Greenhouse gases were the main driver of climate change in the deep past

July 2, 2018, Purdue University
Credit: CC0 Public Domain

Greenhouse gases were the main driver of climate throughout the warmest period of the past 66 million years, providing insight into the drivers behind long-term climate change.

Antarctica and Australia separated around the end of the Eocene (56 to 22.9 million years ago), creating a deep water passage between them and changing . Some researchers believe these changes were the driver of cooling temperatures near the end of the Eocene 'hothouse' period, but some think declining levels of were to blame.

If the cooling had been caused by changes in , regions around the equator would have warmed as the polar regions cooled, shifting the distribution of heat on Earth. But changing the concentration of would affect the total heat trapped in Earth's atmosphere, causing cooling everywhere (including in the tropics), which is what the researchers found. The findings were published in the journal Nature.

The synchronized evolution of tropical and polar we reconstructed can only be explained by forcing," said Margot Cramwinckel, a Ph.D. candidate at Utrecht University in the Netherlands and first author of the paper. "Our findings are uniquely compatible with the hypothesis that the long-term Eocene cooling was driven by greenhouse gasses. This greatly improves our understanding of the drivers behind long-term change, which is important in order to predict the development of future climate change."

Climate change often has more intense effects near the poles than elsewhere on the planet, a phenomenon known as polar amplification.

The study found that temperature change was more dramatic near the poles than in the tropics during the Eocene, even though most of the period was extremely warm, leaving little to no ice near the poles.

"Even in a largely ice-free world, the poles cooled more than the tropics as temperature dropped," Cramwinckel said. "This indicates that greenhouse gas forcing by itself can cause polar amplification."

The researchers had one more question about polar amplification: does it reach some sort of limit?

"Our results support the idea that polar amplification saturates out at some point in warm climates and does not continue to increase with further warming," said Matthew Huber, a professor of earth, atmospheric and planetary sciences at Purdue University and co-author of the paper.

As a proxy for temperature, the research team looked at membrane lipids of simple, sea-surface dwelling organisms called Thaumarchaeota that change their membrane composition as temperatures change in deep sea sediment cores drilled near the Ivory Coast.

They combined these observations with climate models, produced by Huber's team at Purdue, to mesh together a timeline of temperature throughout the Eocene.

"The simulations took about four years of continuous computing to achieve equilibrated climate states at various carbon dioxide levels," Huber said. "For the first time, the climate model is capable of capturing the main trends in tropical sea surface temperatures and temperature gradients across a range of climate encompassing nearly 20 million years. The only problem is that the simulations required more carbon dioxide changes than observed, which demonstrates that this model is not sensitive enough to carbon dioxide."

Historically, researchers have had trouble reproducing temperature gradients between the tropics and the poles throughout the Eocene. These new climate models are capable of overcoming most of the issues faced by past models.

Explore further: New Eocene fossil data suggest climate models may underestimate future polar warming

More information: Synchronous tropical and polar temperature evolution in the Eocene , Nature (2018). DOI: 10.1038/s41586-018-0272-2 , https://www.nature.com/articles/s41586-018-0272-2

Related Stories

From Greenhouse to Icehouse

November 24, 2009

A new study that reconstructed ocean temperatures from millions of years ago could provide new insight into how the Earth responds to climate change.

Recommended for you

11 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

eljo
1.7 / 5 (6) Jul 02, 2018
The only problem is that the simulations required more carbon dioxide changes than observed, which demonstrates that this model is not sensitive enough to carbon dioxide."

Question for a paleoclimatologist if such a rare bird happens to be dropping in: Is there a proxy in the geological record for differences in electrical charge coming from the sun, and only attributable to the sun (not geomagnetism, not radioactivity, not light and other parts of the spectrum)?

jonesdave
3.8 / 5 (10) Jul 02, 2018
The only problem is that the simulations required more carbon dioxide changes than observed, which demonstrates that this model is not sensitive enough to carbon dioxide."

Question for a paleoclimatologist if such a rare bird happens to be dropping in: Is there a proxy in the geological record for differences in electrical charge coming from the sun, and only attributable to the sun (not geomagnetism, not radioactivity, not light and other parts of the spectrum)?



What electrical charge from the Sun?
Solon
1.7 / 5 (6) Jul 02, 2018
"What electrical charge from the Sun?"

The Sun's Electrical Charge
https://www.natur...011202b0
jonesdave
4.2 / 5 (10) Jul 02, 2018
"What electrical charge from the Sun?"

The Sun's Electrical Charge
https://www.natur...011202b0


Sorry, but that is a paper from 1964, cited 3 times, and one of those points out that it's wrong!
Try this more recent one:

On the global electrostatic charge of stars
Neslusan, L.
https://www.aanda...2649.pdf

For our star we are looking at ~ 77 Coulombs, positive.
TheVogon
5 / 5 (3) Jul 02, 2018
"The only problem is that the simulations required more carbon dioxide changes than observed, which demonstrates that this model is not sensitive enough to carbon dioxide."

Which presumably could easily be resolved but as it says "The simulations took about four years of continuous computing "
Da Schneib
3.9 / 5 (11) Jul 02, 2018
For our star we are looking at ~ 77 Coulombs, positive.
I got a battery in my TV remote that holds about 5000 Coulombs.

What I think is amazing is that we can determine such a small charge for such a large body. Has this actually been measured, @jonesy? Take heart, someone is actually asking a question who won't try to twist your answer into proof of the EUdiocy!
Da Schneib
4 / 5 (8) Jul 02, 2018
"The only problem is that the simulations required more carbon dioxide changes than observed, which demonstrates that this model is not sensitive enough to carbon dioxide."

Which presumably could easily be resolved but as it says "The simulations took about four years of continuous computing "
This actually shows that the model in use is conservative in its estimation of the temperature changes expected from changes in CO₂. In other words, accusations from deniers of overblown statistics are nothing but hot air. So to speak.

I wonder if it actually took four calendar years, or if there's some formula at work here where it really took, say, two weeks on 128 processors.
rrwillsj
3.3 / 5 (7) Jul 02, 2018
I have noticed while conversing with denialists, that they lack even a modicum of understanding of the basic mechanisms underlying proposed Climate Change scenarios.

In other words... They do not understand how their own kitchen refrigerator works. The deniallist are completely ignorant of the 'why' of the 'how' a heat exchanging machine results in cold air.

If they even have thought about the subject? They give up in confusion and just accept that the cold air inside a refrigerator and freezer are the result of some sort of 'unknowable' magic of science.

Which brings up the old saw about how advanced technology would seem like magic.

Pretty sad when you realize that 21st century adults think 19th century technology is 'magical'.
Surveillance_Egg_Unit
3.7 / 5 (3) Jul 03, 2018
The only problem is that the simulations required more carbon dioxide changes than observed, which demonstrates that this model is not sensitive enough to carbon dioxide."

Question for a paleoclimatologist if such a rare bird happens to be dropping in: Is there a proxy in the geological record for differences in electrical charge coming from the sun, and only attributable to the sun (not geomagnetism, not radioactivity, not light and other parts of the spectrum)?


says eljo

https://www.jpl.n...ure=6804

"Solar storms often include an eruption on the sun called a coronal mass ejection, or CME. This is a vast cloud of electrically charged particles hurled into space that disturbs the interplanetary magnetic field in our solar system. When these particles and the magnetic disturbances encounter Earth's magnetic field, they interact in a series of complex physical processes, and trigger perturbations in the Earth's magnetic field."
Da Schneib
3.9 / 5 (7) Jul 03, 2018
How heat moves is easily observable from cooking.

If you can cook. Based on their wacky objections I'd say most deniers have trouble eating without stabbing themselves in the face with the fork. I'd add with chopsticks, but denialism seems to be a uniquely American and European phenomenon.
TrollBane
not rated yet Jul 03, 2018
DS, have a look at this survey of climate change denial and related attitudes by country. https://en.wikipe..._country

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.