18 ms·

Climate models are running red hot, and scientists don’t know why

241 points by montalbano 7y ago

vincent-toups 7y ago
I guess climate scientists don't use version control?
- norswap 7y ago
  The article isn't very precise, but my understanding was that the run some kind of machine learning based on past data. Adding in the more recent data changed the predictions dramatically. So it's not an issue of versioning (I assume they could reproduce the old results using the old data).
  - whatshisface 7y ago
    It's not machine learning, it's a physical model. Computers solve a big differential equation that takes in all of the physical things we know about the Earth's climate system and runs them forward in time. The increase in thermal predictions are due to changes in the cloud and aerosol models which were made due to an improved understanding of the physics involved.
    - cultus 7y ago
      The line can be a bit blurry, because they are actually running inverse problems with the PDEs to fit the data. This needs regularization just like statistical ML models. Usually this amounts to solving an iterated least square problem, just like logistic regression. Bayesian methods are becoming more popular, though.
      - dls2016 7y ago
        > because they are actually running inverse problems with the PDEs to fit the data Could you explain this a bit more? Are you talking about data assimilation?
        cultus 7y ago
        Yes, that's right. The issue is that systems like these have a lot of free parameters that have to be estimated from the data. This is basically because you have to make assumptions if you don't want to simulate Earth's systems down to the subatomic level. The inferred values of these parameters are usually very important as well for interpretation. All PDEs are solved numerically by discretizing them into linear or nonlinear systems. If it's convex enough, Tikhonov regularization is often used. Linear PDEs, where the solution depends only linearly on its derivatives, can be discretized into matrices. This gives a system like A m = d, where A is the discretized PDE, m is the "model" or parameter values, and d is the data. This is usually over or under-determined from the data, so it has to be solved by least squares. Since the resulting system is usually almost singular, regularization is applied, usually by penalizing the L2 norm of the model: min || A m -d || + r ||m||^2 If it's nonlinear but convex enough, one can just solve it by fixed point iteration, with the above linear equation being solved at every step (Newton's method often doesn't work well). If it's too nonconvex, then MCMC or other Bayesian methods are better, since a single solution is useless if the parameter values could plausibly around widely separated minima.
  - peterwoerner 7y ago
    They technically use the term constitutive model development. The math is similar to machine learning. Typically we know the basics of the physics, i.e. conservation of energy, momentum and angular momentum which set up the equations. But there a number of constitutive laws which relate parameters between these are "machine learned" but in generally, they are typically linear relations.
- gameswithgo 7y ago
  it isn't that, it is just a badly written article.
adrianN 7y ago
Well, politicians aren't doing anything anyway, whether the models predict catastrophe or CATASTROPHE. Already according to the 3° sensitivity predictions we would need an effort that rivals WW2 to stay below 1.5°. Yet major countries are led by climate denialists.
- truculent 7y ago
  we would need an effort that rivals WW2 to stay below _2.0_
- derg 7y ago
  Can you even imagine how a Total War economy/society based on transitioning to greener energies, cutting emissions and pollutants, and working on improvements to housing and urban planning would end up looking? Like ignoring the whole climate change thing for a moment (though we absolutely should not do that), just the quality of life improvements to our health and well being this kind of mobilization would bring would be astonishing.
  - HenryKissinger 7y ago
    That would not be possible today. The wartime World War Two economy we learn about in school was only made possible because of two factors: 1) A massive surge in federal government spending, financed by borrowing from public markets (incl. war bonds), to buy the materiel needed to fight a war on two fronts (in Europe against Germany and in the Pacific against Japan). Such spending caused the public debt as a share of GDP to surge to its highest historical level ever, from about 40% at the start of the war to 100% at its peak, as you can see on this graph: https://upload.wikimedia.org/wikipedia/commons/a/a7/US_Debt_Held_by_Public.png https://upload.wikimedia.org/wikipedia/commons/a/a7/US_Debt_... . Today, without such a total war effort, we are running trillion dollar deficits. To put it as shortly and bluntly as I could, trying the same thing today would bankrupt the government. Our debt levels are far higher than they were then, in relative terms, and increasing by over a trillion every year. We would be looking at 2 or 3 trillion dollar deficits. Deficits of that magnitude might shake investors' confidence in the U.S.'s ability to service its debt. 2) The United States was coming out of the Great Depression, and the unemployed labor pool was in the double digits, as you can see on this graph: https://upload.wikimedia.org/wikipedia/commons/thumb/6/68/United_States_unemployment_with_incarceration_1892-2016.png/450px-United_States_unemployment_with_incarceration_1892-2016.png https://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Un... . In other words, there were a lot of unemployed people with nothing to do who could quickly be put to work to produce stuff for the war economy. This is not the case today. The economy is running at full employment. The large spare labor pool that existed then doesn't exist today.
aldoushuxley001 7y ago
Scientists making the models prly thought the politicans needed a helping hand.
trevyn 7y ago
At the end of the article, apparently it has something to do with clouds.
- docdeek 7y ago
  I’ve read a few times that clouds are a big problem for climate modelers as they are far more complex in their implications for the climate than my grade school planet heats > evaporation > cloud forms > rain falls understanding of them suggests. There’s a nice article here on the issue and frustration of clouds for climate modelers by the head of the Royal Meteorological Society here: https://www.carbonbrief.org/guest-post-why-clouds-hold-key-better-climate-models https://www.carbonbrief.org/guest-post-why-clouds-hold-key-b...
  - mattrp 7y ago
    Yes water vapor specifically has been a big asterisk for a long time.
ipnon 7y ago
The 27-model average referenced in this article is 3.86 degrees C.
GrayTextIsTruth 7y ago
So, holistically, it would seem like warming (a fever) or Coronavirus (anti-bodies) is part of the planets immune system, but humans are too advanced.
- ddalex 7y ago
  Let's not anthropomorphize things, they don't like it.
  - GrayTextIsTruth 7y ago
    Animals have immune systems too. It’s not a phenomenon unique to humans, as Anthropomorphism would suggest. > they don’t like it Who? HNers? I don’t care. I think it more that people don’t like seeing themselves as the virus or cancer, when we could easily change our behavior and we wouldn’t be.
fabian2k 7y ago
The title seems like clickbait, and the last part of the article does explain that the scientists actually know that new cloud models are mostly responsible for the change. The big question is then of course whether the new cloud model is wrong and the temperature increase therefore as well, or whether the new cloud model is more accurate than previous ones and the temperature increase is a real effect. I found another article that looks at this in a bit more detail: https://news.ucar.edu/132678/ncars-new-climate-model-running-hot https://news.ucar.edu/132678/ncars-new-climate-model-running... The linked paper this is based on has the following as the last sentence: > What scares us is not that the CESM2ECS is wrong (all models are wrong, [Box, 1976]) but that it might be right.
- klodolph 7y ago
  Or a third, frustrating possibility—the new cloud model is more accurate, but some other inaccuracy in the model used to be balanced out by the inaccurate cloud model.
  - Accujack 7y ago
    Or that there are multiple inaccuracies in the model which interact, so finding and correcting each one makes progress but still doesn't improve the model overall.
    - k33n 7y ago
      Software is fun :)
    - cryptica 7y ago
      Having built some models to simulate very basic things myself, I've seen first-hand how the slightest deviation of the model from reality can completely invalidate the entire output of the model. For this reason, I'm skeptical of models that try to simulate very complex systems with a lot of variables and feedback loops. Models that have a large number of variables are particularly difficult to get right because different tiny mistakes in various parts of the model can compound and yield completely arbitrary and contradictory results. Approximating the reality in software is almost impossible.
throw7363 7y ago
Could it be a selection bias?
- makomk 7y ago
  "In all, as many as a fifth of new results published in the last year have come in with anomalously high climate sensitivity." The article suggests that a consensus may well form around the new, higher estimates. So, quite possibly.
novaRom 7y ago
"You are in private mode. Subscribe to continue reading." Ok, that's one more I will not open anymore; seems Bloomberg started using similar "privacy mode" detection as NYT.
- saamm 7y ago
  If you happen to be on Firefox, you can use this extension to get around it: https://addons.mozilla.org/en-US/firefox/addon/temporary-containers/ https://addons.mozilla.org/en-US/firefox/addon/temporary-con...
- 300bps 7y ago
  I use two browsers for this scenario both on iPhone and desktop. The first browser is my regular one (take your pick) and the second one is Brave with scripts Disabled (one click option in settings). I use Brave when going to sites like this. Disabling scripts generally doesn't break these types of sites but it does stop them from detecting whatever it is they are trying to detect.
iongoatb 7y ago
...
- screye 7y ago
  I don't see how you brought socialism into any of this. Ironically, socialism is being sold as a solution that you yourself make very clear. That, the pace of scientific progress is really fast ,and automation is going to make a lot of jobs obsolete. Socialism (in the nordic sense, ie. capitalism with social welfare) is being proposed as a solution to rising inequality and unregulated for-profit forces in the free market of industries where the consumer has no choice. (medicine, education)
  - iongoatb 7y ago
    Unbelievable that people believe that the Nordic model of capitalism is "socialism". Capitalism with social welfare is not socialism.
    - the_gastropod 7y ago
      Socialism isn't as narrow a term as you seem to think it is... It's quite a broad concept that can (and does) coexist with Capitalism.
- bentona 7y ago
  I mostly somewhat agree with you but unless you find a more appealing package for your arguments, you're just going to exacerbate the bifurcation on issues like this, and definitely not convince or enlighten anyone.
deleted 7y ago
[deleted]
justadudeama 7y ago
I am not a climate change denier by a long shot, but stories like these give a ding to the credibility of climate scientists. > "So we can't throw them out yet." This might be an elementary view of science, but I think there is a danger here that while everyone is making their models, if anyone is an outlier they go and tweak their model to match the patterns of others: 'Klaus Wyser’s group "switched off" some of the new cloud and aerosol settings in their model, he said, and that sent climate sensitivity back down to previous levels'. That seems to me a questionable reason to "switch off" part of the model - you should create the most accurate simulation possible and trust the output, not tweak the inputs to match literature data.
- nerdponx 7y ago
  Typically it's not obvious what to switch on and off for "accuracy". If your model produces wildly different results from previous models, either you hit on some really big discovery or you made a mistake. An ethical scientist will try to rule out the latter possibility before accepting the former.
  - gmueckl 7y ago
    It goes deeper than that. If you can tweak your new model to correspond to an older one for which you have results available, you must run tests in which you apply these tweaks and verify that you get the same results. If you get different results, one of the models simply isn't doing what you think it's doing and you need to understand that. And in the vast majority of cases, it's likely a mistake in a model, not any kind of new science. One pretty general debugging/analysis strategy for a complex model is to deactivate it piece by piece until you get it to a point where it should reproduce a result that you can verify by other, independent means. E.g. tweak the parameters of the model so that reproduces a result that is known analytically. For instance, whenever it is possible in a model, a good sanity check is to set parameters that must lead to e.g. a perfect conservation of certain quantities.
- orev 7y ago
  Tweaking the inputs would help one to identify what factor is causing the difference, which allows you to focus on that. It doesn’t mean you permanently leave it out. And it does not make a credibility issue. This is how science works — it is a process that strives to be as accurate as possible, not come up with a static answer and stick to it (that’s what religion does). The ability for science to change and adapt is what makes it so strong. That is the message that needs to always be driven when discussing science; not throwing hands in the air and saying “why do these scientists keep changing their answers? They obviously don’t know what they’re doing”
tu7001 7y ago
Hold my beer :) http://climatechangereconsidered.org/ http://climatechangereconsidered.org/
gbasin 7y ago
Does anyone know if this is actually true? I was under the impression that climate models have been mostly overshooting reality over the past 40 years > One question modeling can help answer is called “climate sensitivity,” an estimate of how much warmer the planet will be once it has adjusted to atmospheric CO₂ at double the pre-industrial level. (At current rates, CO₂ could reach a doubling point in the last decades of this century.) This is the old, reliable number that’s come out to 3°C for 40 years. It was as close as anything gets to certainty.
- wbeckler 7y ago
  Here's a systematic comparison of climate model predictions vs reality, since the 1970s. It turns out that the models have done a great job of predicting reality. https://www.carbonbrief.org/analysis-how-well-have-climate-models-projected-global-warming https://www.carbonbrief.org/analysis-how-well-have-climate-m... I'd be curious where your impression comes from, in terms of what sources of information you're receiving.
  - gbasin 7y ago
    I was thinking of the same data, I guess it's not quite as clear as I thought, but the majority are overestimating the warming: https://www.carbonbrief.org/wp-content/uploads/2017/10/Screen-Shot-2017-10-05-at-16.49.21.png https://www.carbonbrief.org/wp-content/uploads/2017/10/Scree...
    - SiempreViernes 7y ago
      If the idea is that the error in estimation is random around 0, you would expect about half to be overestimating. I think 5 out of 8 is not a very strong difference from 4 out of 8, which is the comparison that makes sense in this context.
  - mistermann 7y ago
    Pardon the pedantry, but "-the- models have done a great job of predicting reality" seems like a bit of an overly strong statement. The link you give and the original article seem to be comparing a completely different set of models, and the main article even says there are "dozens still left to report....".
giarc 7y ago
If you are like me, you hate reading articles like this. You know there is a problem but you feel like you can't do anything about it. You recycle, you turn off lights, you have a programmable thermostat but you know it's a drop in the ocean. I finally decided to do something about it last fall. I researched and have committed to purchasing green power. Every month I purchase 850 kWh for $22 from Bullfrog Power (a Canadian company, I have no affiliation). It's much more reasonable than I thought. I still conserve as much as I can but $22/month allows me to feel like I am doing something. If in 40 years, my kids ask me what I did to prevent climate change, I feel like I'll have an answer I'll be proud of.
- lllr_finger 7y ago
  That's awesome and I'm right there with you on wanting to do more. Have you considered your next step, and do you have any suggestions? Purchasing green power is such a minor sacrifice for my household, I'm still looking for something more.
  - giarc 7y ago
    My next steps will be writing to my government representatives. I live in Alberta and we just elected a right wing party that scrapped our carbon tax (although we now have a federal carbon tax).
- Gravityloss 7y ago
  This is why we have democracies, legislation and international treaties. Trying to solve it on individual goodwill of course helps but is not enough by itself.
- oezi 7y ago
  How about carbon offsetting your own life and that of your children?
- SketchySeaBeast 7y ago
  > If in 40 years, my kids ask me what I did to prevent climate change, I feel like I'll have an answer I'll be proud of. Doesn't it kind of feel like this is the equivalent of a kid in the 70's asking why their parents didn't stop World War 2? We absolutely need to be as vocal as possible, but as individuals, outside of trying to get people with power to affect the change we need, I don't know what we can expect to accomplish. You just can't do enough diet modifications, carbon footprint reduction, or recycling to have it matter on a global scale.
lbsnake7 7y ago
I’m a climate change skeptic almost entirely because I don’t trust models. I believe there are too many dynamic things happening in the world for anyone to be able to predict accurately say the next 100 years (solar, earthquakes, volcanoes etc). One way to make me a believer though is an experiment: if I were to give you a 100 year stretch of history and you were able to accurately predict with the models what exactly happened in those 100 years. The article talks about it a little bit about how the models are used to predict the 19th century to see if they are correct. But the models use the last 100 years as input so of course it will give you accurate output. But the real challenge of the models would be to accurately predict things that are not part of the inputs into the model. I don’t believe that these models can do this and are thus an exercise in straight extrapolation based on very complex and interconnected inputs.
- jknoepfler 7y ago
  So if I asked you to bet at 50/50 odds that next year would be colder on average than this year, you'd take the bet?
  - lazyjones 7y ago
    That's not what climate is about. Also, it depends on location, in many places it was colder in 2019 than in 2018. If you're talking about some calculated "global" temperature, it doesn't exist in a valid form.
    - bannable 7y ago
      Are you claiming that it is not possible to find a trend in a mean temperature of a great many points across the globe, over a long period of time? What makes such a measurement an "invalid form"?
      - lazyjones 7y ago
        It is not possible if there aren't valid temperature measurements available for all points throughout the measured period of time, so that many temperatures are "interpolated", estimated etc.
bentona 7y ago
Is it not possible to backtest these sorts of things? If it were, I would assume results would be the first bullet point on articles like this, but I also don't understand why it wouldn't be possible.
- makomk 7y ago
  The article does sort of address this for one of the models: "The model run by NCAR, one of American’s main climate-science institutions, started producing unusual data last year while trying to reproduce the recent past. “We got some really strange results,” Gettelman said. The scientists went on to try 300 configurations of rain, pollution, and heat flows—something they can do as gods of their own digital earth—before matching the model to history. But by solving that puzzle, Gettelman’s team sent future projections upward at an unheard-of rate." Basically, the backtesting failed to match reality for the recent past, they tweaked parameters to get it to fit, and that produced surprisingly high predictions for the future. I don't think that would leave them anything to backtest on, since they'd used effectively all their historical data to fit the model to.
aazaa 7y ago
It's surprising the article doesn't mention CFCs: > The simulations showed that the rate of Arctic warming in a world without CFCs would be cut in half – a striking effect for a category of substances that are only present in small quantities to begin with. To ensure the result was not simply a quirk of the simulation, the researchers ran the experiment using two different climate models and arrived at a similar outcome. https://www.theglobeandmail.com/canada/article-cfcs-are-a-major-driver-of-arctic-warming-study-finds/ https://www.theglobeandmail.com/canada/article-cfcs-are-a-ma... The danger here is that there's something else we fundamentally don't understand about the atmosphere.
boyadjian 7y ago
We have been warned about high birth rates and over-consumption in 1972, from the Meadows Report of the "Club of Rome", "The limits to Growth". Now we have reached those limits. So, what are we doing, now ?
lazyjones 7y ago
Because they're made by alarmists who are trying to increase political pressure.
leifdenby 7y ago
There is a big observational campaign happening right now that is trying to get to the heart of this called EUREC4A (main website: http://eurec4a.eu http://eurec4a.eu and information sheet: http://eurec4a.eu/fileadmin/user_upload/eurec4a/2019/Press/EURECA4A_factsheet_uk_10_12_2019.pdf http://eurec4a.eu/fileadmin/user_upload/eurec4a/2019/Press/E...). The key uncertainty between different climate models is whether shallow clouds in the tropics (which in general cool the Earth through radiation) will disappear or not and make our planet even warmer - some models predict this (!) We are 100s of individuals from more than 30 national and international partner institutions with planes, drones, ships, ground stations and autonomous buoys trying to understand how and why these clouds form, how that links to their environment, dust from Africa, the ocean current, the jetstream aloft, etc. The positions of the different platforms can be seen live on the main website and the data we are producing is appearing on there too. If you have any questions about what we're doing I'd be very happy to help or point you towards the right people :)
- Angostura 7y ago
  I suppose my immediate question is - is there any way for an non-professional with a pair of eyes and a smartphone to contribute in a crowd-sourcy way?
  - qubex 7y ago
    Why do you want to a horde of “non-professional[s] with a pair of eyes and a smartphone” to contribute if literally hundreds of professionals with high-end equipment, meteorological observation satellites, and oodles of computational firepower are already on the task? The main problem has never been a lack of science, the problem has always been (and alas, continues to be) a lack of political wherewithal to actually rapidly implement the drastic steps necessary to avoid the worst outcomes. Maybe we’re finally getting what we collectively deserve?
    - bumby 7y ago
      I think what precedes the problem you mention (and one of the main points in the article) is the problem of generating reduced uncertainty in the model. Maybe there’s a chance for more granular data to enhance that?
mirthandmadness 7y ago
Why the heck are we debating about 1 degree or 2 degrees or whatever. The imperative should be to reduce emisssions as much as possible as soon as possible.
- yifanl 7y ago
  Its just easier to think about a concrete number.
chrisco255 7y ago
A model isn't reality. A lot of climate research is based entirely on experimenting with these climate models. Of course, the climate is a non-linear dynamic system, so even if you had a perfect model (we don't), if your input parameters were off by the slightest bit, reality would veer off wildly from your prediction within a short time. This is why weather forecasts don't work beyond 10 days.
- danieldk 7y ago
  A lot of climate research is based entirely on experimenting with these climate models. We have a lot of data measured at many points on Earth spanning many decades. The data clearly shows that our planet is warming up and that there is a strong correlation with greenhouse gasses. One can extrapolate from these data points with certain reliability. What is hard is to take into account are tipping points (which is why the IPCC excludes them in their projections), such as the effects of methane release from warming tundra soil. As far as I understand, most known possible tipping points only make things worse, not better. At this point the question is not if climate change is happening (there is near universal agreement on that among climatologists), but whether it will be bad, but manageable, it will be ugly, or life-threatening to mankind. In any of these cases, we have to act now.
  - chrisco255 7y ago
    We have data that shows warming in the early 20th century, cooling in the mid 20th century (through the 70s) and warming in the decades after that. CO2 ppm was increasing steadily through those ups and downs, so it's not correlated perfectly. Meanwhile there are natural phenomenon like the Atlantic Multi-decadal Oscillation, the Pacific Decadal Oscillation, ENSO, NAO, etc that also correlate quite well with climate change. In the terms of "bad, unmanageable" climate change, I would invite you to research the early Holocene, which had temps as much as 7 degrees hotter than modern temps. The early Holocene began about 12K years ago and ended about 6K years ago. The warm temperatures correlate with boom times for humanity. See: Early Holocene Temperature Oscillations Exceed Amplitude of Observed and Projected Warming in Svalbard Lakes https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL084384 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...
jokoon 7y ago
I live in a small, old apartment in the EU, without proper AC. I'm pretty worried about the next summer. I can crash at a friend where the temperature never went above 26C last summer, despite a heatwave. I always hope that if heatwaves keep coming summer after summer, governments/the UN will take tough decisions. If nothing is done and summers are too hot, I clearly see people protesting/striking/blocking roads/etc until governments concede. My biggest fear are consumers that will refuse to adapt their consumption because they will see this as unfair rich-vs-poor restrictions. People addicted to consumerism would easily riot to denounce how capitalism ruined their living standard.
- HenryKissinger 7y ago
  You should get an AC unit. A window one if you have the right kind of window, or a larger, mobile one.
  - danieldk 7y ago
    More AC units are going to make the problem worse as long as we are not using solar/wind/hydro/nuclear-power. Last summer when there was a heat wave here, lot of people bought ACs. Next year, they are also switching them on when it's 30 degrees Celsius outside. The irony.
- luckylion 7y ago
  > because they will see this as unfair rich-vs-poor restrictions Which, in all fairness, it is. It's not like e.g. miles travelled is similar for everyone in any society. You have the upper class with multiple international vacations (usually via airplane, cruise ship etc), you have the middle class with maybe one trip per year to a foreign country, and you have the lower classes with maybe one trip every five or ten years. "Everybody just has to cut one trip a year" really is different for the rich vs the poor, isn't it? The same is true for many related issues. It's not the poor families that own two or three cars (because you sometimes need a small car, can't take your SUV everywhere). What's true is that the masses will have a large impact simply because they exist in large numbers. What's not true (by a long shot) is that they consume anywhere close to what the rich consume.
sbussard 7y ago
https://www.ted.com/talks/allan_savory_how_to_fight_desertification_and_reverse_climate_change/discussion?language=en https://www.ted.com/talks/allan_savory_how_to_fight_desertif...
sbussard 7y ago
I'd like to know others' thoughts on this talk/discussion https://www.ted.com/talks/allan_savory_how_to_fight_desertification_and_reverse_climate_change/discussion?language=en https://www.ted.com/talks/allan_savory_how_to_fight_desertif...
- andersha 7y ago
  legit. He's trying to mimic nature and keep the photosynthesis running by using ruminants to speed up the decomposition of organic matter and by timely management, have the regrowth sequester more atmospheric CO2 without overgrazing and compromising the grass plant or ecosystem.
grandridge 7y ago
Not a good title when the "science is settled"
macinjosh 7y ago
scientific models != scientific facts. They are educate guesses or educated estimates to be more charitable. Our computing capabilities are much too weak to accurately model systems as complex as the entire earth's climate.
samatman 7y ago
I'm reminded of Feynman's famous anecdote about the Millikan oil drop experiment: Millikan underestimated the charge of the electron, and over the ensuing years, subsequent measurements slowly but surely converged on the correct value. Why? Because experimenters who got the correct value figured it must be too high, and ran the experiment again until they got a more-erroneous value, one that was nonetheless higher. Eventually it worked itself out. But climate modeling isn't measuring something objective and static like the charge of the electron. It's prediction. I'm afraid that the incentives are to credit models that predict more warming just a bit more than those which predict less; the expected effect would be that the predicted warming effect would get larger over time. Please note that I'm not calling climate science a "Cargo Cult", as Feynman put it; I accept the basic premise of anthropogenic warming on first principles, and see that historic measurements (not to speak of recent ones) show a warming trend. There is cause to be concerned. Nonetheless, it would be surprising if climate modeling, which is inherently inexact and involves irreducible guesswork, didn't drift toward the more alarming, due to similar social forces to those identified in Feynman's essay.
- SiempreViernes 7y ago
  > I'm afraid that the incentives are to credit models that predict more warming just a bit more than those which predict less; the expected effect would be that the predicted warming effect would get larger over time. This actually doesn't make any sense! In your valued Milikan example, the problem was subsequent experiments were biased towards lower values, meaning that for climate models the bias would be expected towards under heating models. In other words, the lesson from Milikan is that there is a risk our models aren't heating fast enough. So by the quoted example we should be worry that our models under predicts, and yet Milikan is stood up to argue the models are too wild in their warming predictions?
- cagenut 7y ago
  this is textbook middlebrow contrarianism. using some quote from some recognizable name to dismiss the incredible work of dozens of top of their field professionals doing their life's work. its a perfect example of the way hacker news "types" do climate change denial. via endless "well-actuallys" until you're lost and stuck in a level of analysis-paralysis that borders on an anxiety disorder. the problem with solving climate change is not a technology problem any more, its a decision making and coordination problem. we have a third of people in denial, a third of people who want to fix stuff, and this unbelievably infuriating third of people in the middle who can't stop equivocating and triangulating. the thing preventing a simple majority from moving on with solutions is not the outright-deniers, its the people in the middle using the deniers as an excuse to not get on board with the solvers.
aszantu 7y ago
wasn'T there something called global dimming which counters global warming? Since we do filter out more of those particles, we allow for more global warming?
pjkundert 7y ago
> Those now attempting to figure out the mystery of the hot climate models think one factor might have caused the recent unusual results: clouds. It turns out simulated clouds often cause headaches for climate modelers. The impact of cloud cover in these models has been incorrect, and has such a large impact. Doesn't this strike anyone as a major problem? We're burning about 100 billion gallons of aviation fuel per year. > This means each gallon of jet fuel (6.5lbs) will combine with 23lbs of Oxygen and turn into twenty pounds of CO2, and just over nine pounds of water! (see: https://paullaherty.com/2015/01/10/calculating-aircraft-co2-emissions/ https://paullaherty.com/2015/01/10/calculating-aircraft-co2-...). So that's 100B gallons * 9lbs is about a half a billion metric tons of water vapor going into the dry upper troposphere annually from commercial aviation. Which, evidence would seem to suggest, has not been modeled properly (at all?) by these climate models? If I was producing these models, I would be embarassed.
- jbattle 7y ago
  How did you get from > It turns out simulated clouds often cause headaches for climate modelers. to > Which, evidence would seem to suggest, has not been modeled properly (at all?) by these climate models? Embarrassment may be premature
- yaks_hairbrush 7y ago
  So, 500 million metric tons sounds like a lot, doesn't it? But there's the fact that it's getting dumped into an already big system: the atmosphere at large. Let's check it out it percentage terms. According to wikipedia, the mean mass of water vapor in the air is 1.27 * 10^16 kg. To get the units correct, that aviation contribution is 5 * 10^11 kg. Dividing the latter by the former, we find that the annual commercial aviation water vapor represents 0.004% of the mean mass of water vapor. That's rounding error.
  - pjkundert 7y ago
    FL300 is very cold and very dry, and bears almost none of the "atmospheric water". Your estimation of impact is not correct. This is not a linear system.
pdkl95 7y ago
Does anyone know if these models use floating point? If the do, are they properly handling the many subtleties[1] of IEEE 754 (and other floating point implementations)? Many years ago I read something about a model that produced very different results depending on the hardware architecture. If a model is sometimes chaotically sensitive to initial conditions, improper handling of rounding could be catastrophic. [1] https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.h...
- cjbillington 7y ago
  No doubt they are using floats (well, doubles) - these models are usually coupled partial differential equations, propagated forward through time over the earth's surface using finite-difference or finite-element methods. It's unlikely IMHO that floating point rounding oddities would cause catastrophically erroneous results. In my experience from other physics simulations, you usually validate some known behaviour you're not trying to predict, e.g. that energy is conserved, or that total mass of fluid is conserved. Bad numerics will usually violate these conservation laws, so you can use the fact that they are conserved as some evidence that your numerics are actually solving the differential equation relatively correctly. Basically, people would notice broken numerics in this case. There are situations where it is harder to validate numerics (e.g. if your numerics inherently conserve some quantity by construction, then you can't use it to validate the behaviour of the numerics), and to be sure, a concerning fraction of all publications with numerical results contain mistakes. But I don't think floating point rounding is near the top of the list of issues to go looking for in these models.
nharada 7y ago
It's disheartening to read some of the comments here. Scientists are basically saying "we're not sure if it's going to be a disaster or a catastrophe", and some folk's response seems to be "see! scientists don't know! why should we listen to them?"
- viburnum 7y ago
  Some people will do anything to change the subject when the subject makes them uncomfortable. Better to quibble about models than to confront the disaster.
  - deleted 7y ago
    [deleted]
- jimmydddd 7y ago
  I agree it's disheartening. But I think a contributor to these responses is that activists are always saying everything is 100% settled, because SCIENCE (see, e.g., Bill Nye). Then the doubters see that the models are complex, use different criteria, and diverge by differeing amounts. The activists lose credibility, and hurt their cause. I think a more nuanced message would be better received.
qubex 7y ago
It seems to me that the problem has never been a “lack of Science”, but rather a lack of political wherewithal to actually implement the drastic, necessary steps. There’s probably been a collective tendency to (try) to view what was coming our way through rose-tinted glasses, some unconscious effort to lowball the projections in order to have a less catastrophic outlook. Maybe the computers models are finally beginning to converge on a more realistic scenario as they factor in the actual changes that have occurred so far. It has never ceased to amaze me how we have oodles of science fiction films that feature a lone astronomer spotting an incoming asteroid and that then segue into the whole of humanity pulling together to build a fleet of spacecraft to flee on or thermonuclear weapons to blast the thing out of the sky with, but in reality we’ve had people warning us of approaching doom for seventy years and haven’t managed much more than a collective “YOLO LOL”. I have some experience in sensitivity analysis on stochastic systems such as climate models, and it seems to me that feedback loops are probably becoming increasingly tightly correlated, which in my field (macroeconomics) tends to herald massive discontinuities. I am not at all happy about this. At all.
GrumpyNl 7y ago
Just a question, does the temperature of the core of the earth have any influence?
- strainer 7y ago
  Its a quite small influence, about 50 milliWatts per square meter iirc. Overall we are well insulated from heat circulating inside the Earth (by miles of rock) while hundreds of watts per square meter enters the atmosphere from solar radiation.
zmoreira 7y ago
I saw that chart in the article and thought "the predicted warming correlates with the level of wokeness of the country" From Russia 1.83 to Canada 5.64.
trekrich 7y ago
If they are based on models, then you can get any result you want!
Proven 7y ago
That title pretty much sums up the climatist circus since the 90's
allovernow 7y ago
>The scientists went on to try 300 configurations of rain, pollution, and heat flows—something they can do as gods of their own digital earth—before matching the model to history. Having worked with complex geologic (not climate) models in the past, this is the part that gives me pause. The scientists have set out as a first principle to find warming and then are working backwards and, ostensibly, everything is legitimate because model results are calibrated to previous real data. But here's the problem. When you have complex, chaotic models with hundreds of freely tweekable parameters, it's fairly easy to fit data and simultaneously get any future prediction you (or your bias) want. Even when individually each variable is within a reasonable range. We arguably have proof of this happening - climate models have been consistently overpredicting dT for what, 10 years now? There is an institutional problem with climate science, in that there is no real penalty for being wrong, and in fact the more aggressive results probably get the most attention. Because the modeling is so far removed from any sort of experimental or observational data collection, I think the field is dangerously susceptible to institutional bias.
- ilkan 7y ago
  As to your first point, I believe they are looking for the best fit to decades of data, not to a single point in time. As to your second argument, both historically and presently in science the tall nail gets hammered, it's a very conservative field. They look for a consensus (agreed minimum warming of x) rather than (an expected average warming of x).
- imtringued 7y ago
  The scientists are actively trying to tone down their climate change models and your response is that they are overestimating?
deleted 7y ago
[deleted]

241 points by montalbano 7y ago

vincent-toups 7y ago

I guess climate scientists don't use version control?

norswap 7y ago
The article isn't very precise, but my understanding was that the run some kind of machine learning based on past data. Adding in the more recent data changed the predictions dramatically. So it's not an issue of versioning (I assume they could reproduce the old results using the old data).
- whatshisface 7y ago
  It's not machine learning, it's a physical model. Computers solve a big differential equation that takes in all of the physical things we know about the Earth's climate system and runs them forward in time. The increase in thermal predictions are due to changes in the cloud and aerosol models which were made due to an improved understanding of the physics involved.
  - cultus 7y ago
    The line can be a bit blurry, because they are actually running inverse problems with the PDEs to fit the data. This needs regularization just like statistical ML models. Usually this amounts to solving an iterated least square problem, just like logistic regression. Bayesian methods are becoming more popular, though.
    - dls2016 7y ago
      > because they are actually running inverse problems with the PDEs to fit the data Could you explain this a bit more? Are you talking about data assimilation?
      - cultus 7y ago
        Yes, that's right. The issue is that systems like these have a lot of free parameters that have to be estimated from the data. This is basically because you have to make assumptions if you don't want to simulate Earth's systems down to the subatomic level. The inferred values of these parameters are usually very important as well for interpretation. All PDEs are solved numerically by discretizing them into linear or nonlinear systems. If it's convex enough, Tikhonov regularization is often used. Linear PDEs, where the solution depends only linearly on its derivatives, can be discretized into matrices. This gives a system like A m = d, where A is the discretized PDE, m is the "model" or parameter values, and d is the data. This is usually over or under-determined from the data, so it has to be solved by least squares. Since the resulting system is usually almost singular, regularization is applied, usually by penalizing the L2 norm of the model: min || A m -d || + r ||m||^2 If it's nonlinear but convex enough, one can just solve it by fixed point iteration, with the above linear equation being solved at every step (Newton's method often doesn't work well). If it's too nonconvex, then MCMC or other Bayesian methods are better, since a single solution is useless if the parameter values could plausibly around widely separated minima.
- peterwoerner 7y ago
  They technically use the term constitutive model development. The math is similar to machine learning. Typically we know the basics of the physics, i.e. conservation of energy, momentum and angular momentum which set up the equations. But there a number of constitutive laws which relate parameters between these are "machine learned" but in generally, they are typically linear relations.
gameswithgo 7y ago
it isn't that, it is just a badly written article.

adrianN 7y ago

Well, politicians aren't doing anything anyway, whether the models predict catastrophe or CATASTROPHE. Already according to the 3° sensitivity predictions we would need an effort that rivals WW2 to stay below 1.5°. Yet major countries are led by climate denialists.

truculent 7y ago
we would need an effort that rivals WW2 to stay below _2.0_
derg 7y ago
Can you even imagine how a Total War economy/society based on transitioning to greener energies, cutting emissions and pollutants, and working on improvements to housing and urban planning would end up looking? Like ignoring the whole climate change thing for a moment (though we absolutely should not do that), just the quality of life improvements to our health and well being this kind of mobilization would bring would be astonishing.
- HenryKissinger 7y ago
  That would not be possible today. The wartime World War Two economy we learn about in school was only made possible because of two factors: 1) A massive surge in federal government spending, financed by borrowing from public markets (incl. war bonds), to buy the materiel needed to fight a war on two fronts (in Europe against Germany and in the Pacific against Japan). Such spending caused the public debt as a share of GDP to surge to its highest historical level ever, from about 40% at the start of the war to 100% at its peak, as you can see on this graph: https://upload.wikimedia.org/wikipedia/commons/a/a7/US_Debt_Held_by_Public.png https://upload.wikimedia.org/wikipedia/commons/a/a7/US_Debt_... . Today, without such a total war effort, we are running trillion dollar deficits. To put it as shortly and bluntly as I could, trying the same thing today would bankrupt the government. Our debt levels are far higher than they were then, in relative terms, and increasing by over a trillion every year. We would be looking at 2 or 3 trillion dollar deficits. Deficits of that magnitude might shake investors' confidence in the U.S.'s ability to service its debt. 2) The United States was coming out of the Great Depression, and the unemployed labor pool was in the double digits, as you can see on this graph: https://upload.wikimedia.org/wikipedia/commons/thumb/6/68/United_States_unemployment_with_incarceration_1892-2016.png/450px-United_States_unemployment_with_incarceration_1892-2016.png https://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Un... . In other words, there were a lot of unemployed people with nothing to do who could quickly be put to work to produce stuff for the war economy. This is not the case today. The economy is running at full employment. The large spare labor pool that existed then doesn't exist today.

aldoushuxley001 7y ago

Scientists making the models prly thought the politicans needed a helping hand.

trevyn 7y ago

At the end of the article, apparently it has something to do with clouds.

docdeek 7y ago
I’ve read a few times that clouds are a big problem for climate modelers as they are far more complex in their implications for the climate than my grade school planet heats > evaporation > cloud forms > rain falls understanding of them suggests. There’s a nice article here on the issue and frustration of clouds for climate modelers by the head of the Royal Meteorological Society here: https://www.carbonbrief.org/guest-post-why-clouds-hold-key-better-climate-models https://www.carbonbrief.org/guest-post-why-clouds-hold-key-b...
- mattrp 7y ago
  Yes water vapor specifically has been a big asterisk for a long time.

ipnon 7y ago

The 27-model average referenced in this article is 3.86 degrees C.

GrayTextIsTruth 7y ago

So, holistically, it would seem like warming (a fever) or Coronavirus (anti-bodies) is part of the planets immune system, but humans are too advanced.

ddalex 7y ago
Let's not anthropomorphize things, they don't like it.
- GrayTextIsTruth 7y ago
  Animals have immune systems too. It’s not a phenomenon unique to humans, as Anthropomorphism would suggest. > they don’t like it Who? HNers? I don’t care. I think it more that people don’t like seeing themselves as the virus or cancer, when we could easily change our behavior and we wouldn’t be.

fabian2k 7y ago

The title seems like clickbait, and the last part of the article does explain that the scientists actually know that new cloud models are mostly responsible for the change. The big question is then of course whether the new cloud model is wrong and the temperature increase therefore as well, or whether the new cloud model is more accurate than previous ones and the temperature increase is a real effect. I found another article that looks at this in a bit more detail: https://news.ucar.edu/132678/ncars-new-climate-model-running-hot https://news.ucar.edu/132678/ncars-new-climate-model-running... The linked paper this is based on has the following as the last sentence: > What scares us is not that the CESM2ECS is wrong (all models are wrong, [Box, 1976]) but that it might be right.

klodolph 7y ago
Or a third, frustrating possibility—the new cloud model is more accurate, but some other inaccuracy in the model used to be balanced out by the inaccurate cloud model.
- Accujack 7y ago
  Or that there are multiple inaccuracies in the model which interact, so finding and correcting each one makes progress but still doesn't improve the model overall.
  - k33n 7y ago
    Software is fun :)
  - cryptica 7y ago
    Having built some models to simulate very basic things myself, I've seen first-hand how the slightest deviation of the model from reality can completely invalidate the entire output of the model. For this reason, I'm skeptical of models that try to simulate very complex systems with a lot of variables and feedback loops. Models that have a large number of variables are particularly difficult to get right because different tiny mistakes in various parts of the model can compound and yield completely arbitrary and contradictory results. Approximating the reality in software is almost impossible.

throw7363 7y ago

Could it be a selection bias?

makomk 7y ago
"In all, as many as a fifth of new results published in the last year have come in with anomalously high climate sensitivity." The article suggests that a consensus may well form around the new, higher estimates. So, quite possibly.

novaRom 7y ago

"You are in private mode. Subscribe to continue reading." Ok, that's one more I will not open anymore; seems Bloomberg started using similar "privacy mode" detection as NYT.

saamm 7y ago
If you happen to be on Firefox, you can use this extension to get around it: https://addons.mozilla.org/en-US/firefox/addon/temporary-containers/ https://addons.mozilla.org/en-US/firefox/addon/temporary-con...
300bps 7y ago
I use two browsers for this scenario both on iPhone and desktop. The first browser is my regular one (take your pick) and the second one is Brave with scripts Disabled (one click option in settings). I use Brave when going to sites like this. Disabling scripts generally doesn't break these types of sites but it does stop them from detecting whatever it is they are trying to detect.

iongoatb 7y ago

...

screye 7y ago
I don't see how you brought socialism into any of this. Ironically, socialism is being sold as a solution that you yourself make very clear. That, the pace of scientific progress is really fast ,and automation is going to make a lot of jobs obsolete. Socialism (in the nordic sense, ie. capitalism with social welfare) is being proposed as a solution to rising inequality and unregulated for-profit forces in the free market of industries where the consumer has no choice. (medicine, education)
- iongoatb 7y ago
  Unbelievable that people believe that the Nordic model of capitalism is "socialism". Capitalism with social welfare is not socialism.
  - the_gastropod 7y ago
    Socialism isn't as narrow a term as you seem to think it is... It's quite a broad concept that can (and does) coexist with Capitalism.
bentona 7y ago
I mostly somewhat agree with you but unless you find a more appealing package for your arguments, you're just going to exacerbate the bifurcation on issues like this, and definitely not convince or enlighten anyone.

deleted 7y ago

[deleted]

justadudeama 7y ago

I am not a climate change denier by a long shot, but stories like these give a ding to the credibility of climate scientists. > "So we can't throw them out yet." This might be an elementary view of science, but I think there is a danger here that while everyone is making their models, if anyone is an outlier they go and tweak their model to match the patterns of others: 'Klaus Wyser’s group "switched off" some of the new cloud and aerosol settings in their model, he said, and that sent climate sensitivity back down to previous levels'. That seems to me a questionable reason to "switch off" part of the model - you should create the most accurate simulation possible and trust the output, not tweak the inputs to match literature data.

nerdponx 7y ago
Typically it's not obvious what to switch on and off for "accuracy". If your model produces wildly different results from previous models, either you hit on some really big discovery or you made a mistake. An ethical scientist will try to rule out the latter possibility before accepting the former.
- gmueckl 7y ago
  It goes deeper than that. If you can tweak your new model to correspond to an older one for which you have results available, you must run tests in which you apply these tweaks and verify that you get the same results. If you get different results, one of the models simply isn't doing what you think it's doing and you need to understand that. And in the vast majority of cases, it's likely a mistake in a model, not any kind of new science. One pretty general debugging/analysis strategy for a complex model is to deactivate it piece by piece until you get it to a point where it should reproduce a result that you can verify by other, independent means. E.g. tweak the parameters of the model so that reproduces a result that is known analytically. For instance, whenever it is possible in a model, a good sanity check is to set parameters that must lead to e.g. a perfect conservation of certain quantities.
orev 7y ago
Tweaking the inputs would help one to identify what factor is causing the difference, which allows you to focus on that. It doesn’t mean you permanently leave it out. And it does not make a credibility issue. This is how science works — it is a process that strives to be as accurate as possible, not come up with a static answer and stick to it (that’s what religion does). The ability for science to change and adapt is what makes it so strong. That is the message that needs to always be driven when discussing science; not throwing hands in the air and saying “why do these scientists keep changing their answers? They obviously don’t know what they’re doing”

tu7001 7y ago

Hold my beer :) http://climatechangereconsidered.org/ http://climatechangereconsidered.org/

gbasin 7y ago

Does anyone know if this is actually true? I was under the impression that climate models have been mostly overshooting reality over the past 40 years > One question modeling can help answer is called “climate sensitivity,” an estimate of how much warmer the planet will be once it has adjusted to atmospheric CO₂ at double the pre-industrial level. (At current rates, CO₂ could reach a doubling point in the last decades of this century.) This is the old, reliable number that’s come out to 3°C for 40 years. It was as close as anything gets to certainty.

wbeckler 7y ago
Here's a systematic comparison of climate model predictions vs reality, since the 1970s. It turns out that the models have done a great job of predicting reality. https://www.carbonbrief.org/analysis-how-well-have-climate-models-projected-global-warming https://www.carbonbrief.org/analysis-how-well-have-climate-m... I'd be curious where your impression comes from, in terms of what sources of information you're receiving.
- gbasin 7y ago
  I was thinking of the same data, I guess it's not quite as clear as I thought, but the majority are overestimating the warming: https://www.carbonbrief.org/wp-content/uploads/2017/10/Screen-Shot-2017-10-05-at-16.49.21.png https://www.carbonbrief.org/wp-content/uploads/2017/10/Scree...
  - SiempreViernes 7y ago
    If the idea is that the error in estimation is random around 0, you would expect about half to be overestimating. I think 5 out of 8 is not a very strong difference from 4 out of 8, which is the comparison that makes sense in this context.
- mistermann 7y ago
  Pardon the pedantry, but "-the- models have done a great job of predicting reality" seems like a bit of an overly strong statement. The link you give and the original article seem to be comparing a completely different set of models, and the main article even says there are "dozens still left to report....".

giarc 7y ago

If you are like me, you hate reading articles like this. You know there is a problem but you feel like you can't do anything about it. You recycle, you turn off lights, you have a programmable thermostat but you know it's a drop in the ocean. I finally decided to do something about it last fall. I researched and have committed to purchasing green power. Every month I purchase 850 kWh for $22 from Bullfrog Power (a Canadian company, I have no affiliation). It's much more reasonable than I thought. I still conserve as much as I can but $22/month allows me to feel like I am doing something. If in 40 years, my kids ask me what I did to prevent climate change, I feel like I'll have an answer I'll be proud of.

lllr_finger 7y ago
That's awesome and I'm right there with you on wanting to do more. Have you considered your next step, and do you have any suggestions? Purchasing green power is such a minor sacrifice for my household, I'm still looking for something more.
- giarc 7y ago
  My next steps will be writing to my government representatives. I live in Alberta and we just elected a right wing party that scrapped our carbon tax (although we now have a federal carbon tax).
Gravityloss 7y ago
This is why we have democracies, legislation and international treaties. Trying to solve it on individual goodwill of course helps but is not enough by itself.
oezi 7y ago
How about carbon offsetting your own life and that of your children?
SketchySeaBeast 7y ago
> If in 40 years, my kids ask me what I did to prevent climate change, I feel like I'll have an answer I'll be proud of. Doesn't it kind of feel like this is the equivalent of a kid in the 70's asking why their parents didn't stop World War 2? We absolutely need to be as vocal as possible, but as individuals, outside of trying to get people with power to affect the change we need, I don't know what we can expect to accomplish. You just can't do enough diet modifications, carbon footprint reduction, or recycling to have it matter on a global scale.

lbsnake7 7y ago

I’m a climate change skeptic almost entirely because I don’t trust models. I believe there are too many dynamic things happening in the world for anyone to be able to predict accurately say the next 100 years (solar, earthquakes, volcanoes etc). One way to make me a believer though is an experiment: if I were to give you a 100 year stretch of history and you were able to accurately predict with the models what exactly happened in those 100 years. The article talks about it a little bit about how the models are used to predict the 19th century to see if they are correct. But the models use the last 100 years as input so of course it will give you accurate output. But the real challenge of the models would be to accurately predict things that are not part of the inputs into the model. I don’t believe that these models can do this and are thus an exercise in straight extrapolation based on very complex and interconnected inputs.

jknoepfler 7y ago
So if I asked you to bet at 50/50 odds that next year would be colder on average than this year, you'd take the bet?
- lazyjones 7y ago
  That's not what climate is about. Also, it depends on location, in many places it was colder in 2019 than in 2018. If you're talking about some calculated "global" temperature, it doesn't exist in a valid form.
  - bannable 7y ago
    Are you claiming that it is not possible to find a trend in a mean temperature of a great many points across the globe, over a long period of time? What makes such a measurement an "invalid form"?
    - lazyjones 7y ago
      It is not possible if there aren't valid temperature measurements available for all points throughout the measured period of time, so that many temperatures are "interpolated", estimated etc.

bentona 7y ago

Is it not possible to backtest these sorts of things? If it were, I would assume results would be the first bullet point on articles like this, but I also don't understand why it wouldn't be possible.

makomk 7y ago
The article does sort of address this for one of the models: "The model run by NCAR, one of American’s main climate-science institutions, started producing unusual data last year while trying to reproduce the recent past. “We got some really strange results,” Gettelman said. The scientists went on to try 300 configurations of rain, pollution, and heat flows—something they can do as gods of their own digital earth—before matching the model to history. But by solving that puzzle, Gettelman’s team sent future projections upward at an unheard-of rate." Basically, the backtesting failed to match reality for the recent past, they tweaked parameters to get it to fit, and that produced surprisingly high predictions for the future. I don't think that would leave them anything to backtest on, since they'd used effectively all their historical data to fit the model to.

aazaa 7y ago

It's surprising the article doesn't mention CFCs: > The simulations showed that the rate of Arctic warming in a world without CFCs would be cut in half – a striking effect for a category of substances that are only present in small quantities to begin with. To ensure the result was not simply a quirk of the simulation, the researchers ran the experiment using two different climate models and arrived at a similar outcome. https://www.theglobeandmail.com/canada/article-cfcs-are-a-major-driver-of-arctic-warming-study-finds/ https://www.theglobeandmail.com/canada/article-cfcs-are-a-ma... The danger here is that there's something else we fundamentally don't understand about the atmosphere.

boyadjian 7y ago

We have been warned about high birth rates and over-consumption in 1972, from the Meadows Report of the "Club of Rome", "The limits to Growth". Now we have reached those limits. So, what are we doing, now ?

lazyjones 7y ago

Because they're made by alarmists who are trying to increase political pressure.

leifdenby 7y ago

There is a big observational campaign happening right now that is trying to get to the heart of this called EUREC4A (main website: http://eurec4a.eu http://eurec4a.eu and information sheet: http://eurec4a.eu/fileadmin/user_upload/eurec4a/2019/Press/EURECA4A_factsheet_uk_10_12_2019.pdf http://eurec4a.eu/fileadmin/user_upload/eurec4a/2019/Press/E...). The key uncertainty between different climate models is whether shallow clouds in the tropics (which in general cool the Earth through radiation) will disappear or not and make our planet even warmer - some models predict this (!) We are 100s of individuals from more than 30 national and international partner institutions with planes, drones, ships, ground stations and autonomous buoys trying to understand how and why these clouds form, how that links to their environment, dust from Africa, the ocean current, the jetstream aloft, etc. The positions of the different platforms can be seen live on the main website and the data we are producing is appearing on there too. If you have any questions about what we're doing I'd be very happy to help or point you towards the right people :)

Angostura 7y ago
I suppose my immediate question is - is there any way for an non-professional with a pair of eyes and a smartphone to contribute in a crowd-sourcy way?
- qubex 7y ago
  Why do you want to a horde of “non-professional[s] with a pair of eyes and a smartphone” to contribute if literally hundreds of professionals with high-end equipment, meteorological observation satellites, and oodles of computational firepower are already on the task? The main problem has never been a lack of science, the problem has always been (and alas, continues to be) a lack of political wherewithal to actually rapidly implement the drastic steps necessary to avoid the worst outcomes. Maybe we’re finally getting what we collectively deserve?
  - bumby 7y ago
    I think what precedes the problem you mention (and one of the main points in the article) is the problem of generating reduced uncertainty in the model. Maybe there’s a chance for more granular data to enhance that?

mirthandmadness 7y ago

Why the heck are we debating about 1 degree or 2 degrees or whatever. The imperative should be to reduce emisssions as much as possible as soon as possible.

yifanl 7y ago
Its just easier to think about a concrete number.

chrisco255 7y ago

A model isn't reality. A lot of climate research is based entirely on experimenting with these climate models. Of course, the climate is a non-linear dynamic system, so even if you had a perfect model (we don't), if your input parameters were off by the slightest bit, reality would veer off wildly from your prediction within a short time. This is why weather forecasts don't work beyond 10 days.

danieldk 7y ago
A lot of climate research is based entirely on experimenting with these climate models. We have a lot of data measured at many points on Earth spanning many decades. The data clearly shows that our planet is warming up and that there is a strong correlation with greenhouse gasses. One can extrapolate from these data points with certain reliability. What is hard is to take into account are tipping points (which is why the IPCC excludes them in their projections), such as the effects of methane release from warming tundra soil. As far as I understand, most known possible tipping points only make things worse, not better. At this point the question is not if climate change is happening (there is near universal agreement on that among climatologists), but whether it will be bad, but manageable, it will be ugly, or life-threatening to mankind. In any of these cases, we have to act now.
- chrisco255 7y ago
  We have data that shows warming in the early 20th century, cooling in the mid 20th century (through the 70s) and warming in the decades after that. CO2 ppm was increasing steadily through those ups and downs, so it's not correlated perfectly. Meanwhile there are natural phenomenon like the Atlantic Multi-decadal Oscillation, the Pacific Decadal Oscillation, ENSO, NAO, etc that also correlate quite well with climate change. In the terms of "bad, unmanageable" climate change, I would invite you to research the early Holocene, which had temps as much as 7 degrees hotter than modern temps. The early Holocene began about 12K years ago and ended about 6K years ago. The warm temperatures correlate with boom times for humanity. See: Early Holocene Temperature Oscillations Exceed Amplitude of Observed and Projected Warming in Svalbard Lakes https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL084384 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...

jokoon 7y ago

I live in a small, old apartment in the EU, without proper AC. I'm pretty worried about the next summer. I can crash at a friend where the temperature never went above 26C last summer, despite a heatwave. I always hope that if heatwaves keep coming summer after summer, governments/the UN will take tough decisions. If nothing is done and summers are too hot, I clearly see people protesting/striking/blocking roads/etc until governments concede. My biggest fear are consumers that will refuse to adapt their consumption because they will see this as unfair rich-vs-poor restrictions. People addicted to consumerism would easily riot to denounce how capitalism ruined their living standard.

HenryKissinger 7y ago
You should get an AC unit. A window one if you have the right kind of window, or a larger, mobile one.
- danieldk 7y ago
  More AC units are going to make the problem worse as long as we are not using solar/wind/hydro/nuclear-power. Last summer when there was a heat wave here, lot of people bought ACs. Next year, they are also switching them on when it's 30 degrees Celsius outside. The irony.
luckylion 7y ago
> because they will see this as unfair rich-vs-poor restrictions Which, in all fairness, it is. It's not like e.g. miles travelled is similar for everyone in any society. You have the upper class with multiple international vacations (usually via airplane, cruise ship etc), you have the middle class with maybe one trip per year to a foreign country, and you have the lower classes with maybe one trip every five or ten years. "Everybody just has to cut one trip a year" really is different for the rich vs the poor, isn't it? The same is true for many related issues. It's not the poor families that own two or three cars (because you sometimes need a small car, can't take your SUV everywhere). What's true is that the masses will have a large impact simply because they exist in large numbers. What's not true (by a long shot) is that they consume anywhere close to what the rich consume.

sbussard 7y ago

https://www.ted.com/talks/allan_savory_how_to_fight_desertification_and_reverse_climate_change/discussion?language=en https://www.ted.com/talks/allan_savory_how_to_fight_desertif...

sbussard 7y ago

I'd like to know others' thoughts on this talk/discussion https://www.ted.com/talks/allan_savory_how_to_fight_desertification_and_reverse_climate_change/discussion?language=en https://www.ted.com/talks/allan_savory_how_to_fight_desertif...

andersha 7y ago
legit. He's trying to mimic nature and keep the photosynthesis running by using ruminants to speed up the decomposition of organic matter and by timely management, have the regrowth sequester more atmospheric CO2 without overgrazing and compromising the grass plant or ecosystem.

grandridge 7y ago

Not a good title when the "science is settled"

macinjosh 7y ago

scientific models != scientific facts. They are educate guesses or educated estimates to be more charitable. Our computing capabilities are much too weak to accurately model systems as complex as the entire earth's climate.

samatman 7y ago

I'm reminded of Feynman's famous anecdote about the Millikan oil drop experiment: Millikan underestimated the charge of the electron, and over the ensuing years, subsequent measurements slowly but surely converged on the correct value. Why? Because experimenters who got the correct value figured it must be too high, and ran the experiment again until they got a more-erroneous value, one that was nonetheless higher. Eventually it worked itself out. But climate modeling isn't measuring something objective and static like the charge of the electron. It's prediction. I'm afraid that the incentives are to credit models that predict more warming just a bit more than those which predict less; the expected effect would be that the predicted warming effect would get larger over time. Please note that I'm not calling climate science a "Cargo Cult", as Feynman put it; I accept the basic premise of anthropogenic warming on first principles, and see that historic measurements (not to speak of recent ones) show a warming trend. There is cause to be concerned. Nonetheless, it would be surprising if climate modeling, which is inherently inexact and involves irreducible guesswork, didn't drift toward the more alarming, due to similar social forces to those identified in Feynman's essay.

SiempreViernes 7y ago
> I'm afraid that the incentives are to credit models that predict more warming just a bit more than those which predict less; the expected effect would be that the predicted warming effect would get larger over time. This actually doesn't make any sense! In your valued Milikan example, the problem was subsequent experiments were biased towards lower values, meaning that for climate models the bias would be expected towards under heating models. In other words, the lesson from Milikan is that there is a risk our models aren't heating fast enough. So by the quoted example we should be worry that our models under predicts, and yet Milikan is stood up to argue the models are too wild in their warming predictions?
cagenut 7y ago
this is textbook middlebrow contrarianism. using some quote from some recognizable name to dismiss the incredible work of dozens of top of their field professionals doing their life's work. its a perfect example of the way hacker news "types" do climate change denial. via endless "well-actuallys" until you're lost and stuck in a level of analysis-paralysis that borders on an anxiety disorder. the problem with solving climate change is not a technology problem any more, its a decision making and coordination problem. we have a third of people in denial, a third of people who want to fix stuff, and this unbelievably infuriating third of people in the middle who can't stop equivocating and triangulating. the thing preventing a simple majority from moving on with solutions is not the outright-deniers, its the people in the middle using the deniers as an excuse to not get on board with the solvers.

aszantu 7y ago

wasn'T there something called global dimming which counters global warming? Since we do filter out more of those particles, we allow for more global warming?

pjkundert 7y ago

> Those now attempting to figure out the mystery of the hot climate models think one factor might have caused the recent unusual results: clouds. It turns out simulated clouds often cause headaches for climate modelers. The impact of cloud cover in these models has been incorrect, and has such a large impact. Doesn't this strike anyone as a major problem? We're burning about 100 billion gallons of aviation fuel per year. > This means each gallon of jet fuel (6.5lbs) will combine with 23lbs of Oxygen and turn into twenty pounds of CO2, and just over nine pounds of water! (see: https://paullaherty.com/2015/01/10/calculating-aircraft-co2-emissions/ https://paullaherty.com/2015/01/10/calculating-aircraft-co2-...). So that's 100B gallons * 9lbs is about a half a billion metric tons of water vapor going into the dry upper troposphere annually from commercial aviation. Which, evidence would seem to suggest, has not been modeled properly (at all?) by these climate models? If I was producing these models, I would be embarassed.

jbattle 7y ago
How did you get from > It turns out simulated clouds often cause headaches for climate modelers. to > Which, evidence would seem to suggest, has not been modeled properly (at all?) by these climate models? Embarrassment may be premature
yaks_hairbrush 7y ago
So, 500 million metric tons sounds like a lot, doesn't it? But there's the fact that it's getting dumped into an already big system: the atmosphere at large. Let's check it out it percentage terms. According to wikipedia, the mean mass of water vapor in the air is 1.27 * 10^16 kg. To get the units correct, that aviation contribution is 5 * 10^11 kg. Dividing the latter by the former, we find that the annual commercial aviation water vapor represents 0.004% of the mean mass of water vapor. That's rounding error.
- pjkundert 7y ago
  FL300 is very cold and very dry, and bears almost none of the "atmospheric water". Your estimation of impact is not correct. This is not a linear system.

pdkl95 7y ago

Does anyone know if these models use floating point? If the do, are they properly handling the many subtleties[1] of IEEE 754 (and other floating point implementations)? Many years ago I read something about a model that produced very different results depending on the hardware architecture. If a model is sometimes chaotically sensitive to initial conditions, improper handling of rounding could be catastrophic. [1] https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.h...

cjbillington 7y ago
No doubt they are using floats (well, doubles) - these models are usually coupled partial differential equations, propagated forward through time over the earth's surface using finite-difference or finite-element methods. It's unlikely IMHO that floating point rounding oddities would cause catastrophically erroneous results. In my experience from other physics simulations, you usually validate some known behaviour you're not trying to predict, e.g. that energy is conserved, or that total mass of fluid is conserved. Bad numerics will usually violate these conservation laws, so you can use the fact that they are conserved as some evidence that your numerics are actually solving the differential equation relatively correctly. Basically, people would notice broken numerics in this case. There are situations where it is harder to validate numerics (e.g. if your numerics inherently conserve some quantity by construction, then you can't use it to validate the behaviour of the numerics), and to be sure, a concerning fraction of all publications with numerical results contain mistakes. But I don't think floating point rounding is near the top of the list of issues to go looking for in these models.

nharada 7y ago

It's disheartening to read some of the comments here. Scientists are basically saying "we're not sure if it's going to be a disaster or a catastrophe", and some folk's response seems to be "see! scientists don't know! why should we listen to them?"

viburnum 7y ago
Some people will do anything to change the subject when the subject makes them uncomfortable. Better to quibble about models than to confront the disaster.
- deleted 7y ago
  [deleted]
jimmydddd 7y ago
I agree it's disheartening. But I think a contributor to these responses is that activists are always saying everything is 100% settled, because SCIENCE (see, e.g., Bill Nye). Then the doubters see that the models are complex, use different criteria, and diverge by differeing amounts. The activists lose credibility, and hurt their cause. I think a more nuanced message would be better received.

qubex 7y ago

It seems to me that the problem has never been a “lack of Science”, but rather a lack of political wherewithal to actually implement the drastic, necessary steps. There’s probably been a collective tendency to (try) to view what was coming our way through rose-tinted glasses, some unconscious effort to lowball the projections in order to have a less catastrophic outlook. Maybe the computers models are finally beginning to converge on a more realistic scenario as they factor in the actual changes that have occurred so far. It has never ceased to amaze me how we have oodles of science fiction films that feature a lone astronomer spotting an incoming asteroid and that then segue into the whole of humanity pulling together to build a fleet of spacecraft to flee on or thermonuclear weapons to blast the thing out of the sky with, but in reality we’ve had people warning us of approaching doom for seventy years and haven’t managed much more than a collective “YOLO LOL”. I have some experience in sensitivity analysis on stochastic systems such as climate models, and it seems to me that feedback loops are probably becoming increasingly tightly correlated, which in my field (macroeconomics) tends to herald massive discontinuities. I am not at all happy about this. At all.

GrumpyNl 7y ago

Just a question, does the temperature of the core of the earth have any influence?

strainer 7y ago
Its a quite small influence, about 50 milliWatts per square meter iirc. Overall we are well insulated from heat circulating inside the Earth (by miles of rock) while hundreds of watts per square meter enters the atmosphere from solar radiation.

zmoreira 7y ago

I saw that chart in the article and thought "the predicted warming correlates with the level of wokeness of the country" From Russia 1.83 to Canada 5.64.

trekrich 7y ago

If they are based on models, then you can get any result you want!

Proven 7y ago

That title pretty much sums up the climatist circus since the 90's

allovernow 7y ago

>The scientists went on to try 300 configurations of rain, pollution, and heat flows—something they can do as gods of their own digital earth—before matching the model to history. Having worked with complex geologic (not climate) models in the past, this is the part that gives me pause. The scientists have set out as a first principle to find warming and then are working backwards and, ostensibly, everything is legitimate because model results are calibrated to previous real data. But here's the problem. When you have complex, chaotic models with hundreds of freely tweekable parameters, it's fairly easy to fit data and simultaneously get any future prediction you (or your bias) want. Even when individually each variable is within a reasonable range. We arguably have proof of this happening - climate models have been consistently overpredicting dT for what, 10 years now? There is an institutional problem with climate science, in that there is no real penalty for being wrong, and in fact the more aggressive results probably get the most attention. Because the modeling is so far removed from any sort of experimental or observational data collection, I think the field is dangerously susceptible to institutional bias.

ilkan 7y ago
As to your first point, I believe they are looking for the best fit to decades of data, not to a single point in time. As to your second argument, both historically and presently in science the tall nail gets hammered, it's a very conservative field. They look for a consensus (agreed minimum warming of x) rather than (an expected average warming of x).
imtringued 7y ago
The scientists are actively trying to tone down their climate change models and your response is that they are overestimating?

deleted 7y ago

[deleted]