The sea acidification and slowing down of oceanic circulation are among the long term trends that will be reversed only in the most optimistic future in terms of emissions reduction, the new generation Earth System Model developed by the CMCC confirms. Our most recent contribution to the global endeavour of making more and more accurate predictions of the future climate stands for CMCC-ESM2 and is the result of an effort that involved CMCC across the board. 

In the last decades the development of models of increasing complexity has allowed scientists to work with unprecedented accuracy and provide climate information for use in governance, decision-making and in support of a wide range of practical end-user applications.

Results from research teams and projects on a global scale, using different kinds of models, when put together show a high degree of coherence and point towards a whole picture of the changes our planet is undergoing. CMCC is part of this global effort with its second generation Earth System Model (CMCC-ESM2), whose findings confirm trends in ocean chemistry and biology transformations caused by climate change, as shown in the article published by CMCC researchers in the Journal of Advances in Modelling Earth Systems.

One particular  trend that is worth stressing is the oxygen depletion of the oceans. As water warms it holds less oxygen and chokes off crucial oxygen supplies to a variety of marine species. In the long run, the phenomenon will have an impact on deep ocean ecosystems, on where and what creatures eat, on which species live or die.

The model also confirms ocean acidification and predicts that it would be possible to invert this trend only under the most optimistic climate change mitigation scenario. As atmospheric carbon dioxide increases, it accumulates to an even higher effect in the oceans due to their chemical buffering capacity. This leads  to more acidic seawater conditions and hence exposes marine ecosystems and organisms to severe threats.

CMCC-ESM2 projections show also alterations in ocean stratification, which is at the heart of ocean circulation of gases and nutrients and slows, in the words of Momme Butenschön – one of the scientists who developed the model – “the oceanic heart beat, that keeps the ocean’s circulatory system going”. As the oceans warm, ice caps melt and salinity declines. Warm and less salty waters  are less dense and sink less easily, thus slowing down the whole oceanic circulation.

Earth System Models enable scientists to study the interplay between the atmosphere and ecosystems, since they simulate thoroughly the carbon cycle, notably taking into account the biosphere and biogeochemistry of ecosystems, both in the oceans and on land.
This allows gathering information about the response and feedback of the living systems on the climate. The current  generation of Earth System Models further enhance their predecessors with improved representation of both climate dynamics and carbon cycling matured in the latest years of scientific research.

The CMCC-ESM2 model contributes to the sixth Coupled Model Intercomparison Project Phase 6 (CMIP6), a global effort undertaken by the scientific community, coordinated by the World Climate Research Programme (WCRP) to monitor, simulate and project Earth response to an increasing CO₂ atmospheric concentration. Putting together the work of a number of different research institutions around the world, it aims at a better understanding of past, present and future climate changes arising from natural and anthropogenic sources.

The CMCC work provides a coherent representation of present day physical climate and biosphere dynamics in comparison to available observations and data of the recent past. The projected global warming signal and carbon accumulation under future climate scenarios are comparable to the findings of other models involved in the Intercomparison Project, which, as a whole, provide the data basis for the most recent analysis and reports of the IPCC – Intergovernmental Panel on Climate Change.

As Momme Butenschön puts it “Our results are in line with the last IPCC reports. To stop and reverse the trend of climate change a huge effort in removing carbon dioxide from the atmosphere and radical mitigation projects are needed. Our results say that a slowing down of climate change is possible only in the more optimistic scenario.”

The consistency of this model output is confirmed also for land carbon pools and ecosystems. It studies how plants behave and are affected in different scenarios, confirming, for example, the disappearance of forests at high latitudes. Moreover, future projections coherently show prominent global warming over the northern hemisphere with intensified precipitation at high latitudes.

“A project like this is a huge effort of many people” stresses Tomas Lovato, the lead author of the study. “What is really important is the contribution to the global scientific knowledge and the support it gives to people who communicate to the public, the media and policy makers. It’s a contribution to what is necessary to do to keep this planet liveable for everybody.”

For more information: 

Lovato, T., Peano, D., Butenschön, M., Materia, S., Iovino, D., Scoccimarro, E., Fogli, P.G., Cherchi, A., Bellucci, A., Gualdi, S. and Masina, S., 2022. CMIP6 Simulations With the CMCC Earth System Model (CMCC ESM2). Journal of Advances in Modeling Earth Systems, 14(3), p.e2021MS002814. https://doi.org/10.1029/2021MS002814