Three particular responses of the #EarthSystem are critically important for our understanding of #ClimateChange, but remain highly uncertain:

(I) The change in #GlobalMeanSurfaceTemperature for a doubling of atmospheric #CO2, which determines the long-term warming of the Earth.
(II) The rate at which excess heat is sequestered into the deep ocean.
(III) The fraction of #carbonemissions that remains in the atmosphere, which is controlled by the efficacy of ocean and terrestrial #CarbonUptake.