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

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

#241

Post by qubex »

allovernow wrote: post #212
qubex wrote: post #167

Earlier quoted context omitted.

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…

>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? Because the Earth is huge, data collection is expensive, and funds are limited. There is a lot of [literal] ground to cover and it's perfectly feasibl…

Satellites view half the globe at once. But you know that just as well as I do.

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

#242

Post by mistermann »

hannob wrote: post #135
lbsnake7 wrote: post #30

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 exactl…

The best thing we can do to see if the models work is to look how they performed compared to reality in the decades since we have climate models. Turns out: They worked really, really well. https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/201...

> Turns out: They worked really, really well.

Does "they" refer to all models?

The main article's set of models are different than the ones referred to in another link someone in this thread provided, and I suspect the article you've linked will also use yet another unique set.

If it was me trying to persuade people, and all historic climate change models did indeed work really, really well, I'd make an authoritative web page that lists all of these models including their inputs and outputs, and show a detailed quantitative comparison of their outputs. I would think this approach would be more persuasive in multiple ways than hundreds of separate articles written in a narrative style, lacking numbers and consistency in sets of models.

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

#243

Post by [deleted] »

koheripbal wrote: post #216
cagenut wrote: post #150

Earlier quoted context omitted.

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…

This comment is inappropriate and should be removed. It violates the #1 fundamental rule of this forum - to argue the argument , not the arguer .

[deleted]

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

#245

Post by SiempreViernes »

Reedx wrote: post #223
cagenut wrote: post #150

Earlier quoted context omitted.

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…

Pointing out that climate models are predictions is not the problem. The models are in fact predictions and they accumulate errors the further out they project. That's just the reality. The problem is pretending otherwise. That muddies the waters and literally fuels and strengthens climate change deniers as it gives them a leg to stand on. Remove that leg. We need to make it harder to dismiss, which can be better acc…

Climate change deniers fuel themselves, and mostly on the wish to avoid any sacrifice on their own part.

The post you are defending is doing more than simply pointing out that the models are models. It is also claiming, without any proof or even argument in support, that experts all over the world are only publishing high predictions.

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

#246

Post by pjkundert »

pjkundert wrote: post #158

> 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 y…

Remember, before you make the obvious mistake of "well, aktually, the atmosphere contains 5 orders of magnitude more water than that" -- we're not discussing a linear system.

Almost none of that atmospheric water resides at FL300. That's the point. You wildly adjust atmospheric parameters in the real world, with (apparently) not accurately accounting for them, and then claim your model is predictive?

This is why modelling complex, chaotic systems is hard. I've done it, and that's why I would be embarrassed.

Not because of the mistakes. Because I was so certain that my models were correct. The level of hubris displayed here is mind-boggling.

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

#247

Post by cjbillington »

pdkl95 wrote: post #162

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] h…

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.

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

#248

Post by rayiner »

claudeganon wrote: post #169
rayiner wrote: post #91

Earlier quoted context omitted.

Pretty much everybody: https://www.cnbc.com/2019/08/20/climate-change-to-slow-globa... > In other words, if global GDP doubles or halves by 2100, the results suggest real GDP per capita would still be 7.22% below where it would be otherwise. For most of the world, an RCP8.5 scenario is equivalent to knocking out 3-4 years of GDP growth. Bad, but not catastrophic, and probably less bad than the impact of "WWII-style m…

Pointing at GDP over and over again is at a best a fuzzy indicator of overall well-being, especially in the developed world where inequality has unmoored it from improvement in material standards for many people. Amazon stock prices skyrocketing tells you little about the health or well-being of their workforce.

GDP is the number we have. It's not perfect, but it's better than trying to assess the costs without reference to numbers. More significantly, GDP per capita gives a strong measure of the country's capacity to provide for well being, including through redistribution. The specific redistributive policies we adopt or not are mostly orthogonal to climate change.

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

#249

Post by jknoepfler »

lazyjones wrote: post #50
jknoepfler wrote: post #35

Earlier quoted context omitted.

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?

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.

On a crude first pass, I will accept any combination of the following datasets, assuming they are updated in 2020 and 2021:

HadCRUT4 (from UK Met Office Hadley Centre and the University of East Anglia’s Climatic Research Unit)

GISTEMP from the NASA GISS

MLOST from the NOAA

JMA from the Japan Meteorological Agency

I'm open to other datasets. I'm not choosy.

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

#250

Post by lazyjones »

jknoepfler wrote: post #221
protanopia wrote: post #119

Earlier quoted context omitted.

Are you asking about the weather in one specific year? Weather is not climate.

I'm well aware of the distinction between weather and climate. I was asking if the climate change skeptic would take a bet that the global mean temperature (operationalized in some acceptable way) would decline in 2021 compared to 2020. If they believe that the earth is not, on average, getting hotter, then they should be indifferent to this bet (inter-year variation should be random around a fixed point). I don't th…

> If you wouldn't bet against the climate getting warmer, then I don't think you have any place calling yourself a "climate change skeptic"

The climate isn't getting warmer or colder just because next year's temperature does.

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