Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First compilation of tropical ice cores shows two abrupt global climate shifts: One 5,000 years ago

27.06.2006
For the first time, glaciologists have combined and compared sets of ancient climate records trapped in ice cores from the South American Andes and the Asian Himalayas to paint a picture of how climate has changed – and is still changing – in the tropics.

Their conclusions mark a massive climate shift to a cooler regime that occurred just over 5,000 years ago, and a more recent reversal to a much warmer world within the last 50 years.

The evidence also suggests that most of the high-altitude glaciers in the planet's tropical regions will disappear in the near future. The paper is included in the current issue of the journal Proceedings of the National Academy of Science.

Lastly, the research shows that in most of the world, glaciers and ice caps are rapidly retreating, even in areas where precipitation increases are documented. This implicates increasing temperatures and not decreasing precipitation as the most likely culprit.

The researchers from Ohio State University's Byrd Polar Research Center and three other universities combined the chronological climate records retrieved from seven remote locations north and south of the equator. Cores drilled through ice caps and glaciers there have captured a climate history of each region, in some cases, providing annual records and in others decadal averages.

“Approximately 70 percent of the world's population now lives in the tropics so when climate changes there, the impacts are likely to be enormous,” explains Lonnie Thompson, professor of geological sciences at Ohio State.

For the last three decades, Thompson has led nearly 50 expeditions to remote ice caps and glaciers to drill cores through them and retrieve climate records. This study includes cores taken from the Huascaran and Quelccaya ice caps in Peru; the Sajama ice cap in Bolivia; the Dunde, Guliya, Puruogangri and Dasuopu ice caps in China.

For each of these cores, the team -- including research partner Ellen Mosley-Thompson, professor of geography at Ohio State – extracted chronological measurements of the ratio of two oxygen isotopes -- O18 and O16 -- whose ratio serves as an indicator of air temperature at the time the ice was formed. All seven cores provided clear annual records of the isotope ratios for the last 400 years and decadally averaged records dating back 2000 years.

“We have a record going back 2,000 years and when you plot it out, you can see the Medieval Warm Period (MWP) and the Little Ice Age (LIA),” Thompson said. During the MWP, 700 to 1000 years ago, the climate warmed in some parts of the world. The MWP was followed by the LIA, a sudden onset of colder temperatures marked by advancing glaciers in Europe and North America .

“And in that same record, you can clearly see the 20th Century and the thing that stands out – whether you look at individual cores or the composite of all seven – is how unusually warm the last 50 years have been.

“There hasn't been anything in the record like it – not even the MWP,” Thompson said.

“The fact that the isotope values in the last 50 years have been so unusual means that things are dramatically changing. That's the real story here.”

While the isotope evidence is clear throughout all of the cores, Thompson says that the more dramatic evidence is the emergence of unfossilized wetland plants around the margin of the Quelccaya ice cap, uncovered as the ice retreated in recent years.

First discovered in 2002, the researchers have since identified 28 separate sites near the margin of the ice cap where these ancient plants have been exposed. Carbon-dating revealed that the plants range in age from 5,000 to 6,500 years old.

“This means that the climate at the ice cap hasn't been warmer than it is today in the last 5,000 years or more,” Thompson said. “If it had been, then the plants would have decayed.”

The researchers say a major climate shift around 5,000 years ago in the tropics had to have cooled the region since the ice cap quickly expanded and covered the plants. The fact that they are now being exposed indicates that the opposite has occurred – the region has warmed dramatically, causing the ice cap to quickly melt.

The role of precipitation in the global retreat of alpine glaciers may have been clarified by this study. Some researchers, convinced that a reduction in local precipitation is causing their retreat, have been skeptical about the role of rising temperatures.

“While all the glaciers we have measured throughout the tropics are retreating, the local precipitation at all of these sites but one, has increased over the last century,” Thompson said. “That means that the retreat of the ice is driven mainly by rising temperatures.”

Changes in the oxygen isotope ratios over the past 100 years have also pointed to temperature, rather than precipitation, as the engine driving glacial retreat, he said.

“Tropical glaciers are the ‘canaries in the coal mine' for our global climate system,” he says, “as they integrate and respond to most of the key climatological variables – temperature, precipitation, cloudiness, humidity and radiation.”

Thompson said that the evidence arising from the tropics is particularly important. “The uniformity of the climate in the tropics makes these kinds of records so critical since they tell us what is happening to global temperatures.

“What this is really telling us is that our climate system is sensitive, it can change abruptly due to either natural or to human forces,” he said. “If what happened 5,000 years ago were to happen today, it would have far-reaching social and economic implications for the entire planet.

“The take-home message is that global climate can change abruptly, and with 6.5 billion people inhabiting the planet, that's serious.”

Working along with Thompson and Mosley-Thompson on the project were Henry Brecher, Mary Davis, Ping-Nan Lin and Tracy Mashiotta, all with the Byrd Center; Blanca Leon of the University of Texas; Don Les of the University of Connecticut, and Keith Mountain of the University of Louisville.

Support for the research came from the National Science Foundation, the National Oceanic and Atmospheric Administration and Ohio State.

Lonnie Thompson | EurekAlert!
Further information:
http://www.osu.edu

More articles from Earth Sciences:

nachricht Predicting eruptions using satellites and math
28.06.2017 | Frontiers

nachricht NASA sees quick development of Hurricane Dora
27.06.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>