Nav: Home

What the ancient CO2 record may mean for future climate change

October 24, 2016

The last time Earth experienced both ice sheets and carbon dioxide levels within the range predicted for this century was a period of major sea level rise, melting ice sheets and upheaval of tropical forests.

The repeated restructuring of tropical forests at the time played a major role in driving climate cycles between cooler and warmer periods, according to a study led by the University of California, Davis and published today in the journal Nature Geoscience.

Using fossilized leaves and soil-formed minerals, the international team of researchers reconstructed the ancient atmospheric carbon dioxide record from 330 to 260 million years ago, when ice last covered Earth's polar regions and large rainforests expanded throughout the tropics, leaving as their signature the world's coal resources.

The team's deep-time reconstruction reveals previously unknown fluctuations of atmospheric carbon dioxide at levels projected for the 21st century and highlights the potential impact the loss of tropical forests can have on climate.

Climate Change Feeding Off Itself

"We show that climate change not only impacts plants but that plants' responses to climate can in turn impact climate change itself, making for amplified and in many cases unpredictable outcomes," said lead author Isabel Montañez, a Chancellor's Leadership Professor with UC Davis Department of Earth and Planetary Science. "Most of our estimates for future carbon dioxide levels and climate do not fully take into consideration the various feedbacks involving forests, so current projections likely underestimate the magnitude of carbon dioxide flux to the atmosphere."

Similarly to how oceans have served as the primary carbon sink in the recent past, tropical forests 300 million years ago stored massive amounts of carbon dioxide during these ancient glacial periods. The study indicates that repeated shifts in tropical forests in response to climate change were enough to account for the 100 to 300 parts per million changes in carbon dioxide estimated during the climate cycles of the period.

While plant biologists have been studying how different trees and crops respond to increasing carbon dioxide levels, this study is one of the first to show that when plants change the way they function as CO2 rises or falls, it can have major impact, even to the point of extinction.

"We see great resilience in vegetation to climatic changes, millions of years of stable composition and structure despite glacial-interglacial cycles," said co-author William DiMichele, a paleobiologist with the Smithsonian Institution. "But we've come to understand that there are thresholds that, when crossed, can be accompanied by rapid and irreversible biological change."

Co-leading author Jenny McElwain, professor of paleobiology at University College in Dublin, Ireland, said the study indicates that shifts in atmospheric carbon dioxide impacted plant groups differently.

"The forest giants of the period were hit particularly hard because they were the most inefficient of all the plants around at the time, likely losing water like open hose pipes" McElwain said. "Their forest competitors, like tree ferns, were able to outcompete them as the climate dried."

Background: Unprecedented Rise of CO2

Over the past million years, atmospheric carbon dioxide has been generally low and fluctuated predictably within a window of 200 to 300 ppm. This, the researchers explain, has sustained the current icehouse - a time marked by continental ice at the polar regions - under which humans have evolved. This trend has been abruptly interrupted by the pronounced rise of carbon dioxide over the past 100 years to the current level of 401 ppm -- one not seen on Earth for at least the past 3.5 million years.

The current unprecedented rate of rising atmospheric CO2 raises concerns about melting ice sheets, rising sea level, major climate change, and biodiversity loss - all of which were evident more than 300 million years, the only other time in Earth's history when high CO2 accompanied ice at the polar regions.
-end-
Additional co-authoring institutions include University College Dublin, Ireland; University of Michigan; Baylor University; Smithsonian Museum of Natural History; Haverford College; University of Connecticut.

University of California - Davis

Related Climate Change Articles:

The black forest and climate change
Silver and Douglas firs could replace Norway spruce in the long run due to their greater resistance to droughts.
For some US counties, climate change will be particularly costly
A highly granular assessment of the impacts of climate change on the US economy suggests that each 1°Celsius increase in temperature will cost 1.2 percent of the country's gross domestic product, on average.
Climate change label leads to climate science acceptance
A new Cornell University study finds that labels matter when it comes to acceptance of climate science.
Was that climate change?
A new four-step 'framework' aims to test the contribution of climate change to record-setting extreme weather events.
It's more than just climate change
Accurately modeling climate change and interactive human factors -- including inequality, consumption, and population -- is essential for the effective science-based policies and measures needed to benefit and sustain current and future generations.
Climate change scientists should think more about sex
Climate change can have a different impact on male and female fish, shellfish and other marine animals, with widespread implications for the future of marine life and the production of seafood.
Climate change prompts Alaska fish to change breeding behavior
A new University of Washington study finds that one of Alaska's most abundant freshwater fish species is altering its breeding patterns in response to climate change, which could impact the ecology of northern lakes that already acutely feel the effects of a changing climate.
Uncertainties related to climate engineering limit its use in curbing climate change
Climate engineering refers to the systematic, large-scale modification of the environment using various climate intervention techniques.
Public holds polarized views about climate change and trust in climate scientists
There are gaping divisions in Americans' views across every dimension of the climate debate, including causes and cures for climate change and trust in climate scientists and their research, according to a new Pew Research Center survey.
The psychology behind climate change denial
In a new thesis in psychology, Kirsti Jylhä at Uppsala University has studied the psychology behind climate change denial.

Related Climate Change Reading:

The Politically Incorrect Guide to Climate Change (The Politically Incorrect Guides)
by Marc Morano (Author)

Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming
by Paul Hawken (Editor), Tom Steyer (Editor)

The Uninhabitable Earth: Life After Warming
by Tim Duggan Books

The Sixth Extinction: An Unnatural History
by Elizabeth Kolbert (Author)

Climate Change: What Everyone Needs to Know®
by Joseph Romm (Author)

This Changes Everything: Capitalism vs. The Climate
by Naomi Klein (Author)

The Thinking Person's Guide to Climate Change
by Robert Henson (Author)

Climate Change: The Facts 2017
by Jennifer Marohasy (Editor)

Introduction to Modern Climate Change
by Andrew Dessler (Author)

Climate Change: The Facts
by J.Abbot (Author), J.S. Armstrong (Author), A.Bolt (Author), R.Carter (Author), R.Darwall (Author), J.Delingpole (Author), C.Essex (Author), S.Franks (Author), K.Green (Author), D.Laframboise (Author), N.Lawson (Author), B.Lewin (Author), R.Lindzen (Author), J.Marohasy (Author), R.McKitrick (Author), P.Michaels (Author), A.Moran (Author), J.Nova (Author), G.Paltridge (Author), I.Plimer (Author), W.Soon (Author), M.Steyn (Author), A.Watts (Author), Alan Moran (Editor)

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#514 Arctic Energy (Rebroadcast)
This week we're looking at how alternative energy works in the arctic. We speak to Louie Azzolini and Linda Todd from the Arctic Energy Alliance, a non-profit helping communities reduce their energy usage and transition to more affordable and sustainable forms of energy. And the lessons they're learning along the way can help those of us further south.