Research on a Greenland Meltdown 400,000 Years Ago Has Big Implications for Climate Policy

Without sucking out today's CO2, even aggressive emissions cuts won't stave off centuries of rising seas and warming, authors of a new study warn

Join me live today at 3 pm ET at the United Nations (video links) discussing ways to overcome “short termism” in sustainability policy (or catch up later).

Much of Greenland’s ice sheet is two miles thick (left); open areas around the coast today (right) resemble what a far larger portion of that giant island looked like during a warm spell 400,000 years ago.

A new analysis of debris found in a core of ancient ice and sediment extracted in northwest Greenland decades ago reveals there was enormous and sustained warming and ice loss there 400,000 years ago, during a previous long warm spell between ice ages known clunkily as Marine Isotope Stage 11 (MIS 11). Levels of heat-trapping CO2 were lower than those today.

The research, published today in the journal Science, has substantial implications for how much current and projected warming will affect Greenland’s vast ice sheet and how much, and for how long, global sea levels rise.

As the paper’s authors put it:

“If moderate warmth for 29 kya [29,000 years] during MIS 11 resulted in significant ice loss from Greenland, then rapid, prolonged, and considerable anthropogenic Arctic warming will likely cause melting of the [Greenland Ice Sheet], raise sea level, and trigger additional climate feedbacks in the coming centuries.”

Even if the world somehow got on a “safe” Paris Agreement emissions path, co-author Paul Bierman of the University of Vermont says, coastal immersion and heating will persist for thousands of years. The only real brake, he says, would come by drawing down existing concentrations of carbon dioxide. In a video summary he narrates, produced by his daughter, he says:

A new study in the journal Science shows that a mile of ice vanished from northwest Greenland about 400,000 years ago. That natural warming period can help us understand the effects of climate change today, using frozen soil extracted in 1966 from beneath a modern Greenland ice sheet at a military base called Camp Century, an international team dated the loss of ice that drove global sea level up between five and 20 feet. Today, our atmosphere contains 50 percent more heat trapping carbon dioxide than it did when Greenland's ice melted. As a result, Earth is warming quickly. July 2023 brought the four warmest days on Earth since record keeping began by temperatures melt ice sheets. Unless we stop emitting carbon and lower its concentration in the atmosphere, Greenland's behavior 400,000 years ago suggests a largely ice-free future for Earth, characterized by rising sea levels and oppressive heat. The ancient soil warns of trouble ahead.

Here’s the video:

I recorded a conversation a couple of days ago with Bierman and another of the paper’s authors, Tammy Rittenour at Utah State University. Watch and listen here (apologies for some patches of static!) or skim a rough Trint transcript with audio playback. Here’s the video:

Here’s audio:

Here’s one core point from Bierman (I’ll add more highlights and links to other coverage of note, but I’m preparing to get on stage at the United Nations as you see this):

Bierman - Unless we do something active [carbon capture], that carbon dioxide we've put in the atmosphere is not going away any time soon. Yes, a lot of it's going into the ocean, but it's not going to disappear the minute you and I and Tammy stop driving our cars or running our oil heat or whatever we use…. That means we are creating a human equivalent of MIS-11. We're creating a long warm period - except this time it's long warm period on steroids, seeing that heating. So if MIS-11 was one or one and a half degrees Celsius warmer than pre-industrial revolution for us, we're there right now. And we've already had more than a degree Celsius of warming.

And with this sort of global heat wave that's going on right now, we're breaking records. Last week we broke records every day for the hottest day on record. You know, something like eight of the nine last years are the hottest on record.

So you look at all this and see the last time it got this warm for a long time the ice went away and we're headed exactly down that path. It's kind of inescapable to me. And I'm a geologist. So I tend to look in the past for clues to the present and the future, it seems inevitable that we're going to have a warmer, wetter planet with higher sea level going forward. And that could be for a long, long time.

Insert - Leigh Stearns, a University of Kansas climate researcher who just returned from East Greenland, offered this reaction to the paper:

There are several interesting and important implications from this paper. First, it pinpoints the timing and location of Greenland mass loss, which has been hypothesized but not identified in several far-field proxy records. Knowing the timing and location is important for large-scale ice sheet and solid earth models (which provide key parameterizations for ice sheet projections).

Second, it shows that large ice loss occurred during a time of sustained (but not extreme) high summer temperatures. This has large implications for the patterns of warming we see in Greenland currently. We tend to focus on the extreme years, but the sustained warmth (climate vs weather) is more impactful for ice sheet loss.

Read a good Washington piece by Sarah Kaplan. - end insert

In 2004, I had the privilege of standing on top of Greenland’s vast ice sheet - which holds roughly the same volume of water as the entire two-mile-deep Gulf of Mexico. Read my sustained New York Times coverage, and watch this low-rez video I shot:

And if you seek a fresh primer on the state of science, policy, finance and technology of carbon capture and storage, there’s no better guide than Julio Friedmann. I had a recent chat with him ahead of a presentation I gave (online) to the Vietnam-based Vin Future Foundation: