--- license: apache-2.0 --- Logo for the ACE Project # ACE2-SOM Ai2 Climate Emulator (ACE) is a family of models designed to simulate atmospheric variability from the time scale of days to centuries. **Disclaimer: ACE models are research tools and should not be used for operational climate predictions.** ACE2-SOM is the first model we have trained to emulate the sensitivity of climate to substantial increases in carbon dioxide. It consists of ACE2 coupled to a highly simplified physics-based ocean model, called a slab ocean model (SOM), and is trained on equilibrium-climate output from GFDL's SHiELD model coupled to an identical slab ocean with carbon dioxide concentrations of the present-day, double the present-day, and quadruple the present-day (1xCO2, 2xCO2, and 4xCO2). Quick links: - 📃 [Paper](https://arxiv.org/abs/2412.04418) - 💻 [Code](https://github.com/ai2cm/ace) - 💬 [Docs](https://ai2-climate-emulator.readthedocs.io/en/stable/) - 📂 [All Models](https://huggingface.co/collections/allenai/ace-67327d822f0f0d8e0e5e6ca4) Briefly, the strengths of ACE2-SOM are: - accurate emulation of equilibrium climates with CO2 concentrations ranging from 1xCO2 to 4xCO2, including changes in the spatial patterns of temperature and precipitation, and changes in precipitation extremes between climates - realistic emulation of surface and lower-to-middle atmosphere fields with gradually changing CO2 concentration between 1xCO2 and 4xCO2. Some known weaknesses are: - Sea-ice coverage, ocean heat transport, and ocean mixed layer depth are prescribed based on a present-day climatologies and therefore do not respond to changes in CO2. Prescribed sea-ice in particular means projections with ACE2-SOM are missing an important feedback mechanism known to amplify warming in the polar regions. - Abrupt regime shifts in stratospheric temperature and moisture can occur in inference runs with changing CO2 concentration. - Adjustment to an abrupt change in CO2 concentration occurs too quickly, violating energy conservation. - Sensitivities of the surface and top of atmosphere radiative fluxes to changes in CO2 with the atmospheric state held fixed are not always realistic.