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It is absolutely absurd and dishonest to run a computerized climate model 480 years out into the future. These models are not that good and not that accurate. W
by chrisco255 6y ago
It is absolutely absurd and dishonest to run a computerized climate model 480 years out into the future. These models are not that good and not that accurate. We can't even predict weather very well beyond 2 weeks.
The climate is subject to chaos theory.
Chaos: When the present determines the future, but the approximate present does not approximately determine the future.
Uncertainty is an exponential function of time in chaotic, non-linear dynamic systems like the climate. The year 2500 could just as easily be a deep glacial period.
- ordu 6y agoThere is nothing wrong with running model in any way a researcher wish. It would be wrong to make predictions about a real system, without studying validity of that prediction. Authors clearly state "an earth system model shows ..." not the "Earth is going to melt". They say "we encourage other model builders to explore our discovery in their (bigger) models, and report on their findings." Authors work with their model, use it to calculate some results, they do not pretend, that the results are the Truth. Authors know what validity is, they ask others to take a look at it. Nothing wrong with it.
- OneGuy123 6y agoOfcourse the pretend that the results are truth: otherwise they wouldn't post it. If the actually truly understood that they cannot predict climate so far along in the future they wouldn't bother posting.
- adrianN 6y agoWhere in the paper do they claim that? I couldn't find that.
- karmakaze 6y agoAbbreviated original title is better than the editorialized one: "An earth system model shows self-sustained melting of permafrost even if all man-made GHG emissions stop in 2020" Or shortened to "Earth model shows self-sustained melting of permafrost if emissions stop now"
- londons_explore 6y agoThere are plenty of places in earth's history where you could apply a predictor of future temperatures based on current conditions and get a better-than-random output 500 years ahead.
- yongjik 6y ago> We can't even predict weather very well beyond 2 weeks. But we can confidently predict that most of Europe will have higher temperature nine months from now. Also, California will be dry. Sometimes large-scale predictions are easier because you're not concerned with small-scale noise.
- haltingproblem 6y agoSeasonal cycles do not require a model. The discussion here is about weather and climate models.
- adrianN 6y agoI'm pretty sure that the Earth going round the Sun and the Earth's axis being slightly tilted counts as a model using which you can predict the seasons.
- haltingproblem 6y agoYou are not wrong in arguing that the Copernican model is also a model. I think the discussion here is about computational stochastic models. I also don't really need a model to predict warming in the summer and cooling in the winter. A lookup table should suffice. Edit: Can't believe parent is getting downvoted for asking a question that people disagree with.
- Sharlin 6y agoHowever low-confidence those climate projections to 2500 may be, anyone should by know better than to commit the tired old fallacy of equating weather and climate. No matter how chaotic the system, there will not be ”a deep glacial period” in mere 500 years.
- Areading314 6y agoThis post is absurd and dishonest because it is claiming that climate and weather are the same thing. They're not.
- haltingproblem 6y agoCan you please explain why they are not other than just proclaiming they are not? I have never understood this reasoning other than proclamations that they are not.
- Areading314 6y agohttps://www.noaa.gov/explainers/what-s-difference-between-climate-and-weather https://www.noaa.gov/explainers/what-s-difference-between-cl... Plenty of others if you care to look. Weather is a chaotic system whereas climate is not.
- laser 6y agoIt's a matter of scale. If I go outside and turn on a leaf-blower I can tell you with relatively high confidence the speed and direction of general air movement five feet out from the nose. On the other hand, if I tried to tell you the speed and direction of a dozen particles at X, Y, Z location in coordinate space, the effects of chaos (particles individually colliding, etc) would make this infeasible with current technology. Similarly, describing climate is like describing the general direction and speed of air moving out from the leaf blower, while weather is like trying to make the same prediction for small groups of particles within the system. They might sound like similar tasks, but due to chaos one is doable and the other is nearly impossible. All that being said, with regards to this particular study at the scale of 500 years it's likely our climate models nearly completely break down, as we've yet to successfully create one without significant divergence even a few decades out (although maybe that has changed as by definition the best ones we can test against only include those made before the year ~2000)
- Faint 6y agoI think you are mixing weather and climate. Climate is long term average of weather (directly from definition of word "climate"). Weather is very hard to predict 2 weeks ahead. Climate is stuff like "average rainfall in march in past 50 years". Some processes affecting climate may also be chaotic, but they are slow (by definition, otherwise they would be part of weather), and so I don't think 500 years is beyond speculation at all. Glacial periods have lately been around 100000 years, so 500 years to future we are not going to be much more or less glacial than we are now.
- loopz 6y agoRapid rises of temperature have coincident with mass extinctions before. Climate for past 10000 years have been remarkably stable, but is dependent on stable ecological processes (see Attenborough latest documentary on Netflix). https://en.m.wikipedia.org/wiki/Global_temperature_record https://en.m.wikipedia.org/wiki/Global_temperature_record
- crave_ 6y agoFrom what I've head: these models are very accurate in estimating the mean global temperature difference even for long periods of time. While the global trend is clear, they cannot estimate local developments very accurately - these are subject to chaos, and local changes. Note that the authors do not try to predict any local effects.
- travisoneill1 6y agoThey don't know what the model's accuracy is over long periods because it hasn't been around long enough to test.
- brabel 6y agoWhile you can never be sure, you can apply your model to the past and see if it can predict the present.
- deleted 6y ago[deleted]
- orwin 6y agoWell, i think the (honestly quite basic) climate model that came into being in 1974 is 95% accurate then, since it predicted the rise in average temperature until 2020. What climate modelists do is take the data from 1950, put that in their models, and see how well ir predict the temperature and hydrometry of different areas. I think what they were working on in the 2010s was how much the artic polar circle was at risk of breaking more often, and what that would mean for the average temperature (not much) and precipitations (probably drier winters/springs in europe). Sadly they did not amke prediction about how much the polar winds descending south would kill buds and take a toll on orchards.
- scoopertrooper 6y agoDo you have a good reason to believe that there will be a reversal of recent warming trends given the concentration of carbon dioxide and accumulation of other pro-warming gasses in the atmosphere?
- xupybd 6y agoI don't have a good reason but I wouldn't discount the possibility. As life reacts to the higher carbon dioxide levels we will enter into uncharted territory. The biggest possible source would be human climate engineering. That would be a huge feat to pull off but if we desperate enough who knows what we could do in 500 years.
- taxicab 6y ago> approximate present does not approximately determine the future Well that's an absolutely absurd and dishonest take on chaos theory. I can tell you that the five year average of all stocks will probably go up by a predictable amount in the next ten years even if I can't tell you what an individual stock will do two weeks from now. The climate of the earth is an even more stable system that doesn't have to worry about predicting when the next political instability will occur. These models are good and accurate and can be used for predictions beyond 2 weeks.
- polotics 6y agoA greenhouse is a very simple thing. What's absurd is to forget to mention than a 3 degrees average rise means a six degrees rise over landmasses. At the deepest of the last glaciation with oceans 120 meters down and ice covering half of Europe and all of Canada, we only had an average of 5 degrees colder than 1900. Holocaust 2.0, your descendants are all invited. (It's Greek for everything burning)
- holler 6y agowouldn’t people just migrate away from the equator and habitate places like Northern Canada, Siberia, etc? Yeah it’d be terrible to abandon our cities, but we’d have a long runway to prepare and migrate. Life always finds a way...
- dvdkhlng 6y agoThe problem with that is that agricultural output in a 3 degree higher world may not be sufficient to sustain a civilization of almost 8 billion people. "Life always finds a way" may be a little sarcastic once people start starving.
- adrianN 6y agoOne or two million people fleeing from the middle east to Europe caused large political trouble. Imagine what happens when hundreds of millions are displaced.
- haltingproblem 6y agoLet me propose the following thought experiment: for all the folks who claim they can predict climate 400 years (or 100 or 30 years) out, please take the climate models and run them for only 1 year out. This should give you much much lower error bars ergo higher confidence. Use it to predict winter in NE 1 year out? I would posit that if they can predict average temps 400 years out then average temps 1 year out should have higher confidence? These predictions can be used to trade heating oil futures and make tens of billions. I do know that energy firms employ many climate modelers but unsure of the accuracy of their forecast s even 1 year out.
- croon 6y agoImagine you have a gun mounted in a bench vice, pointing down a shooting rage towards a target. You can map out 50 shots from that gun, and pinpoint the average middle, and how much individual shots diverge from that middle. Then you take the average of another 50 shots and notice the recoil has pushed the average middle slightly upwards. So you make a model predicting the average middle in another 50 shots, accounting for the degree change from the recoil meaning a further distance than the previous to average middles. Then comes along a guy asking you to predict just 1 shot, the next one, not an average. Which of course is much less accurate. That is what you're suggesting.
- haltingproblem 6y agoHeating oil futures and natural gas futures for the various regions are tied to the average temperature since oil/gas heating usage is tied to temperature across days and not just the min or max. So to go back to your excellent analogy, I am certainly asking for the average middle (the first moment) and not a point prediction. ps: you should write more, we need better scientific explanations!
- andbberger 6y agoDon't weaponize your poor understanding of chaos theory into climate change denial. One of the defining properties of a chaotic system is that phase-space is bounded. Meaning while it's fundamentally difficult to make predictions about a specific trajectory beyond a certain point, one can still say things about trajectories on average.
- OneGuy123 6y agoFunny that this comment is controversial. People commenting on this don't comprehend that you cannot predict this in the future just like the OP said of this post.
- adrianN 6y agoOf course you can statistically predict the future. The error bars just get bigger the further out you go.
- me_me_me 6y agoThis is wrong and harmful, or fossil troll. Whether is a subject to chaos theory. NOT climate, climate is long term pattern. Climate predictions are not if its going to rain on Thursday at 11 in 2050. If a go to desert and its raining it doesn't mean that you should start planing your apple orchard there as its clearly not a desert. Same people who claim: > We can't even predict weather very well beyond 2 weeks. Will go to bookies to bet on sports games as the figured out pattern of who will win.
- karmakaze 6y agoGiving a year 2500 forecast warning is as silly as using any forecasts in in 1500 to address the situation of today, especially given that change is accelerating.