Nav: Home

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

July 02, 2018

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 ocean circulation patterns. 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 carbon dioxide were to blame.

If the cooling had been caused by changes in ocean circulation, regions around the equator would have warmed as the polar regions cooled, shifting the distribution of heat on Earth. But changing the concentration of greenhouse gases 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 temperature we reconstructed can only be explained by greenhouse gas forcing," said Margot Cramwinckel, a PhD 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 climate 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.
-end-
Researchers from Utrecht University, Purdue, University of Padova, University of Southampton, University of Bremen and the Royal Netherlands Institute for Sea Research collaborated on this research. The research was carried out under the program of the Netherlands Earth System Science Centre and financially supported by the Dutch Ministry of Education, Culture and Science; the Netherlands Organisation for Scientific Research; and the National Science Foundation.

Purdue University

Related Climate Change Articles:

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.
Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.
Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.
Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.
A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.
Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).
Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.
Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.
Could climate change cause infertility?
A number of plant and animal species could find it increasingly difficult to reproduce if climate change worsens and global temperatures become more extreme -- a stark warning highlighted by new scientific research.
Predicting climate change
Thomas Crowther, ETH Zurich identifies long-disappeared forests available for restoration across the world.
More Climate Change News and Climate Change Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.