Regional and Global Earth System Modelling Activities in MERGE

Description

1.What is MERGE?
MERGE stands for ModElling the Regional and Global Earth System, a strategic research area hosted by the Faculty of Science at Lund University. MERGE (www.merge.lu.se) is a collaboration between Lund University, University of Gothenburg, Rossby Centre/SMHI, Linnaeus University, Chalmers University of Technology and the Royal Institute of Technology. Reliable modelling of the Regional and Global Earth system is of utmost importance for society. Even though climate science is sufficiently robust to justify action on climate change mitigation and adaptation, the need to narrow down uncertainties that are central to assessing climate change and its impacts persists. Such uncertainties pertain to climate sensitivity, Earth System feedbacks and interactions and to incomplete understanding of key climate forcings and the interplay of physical and biological climate/Earth System components. This can be tackled with research that in turn supports mitigation and adaptation efforts on global, regional and local arenas. Our main aim is to further develop and evaluate key global and regional Earth System models, focusing on the terrestrial biosphere as a critical climate‐system component. This will lead to improved local, regional and global climate/Earth System models including biophysical and biogeochemical climate/vegetation interactions.

2.The MERGE Research Areas
MERGE research is organized into four interlinked Research Areas (RA), each contributing to this aim. RA1 (Development, modelling and evaluation of climate‐vegetation processes in Earth System Models) aims to develop and implement approaches and model components for regional climate system models (RCMs) and global Earth system models (ESMs). RA2 (Earth System Model evaluation and development with paleoclimate data) aims to use empirical data on past climate and land cover to evaluate and develop ESMs and regional, coupled vegetation‐climate models. Data and modelling communities collaborate on data‐model comparison using paleoclimate data and model output. RA3 (Terrestrial carbon cycle and aerosol–cloud–climate interaction) aims to formulate and validate a model framework linking vegetation, aerosols, clouds and their climate feedbacks. It uses a combination of laboratory studies, field studies and modelling. Process parameterizations are then tested in the EMEP chemical transport model and evaluated against field observations, then to be included in climate models. A particular focus is the representation of the C and N cycles, emissions of biogenic volatile organic compounds (BVOCs) and N‐based trace gases from ecosystems, the subsequent atmospheric oxidation of BVOCs and their secondary organic aerosol (SOA) formation potential, with consequences for clouds, global radiation and precipitation. RA4 (Advanced statistics for model evaluation, simulation set‐up and analysis) aims to improve the analysis and evaluation of RCMs and ESMs by means of systematic methods to combine data of different types and measurement platforms, and over different time and space scales.

3.Regional Earth System Modelling Activities
MERGE research uses a wide array of modelling tools and methods. For regional Earth System modelling, one such tool is the RCA‐GUESS RCM (Smith et al. 2011), which is best described as a regional ESM, or RESM. RCA‐GUESS is the first published RESM and also the result of a long‐standing collaboration between SMHI and Lund University. In RCA‐GUESS, the static vegetation in the RCA RCM (Samuelsson et al. 2011) is replaced and updated with the vegetation as simulated by the LPJ‐GUESS dynamic global vegetation model (Smith et al. 2014) in response to RCA’s dynamically generated climate fields. RCA‐GUESS has been used to study vegetation dynamics and biophysical feedbacks to climate change in Europe (Wramneby et al. 2010), the Arctic (Zhang et al. 2014), Africa (Wu et al. 2016) and South America (Wu et al. 2017). As an example of MERGE regional Earth System modelling, Figure 1 shows the additional temperature change as simulated by RCA‐GUESS (Zhang et al., in revision) due to vegetation feedbacks in the Arctic CORDEX domain, for all four seasons, and for three RCPs. The time period is (2071‐2100) – (1961‐1990). We find strong seasonal and local differences that can be explained by the response of the vegetation to climate change.

4.Global Earth System Modelling Activities
MERGE global Earth System Modelling activities focus on the further development of the EC‐Earth ESM (www.ec‐earth.org), built by a European EC‐Earth consortium with 26 partners. The model will be used in various configurations in CMIP6 (Eyring et al. 2016) to answer research questions posed by the endorsed MIPs, such as ScenarioMIP, LUMIP, C4MIP, PMIP etc. One such configuration is EC‐Earth3‐Veg (Weiss et al. 2014), which is an Earth System configuration that now has interactive vegetation as a result of coupling to LPJ‐GUESS carried out in MERGE. It will be used in CMIP6 ScenarioMIP and LUMIP. Another configuration, EC‐Earth3‐CC, is a fully coupled ESM with a closed carbon cycle, with dynamic vegetation and terrestrial carbon (and nitrogen) cycling coming from LPJ‐GUESS, and ocean biogeochemistry and carbon cycling from the PISCES model. Atmospheric transport of CO2 is handled by TM5. EC‐Earth3‐CC will be used in CMIP6 C4MIP simulations to examine questions relating to coupled climate‐carbon feedbacks.

Period	2018 Jun 11
Event title	2nd Baltic Earth Conference: The Baltic Sea in Transition
Event type	Conference
Location	Helsingör, DenmarkShow on map
Degree of Recognition	International