A new system for studying the effects of climate change

I've talked here before about how difficult it is to attribute any individual climactic catastrophe to climate change, particularly in the short term. Patterns and trends can be said to link to a rise in global temperature, which is linked to a rise in greenhouse gas concentrations in the atmosphere. But a heatwave, or a tornado, or a flood? How can you say which would have happened without a rising global temperature, and which wouldn't?

Some German researchers are trying to make that process a little easier, using a computer model and a whole lot of probability power. They published a paper about this method recently, using their system to estimate an 80% likelihood that the 2010 Russian heatwave was the result of climate change. Wired's Brandon Keim explains how the system works:

The new method, described by Rahmstorf and Potsdam geophysicist Dim Coumou in an Oct. 25 Proceedings of the National Academy of Sciences study, relies on a computational approach called Monte Carlo modeling. Named for that city’s famous casinos, it’s a tool for investigating tricky, probabilistic processes involving both defined and random influences: Make a model, run it enough times, and trends emerge.

“If you roll dice only once, it doesn’t tell you anything about probabilities,” said Rahmstorf. “Roll them 100,000 times, and afterwards I can say, on average, how many times I’ll roll a six.”

Rahmstorf and Comou’s “dice” were a simulation made from a century of average July temperatures in Moscow. These provided a baseline temperature trend. Parameters for random variability came from the extent to which each individual July was warmer or cooler than usual.

After running the simulation 100,000 times, “we could see how many times we got an extreme temperature like the one in 2010,” said Rahmstorf. After that, the researchers ran a simulation that didn’t include the warming trend, then compared the results.

“For every five new records observed in the last few years, one would happen without climate change. An additional four happen with climate change,” said Rahmstorf. “There’s an 80 percent probability” that climate change produced the Russian heat wave.


  1. I don’t see a lot of value to correlating climate change with weather events, from a PR standpoint.  All that does is make it easier for people to say, “if global warming is real then why is it so cold today?” 

    However I understand that it is not science’s job to appeal to the masses.  It’s science’s job to find answers (or more specifically, to find when answers are incorrect).

  2. Just about every board discussing climate change has comments of the form “Computer models can’t even determine the exact and precise temperature that it will be tomorrow at 12:48:13.0838 hrs in downtown Boise, Idaho so how can they predict the temperatures of the whole world years from now?” These are from people who don’t know the meaning of the word “Stochastic”: or pretty much any other scientific word.

    Using similar “logic” we see that cigarette smoking poses no health hazards because we don’t have computer models forecasting the exact state of every cell in your body next Tuesday.  After all, no one’s ever actually seen some molecules from a cigarette invade a specific cell and cause cancer.  The cancer could have been from any number of sources!

    Not surprising to see the fallacy in both areas since the same PR firms that told us how harmless smoking was are now spending hundreds of millions of dollars telling us how harmless greenhouse gases are.

    BTW – The “Bad Computer Models” argument is a Straw Man argument since Global Warming theories were never based mainly on computer models.  Physical chemistry and the laws of thermodynamics are far more central.

  3. I don’t know what new methods they’ve developed, but using Monte Carlo statistical methods with models to find trends and narrow error ranges has been standard practice for years.  I suspect they are saying they have a new model, and are using Monte Carlo to help evaluate the results of that model.

  4. I would like to see an algorithm that would calculate the metric tonnage of evidence necessary to change a climate change skeptic’s mind.  Get on it, science. 

  5. There are many problems with computer modeling of the climate. For instance, the effects of cloud cover is a positive feedback in some models, negative in others. If this fundamental climate phenomenon is still in question, you have to wonder what else is an issue, and results surely need to be taken with a grain of salt.

  6. It is an immensely complicated calculation, to determine exactly where a bullet will hit once fired.  You need to gauge distance, altitude, gravity, dozens of biological elements from the person holding the gun, imperfections in the weapon’s manufacturing, the exact weight and structure of the projectile, the amount of propellant in the shell, the integrity and density of the target, wind speed and direction, the curvature of the earth, each of those in turn determined by dozens of other variables.

    Therefore, bullets do not exist.

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