Detecting climate signals using explainable AI with single-forcing large
ensembles
Abstract
It remains difficult to disentangle the relative influences of aerosols
and greenhouse gases on regional surface temperature trends in the
context of global climate change. To address this issue, we use a new
collection of initial-condition large ensembles from the Community Earth
System Model version 1 that are prescribed with different combinations
of industrial aerosol and greenhouse gas forcing. To compare the climate
response to these external forcings, we adopt an artificial neural
network (ANN) architecture from previous work that predicts the year by
training on maps of near-surface temperature. We then utilize layer-wise
relevance propagation (LRP) to visualize the regional temperature
signals that are important for the ANN’s prediction in each climate
model experiment. To mask noise when extracting only the most robust
climate patterns from LRP, we introduce a simple uncertainty metric that
can be adopted to other explainable artificial intelligence (AI)
problems. We find that the North Atlantic, Southern Ocean, and Southeast
Asia are key regions of importance for the neural network to make its
prediction, especially prior to the early-21st century. Notably, we also
find that the ANN performs better on inputs of observational data after
training on the large ensemble experiment with industrial aerosols held
fixed to 1920 levels. This work illustrates the sensitivity of regional
temperature signals to changes in aerosol forcing in historical
simulations. By using explainable AI methods, we have the opportunity to
improve our understanding of (non)linear combinations of anthropogenic
forcings in state-of-the-art global climate models.