> But DeepMind said GenCast surpassed the precision of the center's forecasts in more than 97 percent of the 1,320 real-world scenarios from 2019 which they were both tested on.

> The model was trained on four decades of temperature, wind speed and air pressure data from 1979 to 2018

The test set is taken from after the training set. I agree it seems likely that it will need to be continuously trained on new data to maintain it's accuracy going forwards, but this seems like a promising sign that it should work as long as you keep updating the model.

Of course the "can compute weather in 8 minutes" thing doesn't include the ongoing training cost... so the "this is much cheaper to run" claim seems slightly suspect.