TDLR:

  • land ecosystems provide a climate regulation service by absorbing ~30% of anthropogenic emissions annually.
  • The temperature dependence of global photosynthesis and respiration determine land carbon sink strength.
  • Under business-as-usual emissions, by 2100, up to half of the terrestrial biosphere could experience temperatures where respiration rates overtake the carbon fixation rate of photosynthesis .
  • However, the impact of elevated temperatures on the land sink is more than a function of cumulative area. Biomes that cycle 40 to 70% of all terrestrial carbon including the Amazon, Southeast Asia and the Taiga of Russia and Canada are some of the first to exceed biome-specific the temperature tipping point for half the year or more.
  • This reduction in land sink strength is effectively front-loaded in that a 45% loss occurs by midcentury, with only an additional 5% loss by the end of the century.