The art of prediction is one that often fails and only the test of time will show who is right and who is wrong. Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. There is a new paper in Nature Geoscience that examines the inertia of carbon dioxide emissions. New research indicates the impact of rising CO2 levels in the Earth's atmosphere will cause effects to the climate for at least the next 1,000 years, causing these researchers to estimate a collapse of the West Antarctic ice sheet by the year 3000, and an eventual rise in the global sea level of at least four meters.
The study is the first full climate model simulation to make predictions out to 1000 years from now. It is based on a best-case, zero-emissions scenarios constructed by a team of researchers from the Canadian Center for Climate Modeling and Analysis and the University of Calgary.
Predicting the future climate is an art and not a science because there are so many variables. It is rare that anyone has gone a 1,000 years into the future in their predictions. What most have in common is a general warming of the Earth and a rise in the ocean level. This has occurred many times in the geologic past.
In this new model the Northern Hemisphere fares better than the south in the computer simulations, with patterns of climate change reversing within the 1,000-year time frame in places like Canada.
Antarctica is likely to trigger widespread collapse of the West Antarctic ice sheet, a region the size of the Canadian prairies.
Researchers hypothesize that one reason for the variability between the North and South is the slow movement of ocean water from the North Atlantic into the South Atlantic. "The global ocean and parts of the Southern Hemisphere have much more inertia, such that change occurs more slowly," says Marshall, one of the authors. "The inertia in intermediate and deep ocean currents driving into the Southern Atlantic means those oceans are only now beginning to warm as a result of CO2 emissions from the last century. The simulation showed that warming will continue rather than stop or reverse on the 1000-year time scale."
Wind currents in the Southern Hemisphere may also have an impact. Marshall says that winds in the global south tend to strengthen and stay strong without reversing. "This increases the mixing in the ocean, bringing more heat from the atmosphere down and warming the ocean."
The paper "Ongoing climate change following a complete cessation of carbon dioxide emissions" by Nathan P. Gillett, Vivek K. Arora, Kirsten Zickfeld, Shawn J. Marshall and William J. Merryfield will be available online at http://www.nature.com/ngeo/index.html
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By. Andy Soos
