Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


New evidence of global warming in Earth’s past supports greenhouse climate theory


New evidence of global warming in Earth’s past supports current models for how climate responds to greenhouse gases

CA--Scientists have filled in a key piece of the global climate picture for a period 55 million years ago that is considered one of the most abrupt and extreme episodes of global warming in Earth’s history. The new results from an analysis of sediment cores from the ocean floor are consistent with theoretical predictions of how Earth’s climate would respond to rising concentrations of greenhouse gases in the atmosphere.

The new study, led by James Zachos, professor of Earth sciences at the University of California, Santa Cruz, will be published online by Science Express on October 23, and will appear in a later print edition of Science magazine.

The researchers analyzed sediments deposited on the seafloor during a period known as the Paleocene-Eocene Thermal Maximum, when a massive release of heat-trapping greenhouse gases is thought to have triggered a runaway process of global warming. Climate theory predicts that the increase in greenhouse gases would have caused temperatures to rise all over the planet, with greater increases in sea surface temperatures at high latitudes than at low latitudes.

Zachos and a team of researchers at UCSC and several other institutions have now obtained the first reliable estimates of the change in tropical sea surface temperatures during this period. When combined with existing records of sea surface temperatures at high latitudes, the findings fit well with the predictions of computer simulations based on current climate theory.

The study provides important backing for the climate models that scientists are using to predict the effects of the current rise in atmospheric carbon dioxide due to industrial emissions, Zachos said.

"The predictions from the models seem to be consistent with the geologic record, so I’d say greenhouse climate theory is alive and well," he said. "People have raised questions about how accurate these models are in terms of handling heat transport in response to rising greenhouse gases, but this study indicates that the climate people have got it right or close to right."

The Paleocene-Eocene Thermal Maximum, starting about 55 million years ago and lasting about 150,000 years, is marked by dramatic changes in the fossil record of life in the ocean and on land. Average global temperatures increased by about 5 degrees Celsius (9 degrees Fahrenheit). The increase in sea surface temperatures at high latitudes was 8 to 10 degrees Celsius, and the new study shows a 4- to 5-degree Celsius increase in tropical sea surface temperatures.

"This event is the best example of greenhouse warming in the geologic record, and for the first time we have been able to document the climate response on a relatively broad planetary scale, from the tropics to polar latitudes," Zachos said.

The temperature estimates were derived from chemical analyses of the shells of microscopic plankton preserved in the seafloor sediments. The chemical composition of the plankton’s calcite shells reflects the temperature of the water in which they were formed. A key measurement examined in this study was the ratio of magnesium to calcium, which increases exponentially with the temperature at which the shells formed.

"The ratio of magnesium to calcium in seawater is relatively constant over the timescale of this event, so the ratio in the shells is really only sensitive to one variable, the calcification temperature," Zachos said.

UCSC graduate students Michael Wara and Steven Bohaty performed most of the chemical analyses. The researchers analyzed sediment cores recovered from a site called Shatsky Rise in the tropical Pacific during an expedition of the ship JOIDES Resolution in 2001 (Leg 198 of the Ocean Drilling Program). The cores provided a complete sequence of deposits representing the boundary between the Paleocene and Eocene epochs.

"There aren’t many places in the Pacific where you can recover sediments of this age in which the fossils are not so recrystallized that they’ve lost their original geochemical signatures," Zachos said.

ODP Leg 198 and a complementary drilling expedition in the Atlantic earlier this year (ODP Leg 208) were designed to test the leading explanation for the Paleocene-Eocene Thermal Maximum, which attributes it to a massive release of methane. Methane, a potent greenhouse gas, accumulates in frozen deposits known as clathrates found in the deep ocean near continental margins and also in the Arctic tundra. For reasons that remain unclear, the clathrates suddenly began to decompose, releasing an estimated 2,000 gigatons (2 trillion tons) of methane.

Once released, the methane would have reacted with dissolved oxygen in the ocean to produce carbon dioxide, another greenhouse gas. Large amounts of both carbon dioxide and methane would have entered the atmosphere, raising temperatures worldwide.

In addition to Zachos, Wara, and Bohaty, the coauthors on the Science paper are Margaret Delaney, professor of ocean sciences at UCSC, Maria Rose Petrizzo and Isabella Premoli-Silva of the University of Milan, Amanda Brill of the University of North Carolina, and Timothy Bralower of Pennsylvania State University. Bralower and Premoli-Silva were co-chief scientists on ODP Leg 198.

Tim Stephens | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Innovative technique for shaping light could solve bandwidth crunch

20.10.2016 | Physics and Astronomy

Finding the lightest superdeformed triaxial atomic nucleus

20.10.2016 | Physics and Astronomy

NASA's MAVEN mission observes ups and downs of water escape from Mars

20.10.2016 | Physics and Astronomy

More VideoLinks >>>