Most thoughtful Christians these days have spent time considering how to be good stewards of the environment. After all, even if environmentalism weren't so fashionable, Christians have a solid biblical motivation to be good stewards of the environment. God's first commands to the human race were to be fruitful and multiply, to have dominion over all living things, and to till and keep the Garden. The word "dominion" here isn't synonymous with "dominate." A closer sense of the intended meaning is the rule of benevolent princes who represent a Good King to the rest of creation.

So from the earliest pages of the Bible the call to good environmental stewardship is clear. But what does that involve in practical terms? Some things are obvious. Don't litter. Don't poison the neighborhood, lake or stream. Don't be wasteful.

But then there are issues much larger than any one individual or community. The big environmental issue nowadays is global warming. Anyone who watches or reads the news even occasionally has been told that humans are causing global warming through all the fossil fuels we're burning. They've also been told that this warming process eventually will prove catastrophic if we don't reverse course as soon as possible.

As thinking Christians and good stewards, how should we respond?

The short answer is, we should respond thoughtfully. Thoughtless stewards are rarely good stewards.

Notice that my brief summary of the global warming controversy bundled together several distinct claims. To think clearly about this issue, we have to tease apart this bundle of claims and consider each one. For each claim, there is a corresponding question we need to answer. And it's only after answering these questions that we can be in a position to determine what, if anything, we ought to do about global warming.

Here are the four central questions:

1. Is the earth warming?
2. If the earth is warming, is human activity (like carbon dioxide emissions) causing it?
3. If the earth is warming, and we're causing it, is that bad overall?
4. If the earth is warming, we're causing it, and that's bad, would any of the proposed "solutions" (e.g., the Kyoto Protocol, legislative restrictions on carbon dioxide emissions) make any difference?

To question 1, I would answer: "Quite probably." That is, based on current evidence, we're probably in a warming trend, if you pick a popular baseline of, say, 1870. Given all of the human industrial activity since 1870, that should give us pause.

That leads to the second question. Are our carbon dioxide (CO2) emissions causing this warming? Remember, the warming and the cause of the warming are two different things. Almost all the evidence discussed in the popular press, when it's accurately presented, is evidence of warming — and nothing else. Pictures of retreating glaciers in the Andes from one decade to the next may be evidence of warming, but they don't tell us why the earth has warmed.

Part of the reason questions 1 and 2 get conflated is that the answer seems so obvious. We know that carbon dioxide is a greenhouse gas. We know that we've been adding carbon dioxide to the atmosphere for the last century and a half. And we know it's gotten warmer (on average) during that time. So surely, it would seem, the increase in carbon dioxide is the main cause of the warming.

Actually, it's not that simple.

Just because carbon dioxide is a greenhouse gas doesn't mean that adding a few parts per million into the atmosphere will warm the planet. Nor is the evidence of a warming trend decisive. The earth has experienced various warming and cooler trends throughout its history. We're probably warmer now than we were 140 years ago, but we're probably cooler now than in the year 1000.

The earth's climate is always changing. And the changes in global climate we're currently experiencing are well within the historical range of variation.¹ By itself then, the fact that we seem to be in a warming trend is trivial.

Besides, there are other possible causes for the warming. The most prominent possible cause is the Sun. Some scientists argue that changes in the Sun's energy or magnetic activity are the main actors in earth's changing climate. They point out that it's also gotten warmer on Mars in recent years.² Earth and Mars don't have Exxon, Shell and Texaco in common. They do have the Sun in common.

But don't we have direct evidence that carbon dioxide is to blame? Well, no. Although you'll rarely see it mentioned in news stories, insiders know that predictions of future global warming are based on the assumptions plugged into computer models, not on direct evidence of what's causing warming. Therefore, at the moment, the prudential answer to question (2) would be: "We don't know."³

What about question (3)? Is it obvious that global warming would be bad, overall? No, it's not. It might lead to droughts in some places, but to warmer, wetter, more productive weather elsewhere. The total might be a net gain. We already know that, within limits, warm weather is better than cold weather — that's why most Canadians live close to their southern border with the US. (It's not because they love Americans.) And less energy is used in warm weather than in cold. So we have little reason to assume that some warming would be bad.

Recent estimates point in that direction. Bjørn Lomborg calculates that about 200,000 people die in Europe each year from extreme heat, but 1.5 million die from extreme cold.⁴ You can't just focus on the 200,000, as is the custom in almost every story about the bad effects of warming. You have to weigh it against the 1.5 million.

Another study suggests that human carbon dioxide emissions could be preventing an overdue ice age.⁵ Neither of these proves warming would be better than cooling on balance. But these are just the sorts of factors that any serious judgment on the issue will have to take into account.

In any case, we don't know what the optimum average global temperature is. We may be moving toward it rather than away from it. So for all we know, the current warming is good rather than bad.

We also need to keep in mind that our planet has all sorts of feedback mechanisms that have kept it from spinning out of equilibrium, even in the face of shocks in the past. One of these natural feedback mechanisms is increased plant growth in the face of rising levels of carbon dioxide (surely a good thing), which in turn sequesters additional carbon dioxide.

Other natural feedback processes involve everything from precipitation and cloud cover and current and wind patterns. Before we start declaring that the sky is falling, we would do well to tend more closely to these many safeguards built into planet earth.

What about question (4)? Is it obvious that reducing carbon dioxide emissions in the U.S., for example, would make much difference? Virtually all experts agree that it would not. Take the Kyoto Protocol, which requires participating countries to reduce annual emissions to 5.2 percent below 1990 levels. The official estimate is that if all participating countries complied, at best it would slow current warming by an undetectable 0.07 degrees centigrade by 2050. In other words, it wouldn't do squat, but it would cost a lot.

To comply, the estimated cost to the worldwide economy would be between $10 and $50 trillion. Imagine what it would cost to reduce carbon emissions by 80-90 percent, without benefit of a new form of energy.

In contrast, the economists that form the "Copenhagen Consensus" have estimated that it would cost about $200 billion to outfit the rest of the world with water sanitation capacity. That's a lot of money, but it's fifty to 250 times cheaper than the estimated cost of Kyoto, and vastly more beneficial to poor people suffering and dying from unclean water. Moreover, unclean water is a much more immediate environmental killer than any plausible outcome of warming and so, deserves more attention.

Unless we're interested in practicing random acts of piety that don't do anything except squander money that would be much better spent elsewhere, we should be skeptical of the Kyoto Protocol and other similar attempts to restrict carbon emissions by fiat.⁶

When it comes to global warming, then, being a good steward of the environment may just mean challenging the official orthodoxy of the environmentalists.

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1. See Guillermo Gonzalez and Jay W. Richards, The Privileged Planet (Washington DC: Regnery Publishing, 2004), pp. 21-43.
2. For a tellingly biased report of this, see Kate Ravilious, "Mars Melt Hints at Solar, Not Human, Cause for Warming, Scientist Says," National Geographic News (February 28, 2007).
3. For a detailed study of global climate variations in geologic history, and the possible causes, see Dennis Avery and Fred Singer, Unstoppable Global Warming: Every 1,500 Years (Lanham, MD: Rowman & Littlefield, 2007).
4. Bjørn Lomborg, Cool It (New York: Knopf, 2007).
5. Ibid., pp. 40-43.
6. The Copenhagen Consensus did a cost-benefit analysis to determine how best to spend $50 billion in humanitarian aid. Their top picks were projects to prevent HIV/AIDS, iron deficiency in women and children, and malaria. The Kyoto Protocol ranked 16th out of 17 ways to spend the money. Moreover, they assumed that carbon dioxide is largely responsible for global warming. See discussion at www.copenhagenconsensus.com. See also the compilation Global Crises, Global Solution, edited by Bjørn Lomborg (Cambridge: Cambridge University Press, 2004).