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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>