Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists find "fingerprint" of human activities in recent tropopause height changes

25.07.2003


Scientists from the Lawrence Livermore National Laboratory have determined that human-induced changes in ozone and well-mixed greenhouse gases are the primary drivers of recent changes in the height of the tropopause.



Earlier research has shown that increases in the height of the tropopause over the past two decades are directly linked to stratospheric ozone depletion and increased greenhouse gases.

The new research uses climate model results to provide more quantitative estimates of the relative contributions of natural and human influences to overall tropopause height changes. This work indicates that 80 percent of the roughly 200-meter increase in tropopause height from 1979 to 1999 is directly linked to human activities. Smaller tropopause height increases over the first half of the 20th century are largely caused by natural variations in volcanic aerosols and solar irradiance.


The tropopause is the boundary between the lowest layer of the atmosphere -- the turbulently mixed troposphere -- and the more stable stratosphere. It lies roughly 10 miles above the Earth´s surface at the equator and five miles above the poles. The location of the tropopause is sensitive to changes in vertical profiles of atmospheric temperature. The Livermore research attempts to understand how different mechanisms affect atmospheric temperatures, and hence tropopause height. It is the first study to show that a model-predicted "fingerprint" of tropopause height changes can be identified in observations.

The paper describing this work, entitled, "Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes," appears in the July 25 edition of Science. It involves a team of Livermore scientists (Benjamin Santer, Karl Taylor and James Boyle) and researchers from Lawrence Berkeley National Laboratory, the National Center for Atmospheric Research, the Institut für Physik der Atmosphäre in Germany and the University of Birmingham in the United Kingdom.

Using a computer model of the climate system, the Lab scientists and their colleagues examined changes in both man-made forcings (well-mixed greenhouse gases, tropospheric and stratospheric ozone, and the scattering effects of sulfate aerosols) and natural external forcings (solar irradiance and volcanic aerosols). Experiments were performed with a model developed jointly by the National Center for Atmospheric Research and Los Alamos National Laboratory. The innovative aspect of these model runs is that climate forcings were varied both individually and in concert. This allowed the researchers to estimate the contribution of each forcing to overall changes in atmospheric temperature and tropopause height. Completion of this very large ensemble of model runs was made possible by recent developments in high performance computing capabilities at U.S. Department of Energy and National Science Foundation facilities. Output from these and other related climate model runs is available at http://www.nersc.gov/projects/gcm_data/.

The model results reveal the key drivers of recent tropopause height increases -- human-caused changes in well-mixed greenhouse gases and stratospheric ozone -- act primarily through warming of the troposphere (greenhouse gases) and cooling of the lower stratosphere (ozone). Both of these effects increase tropopause height.

"Tropopause height is an integrated indicator of human-induced climate change," Santer said. "It reflects global-scale changes in the temperature structure of the atmosphere. Our research shows that the increase in tropopause height over the second half of the 20th century was predominantly due to human activity, and provides independent support for claims of recent tropospheric warming."

Anne Stark | EurekAlert!
Further information:
http://www.berkeley.edu

More articles from Earth Sciences:

nachricht Fossil coral reefs show sea level rose in bursts during last warming
19.10.2017 | Rice University

nachricht NASA finds newly formed tropical storm lan over open waters
17.10.2017 | 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: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>