Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A human-caused climate change signal emerges from the noise

30.11.2012
By comparing simulations from 20 different computer models to satellite observations, Lawrence Livermore climate scientists and colleagues from 16 other organizations have found that tropospheric and stratospheric temperature changes are clearly related to human activities.

The team looked at geographical patterns of atmospheric temperature change over the period of satellite observations. The team's goal of the study was to determine whether previous findings of a "discernible human influence" on tropospheric and stratospheric temperature were sensitive to current uncertainties in climate models and satellite data.

The troposphere is the lowest portion of earth's atmosphere. The stratosphere sits just above the troposphere, between 6 and 30 miles above earth's surface.

The satellite temperature data sets were produced by three different research groups, and rely on measurements of the microwave emissions of oxygen molecules. Each group made different choices in processing these raw measurements, and in accounting for such complex effects as drifts in satellite orbits and in instrument calibrations.

The new climate model simulations analyzed by the team will form the scientific backbone of the upcoming 5th assessment of the Intergovernmental Panel on Climate Change, which is due out in 2014.

In both satellite observations and the computer model simulations of historical climate change, the lower stratosphere cools markedly over the past 33 years. This cooling is primarily a response to the human-caused depletion of stratospheric ozone. The observations and model simulations also show a common pattern of large-scale warming of the lower troposphere, with largest warming over the Arctic, and muted warming (or even cooling) over Antarctica. Tropospheric warming is mainly driven by human-caused increases in well-mixed greenhouse gases.

"It's very unlikely that purely natural causes can explain these distinctive patterns of temperature change," said Laboratory atmospheric scientist Benjamin Santer, who is lead author of the paper appearing in the Nov. 29 online edition of the journal, Proceedings of the National Academy of Sciences. "No known mode of natural climate variability can cause sustained, global-scale warming of the troposphere and cooling of the lower stratosphere."

The team analyzed results from climate model simulations with specified historical changes in human and natural external factors, and from simulations with projected 21st century changes in greenhouse gases and anthropogenic aerosols. They also looked at simulations with no changes in external influences on climate, which provide information on the year-to-year and decade-to-decade "noise" of internal climate variability, arising from such natural phenomena as the El Niño/Southern Oscillation and the Pacific Decadal Oscillation.

The team used a standard "climate fingerprint" method to search for the model signal pattern (in response to human influences, the sun and volcanoes) in the satellite observations. The method quantifies the strength of the signal in observations, relative to the strength of the signal in natural climate noise.

Other contributors include researchers from Remote Sensing Systems of Santa Rosa; the Centre for Australian Weather and Climate Research, Melbourne, Australia; the Canadian Centre for Climate Modeling and Analysis, Victoria, Canada; the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory, Princeton; the University of Colorado, Boulder; the Massachusetts Institute of Technology, Cambridge; the U.K. Met. Office Hadley Centre, Exeter, U.K.; the Centre National de la Recherche Scientifique, Toulouse, France; North Carolina State University; the National Climatic Data Center, Asheville; Lawrence Berkeley National Laboratory; the National Center for Atmospheric Research, Boulder; the University of Adelaide, South Australia; the University of Reading, U.K.; and the Center for Satellite Applications and Research, Camp Springs. The paper is Santer's inaugural article as a member of the U.S. National Academy of Sciences.

Founded in 1952, Lawrence Livermore National Laboratory provides solutions to our nation's most important national security challenges through innovative science, engineering and technology. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.

Anne Stark | EurekAlert!
Further information:
http://www.llnl.gov

More articles from Earth Sciences:

nachricht Geophysicists and atmospheric scientists partner to track typhoons' seismic footprints
16.02.2018 | Princeton University

nachricht NASA finds strongest storms in weakening Tropical Cyclone Sanba
15.02.2018 | 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: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Contacting the molecular world through graphene nanoribbons

19.02.2018 | Materials Sciences

When Proteins Shake Hands

19.02.2018 | Materials Sciences

Cells communicate in a dynamic code

19.02.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>