Featured Research

from universities, journals, and other organizations

Why hasn't Earth warmed as much as expected? New report on climate change explores the reasons

Date:
January 19, 2010
Source:
DOE/Brookhaven National Laboratory
Summary:
Planet Earth has warmed much less than expected during the industrial era based on current best estimates of Earth's "climate sensitivity" -- the amount of global temperature increase expected in response to a given rise in atmospheric concentrations of carbon dioxide. In a new study, researchers examine the reasons for this discrepancy.

A new study examines why Earth has warmed much less than expected during the industrial era based on current best estimates of Earth's "climate sensitivity" -- the amount of global temperature increase expected in response to a given rise in atmospheric concentrations of carbon dioxide.
Credit: iStockphoto

Planet Earth has warmed much less than expected during the industrial era based on current best estimates of Earth's "climate sensitivity" -- the amount of global temperature increase expected in response to a given rise in atmospheric concentrations of carbon dioxide (CO2). In a study to be published in the Journal of Climate, a publication of the American Meteorological Society, Stephen Schwartz, of Brookhaven National Laboratory, and colleagues examine the reasons for this discrepancy.

Related Articles


According to current best estimates of climate sensitivity, the amount of CO2 and other heat-trapping gases added to Earth's atmosphere since humanity began burning fossil fuels on a significant scale during the industrial period would be expected to result in a mean global temperature rise of 3.8F -- well more than the 1.4F increase that has been observed for this time span. Schwartz's analysis attributes the reasons for this discrepancy to a possible mix of two major factors: 1) Earth's climate may be less sensitive to rising greenhouse gases than currently assumed and/or 2) reflection of sunlight by haze particles in the atmosphere may be offsetting some of the expected warming.

"Because of present uncertainties in climate sensitivity and the enhanced reflectivity of haze particles," said Schwartz, "it is impossible to accurately assign weights to the relative contributions of these two factors. This has major implications for understanding of Earth's climate and how the world will meet its future energy needs."

A third possible reason for the lower-than-expected increase of Earth's temperature over the industrial period is the slow response of temperature to the warming influence of heat-trapping gases. "This is much like the lag time you experience when heating a pot of water on a stove," said Schwartz. Based on calculations using measurements of the increase in ocean heat content over the past fifty years, however, this present study found the role of so-called thermal lag to be minor.

A key question facing policymakers is how much additional CO2 and other heat-trapping gases can be introduced into the atmosphere, beyond what is already present, without committing the planet to a dangerous level of human interference with the climate system. Many scientists and policymakers consider the threshold for such dangerous interference to be an increase in global temperature of 3.6F above the preindustrial level, although no single threshold would encompass all effects.

The paper describes three scenarios: If Earth's climate sensitivity is at the low end of current estimates as given by the Intergovernmental Panel on Climate Change, then the total maximum future emissions of heat-trapping gases so as not to exceed the 3.6 threshold would correspond to about 35 years of present annual emissions of CO2 from fossil-fuel combustion. A climate sensitivity at the present best estimate would mean that no more heat-trapping gases can be added to the atmosphere without committing the planet to exceeding the threshold. And if the sensitivity is at the high end of current estimates, present atmospheric concentrations of heat-trapping gases are such that the planet is already committed to warming that substantially exceeds the 3.6 threshold.

The authors emphasize the need to quantify the influences of haze particles to narrow the uncertainty in Earth's climate sensitivity. This is much more difficult than quantifying the influences of the heat-trapping gases. Coauthor Robert Charlson of the University of Washington likens the focus on the heat trapping gases to "looking for the lost key under the lamppost."

Schwartz observes that formulating energy policy with the present uncertainty in climate sensitivity is like navigating a large ship in perilous waters without charts. "We know we have to change the course of this ship, and we know the direction of the change, but we don't know how much we need to change the course or how soon we have to do it."

Schwartz and Charlson coauthored the paper with Ralph Kahn, NASA Goddard Space Flight Center in Maryland; John Ogren, NOAA Earth System Research Laboratory in Colorado; and Henning Rodhe, Stockholm University.


Story Source:

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


Journal Reference:

  1. Stephen E. Schwartz, Robert J. Charlson, Ralph A. Kahn, John A. Ogren, Henning Rodhe. Why Hasn't Earth Warmed as Much as Expected? Journal of Climate, 2007; preprint (2009): 1 DOI: 10.1175/2009JCLI3461.1

Cite This Page:

DOE/Brookhaven National Laboratory. "Why hasn't Earth warmed as much as expected? New report on climate change explores the reasons." ScienceDaily. ScienceDaily, 19 January 2010. <www.sciencedaily.com/releases/2010/01/100119112050.htm>.
DOE/Brookhaven National Laboratory. (2010, January 19). Why hasn't Earth warmed as much as expected? New report on climate change explores the reasons. ScienceDaily. Retrieved October 26, 2014 from www.sciencedaily.com/releases/2010/01/100119112050.htm
DOE/Brookhaven National Laboratory. "Why hasn't Earth warmed as much as expected? New report on climate change explores the reasons." ScienceDaily. www.sciencedaily.com/releases/2010/01/100119112050.htm (accessed October 26, 2014).

Share This



More Earth & Climate News

Sunday, October 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

EU Gets Climate Deal, UK PM Gets Knock

EU Gets Climate Deal, UK PM Gets Knock

Reuters - Business Video Online (Oct. 24, 2014) EU leaders achieve a show of unity by striking a compromise deal on carbon emissions. But David Cameron's bid to push back EU budget contributions gets a slap in the face as the European Commission demands an extra 2bn euros. David Pollard reports. Video provided by Reuters
Powered by NewsLook.com
Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Raw: Tornado Rips Roofs in Washington State

Raw: Tornado Rips Roofs in Washington State

AP (Oct. 24, 2014) A rare tornado ripped roofs off buildings, uprooted trees and shattered windows Thursday afternoon in the southwest Washington city of Longview, but there were no reports of injuries. (Oct. 24) Video provided by AP
Powered by NewsLook.com
Fast-Moving Lava Headed For Town On Hawaii's Big Island

Fast-Moving Lava Headed For Town On Hawaii's Big Island

Newsy (Oct. 24, 2014) Lava from the Kilauea volcano on Hawaii's Big Island has accelerated as it travels toward a town called Pahoa. 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