The three-phases of research and engagement (2008–2023) of the ESRC-funded Centre for Climate Change Economics and Policy (CCCEP) ended in December 2023. All CCCEP publications are available on this legacy website. Any new outputs will be uploaded to the site between 2024 and 2028.

Water availability in +2ºC and +4ºC worlds

Abstract

While the parties to the UNFCCC agreed in the December 2009 Copenhagen Accord that a 2°C global warming over pre-industrial levels should be avoided, current commitments on greenhouse gas emissions reductions from these same parties will lead to a 50 : 50 chance of warming greater than 3.5°C. Here, we evaluate the differences in impacts and adaptation issues for water resources in worlds corresponding to the policy objective (+2°C) and possible reality (+4°C). We simulate the differences in impacts on surface run-off and water resource availability using a global hydrological model driven by ensembles of climate models with global temperature increases of 2°C and 4°C. We combine these with UN-based population growth scenarios to explore the relative importance of population change and climate change for water availability. We find that the projected changes in global surface run-off from the ensemble show an increase in spatial coherence and magnitude for a +4°C world compared with a +2°C one. In a +2°C world, population growth in most large river basins tends to override climate change as a driver of water stress, while in a +4°C world, climate change becomes more dominant, even compensating for population effects where climate change increases run-off. However, in some basins where climate change has positive effects, the seasonality of surface run-off becomes increasingly amplified in a +4°C climate.

Reference

Fung, F., Lopez, A., and New, M. January 2011. Water availability in +2ºC and +4ºC worlds. Philosophical Transactions of the Royal Society A, v.369 (1934), pp.99-116.