Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New interpretation of satellite measurements confirms global warming

06.05.2004


For years the debate about climate change has had a contentious sticking point – satellite measurements of temperatures in the troposphere, the layer of atmosphere where most weather occurs, were inconsistent with fast-warming surface temperatures.



But a team led by a University of Washington atmospheric scientist has used satellite data in a new and more accurate way to show that, for more than two decades, the troposphere has actually been warming faster than the surface. The new approach relies on information that better separates readings of the troposphere from those of another atmospheric layer above, which have disguised the true troposphere temperature trend.

"This tells us very clearly what the lower atmosphere temperature trend is, and the trend is very similar to what is happening at the surface," said Qiang Fu, a UW associate professor of atmospheric sciences.


He is lead author of a paper documenting the work published in the May 6 edition of the journal Nature. Co-authors are Celeste Johanson, a UW research assistant and graduate student in atmospheric sciences; Stephen Warren, a UW professor of atmospheric sciences and Earth and space sciences; and Dian Seidel, a research meteorologist with the National Oceanic and Atmospheric Administration’s Air Resources Laboratory in Silver Spring, Md.

The team examined measurements from devices called microwave-sounding units on NOAA satellites from January 1979 through December 2001. The satellites all used similar equipment and techniques to measure microwave radiation emitted by oxygen in the atmosphere and determine its temperature.

Different channels of the microwave-sounding units measured radiation emitted at different frequencies, thus providing data for different layers of the atmosphere. In the case of the troposphere – which extends from the surface to an altitude of about 7.5 miles – it was believed there was less warming than what had been recorded at the surface.

The troposphere temperature was measured by channel 2 on the microwave sounding units, but those readings were imprecise because about one-fifth of the signal actually came from a higher atmospheric layer called the stratosphere.

"Because of ozone depletion and the increase of greenhouse gases, the stratosphere is cooling about five times faster than the troposphere is warming, so the channel 2 measurement by itself provided us with little information on the temperature trend in the lower atmosphere," Fu said.

Stratosphere temperatures are measured by channel 4 on the microwave units. Fu’s team used data from weather balloons at various altitudes to develop a method in which the two satellite channels could be employed to deduce the average temperature in the troposphere. The scientists correlated the troposphere temperature data from balloons with the simulated radiation in the two satellite channels to determine which part of the channel 2 measurement had come from the cooling stratosphere and should be removed.

What remained indicated that the troposphere has been warming at about two-tenths of a degree Celsius per decade, or nearly one-third of a degree Fahrenheit per decade. That closely resembles measurements of warming at the surface, something climate models have suggested would result if the warmer surface temperatures are the result of greenhouse gases. The previous lack of demonstrable warming in the troposphere has prompted some to argue that climate models are missing unrecognized but important physical processes, or even that human-caused climate change is not happening.

One reason previous data have not shown enough warming in the troposphere, Fu said, is because the stratosphere influence on the channel 2 temperature trend has never been properly quantified, even though there have been attempts to account for its influence. Those attempts had large uncertainties, so many researchers had simply used the unadjusted channel 2 temperature trends to represent the temperature trends in the middle of the troposphere.

Fu’s work is supported by the U.S. Department of Energy, the National Science Foundation and the National Aeronautics and Space Administration.

The findings, he said, could offer a new context for climate change discussion.

"I think everyone can understand our approach," he said. "I think this could convince not just scientists but the public as well."


For more information, contact Fu at 206-685-2070 or qfu@atmos.washington.edu

Vince Stricherz | EurekAlert!
Further information:
http://www.washington.edu/

More articles from Earth Sciences:

nachricht Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>