The Iris Effect

Andy Kessler writes on tech topics for the Wall Street Journal and this week's column addresses climate change. It's interesting because he thinks the earth has a built-in means to heal itself. It's called the Iris Effect.

Here's his lede:

Stop with all the existential-crisis talk. President Biden said, “Climate change is literally an existential threat to our nation and to the world.” Defense Secretary Lloyd Austin also talks about the “existential threat” of climate change. National security adviser Jake Sullivan identifies an “accelerating climate crisis” as one reason for a “new consensus” for government picking winners and losers in the economy.

Be wary of those touting consensus.

But what if the entire premise is wrong? What if the Earth is self-healing? Before you hurl the “climate denier” invective at me, let’s think this through. Earth has been around for 4.5 billion years—living organisms for 3.7 billion. Surely, an enlightened engineer might think, the planet’s creator built in a mechanism to regulate heat, or we wouldn’t still be here to worry about it.

The theory of climate change is that excess carbon dioxide and methane trap the sun’s radiation in the atmosphere, and these man-made greenhouse gases reflect more of that heat back to Earth, warming the planet. Pretty simple. Eventually, we reach a tipping point when positive feedback loops form—less ice to reflect sunlight, warm oceans that can no longer absorb carbon dioxide—and then we fry, existentially.

But nothing is simple. What about negative feedback loops? Examples: human sweat and its cooling condensation or our irises dilating or constricting based on the amount of light coming in. Clouds, which can block the sun or trap its radiation, are rarely mentioned in climate talk.

He goes on to talk about why clouds are difficult to model in the computer simulations run by climatologists and then he explains why clouds may be the means by which the earth prevents the runaway greenhouse effect:

Cumulus clouds, the puffy ones often called thunderclouds, are an important convection element, carrying heat from the Earth’s surface to the upper atmosphere. Above them are high-altitude cirrus clouds, which can reflect heat back toward the surface.

A 2001 Lindzen [Richard Lindzen, a professor at the Massachusetts Institute of Technology and lead author of an early Intergovernmental Panel on Climate Change] paper, however, suggests that high-level cirrus clouds in the tropics dissipate as temperatures rise.

These thinning cirrus clouds allow more heat to escape. It’s called the Iris Effect, like a temperature-controlled vent opener for an actual greenhouse so you don’t (existentially) fry your plants. Yes, Earth has a safety valve.

Mr. Lindzen says, “This more than offsets the effect of greenhouse gases.”

There've been numerous attempts to debunk Lindzen and the Iris Effect, Kessler writes, but the theory has withstood these critiques. If cirrus cloud cover diminishes as the temperature rises beyond some equilibrium point all the concern about impending global catastrophe will look silly in retrospect.

Kessler concludes with this:

A 2021 paper co-authored by Mr. Lindzen shows strong support for an Iris Effect. Maybe Earth really was built by an engineer. Proof? None other than astronomer Carl Sagan described the Faint Young Sun Paradox that, 2.5 billion years ago, the sun’s energy was 30% less, but Earth’s climate was basically the same as today.

Cirrus clouds likely formed to trap heat—a closed Iris and a negative feedback loop at work.

In a 2015 Nature Geoscience paper, Thorsten Mauritsen and Bjorn Stephen at the Max Planck Institute for Meteorology reran climate models using the Iris Effect and found them better at modeling historic observations.

One question Kessler's column raises is, if the Iris Effect is a real thing how hot does the planet have to get before the valve opens up and we can see that the effect is real and that it works?