Or, as his co-chair climate scientist Qin Dahe of the Chinese Academy of Sciences, put it via a translator in answer to a question about consumption in China: "If every Chinese has two or three cars like in the U.S., it will be a disaster for China as well as for the world." At present pace, the trillionth tonne would be emitted just before Christmas in 2040, according to calculations by Oxford physicist Myles Allen, and there's more than enough coal, oil and natural gas left in the ground to cook the climate. That's part of the reason why the IPCC included a final paragraph on geoengineering, or large-scale attempts to alter the climate by either blocking sunlight or removing CO2 (or other greenhouse gases) from the atmosphere. Of course, there's "limited evidence" and "insufficient knowledge" about whether such approaches could even work, particularly without their own side effects, the IPCC notes.
And keep this in mind, some of the greenhouse gases in the atmosphere today will persist for centuries. Even if CO2 emissions stopped tomorrow, climate change would continue. In other words, humanity is in the process of setting the Earth's thermostat. The world has already warmed by roughly 0.85 degree C since 1880 and further heat extremes are "virtually certain." So the question is: how much hotter can we stand? Or as United Nations Secretary General Ban-ki Moon put it in a video address to the IPCC press conference: "The heat is on. Now we must act."