2021-06-16

Understanding the uncertainty of climate change Ocean circulation data is the key to accurate predictions

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Understanding the uncertainty of climate change Ocean circulation data is the key to accurate predictions

The work of Katinka Bellomo and colleagues at the Institute of Atmospheric Sciences and Climate of the Italian National Research Council was published today in Nature Communications “On, it is part of the European TiPES scientific cooperation, coordinated by the University of Copenhagen.

All climate models are different in details. The adjustment of atmospheric pressure, cloud cover, temperature gradient, sea surface temperature and other variables are slightly different interactions for each model. This means that the predictions of many models are also different.

Understanding the uncertainty of climate change Ocean circulation data is the key to accurate predictions(1)

The International Modeling Center runs a set of coordinated The climate model simulation is then evaluated by the IPCC and summarized in a balance report. But naturally, an uncertainty still exists, reflecting many different adjustments of the model.

Bellomo and colleagues analyzed simulation results from thirty different climate models and found an important difference. Different models differ in the descending speed of the Atlantic Meridional Overturning Circulation (AMOC). AMOC is a large ocean current system in the North Atlantic Ocean. It flips surface water to deep ocean currents and plays a key role in the distribution of heat from the tropics to the northern hemisphere. effect.

“In order to understand how this difference is reflected in the prediction of future climate, we grouped the top ten models (from a total of thirty models) with smaller AMOC declines into one group. Then we Compare this set of models with the average of the 10 models with the largest decline,” Bellomo explained. The analysis revealed two different types of climate scenarios. In the model with a large decrease in AMOC, Europe is only warming slightly, but the wind direction in Europe and the precipitation pattern in the tropics have undergone huge changes. However, in the model with a smaller AMOC decline, the northern hemisphere has increased significantly, and the well-known pattern of wet areas getting wet and dry areas getting dry appears.

This means that the uncertainty of future climate predictions may depend to a large extent on how climate models predict changes in the North Atlantic overturning circulation. Therefore, this result challenges the previous understanding of the mechanisms that control climate change in the North Atlantic, where the parameterization of the atmosphere is suspected to be the main part of the uncertainty.

“This is important because it points out that AMOC is one of the biggest sources of uncertainty in climate forecasts,” Katinka Bellomo said. “I’m excited about this research. Because there are many things that can be done besides this. We need to study the processes that lead to differences in ocean circulation response between models, the link between ocean circulation response and precipitation changes, and we also need Compare it with forecasts of climate change in the near future.”