The children’s crusade, 2019
„Like many complex models being considered today, for instance in medicine, climate models are stochastic, meaning that they have random trajectories starting from a fixed initial condition. This means that predictions are not single outcomes, but are distributions of outcomes. Therefore, for even a single initial condition, one would have to observe many independent climate systems for decades to see if the predicted distribution is in agreement with the test distribution. This is clearly impossible.
As stated by climate scientists Nina Tibaldi and Reno Knutti in their 2007 paper in the Philosophical Transactions of the Royal Society, “Climate projections, decades or longer in the future by definition, cannot be validated directly through observed changes.”
It is not merely that one observation would take decades; a deeper problem is that we only have one Earth and cannot observe multiple independent climate trajectories.“ (…)