Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Methane gyrations last 2,000 years show human influnece on atmosphere

09.09.2005


Humans have been tinkering with greenhouse gas levels in Earth’s atmosphere for at least 2,000 years and probably longer, according to a surprising new study of methane trapped in Antarctic ice cores conducted by an international research team.



The study showed wild gyrations of methane from biomass burning from about 1 A.D. to present, said Dominic Ferretti, lead study author and a University of Colorado at Boulder researcher with a joint appointment at the National Institute of Water and Atmospheric Research, or NIWA in Wellington, New Zealand. Scientists had expected to see slowly increasing concentrations of methane, a major greenhouse gas produced primarily by burning and anaerobic activity from agriculture, livestock and natural sources, up until the onset of the Industrial Revolution in the late 1700s, he said.

For the first time, researchers were able to separate "pyrogenic" and anaerobic methane sources using a stable-isotope analysis of the ice cores, said James White of CU-Boulder’s Institute of Arctic and Alpine Research and study co-author. They found methane emissions from burning dropped about 40 percent from 1000 to 1700, likely due in large part to decreased landscape burning by indigenous populations in the Americas devastated by diseases brought to the New World by European explorers.


Undertaken by a team from CU-Boulder, NIWA, Australia’s Commonwealth Scientific and Industrial Research Organization, or CSIRO, Australia’s Department of the Environment and Heritage and the National Oceanic and Atmospheric Administration, the study was published in the Sept. 9 issue of Science.

"The results frankly were a shock," said White. "We can see human fingerprints all over atmospheric methane emissions for at least the last 2,000 years. Humans have been an integral part of Earth’s carbon cycle for much longer than we thought."

The researchers recorded a huge drop in methane levels from biomass burning from 1500 to 1600, when anthropologists say indigenous humans in South and Central America -- who had been expanding in population and range -- declined by 90 percent. Since most forests in Europe and China had been mostly cleared for agricultural or habitable lands by 1 A.D., "the seemingly small indigenous populations of the Americas would have had a disproportionate influence on anthropogenic methane emissions from fires," the researchers wrote in Science.

The study is important because methane increases have had the second highest impact on climate change over the past 250 years behind carbon dioxide, accounting for about 20 percent of the warming from all greenhouse gas increases, White said. Methane is more powerful than carbon dioxide in slowing the release of radiated heat away from Earth, he said.

About 60 percent of atmospheric methane is generated from human-related activities, according to the International Panel on Climate Change. Methane increases in the past 200 years are due to increased burning of grasslands, forests and wood fuels, more intense livestock activity and rice cultivation and gas leaked from fossil fuel production and waste management. In addition, natural sources of methane include wetlands, termites and wildfires.

Overall methane levels in the atmosphere increased about 2 percent from about 1 A.D. to 1000 and decreased by 2 percent from 1000 to 1700, according to the study. Since the 1700s, the levels have increased by nearly 300 percent, said White.

Surprisingly, the study showed the amount of methane produced from burning was about the same 1,000 years ago as it is today, said White. "There has been a naïve idea out there that humans were just passive, pastoral passengers on the planet up until just a few hundred years ago," he said. "We have shown that is not the case."

The study also suggests that natural climate change has played a role in changing methane levels in the atmosphere, at least on a regional level, White said. During the Medieval Warm Period from about 1000 to 1270, there appears to have been a slight increase in biomass burning in Europe. In cooler periods like the Little Ice Age from roughly 1300 to 1850, biomass burning in the Northern Hemisphere appears to have decreased somewhat while anaerobic activity by bacteria in bogs and swamps probably increased, he said.

Involving the United States, New Zealand and Australia, the international project focused on ice cores from Antarctica’s Law Dome, White said. "We could not have undertaken this study without all three countries," he said. "These types of projects are not cheap, and each group brought a unique line of expertise."

White said the team hopes to look at methane levels going back prior to 2,000 years ago. "The larger question is when humans began influencing the climate and nutrient system," he said. "We are in an unusually long interglacial period right now, and another interesting but unresolved question is whether humans, without forethought, have inadvertently kept Earth out of the next ice age by altering its energy budget."

James White | EurekAlert!
Further information:
http://www.colorado.edu

More articles from Earth Sciences:

nachricht Ice cave in Transylvania yields window into region's past
28.04.2017 | National Science Foundation

nachricht Citizen science campaign to aid disaster response
28.04.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>