Friday, August 29, 2014

Why trust climate models?

Thanks to a tip from Sou over at HotWhopper, I came across an excellent introduction to climate models that's definitely worth sharing... {and it'll make a nice break from the crazy-makers I've been featuring over here} because in the process I became familiar with an impressive young rationalist.  Scott Johnson who's a hydrogeologist, geoscience educator and freelance science writer and has a blog at  

I thought he did a good job of explaining some of the details and facts of climate models and how they are used to inform scientific learning.  

Since Climate Models are constantly being misrepresented and derided based on false claims and deliberate misperceptions, this is an article worth becoming familiar with.  I'm hoping to get permission to repost more highlights from the text in the future, right now I'll limit myself to the introduction and one paragraph from the closing and short descriptions of the sections of his article.

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Why trust climate models? 
It’s a matter of simple science

How climate scientists test, test again, and use their simulation tools.

It starts out:

¶1 " Talk to someone who rejects the conclusions of climate science and you’ll likely hear some variation of the following: “That’s all based on models, and you can make a model say anything you want.” Often, they'll suggest the models don't even have a solid foundation of data to work with—garbage in, garbage out, as the old programming adage goes. But how many of us (anywhere on the opinion spectrum) really know enough about what goes into a climate model to judge what comes out?
¶2  Climate models are used to generate projections showing the consequences of various courses of action, so they are relevant to discussions about public policy. Of course, being relevant to public policy also makes a thing vulnerable to the indiscriminate cannons on the foul battlefield of politics.
¶3  Skepticism is certainly not an unreasonable response when first exposed to the concept of a climate model. But skepticism means examining the evidence before making up one’s mind. If anyone has scrutinized the workings of climate models, it’s climate scientists—and they are confident that, just as in other fields, their models are useful scientific tools."
It’s a model, just not the fierce kind (¶4-¶13)
{Touches on equations, comparing them with earth observations, explaining how various components of the climate present challenge and how dealing with those challenges helps explore the complexities of climate.  Andrew Weaver, a researcher at the University of Victoria, described the model evaluation process in three general phases.}

Coding the climate (¶14-¶22)
{Get's into questions of verification and validation of climate models, and Steve Easterbrook's review of climate modeling groups and what he found.}

Firing up the wayback machine (¶23-26)
{Looking at the work of Bette Otto-Bliesner at the National Center for Atmospheric Research on their Community Earth System Model, researching past climate.  Taking model simulations one step further by mimicking the creation of proxy records such as ocean sediments and comparing that with actual depositions.}

Setting the bar (¶27-¶30)
{Then, on to Gavin Schmidt a climate researcher at the NASA Goddard Institue for Space Studies, who evaluates climate models and studies issues with comparisons between models and observations, "Improving the model means better simulating physical processes"}

Why so cirrus? (¶31-¶35)
{Next up is Tony Del Genio, also from at the NASA Goddard Institute for Space Studies who studies complex cloud modeling.  Looking for weakness, and improving next-generation versions: "We then run the model with the new process in it and we look for two things: whether the process as we have portrayed it behaves the way it does in the real world and whether or not it makes some aspect of the model's climate more realistic. We do this by comparison to observations, either field experiment, satellite, or surface remote sensing observations, or by comparing to fine-scale models that simulate individual cloud systems." }

Ice, on the rocks (¶36-¶41)
{Finishing with Richard Alley the well know Penn State glaciologist who's an expert on ice cores and modeling ancient climate discussing his work.}

Community service (¶42-¶47)
{Comparing climate models with each other, the “model intercomparison projects,” including ones focused on atmospheric models, paleoclimate simulations, or geoengineering research. Explains what the Coupled Model Intercomparison Project (CMIP) is about.}

No crystal ball—but no magic 8 ball, either (¶48-¶53)
¶49  "But climate scientists know models are just scientific tools—nothing more. In studying the practices of climate modeling groups, Steve Easterbrook saw this firsthand. g he said. "The models are perfectly suited for this. They get the basic physical processes right but often throw up surprises in the complex interactions between different parts of the Earth system. It is in these areas where the scientific knowledge is weakest. So the models help guide the scientific process." 

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