Featured Research

from universities, journals, and other organizations

Researchers Discover That Volcanic Eruptions Masked Global Warming During The Past 20 Years

Date:
November 28, 2001
Source:
Lawrence Livermore National Laboratory
Summary:
Researchers at Lawrence Livermore National Laboratory, who examined temperature data from 1979 to 1999, have discovered that large volcanic eruptions cooled the lower troposphere (the layer of atmosphere from the Earth’s surface to roughly 8 km above it) more than the surface, and likely masked the actual warming of the troposphere.

LIVERMORE, Calif. — Researchers at Lawrence Livermore National Laboratory, who examined temperature data from 1979 to 1999, have discovered that large volcanic eruptions cooled the lower troposphere (the layer of atmosphere from the Earth’s surface to roughly 8 km above it) more than the surface, and likely masked the actual warming of the troposphere.

This research helps explain the apparent difference in warming rates at the Earth’s surface and in the lower troposphere. While the surface has warmed markedly over the past 20 years, temperatures in the lower troposphere have shown little or no increase. This discrepancy has been the focus of considerable scientific and political attention.

The research is presented in "Accounting for the Effects of Volcanoes and ENSO in Comparisons of Modeled and Observed Temperature Trends," in the November edition of the Journal of Geophysical Research-Atmospheres. LLNL researchers Benjamin Santer, Charles Doutriaux, James Boyle, Sailes Sengupta and Karl Taylor teamed with scientists from the National Center for Atmosphere Research, NASA/Goddard Institute for Space Studies, the Climatic Research Unit at the University of East Anglia in the United Kingdom, and the Max-Planck Institute for Meteorology in Germany.

The paper attempts to quantify volcanic influences on surface and tropospheric temperatures. Volcano "signals" are themselves masked by the temperature changes caused by El Niño events. The eruption of El Chichón in Mexico in 1982 coincided with a large El Niño event during the winter of 1982-83, while the eruption of Mt. Pinatubo in the Philippines in 1991 occurred at the same time as El Niño of 1991-92. To study volcanic effects on temperature, El Niño influences must first be removed.

The atmospheric scientists used a statistical procedure to separate El Niño and volcanic effects in observed temperature records. They found that aerosol particles from El Chichón and Pinatubo cooled the lower troposphere and probably masked the actual warming of the troposphere. Volcanoes therefore supply at least part of the explanation for the different temperature trends at the Earth’s surface and in the troposphere.

This research undercuts claims by greenhouse skeptics that no warming has occurred during the last two decades. These claims are based on satellite measurements of temperatures in the lower troposphere, which show little or no warming since the beginning of the satellite record in 1979.

"Our recent work shows that some of the differences between warming rates at the Earth's surface and in the lower troposphere are due to the effects of volcanic eruptions and stratospheric ozone depletion," said Santer, who works in LLNL’s Program for Climate Model Diagnosis and Intercomparison and is lead author of the JGR-A paper. "Both of these factors probably cooled the lower troposphere by more than the surface, for physical reasons that are well-understood. Without ozone depletion and the recent eruptions of El Chichon and Pinatubo, it is highly likely that the lower troposphere would have warmed over the last two decades."

Results from numerical models of the climate system reinforce these conclusions. Computer model experiments examined by the LLNL scientists suggest that it is important to include the effects of volcanoes and stratospheric ozone depletion (in addition to changes in other greenhouse gases, such as carbon dioxide and methane). Doing so brings simulated surface and tropospheric temperature changes into better agreement with the observations.

Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy's National Nuclear Security Administration.


Story Source:

The above story is based on materials provided by Lawrence Livermore National Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

Lawrence Livermore National Laboratory. "Researchers Discover That Volcanic Eruptions Masked Global Warming During The Past 20 Years." ScienceDaily. ScienceDaily, 28 November 2001. <www.sciencedaily.com/releases/2001/11/011128035329.htm>.
Lawrence Livermore National Laboratory. (2001, November 28). Researchers Discover That Volcanic Eruptions Masked Global Warming During The Past 20 Years. ScienceDaily. Retrieved August 27, 2014 from www.sciencedaily.com/releases/2001/11/011128035329.htm
Lawrence Livermore National Laboratory. "Researchers Discover That Volcanic Eruptions Masked Global Warming During The Past 20 Years." ScienceDaily. www.sciencedaily.com/releases/2001/11/011128035329.htm (accessed August 27, 2014).

Share This




More Earth & Climate News

Wednesday, August 27, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Calif. Quake Underscores Need for Early Warning

Calif. Quake Underscores Need for Early Warning

AP (Aug. 26, 2014) — Researchers at UC Berkeley are testing a prototype of an earthquake early warning system that California is pursuing years after places like Mexico and Japan already have them up and running. (August 26) Video provided by AP
Powered by NewsLook.com
Hurricane Marie Brings Big Waves to California Coast

Hurricane Marie Brings Big Waves to California Coast

Reuters - US Online Video (Aug. 26, 2014) — Huge waves generated by Hurricane Marie hit the Southern California coast. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Brazil Tries Genetically Modified Mosquitoes to Fight Dengue

Brazil Tries Genetically Modified Mosquitoes to Fight Dengue

AFP (Aug. 25, 2014) — A factory in the industrial state of Sao Paulo produces genetically modified mosquitoes to fight dengue, a deadly tropical disease more prevalent in Brazil than anywhere else in the world. Duration: 00:57 Video provided by AFP
Powered by NewsLook.com
Raw: Prime Minister at Japan Landslide Site

Raw: Prime Minister at Japan Landslide Site

AP (Aug. 25, 2014) — Japanese Prime Minister Shinzo Abe visited Hiroshima on Monday as rescuers expanded their search for dozens still missing from landslides around the western Japanese city that killed at least 50 people. (Aug. 25) Video provided by AP
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:
from the past week

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