Earth as a whole has warmed about 1°C since 1850-1900. And the goal of the Paris Agreement is to forestall 1.5°C or at least 2°C of warming. What is easy to overlook is that these numbers represent an average.
Oceans comprise 71% of earth’s surface and take longer to warm than land. They have indeed warmed about 1°C. Since 1979 land surface temperature – which affects us most directly – has risen about double that of ocean surface temperatures. According to NASA, since the year 2000, land temperature changes are 50% greater in the U.S. than ocean temperature changes; two to three times greater in Eurasia and three to four times greater in the (Ant)Arctic.
So when scientist discuss “preventing 2°C of global warming” they are really talking about forestalling around 3°C to 6°C warming on most land surfaces.
The Arctic warms fastest; a phenomenon known as ‘Arctic amplification’ (see figure above). This is also supported by paleoclimatologic data: In the early Eocene (54-48mln years ago), while sea surface temperature at the tropics was about 6°C warmer, at the poles it was about 14°C warmer.
Different places and surfaces warming at different speed will have huge consequences. For example, the just mentioned reduction of the difference between temperature at the tropics and the poles, the ‘Equator-to-pole surface temperature gradient’ (from e.g. 28°C now to 20°C), has been linked to changes in ocean circulation, behaviour of the jet stream, and the shifting of the Intertropical Convergence zone (ITCG) – determining a.o. Sahel rainfall, tropical storm activity and Californian drought.