Understanding the connections between large-scale climate change and local impacts remains a significant challenge which the scientific community is trying to solve through the development of climate models that have higher horizontal resolution (i.e. reduced grid spacing) that better represent key components of the Earth system.
These models also provide useful information for impact studies, especially when talking about extreme events as certain processes – such as tropical cyclones and extreme precipitation for example – can be represented only with horizontal resolution that is high enough to capture the dynamic behind the process formation.
“When climate models use higher resolution, they can show extreme weather events like hurricanes and floods more clearly,” says CMCC researcher Enrico Scoccimarro whose recent contributions to the High Resolution Model Intercomparison Project (HighResMIP) culminated in a new publication titled: High-Resolution Model Intercomparison Project phase 2 (HighResMIP2) towards CMIP7.
CIMP7 is a significant step forward compared to previous generations of the project. The first phase of the project, HighResMIP1, was successful at producing a baseline multi-model assessment of global simulations with model grid spacings of 25–50 km in the atmosphere and 10–25 km in the ocean, a significant increase when compared to models with standard resolutions on the order of 1° that are typically used as part of the Coupled Model Intercomparison Project (CMIP) experiments.
In addition to over 250 peer-reviewed manuscripts using the published High-ResMIP1 datasets, the results were also widely cited in Intergovernmental Panel on Climate Change (IPCC) reports and formed the basis of a variety of derived datasets, including tracked cyclones (both tropical and extratropical), river discharge, storm surge, and impact studies.
However, the new project seeks to address some of the compromises – such as experimental design and simulation length, complexity, and resolution – that HighResMIP1 made in light of recent major advances in modelling and computing resources.
HighResMIP2 is the next phase of the project, bringing together climate scientists from around the world in a truly international collaborative effort whose main goal is to generate climate models that use much finer grids.
“HighResMIP2 improves and extends the previous work, further advancing our understanding of the role of horizontal resolution (and hence process representation) in state-of- the-art climate simulations,” says Scoccimarro.
CMCC has a long history of working on high-resolution climate models. Since 2007, it has provided some of the most detailed climate simulations in the world, including modeling of powerful tropical storms and category 5 hurricanes. CMCC efforts have therefore improved our knowledge of the relationship between mean climate and extreme events, not only in terms of the effects of a changing climate on extremes but also in terms of the role that extreme events can have in modulating the climate system itself.
“Running high-resolution simulations with a fully coupled climate model is one of the best ways to study how extreme events and the climate system interact,” says Scoccimarro. “This allows us to see the whole picture during events like hurricanes and helps investigate the relationship between events and the surrounding environment. For example, using different climate scenarios, we can see how a warmer world might change extreme events. Furthermore, positioning such efforts in an international and coordinated context such as HigResMIP2 generates added value in terms of avenues for collaboration with colleagues working on the same topic, ultimately improving our understanding of the mechanisms at the base of climate dynamics.”