Asynchronous exposure to global warming: freshwater resources and terrestrial ecosystems uri icon

abstract

  • This modelling study demonstrates at what level of global mean temperature rise (Delta T-g) regions will be exposed to significant decreases of freshwater availability and changes to terrestrial ecosystems. Projections are based on a new, consistent set of 152 climate scenarios (eight Delta T-g trajectories reaching 1.5-5 degrees C above pre-industrial levels by 2100, each scaled with spatial patterns from 19 general circulation models). The results suggest that already at a Delta T-g of 2 degrees C and mainly in the subtropics, higher water scarcity would occur in >50% out of the 19 climate scenarios. Substantial biogeochemical and vegetation structural changes would also occur at 2 degrees C, but mainly in subpolar and semiarid ecosystems. Other regions would be affected at higher Delta T-g levels, with lower intensity or with lower confidence. In total, mean global warming levels of 2 degrees C, 3.5 degrees C and 5 degrees C are simulated to expose an additional 8%, 11% and 13% of the world population to new or aggravated water scarcity, respectively, with >50% confidence (while similar to 1.3 billion people already live in water-scarce regions). Concurrently, substantial habitat transformations would occur in biogeographic regions that contain 1% (in zones affected at 2 degrees C), 10% (3.5 degrees C) and 74% (5 degrees C) of present endemism-weighted vascular plant species, respectively. The results suggest nonlinear growth of impacts along with Delta T-g and highlight regional disparities in impact magnitudes and critical Delta T-g levels.

publication date

  • 2013
  • 2013