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Climate Change 

July 24, 2007

Models! Pt. I

Warning: Long post…

Okay, let’s talk about models, uncertainty, feedbacks, prediction, etc., etc. Models are fundamental tools in modern science. They are very important to our understanding of the reality and impacts of climate change, as well as the potential solutions. So what is a model? A scientific model is a simplified view of some aspect of the natural world. A good scientific model is a well-crafted balance between simplicity and complexity. Too simple a model ignores knowledge that may be critical to our problem. Limits to model complexity, on the other hand, are usually set by limited knowledge of the problem, or how all the bits of knowledge fit together, or how to actually make those bits work together when we know that they should, or most commonly, the model becomes so specific that it fails to be useful for general inference.

An example of good models is the family of General Circulation Models (GCMs), those mathematical descriptions of how geophysical fluids (atmosphere and oceans) flow about the Earth. We’ve had atmospheric and oceanographic GCMs for decades, but the really cool ones are the coupled atmosphere-ocean GCMs. Today we use these models to predict what global temperatures (among other things) might be in the future under different conditions (e.g. different levels of carbon dioxide emissions). Generally, a GCM divides up the Earth’s surface into a grid, and the atmosphere into cuboids, inputs known or speculative data for each grid or cuboid (a “cell”), and using the laws of physics (thermodynamics, hydrodynamics, etc.), sets the whole thing flowing. The model is run for N number of time stps, the properties of each cell being updated at each step. Eventually, the model is stopped and the result is a time (and space) series of global climate history or predictions.

Is this a big deal? Oh, very much so. At the very least, we have to keep track of what every cell looks like. A trivial GCM might look something like this:trivial_model.jpg
We plug a CO2 concentration into each cell and a formula produces a temperature. You could do this on a spreadsheet (such as OO_Calc), with each row a cell on the Earth’s surface, and each column a time step. The more cells you have, the more finely you’ve divided up the surface, and the higher the resolution of your model! If you really wanted to do this right, you’d need a big machine, like this one. Now imagine that the cells are not independent of each other, but that they can exchange properties such as CO2 or temperature. Certainly a region of high CO2 emissions is likely to spill some over to its neighbours (Ahem nations: you know who I’m talking about). Our model might now look like this:complex_model.jpg
A bit more “complex”; the model now comprises numerous interacting parts. (By the way, if you figure out how to run this one on your spreadsheet, let me know; you’ll probably need a bigger machine).

Finally, consider that not only cells, but the processes in cells might interact. For example, increasing CO2 leads to warmer air temperatures over Siberia, where the permafrost in turn begins to thaw, which in turn causes decomposition of buried organic materials, which in turn causes the release of methane gas, which in turn adds to the greenhouse effect in the atmosphere and, on the short-term adds to temperature increase, and on the long-term is converted to CO2 thus further adding to the model input. Whew. Our model might now look like this:feedback_model.jpg
Now that’s feedback! In this case a positive feedback, because it amplifies the processes.

Okay, if your head now hurts, just dim your monitor and don’t blame me (or any other modelers); the world is as the world is. More next time.

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Filed under: Climate Change — Peter @ 9:30 pm

July 14, 2007

Grapes of Wrath

roop_pict0008.jpgHere it is, the long awaited return to the topic of “uncertainty”! But we won’t deal with technical details of feedbacks and models yet. Instead, let’s approach it with discussion of a topic fundamental to much of human civilization–wine. The BBC ran a short story online yesterday that talked about the impact of climate change on the wine industry. The National Academy of Sciences of the US predicts that by the end of the century, 81% of current wine-producing regions worldwide could be affected negatively by climate change. Some of the negative impacts would be increasingly hot summers, extended periods of heat, and increasingly dry conditions. This is alarming for many premier regions, such as Spain, where things are expected to heat up in the not too distant future. Some regions, such as Bordeaux, could benefit on the short-term from a wee bit more consistency in their summers. But ultimately, prime growing conditions would shift north. Personally, I’m more of a single malt and beer lover. Wine lovers, please do not be offended; my definition of what constitutes good beer is exceedingly narrow, and as long grape production does not interfere with barley fields in Scotland, we’ll have no issues with each other.

Anyway, what interested me most about the BBC’s article were comments made by some growers right here in California’s Napa Valley. The Valley is one of those places that is just perfectly suited to grape growing. The growers in the article, while acknowledging the growing threat of climate change, suggest that it could be beneficial for Napa, or that Napa will escape the worst of it. The reason, they claim, is that as inland California (the Central Valley) heats up, as it does this time of year, the rising hot air pulls in cool air from the cool Pacific Ocean. True; this morning in Berkeley was quite foggy and cool. Therefore, as things heat up this century, they expect more of this microclimate cooling.

The line of argument would be fine, if we lived in a poorly connected world without feedbacks, and we plan on the short-term. To understand this at the simplest level, consider that ocean temperature is increasing along with atmospheric temperature (albeit more slowly). The moderating and cooling effects of the coastal eastern Pacific will therefore diminish as ocean temperatures increase. Water and precipitation cycles will also change, since evaporation from the oceans, and tropical forests, are major players in atmospheric water movement. A more complicated feedback could involve potential changes in ocean circulation as the oceans warm, and there is less production of cold water in polar regions, the engines of global ocean circulation. The impacts here are less well understood, but probably will mean less productive coastal fisheries, changes in coastal climates and precipitation, and even desertification. The economic impacts on these important regions globally could result in greater consumption of premium beer (cheaper) and reduced wine consumption (pricier). It’s all connected. Will there be any positive impacts of climate change? I keep looking for them, and there should be for some members of the natural world, but for most, I don’t think so. And I really can’t find many for humans. The Napa farmers do go on in the article to articulate their impressive conversions to organic farming, and great concern for global climate change in general. And, in the end, if more dust bowls produce more Steinbecks, that wouldn’t be bad.

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Filed under: Climate Change — Peter @ 11:08 am

July 7, 2007

Oh The Absurdity

I’m sitting here watching The Police perform for the Live Earth concert. Cool. I am a hard rock/heavy metal/progressive rock/punk/reggae child of the 1970s, and am loving this (no matter how Stingified). I remember Live Aid, and Farm Aid, and the awareness-raising aftermaths of those events, however fleeting they were. Today’s series of concerts is yet the latest of the generation-expressing genre to speak out and about the concerns of a changing world (I have a friend who was at Woodstock; he swears!). Yet the critics have been out in full force: “But critics have said it was hypocritical for performers who fly around the world on tours to push the message of cutting down on carbon emissions.” Gets even better. In a rare moment, I’ll criticize. This just in from the Climate Change Outreach Information Network, regarding their alternative to Live Earth, the Alive Earth internet concerts: “And, because this concert will be on the web, there will be no executive jets, no cars, no floodlighting, no air conditioning, no paper, no plastic, no cans. Truly low carbon.” Okay, true. But, listen up folks, computers do not run on fairy dust. It’s all about choices. I am not willing to give up my computers because of irresponsible Detroit automakers and the consumers who support them, nor because industrialized nations will not build cleaner power plants. And I am certainly not willing to give up my music, nor the musicians who take their art to all corners of the planet. Exactly what sort of planet do we wish for ourselves? We have to acknowledge, accept, and solve the problem of climate change for the preservation of both the natural world, and the human world that we love. And we have to do it together. A young(er) scientist asked me the other day why I’m an optimist about our planet’s future. I am because I see the growing awareness, expression, political and economic activation; and because I get to interact with young scientists and other bright minds who ask me such questions. And if we can’t do it, let’s nevertheless give it our best, and most dignified shot. It is, after all, better to burn out than to fade away.

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Filed under: Climate Change — Peter @ 11:16 pm

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