NULL HYPOTHESIS climate.nasa.gov/scientific-consensus/ washingtonpost/…/atmospheric-carbon-dioxide…/ mnn/earth-matters/climate-weather/blogs/earths-oceans-hit-warmest-temperatures-ever-recorded#ixzz3JNimWMc9 esrl.noaa.gov/gmd/dv/iadv/graph.php… Scientists: Human activity has pushed Earth beyond four of nine ‘planetary boundaries’ The Washington Post Better understood is the role of carbon dioxide as a greenhouse gas. The safe-operating-zone boundary for CO2 had previously been estimated at levels up to 350 parts per million. That’s the boundary — and we’re already past that, with the current levels close to 400 ppm, according to the paper. That puts the planet in the CO2 zone of uncertainty that the authors say extends from 350 to 450 ppm. At the rate CO2 is rising — about 1 or 2 ppm per year — we will surpass 450 ppm in just a couple of decades, said Katherine Richardson, a professor of biological oceanography at the University of Copenhagen in Denmark and a co-author of the new paper. At the rate things are going, the Earth in the coming decades could cease to be a “safe operating space” for human beings. That is the conclusion of a new paper published Thursday in the journal Science by 18 researchers trying to gauge the breaking points in the natural world. The paper contends that we have already crossed four “planetary boundaries.” They include the extinction rate; deforestation; the level of carbon dioxide in the atmosphere; and the flow of nitrogen and phosphorous (used on land as fertilizer) into the ocean. “What the science has shown is that human activities – economic growth, technology, consumption – are destabilizing the global environment,” said Will Steffen, who holds joint appointments at the Australian National University and the Stockholm Resilience Center, and is the lead author of the paper.
Posted on: Fri, 16 Jan 2015 02:19:51 +0000
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