UQx Denial101x Making Sense of Climate Science Denial

Why we can trust climate models

Duration: 4:03 661 transcript words EN summary

Video summary

Climate models are sophisticated computer programs built upon fundamental physical laws that have been understood for centuries, such as Newton's laws of motion and the conservation of energy and mass. These models function by dividing the Earth into a grid of boxes, similar to constructing a world out of LEGO blocks, where the size of these blocks represents the model's resolution. Over the decades, modern climate models have undergone significant reconstruction, moving from coarse grids of 700 by 500 kilometers to much finer resolutions of 100 by 100 kilometers. This increase in detail has been accompanied by dramatic improvements in vertical resolution, the proper coupling of ocean systems, a complete revision of land surface processes, and substantial enhancements in sea ice and cloud modeling. The evolution of these models is comparable to the technological leap between a Formula 1 car from 1970 and one from 2014, where almost every component has been upgraded rather than simply retaining old parts. As computer power has increased, scientists have been able to simulate the same amount of time with much greater precision, resolving complex issues such as water vapor feedback. This continuous advancement ensures that the models are not just theoretical constructs but highly detailed simulations capable of capturing the intricate interactions within the atmosphere, oceans, and land surfaces. The foundation of these models remains sound because they rely on basic physics, chemistry, biology, and applied mathematics rather than unproven assumptions specific to climate science alone. Confidence in the reliability of climate models is supported by multiple lines of evidence beyond their theoretical basis. First, these models are routinely used for weather forecasting, a field that has become shockingly accurate over recent decades; if one were to track five-day forecasts from the past, they would find them to be highly precise. Second, scientists regularly test model outputs against historical observations spanning the last century and earlier, where the models demonstrate an excellent ability to replicate real-world climate patterns. Finally, models are validated by simulating specific perturbations, such as volcanic eruptions, to ensure they respond appropriately to known atmospheric changes. Ultimately, there is a robust consensus that climate models are trustworthy tools for the problems they were designed to solve. The convergence of fundamental physical theory, proven accuracy in weather prediction, successful replication of historical data, and correct responses to simulated events provides strong assurance in their skill. These multiple tests confirm that despite the complexity of the Earth's systems, the models effectively encapsulate our best understanding of how the planet's atmosphere and oceans function physically. Therefore, the scientific community can rely on these simulations to project future climate scenarios with a high degree of confidence.

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The usual use of the word for climate model is a piece of computer code, um a list of in- instructions to a computer that encapsulate our very best understanding of the way that the atmosphere of our planet and the ocean work in a physical sense. The basic underpinning laws that climate models are built from uh includes the basic Newton's laws of motion, conservation of energy, conservation of mass, basic uh physical principles that uh uh physicists discovered a very long time ago. So, all these models um share lots of characteristics and of course the physics of the models are very, very similar because they're all based on on the fundamental same equations of fluid dynamics. The same equation that we knew that we created since hundreds of years. The way that climate models work is that they divide the world up into a series of boxes. So, it's very like LEGO, if you like. Basically, a model is is like if you would construct your world out of little LEGO blocks. And it's basically the size of the LEGO blocks. So, you can buy really expensive LEGO Star Wars ship, my son has those. They are very big, expensive, takes a poor parent two days to build them, and they have lots of detail. Or you can buy a little car for three-year-old, which doesn't have that much detail, but it's made out of big, big blocks. There's pro- probably no parts of a climate model of a modern climate model that still reflects what was done in the '70s. Almost everything's been rebuilt or rewritten, I think. Um the resolution's increased from something around 700 by 500 km to 100 by 100 km. Uh the detail in the vertical has increased dramatically. Oceans have been properly and fully coupled. The land surface has been uh completely revised to incorporate a whole suite of processes. Uh sea ice models have improved dramatically. Uh cloud parameterizations have improved. We've resolved most of the water vapor feedback problem. It's like asking uh what's the relationship between a Formula 1 Grand Prix car in 2014 compared to 1970. And the answer is there probably isn't a single widget that's shared. The resolution is getting higher. In other words, the boxes are getting smaller and smaller, but the computer power is also increasing. And so, we're able to simulate sort of the same amount of time, if you like, in with one of these models. There's a whole range of reasons why we're confident in in the skill of climate models for the problems that they were designed for. First of all, they're built upon physical principles, and those physical principles are known, unless of course that Newton was stupid, which I don't think he was. Um So, we have basic fundamental theory, not sourced from climate science, but sourced from basic chemistry, basic physics, basic biology that uh and applied mathematics that says the core of climate models uh is sound. Secondly, of course, they're used routinely in other applications like weather forecasting, and so we have effectively can evaluate a lot of our science routinely, and weather forecasting is becoming increasingly accurate, irrespective of of what some of your listeners might think. Um if they actually write a diary of a five-day forecast, and then check off how those five-day forecasts evolved, they'll find that they are shockingly accurate nowadays. So, that's the second test. Thirdly, we routinely test our models against observations over the last century and earlier, and they do extremely well in that in that respect. And finally, we can test our models against perturbations. So, we can, for instance, simulate a volcanic eruption, for example, and check that the climate models respond appropriately to to what a volcano does to the atmosphere. So, there are multiple lines of evidence, and they all point to the climate models being um reliable for what they were designed.