Featured Research

from universities, journals, and other organizations

Earth's Ecosystems Slowed Greenhouse Gas Buildup In 1990s, Climate Changes Could Speed It Up Again

Date:
November 22, 2001
Source:
National Center For Atmospheric Research/University Corporation For Atmospheric Research
Summary:
The earth's land-based ecosystems absorbed all of the carbon released by deforestation plus another 1.4 billion tons emitted by fossil fuel burning during the 1990s, but we can't rely on this convenient uptake to head off global warming in the future, according to a new study published this week in the journal Nature. Carbon dioxide (CO2) is the primary greenhouse gas entering the atmosphere from human activities.

BOULDER -- The earth's land-based ecosystems absorbed all of the carbon released by deforestation plus another 1.4 billion tons emitted by fossil fuel burning during the 1990s, but we can't rely on this convenient uptake to head off global warming in the future, according to a new study published this week in the journal Nature. Carbon dioxide (CO2) is the primary greenhouse gas entering the atmosphere from human activities.

Related Articles


"We could easily see this robust transfer of carbon out of the atmosphere and into land-based ecosystems that occurred in the 1990s slow down in the future," says the paper's lead author, David Schimel, of the National Center for Atmospheric Research (NCAR).

Fossil-fuel burning, cement manufacture, and deforestation gave off about 7 billion tons of carbon per year during the 1980s and 8 billion tons annually during the 1990s, about half of it ending up in the earth's atmosphere, according to the study. In the 1980s the amount of carbon released to the atmosphere from deforestation about equaled that taken up by land ecosystems into various "sinks." During the 1990s the balance tipped, and 1.4 billion tons more carbon ended up in the land-based biosphere than in the atmosphere, despite continuing deforestation.

Land-use changes in the Northern Hemisphere have been partly responsible for carbon uptake during the 1990s. In the United States, trees and other growth expanded on abandoned agricultural land, while a reduction in fires allowed forests to spread. Enhanced plant growth spurred by increasing carbon dioxide and nitrogen deposits -- a process more noticeable in Europe and Asia -- also helped clear the air of CO2 buildup.

"Forests can only replace farms for so long," explains Schimel. "Eventually new trees and grasses reach maturity and soak up less carbon dioxide. Similarly, there's a limit to how much forests can fill in and spread, even with successful fire suppression." The boost in CO2 and nitrogen fertilization will peak as well, though at high levels. Over time the effects of climate change on ecosystems will probably reduce sinks globally, write the authors. Meanwhile, carbon dioxide emissions are expected to continue to rise because of human activities.

An unusually large uptake of atmospheric carbon in the early 1990s was due to the climate's natural variability, researchers suspect. Globally there appears to be a net release of carbon into the atmosphere during warm, dry years and a net uptake during cooler years. Recently, evidence has grown linking changing levels of atmospheric CO2 to the El Niño/Southern Oscillation and its widespread impacts.

For the tropics, scientists expected computer models to show a large increase in atmospheric carbon dioxide released by deforestation during recent decades. In fact, no such increase emerged, indicating a potentially large sink in the low latitudes. Local-scale studies show carbon absorption by a range of mature tropical forest types, but the authors warn that such processes may not be true of the entire region, since tropical ecosystems vary widely. The lack of data, both atmospheric and ecological, combined with a complex meteorology, make estimates of tropical fluxes highly uncertain, they caution.

Previous attempts to evaluate carbon uptake in North America compared to that occurring in Europe and Asia have been controversial. In this paper, the authors conclude that the 1990s sink was roughly split between Eurasia and North America, with Eurasia slightly leading. Because they used only atmospheric data in their analyses, the authors caution that the resulting distribution pattern is highly uncertain. Even so, it appears consistent with independent analyses of satellite vegetation data. The uptake patterns across the continents also make sense physically: they appear to be driven by broad climate patterns interacting with historic human management of ecosystems.

Carbon accumulates at higher rates in intensively managed ecosystems and those recovering from disturbance, the researchers note. For example, Chinese inventory studies of continental plant growth show a major carbon sink resulting from extensive programs in foresting and reforesting.

Schimel's portion of this research was funded by NASA and by the National Science Foundation, NCAR's primary sponsor.


Story Source:

The above story is based on materials provided by National Center For Atmospheric Research/University Corporation For Atmospheric Research. Note: Materials may be edited for content and length.


Cite This Page:

National Center For Atmospheric Research/University Corporation For Atmospheric Research. "Earth's Ecosystems Slowed Greenhouse Gas Buildup In 1990s, Climate Changes Could Speed It Up Again." ScienceDaily. ScienceDaily, 22 November 2001. <www.sciencedaily.com/releases/2001/11/011120050810.htm>.
National Center For Atmospheric Research/University Corporation For Atmospheric Research. (2001, November 22). Earth's Ecosystems Slowed Greenhouse Gas Buildup In 1990s, Climate Changes Could Speed It Up Again. ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2001/11/011120050810.htm
National Center For Atmospheric Research/University Corporation For Atmospheric Research. "Earth's Ecosystems Slowed Greenhouse Gas Buildup In 1990s, Climate Changes Could Speed It Up Again." ScienceDaily. www.sciencedaily.com/releases/2001/11/011120050810.htm (accessed December 21, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Sunday, December 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Lava on Track to Hit Hawaii Market

Raw: Lava on Track to Hit Hawaii Market

AP (Dec. 19, 2014) — Lava from an active volcano on Hawaii's Big Island slowed slightly but stayed on track to hit a shopping center in the small town of Pahoa. (Dec. 19) Video provided by AP
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) — A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. Video provided by Newsy
Powered by NewsLook.com
Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) — The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Arctic Warming Twice As Fast As Rest Of Planet

Arctic Warming Twice As Fast As Rest Of Planet

Newsy (Dec. 18, 2014) — The Arctic is warming twice as fast as the rest of the planet, thanks in part to something called feedback. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins