On the heels of an unprecedented wildfire season, climate is yet again a hot topic in Australia. In a new study, researchers examine the performance and projections of the latest generation of global climate models for the Australian continent.
Efforts to understand how climate change will unfold under various emissions scenarios rely on the sophisticated computer models of the Coupled Model Intercomparison Project (CMIP), which combines dozens of models to create as complete a picture of Earth’s climate as possible. The recently released sixth phase of CMIP incorporates several new features, including a more diverse set of emissions scenarios that correspond to possible future socioeconomic changes in the world. It also allows researchers to compare results from the new models with those from previous CMIP generations, addressing whether the models simulate the current climate any better and whether they give new insights about the future.
In the new study, Grose et al. conclude that the CMIP6 models do improve on CMIP5 in incremental but important ways. The models more accurately capture the impact of large-scale climate drivers on rainfall, represent dynamic sea level, and simulate extreme heat events in the atmosphere and in the surrounding ocean.
The researchers write that the projections of future conditions broadly agree with the data from CMIP5, thereby increasing confidence in most aspects of the existing projections. However, although both generations of models project further warming in the coming century, the upper range of the CMIP6 predictions beyond 2050 is higher than in CMIP5 models, meaning a worst-case scenario could be even worse than previously thought. The scientists say that these higher values in some CMIP6 models arise largely because the models have higher “climate sensitivity” to greenhouse gas increases. If these models are, in fact, the most credible, then limiting global warming to less than 2°C—the goal established in the Paris Agreement—will require larger emissions reductions than previously thought. (Earth’s Future, https://doi.org/10.1029/2019EF001469, 2020)
—David Shultz, Science Writer