"Since 1970 the global average temperature has been rising at a rate of 1.7°C per century" (54).
Global Warming of 1.5°C. Intergovernmental Panel on Climate Change, 2018.
"[C]limate change is a special kind of problem. Carbon dioxide hangs around in the atmosphere for centuries, even millennia. This means that even if we were to start cutting emissions today, the amount of CO2 in the atmosphere and the problem of climate change would continue to grow—just as the water level in a bathtub will continue to rise if you reduce but don't shut off the flow from the tap. Earth will keep warming until we shut down emissions completely. Meanwhile, we've yet to experience the full effects of the CO2 we've already emitted, mostly because it takes the huge oceans a long time to warm up in response to a given level of CO2. Average global temperatures have risen by about 1 degree Celsius . . . since the 1880s, but owing to the time lag in the system, scientists estimate we're committed to another half a degree or so Celsius. . . . How hot can it get before truly catastrophic changes are set in motion? . . . Scientists warn that the threshold is probably about 2 degrees Celsius warmer than preindustrial times and perhaps even 1.5 degrees. Because temperatures already have risen about a degree and there's another half a degree of 'commitment,' we're all but assured of passing 1.5 degrees. To keep temperatures under the 2-degree threshold, global emissions would have to drop by at least half over the next few decades, and all the way to zero by 2070 or so" (18).
Kolbert, Elizabeth. “The Case for Catastrophe.” National Geographic, vol. 237, no. 4, Apr. 2020, p. 14-21.
"It turns out that the best estimates indicate that limiting CO2 to 450 ppm yields roughly a 67 percent likelihood of keeping warming below the [2°C] 'dangerous' level. . . . In what other circumstances would we accept a 33 percent chance of a catastrophic outcome as acceptable?" (49‑50).
Michael E. Mann, and Tom Toles. The Madhouse Effect : How Climate Change Denial Is Threatening Our Planet, Destroying Our Politics, and Driving Us Crazy. Columbia UP, 2016.