Tag Archives: fourier

Models and Books

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Working as a summer student continues to be rewarding. I get to spend all day reading interesting things and playing with scientific software. What a great deal!

Over the weekend, I ran the “Global Warming_01” simulation from EdGCM, which is an old climate model from NASA with a graphical user interface. Strangely, they don’t support Linux, as their target audience is educators – I doubt there are very many high school teachers running open-source operating systems! So I ran the Windows version on my laptop, and it took about 36 hours. It all felt very authentic.

Unfortunately, as their Windows 7 support is fairly new, there were some bugs in the output. It refused to give me any maps at all! The terminal popped up for a few seconds, but it didn’t output any files. All I could get were zonal averages (and then only from January-March) and time series. Also, for some reason, none of the time series graphs had units on the Y axis. Anyway, here are some I found interesting:

CO2 concentrations increase linearly from 1958 to 2000, and then exponentially until 2100, with a doubling of CO2 (with respect to 1958) around 2062. (This data was output as a spreadsheet, and I got Excel to generate the graph, so it looks nicer than the others.)

Global cloud cover held steady until around 2070, when it decreased. I can’t figure out why this would be, as the water vapour content of the air should be increasing with warming – wouldn’t there be more clouds forming, not less?

Global precipitation increased, as I expected. This is an instance where I wish the maps would have worked, because it would be neat to look at how precipitation amount varied by location. I’ve been pretty interested in subtropical drought recently.

Albedo decreased about 1% – a nice example of the ice-albedo feedback (I presume) in action.

I also ran a simulation of the Last Glacial Maximum, from 21 thousand years ago. This run was much quicker than the first, as (since it was modeling a stable climate) it only simulated a decade, rather than 150 years. It took a few hours, and the same bugs in output were apparent. Time series graphs are less useful when studying stable conditions, but I found the albedo graph interesting:

Up a few percent from modern values, as expected.

It’s fairly expensive to purchase a licence for EdGCM, but they offer a free 30-day trial that I would recommend. I expect that it would run better on a  Mac, as that’s what they do most of the software development and testing on.

Now that I’ve played around with EdGCM, I’m working on porting CESM to a Linux machine. There’s been trial and error at every step, but everything went pretty smoothly until I reached the “build” phase, which requires the user to edit some of the scripts to suit the local machine (step 3 of the user guide). I’m still pretty new to Linux, so I’m having trouble working out the correct program paths, environment variables, modules, and so on. Oh well, the more difficult it is to get working, the more exciting it is when success finally comes!

I am also doing lots of background reading, as my project for the summer will probably be “some sort of written something-or-other” about climate models. Steve has a great collection of books about climate change, and keeps handing me interesting things to read. I’m really enjoying The Warming Papers, edited by David Archer and Ray Pierrehumbert. The book is a collection of landmark papers in climate science, with commentary from the editors. It’s pretty neat to read all the great works – from Fourier to Broecker to Hansen – in one place. Next on my list is A Vast Machine by Paul Edwards, which I’m very excited about.

A quick question, unrelated to my work – why do thunderstorms tend to happen at night? Perhaps it’s just a fluke, but we’ve had a lot of them recently, none of which have been in the daytime. Thoughts?

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The Discovery of Global Warming

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A common remark I make about climate change books I like is that “it wasn’t like a textbook”. I like non-fiction books that I can carry around and read cover-to-cover just like I would a novel. I like them to draw me in and catch my interest as if they were a suspenseful PD James or just a comfortable Maeve Binchy.

The Discovery of Global Warming, by Spencer Weart, had all of these qualities and more: It contained as much information as a textbook, even if it didn’t read like one. That, I think, is the benefit of science history. It can be written in a way that is compelling as fiction, but it’s all true.

I think I will place this book near the top of my list of resources for concerned citizens who are looking for more information on climate change. It is so helpful because, instead of saying “scientists are confident that humans are causing the Earth to warm”, it traces back through history and follows this discovery all the way through, from Fourier to the AR4. We see the top of the credibility spectrum in action, and examine exactly where the conclusions of the scientific community came from.

There are lots of great details in this book to sink your teeth into. How did the Cold War pave the way for much of our knowledge about the atmosphere? Why does chaos theory apply to weather models much more than climate models? And, of course, my very favourite – the 1970s aerosol debate. How did scientists realize that the warming force of greenhouse gases would overpower the cooling force of aerosols, long before the warming was actually observed?

All of this is written in an incredibly elegant and engaging tone. Weart’s style of writing somehow reminds me of Sir Arthur Conan Doyle in The Lost World – succinct characterization, unintended (or just well-hidden) satire, a calm detachment from the story that somehow makes it all the more fascinating.

I read the “Revised and Expanded Edition”, so I’m not sure if all editions of The Discovery of Global Warming contain all the extras in the back: a timeline, an index, and a chapter entitled “Reflections” that is full of Weart’s musings about risk management and science communication. “Unlike, say, the orbits of planets,” he writes, “the climate in the future actually does depend in part on what we think about it. For what we think will determine what we do.”

A tangible alternative to the more comprehensive online version (really, who wants to read a book by navigating a web of links and scrolling through chapters on a computer screen?), The Discovery of Global Warming is worth every cent, and every minute of your time it takes to read it. I look forward to future volumes as this story continues to unfold.