not obvious. And is it obvious, as this evangelical statement implies, that a call for restrictions on CO2 emissions would benefit the poor? No, it’s not.

Here, then, is the problem with the statement by this group of evangelical leaders. It treats the answers to these four questions as obviously “yes.” And it’s only on that baseless assumption that the statement can connect our responsibility as stewards with a specific policy position.

My point here is not to make any decisive pronouncements on global warming, or its more recent, and more vacuous substitute, “climate change.” My point is, rather, to plead with evangelical leaders not to do so, and not to pretend that they know more than they can possibly know. That’s especially true when es to the media-hyped global warming bandwagon, of which these evangelical leaders have now, unwittingly, e a part.