CHIRP II

Modeling the water cycle in a changing climate – a multiscale interaction challenge

Context

Global climate change represents one of the grand challenges facing humanity. Although there are major efforts underway to develop and implement international agreements to limit further growth of the underlying drivers, i.e., primarily the emission of greenhouse gases, substantial changes in Earth’s climate are ahead.

In fact, through the forcing by current greenhouse gases concentrations alone, humankind is already committed to a warming of about 1.2°C since pre-industrial times (IPCC, 2007). About 0.8°C of that warming has occurred, while approximately another 0.4°C are in the store due to the inertia of the Earth’s climate system (IPCC, 2007). Hence, even if greenhouse gases wouldn't rise any further, Earth will move into another climate state, and due to the slowness of the natural process removing these greenhouse gases from the air, it will remain in this state for the next few centuries (Solomon et al., 2009; Gillett et al., 2011).

Consequently, the development of strategies to cope with climate change is urgently required irrespective of how successful mitigation efforts will be in the coming decades.

Objectives

This project aims to make fundamental advances in our understanding and our ability to quantitatively model a number of key processes and interactions within the Earth’s hydrological cycle, with a special emphasis on those involving strong scale interactions. We focus on four clusters of interactions and processes that were identified to be particularly limiting scientific progress:

i) local to regional processes governing clouds and rainfall over complex topography, with a view towards the challenge of downscaling climate change information to local scales;

ii) regional to global processes relevant for the Earth’s energy budget and the global hydrological cycle, including change in solar radiation and aerosol loads;

iii) atmosphere-ocean interactions determining the net transfer of freshwater and the resulting impacts on atmosphere and ocean dynamics in the Southern Ocean region; and

iv) atmosphere-land-surface interactions that are essential in determining the water vapor and energy exchange fluxes in Europe and hence altering droughts and rainfall patterns.