Climate Models versus Reality: Part I:
A 2011 study in the Journal of Forecasting took the same data set and compared model predictions against a “random walk” alternative, consisting simply of using the last period’s value in each location as the forecast for the next period’s value in that location. The test measures the sum of errors relative to the random walk. A perfect model gets a score of zero, meaning it made no errors. A model that does no better than a random walk gets a score of 1. A model receiving a score above 1 did worse than uninformed guesses. Simple statistical forecast models that have no climatology or physics in them typically got scores between 0.8 and 1, indicating slight improvements on the random walk, though in some cases their scores went as high as 1.8.
The climate models, by contrast, got scores ranging from 2.4 to 3.7, indicating a total failure to provide valid forecast information at the regional level, even on long time scales. The authors commented: “This implies that the current [climate] models are ill-suited to localised decadal predictions, even though they are used as inputs for policy making.”
Indeed. Nor is the problem confined just to a few models. In a 2010 paper I and a coauthor10 looked at how well an average formed from all 23 climate models used for the 2007 IPCC report did at explaining the spatial pattern of temperature trends on land after 1979, compared to a rival model that all the experts keep telling me should have no explanatory power at all: the regional pattern of socioeconomic growth. Any effects from those factors, I have been told many times, are removed from the climate data before it is published. And yet I keep finding the socioeconomic patterns do a very good job of explaining the patterns of temperature trends over land. In our 2010 paper we showed that the climate models, averaged together, do very poorly, while the socioeconomic data does quite well.
I accept that there’s been some warming. I’m not convinced that it’s due to anthropogenic factors (and the long lull since 1998 has cast doubt on that for a lot of people). All of the scary scenarios are based on computer models, which aren’t science.
More to the point, all of the solutions to what we should do about the scary scenarios are public policy, which sure as heck isn’t science. Even if the scientists could tell us what was going to happen, which is dubious to begin with, they couldn’t tell us what we should do about it.
What to do about it gets into questions of values. Should we stop development, quit building roads, limit how much electricity people can use? Those are loaded political questions. Scientists are no better equipped to answer those questions than anyone else. Science can inform public policy, but it can’t control it.
RSS Posts Feed
Speak of the devil:
http://www.theregister.co.uk/2012/06/25/antarctic_ice_not_melting/
If you know that computer models are not science, then why are you quoting heavily from a report that treats them as if they are science? Assessing global climate models based on how well they predict regional trends is a rigged game. That is not what they are designed to do. They are designed to model carbon and water vapor cycles, oceanic processes and that sort of thing, on a global and not a regional scale. They are global models because calibrating them to regional resolution is orders of magnitude harder than settling for global resolution.
Researchers have tried to ratchet the models down to regional resolution because knowing which areas might become wetter or drier would be great information to have, but at this point that is merely a learning exercise to try and understand whether and how it can even be done. Those modelers know perfectly well that they are not generating useful predictions. It’s McKitrick who is making the claim that the predictions are intended to be accurate, and he is doing so disingenuously so that he can knock down a strawman.
Your whole frame of reference here is also disingenuous. Scientists are not trying to explain a warming trend; they are trying to understand what emissions are doing to the planet. Warming is a given. CO2 levels have just crested 400ppm, and we know from rigorous, repeatable science that carbon gases trap more heat than they reflect. So we know with certainty that the planet is warming due to our emissions. What we don’t know is how much of that heat will be absorbed by the oceans vs. the atmosphere, dissipated through storm systems, etc. Likewise, we don’t know how much carbon the oceans and forests and soils can absorb. Our knowledge of these processes is growing ever more precise, and modelling is a big part of that. We make climate models because a virtual planet is the only tool we can create for understanding the actual Earth.
Scientists know those models are not yet useful for making regional predictions, but that does not keep guys like McKitrick from packaging that message as a discovery and selling it to wealthy interests who are always happy to put Denialist Chow in your bowl.
“CO2 levels have just crested 400ppm, and we know from rigorous, repeatable science that carbon gases trap more heat than they reflect.”
Right. Greenhouse effect. Got it. But is that effect swamped by other things, is there is a plateau, et cetera, ad naseum. You know the counter arguments. And I get that the models are trying to figure that out.
But in the end they’re just models, filled with assumptions and fudge factors. And there isn’t just one model. There are multiple, competing models with different predictions. They can’t be all right.
And in the end the models are only as good as their predictive powers. All of those models failed to predict the lull in warming since 1998. Why? If the models were any good why didn’t they see the long pause in warming coming? Is the basic assumption about the relationship between greenhouse gases and warming wrong?
There is no “lull in warming since 1998.” That’s more packaged Denialist Chow. The two hottest years on record are 2010 and 2005, and we just broke the record for hottest 12-month period on record. 1998 was anomalous due to an exceptionally strong El Nino phase, and using that year as a baseline reference point is dishonest. Observational data for oceanic heat content, running 11-year averages of surface air temperatures and other measures that reveal long-term trends show consistent and persistent warming.
And the relationship between greenhouse gases and warming is not an assumption. It’s physics. It has been studied and measured with precision.
Hey, don’t listen to me saying there’s been a lull. Listen to global warming supporters say there’s been a lull.
Environmental Guru and Inventor of the “Gaia” Theory of the Living Earth James Lovelock: I Was a Climate Change “Alarmist” And So Is Al Gore:
“The world has not warmed up very much since the millennium. Twelve years is a reasonable time… it (the temperature) has stayed almost constant, whereas it should have been rising — carbon dioxide is rising, no question about that,” he added.
Climategate U-turn as scientist at centre of row admits: There has been no global warming since 1995 though reading deeper it’s no “statistically significant warming”.
You’re complaining about a lack of science? Vague quotes from two scatterbrained Brits hardly count as data, much less science. Here’s some data compiled at Skeptical Science:
Earth’s total heat content by year
11-year moving averages
and a fun one!
Phil Jones may in fact be a scatterbrained Brit, but until recently he was the director of the East Anglia Climatic Research Unit. So there’s that.
You want graphs? I’ve got graphs, too.
Here’s a graph from Peter Gleick. I know you can trust him, because he fabricated documents to embarrass the Heartland Institute, so his global warming bona fides are second to none.
http://blogs-images.forbes.com/petergleick/files/2012/02/GlobalT-Decade.png
Looks like a pretty darned flat line to me, with the slightest of slopes upwards. Compared that to his other graphs of warming in previous decades and clearly global warming is in fact in a lull compared to the rapid upward slopes of earlier decades. Greenhouse gas concentrations are still on a rapid upward slope, so what happened?
http://www.forbes.com/sites/petergleick/2012/02/05/global-warming-has-stopped-how-to-fool-people-using-cherry-picked-climate-data/
Gleick’s article is an attempt to refute the “global warming has stopped” argument, but it’s incredibly weak. It falls back to looking at these longer time periods, which have nothing to do with the last 15 years.
Gleick also uses the “warmest decade” argument. Saying that the aughts were the “warmest decade” is like saying that a child is going to keep growing in his thirties because his twenties were his “tallest decade.”
The vast majority of excess heat is absorbed into the oceans, where the warming trend is consistent and apparent. So the main answer to your question is that you are looking in the wrong place. The warming signal is strongest in the ocean.
Only a fraction of the excess heat stays in the atmosphere, so the warming trend there is more variable. Heat in the atmosphere can be dissipated by storm systems, where it manifests as intensification of weather patterns. The warming signal in surface temperature observations can be masked by weather events, which convert the heat to thermodynamically useful forms like convection columns or tornadoes. Heat that gets used up by storms is no longer available to do things like nudge thermometers to higher readings.
The possibility exists as well of the heat in the oceans being put to work thermodynamically. Researchers worry that we may eventually see ocean currents shift or experience a massive thermal inversion, events that would have huge impacts on fisheries, shipping and atmospheric climate. But, hey, better to pretend such risks do not exist than to let markets deal with them, right?