The real-life impacts of current levels of global warming, and of either hitting or missing the targets in the Paris Agreement, will depend very much on where in the world you live, a recent analysis concludes.
Proximity to oceans is already a mitigating factor, Carbon Brief notes, “with ocean temperatures increasing more slowly than land temperatures because oceans lose more heat by evaporation, and they have a larger heat capacity.” So while the planet as a whole has gained an average of about 1.0°C over the last 100 years, oceans “have only warmed by around 0.8°C,” land masses by 1.3°.
Latitude is also a critical variable, with polar regions warming “faster than the global average due to positive feedbacks from the retreat of ice and snow.” Furthermore, writes author and climate scientist Zeke Hausfather, in a phenomenon known as polar amplification, “an increased transfer of heat from the tropics to the poles in a warmer world also enhances warming.”
Thus, “some parts of the Arctic have warmed by more than 2.0°C, with a few hotspots of even greater warming where cooler sea ice has been replaced by warmer open water.”
To deepen its analysis about regional experiences of planetary warming, Carbon Brief combined its climate model predictions, spanning average global warming from “well below” 2.0° to 4.8°C by 2100, with NASA projections of the global population distribution in 2020.
“While predicting exactly how the distribution of population will change by the end of the century is difficult,” writes Hausfather, “the existing population locations are still likely to be among the heaviest populated in 2100,” although “rapid population growth is also expected in Africa, which may be home to up to 40% of the world’s population by 2100.”
Just how hot these population centres get will depend on how swiftly and comprehensively greenhouse gas emissions are reduced.
“In a low-emission RCP2.6 scenario,” he notes, “where global temperatures stay well below 2.0°C, about 14% of the population will still experience warming exceeding 2.0°C.” In the RCP4.5 scenario, with average warming as high as 2.6°C, “nearly the entire global population experiences warming over 2.0°C, with 26% seeing warming over 3.0°C.” In the RCP6.0 scenario, with average warming up to 3.1°C, 63% of the population sees warming above 3.0°C and another 6% exceeds 4.0°C. In the high-emission RCP8.5 scenario, with average warming up to 4.8°C, “most of the human population would experience warming above 4.0°C, with 44% exceeding 5.0°C and 7% exceeding 6.0°C.”
