New Climate Model Reveals "Discernible Human Influence"
The Lawrence Livermore National Laboratory (LLNL) is a federally funded research and development center located in Livermore, California. Their mission, in part, is to respond with vision, quality, integrity, and technical excellence to scientific issues of national importance. One such issue, which is tough to dispute, is the changing climate. The top-rate researchers at LLNL created a new climate model by comparing 20 different computer models to satellite observations. They found that tropospheric and stratospheric temperature changes are clearly related to human activities.
The troposphere is the portion of the atmosphere closest to the Earth's surface, where all life forms live and breathe. The stratosphere rests just above the troposphere, between 6 and 30 miles above the Earth's surface.
Three different research groups produced the satellite temperature data sets, relying on microwave emissions of oxygen molecules. The raw data was processed in different ways by the three groups, accounting for complex effects such as instrument calibrations in different ways.
Together, their new climate model simulations will form the scientific backbone for the upcoming 5th assessment of the Intergovernmental Panel on Climate Change (IPCC) in 2014.
The researchers found that the lower stratosphere has been cooling over the past 33 years in response to human-caused depletion of the ozone layer. They also found large-scale warming of the lower troposphere, with the largest increases over the Arctic and much lesser warming (if not cooling) over Antarctica. The conclusion was that the temperature increase in the lower troposphere was due to 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. "No known mode of natural climate variability can cause sustained, global-scale warming of the troposphere and cooling of the lower stratosphere."
The LLNL study has been published in the journal, Proceedings of the National Academy of Sciences.
Link to video showing the LLNL climate model animation
Earth Atmosphere image via Shutterstock