The fossil-fuel burning power plants, factories, vehicles, and buildings we've already built will, if operated normally over their full lifetimes, almost certainly warm the Earth more than the Paris Agreement climate target of 1.5 degrees Celsius (2.7 degrees Fahrenheit), a new study concludes.
The implications are striking: To limit warming to 1.5 degrees Celsius, not only should no new fossil-fuel-using infrastructure be built, ever again, some existing power plants need to shut down early-and yet today many new power plants are under construction or planned.
"Our study is dead simple," said Steven Davis of the University of California, Irvine, a co-author of the paper published in Nature. "We wanted to know what happens if we don't build any more fossil-fuel-burning stuff as of 2018."
To answer that question Davis and colleagues looked at all the emissions from electricity, energy, transport, residential, and commercial infrastructure as of 2018. They then estimated the total "carbon commitment"-the future CO2 emissions from those structures and devices, based on the average number of years they'd be in service.
A new coal plant built today, for example, will emit millions of tons of CO2 every year throughout its 40-year lifespan. A new car that emits four tons of CO2 a year has a lifetime carbon commitment of 60 tons based on a 15-year lifespan. Although some of that CO2 gets soaked up by forests and oceans, most will remain in the atmosphere, trapping heat, for hundreds of years-unless we deploy technologies to suck it back out again.
Add up all those lifetime emissions from existing infrastructure, Davis and his colleagues estimated a total carbon commitment of about 658 billion metric tons of CO2. That's 78 billion tons above the maximum the Intergovernmental Panel on Climate Change, or IPCC, says can be emitted to have a better than 50 percent chance of stabilizing temperatures at 1.5 degrees Celsius of warming.
Because the study does not include all sources of CO2 emissions, its projections of the challenge posed by our carbon commitment might be considered conservative rather than alarmist.
It doesn't include emissions from agriculture, deforestation and other land-use changes, which represent about 24 percent of total emissions today. Nor does it include the considerable emissions involved in getting fossil fuels out of the ground. To get oil from Canada's oil sands, for example, requires the burning of nearly one-third of the country's natural gas production.
