🌎 My chat (+transcript) with climate scientist Zeke Hausfather

Is climate change an impending existential threat, or a serious but manageable problem we can tackle with innovation and human ingenuity? Zeke Hausfather joins this episode of Faster, Please! — The Podcast to explain the basics of climate modeling and give a clear-eyed assessment of the risks we face and the measures we can take.

Zeke is a climate scientist and energy systems analyst. He is the climate research lead for Stripe and a research scientist at Berkeley Earth.

In This Episode

* Human impact on the climate (1:11)

* Global temperature forecasting (6:33)

* Low-probability, high-risk scenarios (15:07)

* Reducing carbon emissions (17:06)

* Carbon capture and carbon removal (25:25)

Below is an edited transcript of our conversation

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Human impact on the climate

James Pethokoukis: How do we know that our planet is warming? And secondarily, how do we know the actions of people are playing a key role?

Zeke Hausfather: That's a great question. In terms of how we know it's warming: We've been monitoring the Earth's climate with reasonably dense measurements since the mid-1800s. That's when groups like NASA, NOAA, the UK Hadley Centre, my own Berkeley Earth group, have been able to put together reliable global surface temperature estimates. And we've seen in the period…

That's since the 1980s?

1850.

1850. NASA was not around in 1850.

No. But enough measurements were being taken both at weather stations around the world and on ships in the oceans that we can reconstruct global temperatures with an accuracy of a couple tenths of a degree going back that far. We know that the world has warmed by about 1.2 degrees centigrade since 1850 with the vast majority of that warming, about 1 degree of it, happening since 1970. That isn't in much dispute in the scientific community at all. Now, going further back is harder, obviously. We only invented the thermometer in the early 1700s. There are a few locations on land that go back that far, but to go back further in time, we need to rely on what we call climate proxies: things like ice cores, tree rings, coral sediments, pollen in lakes — various natural factors that are in some way related to the temperature when those things occurred.

Those have much higher uncertainties, of course, but we do know using those reconstructions that current temperature levels are probably unprecedented in at least the last 2000 years and are at the high end of anything we've seen in the last 120,000 years or so. Certainly if current temperatures were to stay at today's levels for another century, they'd be higher than anything we've seen in 120,000 years. But it's harder to precisely make those claims because the time resolution of these indirect proxy measurements is very coarse when we go back further in time. You might have one ice core measurement reflect a hundred-year average period, for example, rather than a specific year. We know from the temperature record that the world has warmed. How do we know that human activity is playing a role? Well, we've known since the mid-1800s, due to pioneering work by folks like John Tyndall or Arrhenius, that carbon dioxide is a greenhouse gas and that greenhouse gases like carbon dioxide, water vapor, methane are critical to maintain a habitable planet. Without greenhouse gases in our atmosphere, the Earth would be a snowball and life would probably not exist.

We also know that the amount of carbon dioxide in the atmosphere has increased pretty dramatically. We have measurements from ice cores going back about 800,000 years of carbon dioxide in the atmosphere at a reasonably high resolution. And because carbon dioxide is well mixed, knowing it in one location in one ice core gives us a good picture of carbon dioxide for the whole planet. And we know that prior to the year 1850, carbon dioxide concentrations in the atmosphere varied between about 170 to 280 parts per million. They're lower during ice age periods; they're higher during warmer interglacial periods. But since the 1850s, that value has increased dramatically. The amount of carbon dioxide in the atmosphere has increased by about 50 percent. It's gone from 280 parts per million, which was over the last 10,000 years since the end of the last ice age, up to about 420 parts per million today.

And that reflects a huge amount of carbon dioxide in the atmosphere. I don't think people realize quite the magnitude we're talking about. The amount of carbon dioxide that humans have added to the atmosphere by digging up stuff from underground and burning it is roughly equal in mass to the entire biosphere. We took every single bit of life on Earth and burned it. That was about how much CO2 we put up in the atmosphere since the Industrial Revolution. Or to put it another way, it's equal in mass to all of everything humans have ever built: the pyramids, every skyscraper, every road. We took all that mass and put it up into the atmosphere. That's the amount of CO2 we've emitted. And so that's had a p