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SYFY WIRE Bad Astronomy

BREAKING NEWS: Scott Pruitt, head of EPA, doesn’t think carbon dioxide is the main driver of global warming

By Phil Plait

Hot on the heels of my post earlier today about the reality of global warming comes this jaw-dropper: Scott Pruitt, who was recently approved by the Senate to run the United States Environmental Protection Agency (EPA), says that carbon dioxide is not the main cause of global warming.

Holy. Wow.

In a CNBC interview, when asked, “Do you believe that it’s been proven that CO2 is the primary control knob for climate?” he replied this way:

No, I think that measuring with precision human activity on the climate is something very challenging to do and there’s tremendous disagreement about the degree of impact. So no, I would not agree that it’s a primary contributor to the global warming that we see.

This is science denialism at a stunning level. And it’s incredibly disingenuous, too. Note his phrasing: He’s saying that disagreement about the amount of human-caused warming means CO2 is not the primary driver of warming. That’s like saying, “I don’t know if there’s a traffic jam at the corner of Main and 1st street or Main and 2nd, therefore cars don’t exist.”

That’s a classic denial method of distraction, sowing confusion about one issue to downplay another. Not only that, it’s utter baloney. We know for a fact that carbon dioxide is a greenhouse gas, and the main driver for the increased global warming we’ve seen over the past few decades. We also know for a fact that all or nearly all of that warming we’ve seen is caused by human activity.

The science behind greenhouse gases is pretty simple (and in fact understood for a century or so). A gas like carbon dioxide is transparent to visible light. Sunlight passes right by CO2 in the air, and hits the ground, warming it up. A warm object emits infrared light, so the ground radiates that absorbed energy from sunlight back into the sky. But CO2 is not transparent to infrared; it absorbs some of it, trapping a little bit of extra heat on Earth.

CO2 is a greenhouse gas

There are other greenhouse gases, including water vapor and methane. But, in general, the amounts of these gases in the atmosphere are in balance; water vapor condenses to form liquid water at about the same rate it vaporizes, so the amount in the air is steady. Methane is a very fragile molecule, and doesn’t last long once it’s in the atmosphere (ironically, it breaks down into carbon dioxide and water). So, while these are actually stronger greenhouse gases per molecule than CO2, they are in balance in the air, and don’t contribute much to rising temperatures.

The reason CO2 is the main driver of global warming is that we humans are producing prodigious quantities of it and dumping it into the air. How much? 40 billion tons per year. Yes, billion. That’s far more than any other natural source on the planet (even a big volcanic eruption puts out far less than that, despite claims by many deniers).

That’s why we’re getting hotter. It’s the extra CO2 in the air over time that’s trapping more heat from sunlight, warming us up. If we weren’t putting that extra carbon dioxide in the atmosphere we wouldn’t be experiencing global warming as we are. Also, CO2 is a very stable molecule, so any of it we put in the air stays there, lasting for decades or even centuries.

As to Pruitt’s second point, computer models that take into account all known physical factors show that humans are not only the main cause of warming, but that we may be causing all of it. Like 100%.

Humans are the main source of global warming

The graphic shows this; various models using different methods all show that humans are behind the vast majority of extra warming we see. Natural factors cause very little. In fact, many natural factors actually cool the planet, but we’re so vigorously churning out CO2 that we’re actually reversing that! That’s how humans can actually cause more than 100% of the warming.

The confusion Pruitt is sowing is due to a very minor point: The question of just how much temperatures go up as CO2 increases. If you double the CO2 in the air, for example, does the temperature go up 2° Celsius, or 3 or 4? This is a complicated question, because in the short term the temperature may only go up a degree or so, but over time an equilibrium is reached that can be much higher, like 3-4°. But no matter what, Pruitt is still bearing false witness: We know the temperature is going up, and we know it’s from CO2, and we know it’s the extra CO2 we’re generating that’s doing it.

So, everything Pruitt said in that short answer was complete nonsense. I just wish it were unexpected; it’s been clear for some time that nearly every single person Donald Trump has nominated to a position of power denies global warming.

But that’s why this is so very serious. Pruitt is the head of the EPA, the agency created to make sure we humans don’t screw up our environment. The EPA was created under Nixon and has been amazingly successful at cleaning up the disasters humans have left behind us as our technology grows. It’s been vital in preventing future disasters, too. This includes the effects of global warming. That’s why the EPA classified CO2 as a pollutant; that way it can be regulated so that we don’t pour even more of it into the air by burning fossil fuels.

And that is why so many scientists are up in arms over the Trump administration's bizarre and terrible appointees to science agencies, like Pruitt. They aren’t just ignorant of basic science; they’re openly antagonistic toward it. And that’s why we must continue to speak up, make our voices heard, and do what we can to prevent these people for destroying the one planet we’ve got.

They want to turn up the heat on Earth? Then we must turn the heat up on them.