Justin Gillis in The New York Times:
The issue can be overwhelming. The science is complicated. Predictions about the fate of the planet carry endless caveats and asterisks. We get it. And so, as the Paris climate talks get underway, we’ve provided quick answers to often-asked questions about climate change. You can submit your own questions here.
How much is the planet heating up?
1.7 degrees is actually a significant amount. As of this October, the Earth had warmed by about 1.7 degrees Fahrenheit since 1880, when tracking began at a global scale. That figure includes the surface of the ocean. The warming is greater over land, and greater still in the Arctic and parts of Antarctica. The number may sound low, but as an average over the surface of an entire planet, it is actually high, which explains why much of the land ice on the planet is starting to melt and the oceans are rising at an accelerating pace. The heat accumulating in the Earth because of human emissions is roughly equal to the heat that would be released by 400,000 Hiroshima atomic bombs exploding across the planet every day. Scientists believe most and probably all of the warming since 1950 was caused by the human release of greenhouse gases. If emissions continue unchecked, they say the global warming could ultimately exceed 8 degrees Fahrenheit, which would transform the planet and undermine its capacity to support a large human population.