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> climate models are basically useless for predicting anything That is false. Although you’re correct that climate is very complex and it is impossible to mode

> climate models are basically useless for predicting anything That is false. Although you’re correct that climate is very complex and it is impossible to model every detail. The notion that you cannot make valid conclusions from modeling because a set of observations do not match models is fallacious because it discounts the correct conclusions that climate models have achieved. For example, the first climate models from the 1960s predicted that the mesosphere will contract and cool as a result of increasing co2 concentrations, and this conclusion has been backed by empirical observations. Furthermore, modeling from the 1970s by scientists at Exxon Mobile found that by 2020, net warming would reach an average of 1 degree centigrade, which we’ve since exceeded.

adamrezich 5y ago
how is this different than a broken clock being correct twice a day? by this I mean to say, just because some predictions made using some models turned out to be correct, why does this validate those or all climate models as accurate predictors of the future? the system is so complex, poorly-understood, infinitely fractal, with endless variables depending upon each other in ways that we mostly don't understand... the models are so varied, based on different data sources, some omitting entire classes of data entirely... I would be more surprised if some predictions some models made didn't end up being true after several years. but that doesn't mean they're useful at predicting things going forward, by any means.
- vegetablepotpie 5y ago
  It’s not the results that make models valid/invalid. It’s how well the model approximates the underlying processes that lead to the results, which make it valid. A clock that is stuck is a poor model of time because it does not model the progression of time, even though it is still correct twice a day. We can make a very simplistic climate model that would be valid. We have a sphere of radius 6,357km, which is illuminated by electro-magnetic radiation centered at wavelengths of 0.6um. When the light hits the surface, it is absorbed and is re-emitted as black body radiation with a wavelength centered at 10um. It has an atmosphere, which contains a gas, which blocks the escape of wavelengths at 4um and 15um. This reflects some of the black body radiation back to the sphere, causing it to warm. In 2009 for the earth, this lead to a net accumulation of 0.6 W/m^2 of energy absorption [1]. If accumulated over the entire area of the sphere and accumulated over time, this would lead to an increase in temperature. Although the model does not take into account land formations, ocean currents, air currents, seasons, etc, it still models the underlying process of the earth’s energy balance and can answer the question of whether the planet will warm and can provide estimates at how quickly this will occur. I think you’re hinting at systems being so complex that they can vary based on minute changes in initial conditions, you’d be correct to say that climate is chaotic. Not all chaotic systems are the same though. A double pendulum will swing in eccentric motions, but if you look at something like the stock market, there’s a lot of short term variability with long term certainty. I cannot tell you what my stocks will do next week. But markets generally converge on a doubling of money in 10 years. In fact that’s reliable enough that I’m willing to have a 401k. With the pendulum, I can tell you with a lot of certainty that if it’s damped, it will settle to its lowest energy state and stay there permanently. A climate model will not predict the weather. But in the same way that I can tell you that winter will be cold, I can also tell you that Arctic amplification and Hadley cell expansion will lead to very different weather patterns that civilization has not seen before, such as much more extreme swings in temperature and weather. [1] https://en.m.wikipedia.org/wiki/Earth's_energy_budget#/media/File%3AThe-NASA-Earth's-Energy-Budget-Poster-Radiant-Energy-System-satellite-infrared-radiation-fluxes.jpg https://en.m.wikipedia.org/wiki/Earth's_energy_budget#/media...
homarp 5y ago
https://www.carbonbrief.org/analysis-how-well-have-climate-models-projected-global-warming https://www.carbonbrief.org/analysis-how-well-have-climate-m... Conclusion Climate models published since 1973 have generally been quite skillful in projecting future warming. While some were too low and some too high, they all show outcomes reasonably close to what has actually occurred, especially when discrepancies between predicted and actual CO2 concentrations and other climate forcings are taken into account.

adamrezich 5y ago

how is this different than a broken clock being correct twice a day? by this I mean to say, just because some predictions made using some models turned out to be correct, why does this validate those or all climate models as accurate predictors of the future? the system is so complex, poorly-understood, infinitely fractal, with endless variables depending upon each other in ways that we mostly don't understand... the models are so varied, based on different data sources, some omitting entire classes of data entirely... I would be more surprised if some predictions some models made didn't end up being true after several years. but that doesn't mean they're useful at predicting things going forward, by any means.

vegetablepotpie 5y ago
It’s not the results that make models valid/invalid. It’s how well the model approximates the underlying processes that lead to the results, which make it valid. A clock that is stuck is a poor model of time because it does not model the progression of time, even though it is still correct twice a day. We can make a very simplistic climate model that would be valid. We have a sphere of radius 6,357km, which is illuminated by electro-magnetic radiation centered at wavelengths of 0.6um. When the light hits the surface, it is absorbed and is re-emitted as black body radiation with a wavelength centered at 10um. It has an atmosphere, which contains a gas, which blocks the escape of wavelengths at 4um and 15um. This reflects some of the black body radiation back to the sphere, causing it to warm. In 2009 for the earth, this lead to a net accumulation of 0.6 W/m^2 of energy absorption [1]. If accumulated over the entire area of the sphere and accumulated over time, this would lead to an increase in temperature. Although the model does not take into account land formations, ocean currents, air currents, seasons, etc, it still models the underlying process of the earth’s energy balance and can answer the question of whether the planet will warm and can provide estimates at how quickly this will occur. I think you’re hinting at systems being so complex that they can vary based on minute changes in initial conditions, you’d be correct to say that climate is chaotic. Not all chaotic systems are the same though. A double pendulum will swing in eccentric motions, but if you look at something like the stock market, there’s a lot of short term variability with long term certainty. I cannot tell you what my stocks will do next week. But markets generally converge on a doubling of money in 10 years. In fact that’s reliable enough that I’m willing to have a 401k. With the pendulum, I can tell you with a lot of certainty that if it’s damped, it will settle to its lowest energy state and stay there permanently. A climate model will not predict the weather. But in the same way that I can tell you that winter will be cold, I can also tell you that Arctic amplification and Hadley cell expansion will lead to very different weather patterns that civilization has not seen before, such as much more extreme swings in temperature and weather. [1] https://en.m.wikipedia.org/wiki/Earth's_energy_budget#/media/File%3AThe-NASA-Earth's-Energy-Budget-Poster-Radiant-Energy-System-satellite-infrared-radiation-fluxes.jpg https://en.m.wikipedia.org/wiki/Earth's_energy_budget#/media...

homarp 5y ago

https://www.carbonbrief.org/analysis-how-well-have-climate-models-projected-global-warming https://www.carbonbrief.org/analysis-how-well-have-climate-m... Conclusion Climate models published since 1973 have generally been quite skillful in projecting future warming. While some were too low and some too high, they all show outcomes reasonably close to what has actually occurred, especially when discrepancies between predicted and actual CO2 concentrations and other climate forcings are taken into account.