Famed physicist Stephen Hawking has just issued (yet another) dire, apocalyptic warning: the US pullout from the Paris Accords could very well be the thing that pushes Earth into a hothouse meltdown. In his words, “We are close to the tipping point where global warming becomes irreversible. Trump's action could push the Earth over the brink, to become like Venus, with a temperature of two hundred and fifty degrees, and raining sulfuric acid.”

He continued, “Climate change is one of the great dangers we face, and it's one we can prevent if we act now. By denying the evidence for climate change, and pulling out of the Paris Climate Agreement, Donald Trump will cause avoidable environmental damage to our beautiful planet, endangering the natural world, for us and our children.”

How to assess such a claim? If one of the world’s smartest scientists says that we’re about to become a second Venus, shouldn’t we panic? Or, should we curtly dismiss such dramatic apocalypticism as yet another example of politically-charged environmental extremism?

Oh wait—I just discovered a third option. How about discussing Global Warming rationally? That’s the correct and very Catholic thing to do. (The following is a summary of a chapter on Global Warming in my book, In Defense of Nature, where more detail is provided.)

The whole Global Warming question is complicated. Let’s look at one angle on it, whether (as Hawking fears) we’re in imminent danger of becoming another Venus.

Venus is the hottest planet in the solar system, due in great part (you guessed it) to a very, very thick, heat-trapping CO2 atmosphere. Travelers interested in visiting this beautiful planet should expect daytime temperatures over 850 degrees Fahrenheit. If we subtracted the thick shroud of CO2 from Venus, the mean surface temperature would drop to about 130 degrees Fahrenheit, which would put it within the temperature range of habitability, at least in the abstract.

How close are we to becoming another Venus, i.e., how do our levels of atmospheric CO2 compare? Venus’s atmosphere consists of 96% carbon dioxide, and Earth’s a mere .04% (again, not 4%, but four one-hundredths of one percent).

BIG difference.

That’s an interesting fact because Earth and Venus have about the same sum total amount of CO2, counting both the CO2 in the atmosphere and that which is locked up in the ground. But while almost all of Venus’s carbon dioxide resides in the atmosphere, almost all of Earth’s resides in the ground.

What causes the immense difference? The Earth’s amazing carbon cycle, which is part of its absolutely ingenious thermostatic regulatory system.

When things heat up on Earth, it causes increased evaporation from our bountiful supply of surface water in oceans and lakes. This has a kind of double effect. Water vapor is a greenhouse gas, so increasing it in the atmosphere contributes to warming. But water vapor also gives us more clouds. Clouds actually deflect a good bit of the incoming sun’s rays, thereby leading to a decrease in temperature. But even more important, the ensuing rain washes CO2 out of the atmosphere, thereby reducing the effect of this greenhouse gas, and the temperature cools.

What happens to the CO2? Rain is actually made somewhat more acidic by the dissolving of atmospheric CO2.  Happily, the slightly acidic rain helps to weather rocks on land and in the ocean, thereby releasing minerals, in particular, silicates. These now-available silicates bring about a chemical reaction with CO2 that produces limestone, the result being a reduction of carbon dioxide and a further cooling down of Earth’s thermostat. As Harvard astronomer Owen Gingerich points out, “The earth’s atmosphere would be similar [to Venus’s] if the oceans [of Earth] had not dissolved the carbon dioxide and precipitated the excess in the form of limestone.”

It seems exceedingly unlikely that we are (as Hawking suggests) at a tipping point, about to become a second Venus. Earth’s self-regulating thermostat kicks in when things warm up, as it has done for millions upon millions of years. That we have such an astounding, self-regulating thermostatic system is a cause for wonder, and gratitude to the Creator—and I have only described part of it in this article.

Does that mean we have nothing at all to worry about? Just because we’re not about to become another Venus, doesn’t mean that we have no cause for concern. Life is delicate, and the temperature range of habitability is relatively thin. The delicacy of our situation on Earth is actually the result of a host of exceedingly precise conditions that allow for such abundant life here—conditions that are so rare, we may very well be the only planet that enjoys them.

In sum, Earth is fine-tuned for life, a sign that we do not live on an ordinary planet (and a sign for Christians of God’s creative genius). But that privilege brings with it responsibility. Earth enjoys a wide variety of complex and delicate ecosystems, with creatures formed to fit them rather precisely. While we may not be about to boil away our oceans and create a hell on Earth, a few degree increase could very well have destructive effects, which are hard to predict until it’s too late. Or, our temperature may remain stable thanks to the carbon cycle, but increased acidic rain might significantly damage the creatures of the ocean.

But justified caution is not the same as apocalypticism. The problem with “the sky is falling” rhetoric of someone of Hawking’s stature is that it creates an all-or-nothing drastic scenario.

Those who embrace Hawking’s alarmism, are then ready and willing to give enormous power to national and transnational organizations to save us from being tipped into annihilation. That is a recipe for creating a tyranny of alleged experts (as happened with the so-called “Population Crisis” of the 1970s, which resulted in an enormous international push for birth control and abortion).

On the other hand, those who realize that there are a significant number of scientific reasons for being skeptical of the apocalyptic claims of Global Warming enthusiasts—and there are many more reasons I could provide—then feel free to dismiss any concern for the ill effects of our actions on the environment.

It is far better to approach the Global Warming debate with a much cooler head. That, I believe, is the Catholic thing to do.