AVOID 1: Global-scale impacts of climate change at different levels of forcing

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AVOID 1: Global-scale impacts of climate change at different levels of forcing

November 23, 2012
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This report describes the global and regional results of research on the physical impacts of climate change conducted under Work Stream 1, Deliverable 3 of the AVOID programme. It examines the climate change impacts under the four IPCC RCP scenarios (RCPs 2.6, 4.5, 6.0 and 8.5) across a number of sectors (water resources, river flooding, drought frequency, crop suitability and energy demands for heating/cooling). The results extend to 2100, but results for several time horizons before then are given, including 2020, 2050, and 2080. The results in this report are based on model projections from seven climate models used in CMIP5, and the robustness and uncertainty arising from this approach is described. Comparisons are made between the highest and lowest RCP scenarios to describe the damages which could be avoided under a lower concentration pathway.

Key findings

  1.  The highest forcing scenario produces an increase in global mean temperature of 20 C in 2050.
  2.  Under this scenario up to 31% of the world’s population would be exposed to increased water stress. Between one fifth and one half of flood-prone people would be exposed to a doubling of river flood frequency.
  3. A significant area (28-58%) of cropland would see a decline in suitability for cropping.
  4. Global residential cooling energy demand would increase by about half to three-quarters. Heating demand would decrease by 20 to 34%.
  5. The impacts for each scenario show a range which is mostly due to the differences between the seven climate models.
  6. The range in regional variability also is a reflection of the different results between the seven climate models.
  7. The global impacts avoided by the lowest scenario compared with the highest shows considerable variation between the seven climate models mostly because the new climate scenarios incorporate unforced climatic variability in addition to climate change.
  8. The results are relatively robust to uncertainty in socio-economic scenario, although variation in the relative distribution of population between regions between the scenarios does introduce some variability. When expressed in absolute terms, however, impacts under different socio-economic scenarios can be very different, with major implications for the estimated future costs of climate change impacts.