Humanity has yet to reach the point of no return when it comes to catastrophic climate change, according to new calculations. If we content ourselves with the existing fossil-fuel infrastructure we can hold greenhouse gas concentrations below 450 parts per million in the atmosphere and limit warming to below 2 degrees Celsius above preindustrial levels—both common benchmarks for international efforts to avoid the worst impacts of ongoing climate change—according to a new analysis in the September 10 issue of Science. The bad news is we are adding more fossil-fuel infrastructure—oil-burning cars, coal-fired power plants, industrial factories consuming natural gas—every day.
A team of scientists analyzed the existing fossil-fuel infrastructure to determine how much greenhouse gas emissions we have committed to if all of that kit is utilized for its entire expected lifetime. The answer: an average of 496 billion metric tons more of carbon dioxide added to the atmosphere between now and 2060 in “committed emissions”.
That assumes life spans of roughly 40 years for a coal-fired power plant and 17 years for a typical car—potentially major under- and overestimates, respectively, given that some coal-fired power plants still in use in the U.S. first fired up in the 1950s. Plugging that roughly 500 gigatonne number into a computer-generated climate model predicted CO2 levels would then peak at less than 430 ppm with an attendant warming of 1.3 degrees C above preindustrial average temperature. That’s just 50 ppm higher than present levels and 150 ppm higher than preindustrial atmospheric concentrations.
Still, we are rapidly approaching a point of no return, cautions climate modeler Ken Caldeira of the Carnegie Institution for Science’s Department of Global Ecology at Stanford University, who participated in the study.