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

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers shoot for success with simulations of laser pulse-material interactions

29.03.2017 | Materials Sciences

Igniting a solar flare in the corona with lower-atmosphere kindling

29.03.2017 | Physics and Astronomy

As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation

29.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>