Climate processes

NextGEMS will develop two prototype storm resolving ESMs (based on ICON and IFS from ECMWF) into production systems to produce multi-decadal (30 y) projections of future climate change.

Storm-Resolving Earth System Models (SR-ESMs) are distinguished by their km scale grid in the atmosphere and ocean. This allows a more physical representation of atmospheric and oceanic circulation systems, including their coupling to Earth-system processes such as the carbon, nutrients, water and atmospheric particulate (aerosol) cycles.  A more physically based representation of key climate processes is expected to reduce biases and enhance the realism of SR-ESM simulations as compared to traditional climate models. 

As part of NextGEMS, we will lead the development and implementation of a reduced complexity aerosol scheme, suitable for deployment in storm resolving modelling. This scheme will remain fully traceable to the microphysical aerosol model HAM (Stier et al., 2005).  

NextGEMS specific objectives are:

• To develop two SR-ESMs for applications (i) by demonstrating their capacity to more realistically represent the coupled (land-ocean-atmosphere) climate system, also through an ability to better leverage observations; (ii) by performing the first global multi-decadal (30 y) SR-ESM based climate projections, testing for out-of-sample climate trajectories, i.e., surprises, and thereby giving a new perspective on uncertainty; and (iii) by expanding their scope to begin more physically coupling ‘Earth-system’ processes, including the carbon cycle and the atmospheric aerosol.
   
• To use SR-ESMs to test emerging and long-standing hypotheses underpinning our understanding of climate change: (i) that convective organization contributes importantly to Earth’s energy budget and the strength of cloud feedbacks; (ii) that a more explicit representation of cloud-aerosol interactions mutes aerosol-radiative forcing; (iii) that 2 km to 200 km scale atmospheric and oceanic circulations are of leading order importance for air-sea fluxes in the tropics, thereby influencing not only the mean tropical and mid-latitude climate, but also its variability, including extremes; (iv) that storm-scale variability in weather systems and of the land surface strongly influence extra-tropical climate and extremes, for instance by conditioning circulation regimes, like blocking; (v) that capturing landscape variability globally greatly improves the realism with which regional climate can be simulated; and (vi) that storm-scale variability through its impact on hydrological extremes affects the carbon budget, with associated implications for the global carbon (emissions) stock-take.
   
• To build new, more integrated, communities of ESM users by: (i) exploiting the necessity of developing SR-ESMs around a centralized infrastructure to create development and analysis paradigms that can more directly involve a broader and more distributed scientific community; and (ii) by exploiting the affinity between what people experience and what SR-ESMs simulate (i.e., events, in addition to statistics) to more directly involve non-scientific users in model development, thereby fostering Knowledge Coproduction.
   

To meet these objectives NextGEMS will make innovative use of agile methods such as Scrum, hackathons or Extreme Programming. Through these measures, and by focusing its efforts on just two models, NextGEMS aims to nurture a new European community of scientists and users around a technologically more ambitious modelling enterprise.