Real Climate

[speedy 0]

I spent a few weeks looking at realclimate.org and those guys really scare me.
They are so hooked on computer models.
I program stuff all day for a living, but predicting the climate with a computer
GIGO

Dave

Fallschirmsport Marl

[billvon 3,119]

>I program stuff all day for a living, but predicting the climate with a computer . . .

Yeah, next thing you know, they'll be predicting how airplanes fly with computer models! That's what they did with the Boeing 767 - and every single one of them crashed. (At least I think they did.)

Well, at least they're not predicting weather using computer models. That would never work.

[kallend 2,150]

Quote

>I program stuff all day for a living, but predicting the climate with a computer . . .

Yeah, next thing you know, they'll be predicting how airplanes fly with computer models! That's what they did with the Boeing 767 - and every single one of them crashed. (At least I think they did.)

Same with the B2 and F22.

...

The only sure way to survive a canopy collision is not to have one.

[ExAFO 0]

F-22: an aircraft for an obsolete mission...and the cause of thousands of hardworking servicemembers being RIF'ed...

Illinois needs a CCW Law. NOW.

[jakee 1,595]

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F-22: an aircraft for an obsolete mission...and the cause of thousands of hardworking servicemembers being RIF'ed...

All because of long term climate computer models.

For shame

Do you want to have an ideagasm?

[speedy 0]

Quote

Well, at least they're not predicting weather using computer models. That would never work.

Yeah, you are right, it doesn't seem to work that well at all. Yesterday they were predicting rain. 2 hours before the rain was due to arrive they changed their minds and said no rain.

Its a bit like the guys at real climate, they predict something, and when the observations don't tally, they tweek the model until it matches the observations. The model works for a while until the next observation screws things up again.

Don't ge me wrong, I am not saying they should not be using computer models, I am just surprised that they lend so much weight to the models.

Also, I am sure both you and Kallend understand the huge difference between modelling the climate and modelling how an aircraft flies through the air.

Dave

Fallschirmsport Marl

[philh 0]

Well there is not a consensus on one model and the majority of climatolgists are aware that modelling is a difficult process and what the uncertainties are . That is why there are many models considered and they are all tested with real data. That is why the IPCC publishess a range of different predictions for future climate. The unfortunate thing is all the different models and all the different assumptions say the same thing, that the Earth is warming.This is based on well understood physics. What is not known are two primary inputs in particular 1) cloud feedback and 2) Co2 emmissions in the future. The lower estaimates by the IPCC assume we are going to lower Co2 emmisions.

The models say the same thing to different degrees, the latest IPCC forecast is beteen 1.1 and 6.4 degree warming for the next 100 years. Now 1.1 probably wont be that serious, but 6.4 will be very serious. Yes its possible that all the models are wrong, but thats true on the upside as well as the down. We have act to act on the best information we have and that implies tackling the climate change problem not sitting on our butts.

[vpozzoli 0]

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Its a bit like the guys at real climate, they predict something, and when the observations don't tally, they tweek the model until it matches the observations. The model works for a while until the next observation screws things up again.

I believe what you're describing is commonly referred to as "the scientific process"?
Cheers,

Vale

[billvon 3,119]

>Yesterday they were predicting rain. 2 hours before the rain was due
>to arrive they changed their minds and said no rain.

Right, and sometimes a two pack a day smoker lives to age 85. Doesn't mean that smoking is good for you. The vast majority of the time, weather forecasts nowadays are pretty dang accurate.

>Its a bit like the guys at real climate, they predict something, and
>when the observations don't tally, they tweek the model until it matches
>the observations. The model works for a while until the next observation
>screws things up again.

And every time you go through that process you get closer to an accurate predictive model.

>Also, I am sure both you and Kallend understand the huge difference
>between modelling the climate and modelling how an aircraft flies through
>the air.

Both are inherently insoluble problems; both are amenable to numerical approximations that USUALLY work. To put it another way, aerodynamic simulations are accurate enough that you can design an airplane, build it and have test pilots take it up for its first flight and be reasonably sure it won't crash. They are not accurate enough to let you skip those test flights.

[NCclimber 0]

Quote

>Yesterday they were predicting rain. 2 hours before the rain was due
>to arrive they changed their minds and said no rain.

Right, and sometimes a two pack a day smoker lives to age 85. Doesn't mean that smoking is good for you. The vast majority of the time, weather forecasts nowadays are pretty dang accurate.

Are you saying weather forecasters get it wrong on the same frequency as two pack a day smokers live to age 85?

I didn't know 25 percent of two pack a day smokers live to age 85.

[speedy 0]

"For the global mean [temperature], the most trusted models produce a value of roughly 14 Celsius, i.e. 57.2 F, but it may easily be anywhere between 56 and 58 F and regionally, let alone locally, the situation is even worse." The Elusive Absolute Surface Air Temperature (SAT) (NASA Goddard Institute for Space Studies)

"The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change." -- James Hansen, "Climate forcings in the Industrial era", PNAS, Vol. 95, Issue 22, 12753-12758, October 27, 1998.

"In sum, a strategy must recognize what is possible. In climate research and modeling, we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that the prediction of a specific future climate state is not possible." -- Final chapter, Draft TAR 2000 (Third Assessment Report), IPCC (Intergovernmental Panel on Climate Change).

"Because there is considerable uncertainty in current understanding of how the climate system varies naturally and reacts to emissions of greenhouse gases and aerosols, current estimates of the magnitude of future warming should be regarded as tentative and subject to future adjustments (either upward or downward)." -- Climate Change Science - An Analysis Of Some Key Questions, p1 (Committee on the Science of Climate Change, National Research Council) ISBN 0-309-07574-2.

"Reducing the wide range of uncertainty inherent in current model predictions of global climate change will require major advances in understanding and modeling of both (1) the factors that determine atmospheric concentrations of greenhouse gases and aerosols, and (2) the so-called “feedbacks” that determine the sensitivity of the climate system to a prescribed increase in greenhouse gases." -- Climate Change Science - An Analysis Of Some Key Questions, p1 (Committee on the Science of Climate Change, National Research Council) ISBN 0-309-07574-2.

"Because climate is uncontrollable . . . the models are the only available experimental laboratory for climate. . . . However, climate models are imperfect. Their simulation skill is limited by uncertainties in their formulation, the limited size of their calculations, and the difficulty of interpreting their answers that exhibit almost as much complexity as in nature." -- Climate Change Science - An Analysis Of Some Key Questions, p15 (Committee on the Science of Climate Change, National Research Council) ISBN 0-309-07574-2.

So, how far have we progressed in the modeling game over the last decade? Not very far at all. In a pending paper, Dangerous human-made interference with climate: a GISS modelE study we find the following text regarding GISS modelE, fairly described as a state-of-the-art climate model:

2.4 Principal Model Deficiencies

ModelE (2006) compares the atmospheric model climatology with observations. Model shortcomings include ~25% regional deficiency of summer stratus cloud cover off the west coast of the continents with resulting excessive absorption of solar radiation by as much as 50 W/m 2 , deficiency in absorbed solar radiation and net radiation over other tropical regions by typically 20 W/m 2 , sea level pressure too high by 4-8 hPa in the winter in the Arctic and 2-4 hPa too low in all seasons in the tropics, ~20% deficiency of rainfall over the Amazon basin, ~25% deficiency in summer cloud cover in the western United States and central Asia with a corresponding ~5 ° C excessive summer warmth in these regions. In addition to the inaccuracies in the simulated climatology, another shortcoming of the atmospheric model for climate change studies is the absence of a gravity wave representation, as noted above, which may affect the nature of interactions between the troposphere and stratosphere. The stratospheric variability is less than observed, as shown by analysis of the present 20-layer 4°×5° atmospheric model by J. Perlwitz (personal communication). In a 50-year control run Perlwitz finds that the interannual variability of seasonal mean temperature in the stratosphere maximizes in the region of the subpolar jet streams at realistic values, but the model produces only six sudden stratospheric warmings (SSWs) in 50 years, compared with about one every two years in the real world.

The coarse resolution Russell ocean model has realistic overturning rates and inter-ocean transports (Sun and Bleck, 2006), but tropical SST has less east-west contrast than observed and the model yields only slight El Nino-like variability (Fig. 17, Efficacy , 2005). Also the Southern Ocean is too well-mixed near Antarctica (Liu et al., 2003), deep water production in the North Atlantic Ocean does not go deep enough, and some deep-water formation occurs in the Sea of Okhotsk region, probably because of unrealistically small freshwater input there in the model III version of modelE. Global sea ice cover is realistic, but this is achieved with too much sea ice in the Northern Hemisphere and too little sea ice in the Southern Hemisphere, and the seasonal cycle of sea ice is too damped with too much ice remaining in the Arctic summer, which may affect the nature and distribution of sea ice climate feedbacks.

Despite these model limitations, in IPCC model inter-comparisons the model used for the simulations reported here, i.e, modelE with the Russell ocean, fares about as well as the typical global model in the verisimilitude of its climatology. Comparisons so far include the ocean’s thermohaline circulation (Sun and Bleck, 2006), the ocean’s heat uptake (Forest et al., 2006), the atmosphere’s annular variability and response to forcings (Miller et al., 2006), and radiative forcing calculations (Collins et al., 2006). The ability of the GISS model to match climatology, compared with other models, varies from being better than average on some fields (radiation quantities, upper tropospheric temperature) to poorer than average on others (stationary wave activity, sea level pressure).

Dave

Fallschirmsport Marl