Guest essay by Eric Worrall
How do you falsify a climate model? Australian National University Climate scientist Sophie Lewis acknowledges that climate models are not falsifiable – yet claims we should trust them anyway.
Climate change has changed the way I think about science. Here’s why
Research fellow, Australian National University
August 10, 2017 3.30pm AEST
I’ve wanted to be a scientist since I was five years old.
My idea of a scientist was someone in a lab, making hypotheses and testing theories. We often think of science only as a linear, objective process. This is also the way that science is presented in peer reviewed journal articles – a study begins with a research question or hypothesis, followed by methods, results and conclusions.
It turns out that my work now as a climate scientist doesn’t quite gel with the way we typically talk about science and how science works.
1. Methods aren’t always necessarily falsifiable
Climate models are important and complex tools for understanding the climate system. Are climate models falsifiable? Are they science? A test of falsifiability requires a model test or climate observation that shows global warming caused by increased human-produced greenhouse gases is untrue. It is difficult to propose a test of climate models in advance that is falsifiable.
Science is complicated – and doesn’t always fit the simplified version we learn as children.
This difficulty doesn’t mean that climate models or climate science are invalid or untrustworthy. Climate models are carefully developed and evaluated based on their ability to accurately reproduce observed climate trends and processes. This is why climatologists have confidence in them as scientific tools, not because of ideas around falsifiability.
The problem with Sophie’s position is that fitting a model to past observations is not a test of whether the model is right; all fitting the model tells you is that you have found a way to fit the model. What counts is the ability of the model to predict the future – to accommodate observations which were unknown at the time the model was created.
“Careful development” just means current prejudices are carefully applied. But there are many more ways to be wrong than right – especially about something as complex as the global climate.
Climate scientists are desperate for their educated guesses to be accepted as science; so desperate that at least some climate scientists openly challenge the very keystone of science, the requirement that scientific theories must provide a means by which they can be falsified.