Even 50-year-old climate models correctly predicted global warming • Hacker News Board

Re: Even 50-year-old climate models correctly predicted global warming

#161

Post by henrifdrake » Thu, Dec 05, 2019, 1:52 AM UTC

jml7c5 wrote: post #157

ekianjo wrote: post #48

Where is the story hère though? So they looked retroactively and found some models in the past that fitted with current observations even though they had no clue that China would become such a powerful force in terms of CO2 emissions? If you run random models and wait long enough you will always be able to find at least one model that predicted the current observations. That does NOT mean the models were right, it me…

According to: http://www.realclimate.org/index.php/archives/2019/12/how-go... >We gathered all the climate models published between 1970 and the mid-2000s that gave projections of both future warming and future concentrations of CO2 and other climate forcings – from Manabe (1970) and Mitchell (1970) through to CMIP3 in IPCC 2007. If you're a cynic or suspicious: "projections of future warming" means they intentionall…

P.S. Our coauthor at NASA was able to host the paper on their official site for anyone to read. https://pubs.giss.nasa.gov/abs/ha08910q.html

I share your wish for open access journals.

Re: Even 50-year-old climate models correctly predicted global warming

#162

Post by henrifdrake » Thu, Dec 05, 2019, 1:54 AM UTC

svara wrote: post #119

ekianjo wrote: post #48

Where is the story hère though? So they looked retroactively and found some models in the past that fitted with current observations even though they had no clue that China would become such a powerful force in terms of CO2 emissions? If you run random models and wait long enough you will always be able to find at least one model that predicted the current observations. That does NOT mean the models were right, it me…

So, you dismiss this work based on your speculation on what the authors could in principle have done wrong? There would actually be substance to your comment if you could point us to the models the authors didn't consider.

Indeed, the authors (I am one of them) would appreciate this. I'll personally add any extra papers you find to the plots. If it turns out we really left out some important papers, we (or at least I) will publish a revision to the paper.

Re: Even 50-year-old climate models correctly predicted global warming

#163

Post by henrifdrake » Thu, Dec 05, 2019, 1:57 AM UTC

starpilot wrote: post #59

ekianjo wrote: post #48

Where is the story hère though? So they looked retroactively and found some models in the past that fitted with current observations even though they had no clue that China would become such a powerful force in terms of CO2 emissions? If you run random models and wait long enough you will always be able to find at least one model that predicted the current observations. That does NOT mean the models were right, it me…

Yeah, this could be survivorship bias: https://motls.blogspot.com/2017/03/selection-of-climate-mode... As someone who's written basic fluid dynamics codes, I'm blown away by the complexity of climate models. The errors I ran into in debugging my relatively straightforward codes were incredibly subtle. Like pressures, velocities still "looking right" but still being wrong, due to numerical viscosity and other artifact…

How can you distinguish survivorship bias different from... developing better models? If there are any models that made quantitative predictions of global temperature change (whether warming, cooling, or neither), please let me know. I am extremely interested :)

P.S. Read the paper here: https://pubs.giss.nasa.gov/abs/ha08910q.html

Re: Even 50-year-old climate models correctly predicted global warming

#164

Post by henrifdrake » Thu, Dec 05, 2019, 1:58 AM UTC

starpilot wrote: post #54

It does seem like survivorship bias could be a factor. The article talks about how some of the old models were off until they "corrected" them. All right, and did they apply the same scrutiny to the apparently "correct" ones? "All of the models predicted this (except for the ones that didn't.)

The correction is based on physics is really quite straightforward...

Re: Even 50-year-old climate models correctly predicted global warming

#165

Post by bitlax » Thu, Dec 05, 2019, 2:01 AM UTC

pstuart wrote: post #153

bitlax wrote: post #88

Earlier quoted context omitted.

Well I'll take that bet. Climate activists have advocated that precisely the opposite should happen: that they should maintain or even increase their growth since they are developing economies.

You're betting that Trump is going to push policies that address climate change? The same individual who says that climate change is a hoax? Who praises clean coal and says that wind turbines cause cancer?

No, I'm betting that changes in U.S. production will have little to no impact on inspiring China and India to decrease their emissions.

Re: Even 50-year-old climate models correctly predicted global warming

#166

Post by vmchale » Thu, Dec 05, 2019, 2:02 AM UTC

svara wrote: post #30

Svante Arrhenius got it basically right in 1896 [1]. There is no scientific controversy and there never has been. Unfortunately, arguing about this might just reinforce the mistaken view that there are different valid "sides" to this. [1] https://en.m.wikipedia.org/wiki/Svante_Arrhenius#Greenhouse_... Edit: That doesn't detract from the article's more subtle point about the precision of climate models in the past, I…

Supposedly Fourier had some insight as well.

Re: Even 50-year-old climate models correctly predicted global warming

#167

Post by SlowRobotAhead » Thu, Dec 05, 2019, 2:03 AM UTC

gameswithgo wrote: post #152

starpilot wrote: post #59

Earlier quoted context omitted.

Yeah, this could be survivorship bias: https://motls.blogspot.com/2017/03/selection-of-climate-mode... As someone who's written basic fluid dynamics codes, I'm blown away by the complexity of climate models. The errors I ran into in debugging my relatively straightforward codes were incredibly subtle. Like pressures, velocities still "looking right" but still being wrong, due to numerical viscosity and other artifact…

total heat content of the planet is way way simpler than fluid dynamics

... this is sarcasm? I honestly can’t tell.

Can you elaborate your point of view a little more?

Re: Even 50-year-old climate models correctly predicted global warming

#168

Post by ekianjo » Thu, Dec 05, 2019, 2:05 AM UTC

skosch wrote: post #130

throwyweather wrote: post #109

Earlier quoted context omitted.

Correctness of numerical codes is a huge and under-appreciated concern in climate models. There have been some attempts to apply software correctness techniques to climate models. For example, https://people.engr.ncsu.edu/jwb/papers/altuntas-correctness... Much more work in this direction is needed.

... but if you think, "hey, so the models could be wrong, how reassuring", think again. It's just as likely that reality is worse than predicted.

How can you say that unless we know how to sort good models from bad ones before observations kick in? As far as I know its always very easy to fit historical data with thousands of models but very few will actually be useful for prediction and we have no idea which ones.

Re: Even 50-year-old climate models correctly predicted global warming

#169

Post by ekianjo » Thu, Dec 05, 2019, 2:12 AM UTC

hcknwscommenter wrote: post #126

mistermann wrote: post #103

Earlier quoted context omitted.

> As noted in TFA, they looked at 17 forecasts from 14 models Pardon a little pedantry: >> The researchers compared annual average surface temperatures across the globe to the surface temperatures predicted in 17 forecasts. Those predictions were drawn from 14 separate computer models released between 1970 and 2001. In some cases, the studies and their computer codes were so old that the team had to extract data publ…

TFA article does say. They looked at 17 forecasts drawn from 14 models. You are the one who implicitly believes they are lying about that and only reporting 17 out of some huge unknown number. The reality is that the vast majority (>99%) of climate change research does not produce the type of forecast, or really any forecast at all, that one could do this analysis on. Therefore, the 17 forecast number is actually ver…

How many models are currently published for reference?

Re: Even 50-year-old climate models correctly predicted global warming

#170

Post by ekianjo » Thu, Dec 05, 2019, 2:15 AM UTC

namirez wrote: post #73

ekianjo wrote: post #48

Where is the story hère though? So they looked retroactively and found some models in the past that fitted with current observations even though they had no clue that China would become such a powerful force in terms of CO2 emissions? If you run random models and wait long enough you will always be able to find at least one model that predicted the current observations. That does NOT mean the models were right, it me…

> even though they had no clue that China would become such a powerful force in terms of CO2 emissions I think you're making the same mistake that you're attributing to the story. It really doesn't matter what China does per se. The global energy consumption, roughly, follows a log-linear trend. If the energy comes from fossil fuels, the CO2 emissions would also follow the same trend [1]. It doesn't matter whether it…

Disagree. China's move to a more market based economy has resulted in them tripling their fossil CO2 emissions compared to the 1990s. India doubled. EU and the US are slowing down in emissions but on the whole China is driving the huge increase of CO2 emissions worldwide, matching their rapid economic development. If you did not take that into account you would miss on the acceleration of CO2 content in the atmosphere over time.