A hot bath

As long as we are putting more carbon dioxide into the atmosphere than plants, oceans, soils and rocks have time to absorb, global warming will continue. That relatively simple premise is one John Sterman found difficult for his graduate students at the MIT Sloan School of Management to grasp, and they’re hardly dummies. In the December issue of National Geographic magazine, Sterman compares the carbon dioxide inflow and outflow to a bathtub “with the tap running and the drain open.” To avoid climate disaster, some experts say the “water level” in this bathtub analogy for CO2 should be 350 parts per million—a number we’ve surpassed. In 2008, it was at 385 ppm. We’re currently pumping 9.1 billion metric tons of carbon into the atmosphere each year, and soaking up only 5 billion metric tons. At this rate, we’ll reach 450 ppm—a number considered dangerously high—before 2050. It will take centuries to absorb all the human-made CO2, meaning halting global warming may be harder, and take longer, than the public realizes. Sterman says to stop emissions even at the 450 ppm mark, the world will have to reduce emissions—predominantly from cars, power plants and factories—by about 80 percent by 2050.

The UN Climate Change Conference kicks off Dec. 7 in Copenhagen, Denmark, where world leaders will discuss emissions reduction targets and a global climate treaty. The United States will propose a 2020 target of about 17 percent below 2005 levels and an 83 percent reduction by 2050.

Meanwhile, the “climategate” scandal, involving hacked emails written by climate researchers at University of East Anglia in England, has refocused the media attention—and fueled skepticism—on global warming. Attention on it has masked other research, such as that by 26 climatologists, more than half from the Intergovernmental Panel on Climate Change (IPCC), that shows climate change is much worse than the IPCC has reported. For instance, the authors found that arctic sea ice is melting 40 percent faster and global sea levels are rising 80 percent more per year than the IPCC has said. The climatologists said that global emissions need to peak between 2015 and 2020 and then decline rapidly.