August 27, 2010

This Week's Finds in Mathematical Physics (Week 301)

John Baez

The first 300 issues of This Week's Finds were devoted to the beauty of math and physics. Now I want to bite off a bigger chunk of reality. I want to talk about all sorts of things, but especially how scientists can help save the planet. I'll start by interviewing some scientists with different views on the challenges we face — including some who started out in other fields, because I'm trying to make that transition myself.

By the way: I know "save the planet" sounds pompous. As George Carlin joked: "Save the planet? There's nothing wrong with the planet. The planet is fine. The people are screwed." (He actually put it a bit more colorfully.)

But I believe it's more accurate when he says:

I think, to be fair, the planet probably sees us as a mild threat. Something to be dealt with. And I am sure the planet will defend itself in the manner of a large organism, like a beehive or an ant colony, and muster a defense.

I think we're annoying the biosphere. I'd like us to become less annoying, both for its sake and our own. I actually considered using the slogan how scientists can help humans be less annoying — but my advertising agency ran a focus group, and they picked how scientists can help save the planet.

Besides interviewing people, I want to talk about where we stand on various issues, and what scientists can do. It's a very large task, so I'm really hoping lots of you reading this will help out. You can explain stuff, correct mistakes, and point me to good sources of information. With a lot of help from Andrew Stacey, I'm starting a wiki where we can collect these pointers. I'm hoping it will grow into something interesting.

But today I'll start with a brief overview, just to get things rolling.

In case you haven't noticed: we're heading for trouble in a number of ways. Our last two centuries were dominated by rapid technology change and a rapidly soaring population:

The population is still climbing fast, though the percentage increase per year is dropping. Energy consumption per capita is also rising. So, from 1980 to 2007 the world-wide usage of power soared from 10 to 16 terawatts.

96% of this power now comes from fossil fuels. So, we're putting huge amounts of carbon dioxide into the air: 30 billion metric tons in 2007. So, the carbon dioxide concentration of the atmosphere is rising at a rapid clip: from about 290 parts per million before the industrial revolution, to about 370 in the year 2000, to about 390 now:


As you'd expect, temperatures are rising:

But how much will they go up? The ultimate amount of warming will largely depend on the total amount of carbon dioxide we put into the air. The research branch of the National Academy of Sciences recently put out a report on these issues:

Here are their estimates:

You'll note there's lots of uncertainty, but a rough rule of thumb is that each doubling of carbon dioxide will raise the temperature around 3 degrees Celsius. Of course people love to argue about these things: you can find reasonable people who'll give a number anywhere between 1.5 and 4.5 °C, and unreasonable people who say practically anything. We'll get into this later, I'm sure.

But anyway: if we keep up "business as usual", it's easy to imagine us doubling the carbon dioxide sometime this century, so we need to ask: what would a world 3 °C warmer be like?

It doesn't sound like much... until you realize that the Earth was only about 6 °C colder during the last ice age, and the Antarctic had no ice the last time the Earth was about 4 °C warmer. You also need to bear in mind the shocking suddenness of the current rise in carbon dioxide levels

You can see several ice ages here — or technically, 'glacial periods'. Carbon dioxide concentration and temperature go hand in hand, probably due to some feedback mechanisms that make each influence the other. But the scary part is the vertical line on the right where the carbon dioxide shoots up from 290 to 390 parts per million — instantaneously from a geological point of view, and to levels not seen for a long time. Species can adapt to slow climate changes, but we're trying a radical experiment here.

But what, specifically, could be the effects of a world that's 3 °C warmer? You can get some idea from the National Research Council report. Here are some of their predictions. I think it's important to read these, to see that bad things will happen, but the world will not end. Psychologically, it's easy to avoid taking action if you think there's no problem — but it's also easy if you think you're doomed and there's no point.

Between their predictions (in boldface) I've added a few comments of my own. These comments are not supposed to prove anything. They're just anecdotal examples of the kind of events the report says we should expect.

This summer has certainly been exceptionally warm: for example, worldwide, it was the hottest June in recorded history, while July was the second hottest, beat out only by 2003. Temperature records have been falling like dominos. This is a taste of the kind of thing we might see.

Back home in southern California we're in our fourth year of drought, which has led to many wildfires.

We are already getting some unusually intense fires: for example, the Black Saturday bushfires that ripped through Victoria in February 2007, the massive fires in Greece later that year, and the hundreds of wildfires that broke out in Russia this July.

The extent to which these events cause floods, and the extent to which these floods cause serious damage, will depend on many complex factors. But today it hard not to think about the floods in Pakistan, which left about 20 million homeless, and ravaged an area equal to that of California.

It's a bit counterintuitive that warming could decrease the number of cyclones, while making them stronger. I'll have to learn more about this.

The area of Arctic ice reached a record low in the summer of 2007, and the fabled Northwest Passage opened up for the first time in recorded history. Then the ice area bounced back. This year it was low again... but what matters more is the overall trend:


The first sentence there is the main piece of good news — though not if you're a poor farmer in central Africa.

Coral reefs are also having trouble due to warming oceans. For example, this summer there was a mass dieoff of corals off the coast of Indonesia due to ocean temperatures that were 4 °C higher than average.

I have a strong fondness for the diversity of animals and plants that grace this planet, so this particularly perturbs me. The report does not venture a guess for how many species may go extinct due to climate change, probably because it's hard to estimate. However, it states that the extinction rate is now roughly 500 times what it was before humans showed up. The extinction rate is measured extinctions per million years per species. For mammals, it's shot up from roughly 0.1-0.5 to roughly 50-200. That's what I call annoying the biosphere!

So, that's a brief summary of the problems that carbon dioxide emissions may cause. There's just one more thing I want to say about this now.

Once carbon dioxide is put into the atmosphere, about 50% of it will stay there for decades. About 30% of it will stay there for centuries. And about 20% will stay there for thousands of years:

This particular chart is based on some 1993 calculations by Wigley. Later calculations confirm this idea: the carbon we burn will haunt our skies essentially forever:

This is why we're in serious trouble. In the above article, James Hansen puts it this way:

Because of this long CO2 lifetime, we cannot solve the climate problem by slowing down emissions by 20% or 50% or even 80%. It does not matter much whether the CO2 is emitted this year, next year, or several years from now. Instead ... we must identify a portion of the fossil fuels that will be left in the ground, or captured upon emission and put back into the ground.

But I think it's important to be more precise. We can put off global warming by reducing carbon dioxide emissions, and that may be a useful thing to do. But to prevent it, we have to cut our usage of fossil fuels to a very small level long before we've used them up.

Theoretically, another option is to quickly deploy new technologies to suck carbon dioxide out of the air, or cool the planet in other ways. But there's almost no chance such technologies will be practical soon enough to prevent significant global warming. They may become important later on, after we've already screwed things up. We may be miserable enough to try them, even though they may carry significant risks of their own.

So now, some tough questions:

If we decide to cut our usage of fossil fuels dramatically and quickly, how can we do it? How should we do it? What's the least painful way? Or should we just admit that we're doomed to global warming and learn to live with it, at least until we develop technologies to reverse it?

And a few more questions, just for completeness:

Could this all be just a bad dream — or more precisely, a delusion of some sort? Could it be that everything is actually fine? Or at least not as bad as you're saying?

I won't attempt to answer any of these now. We'll have to keep coming back to them, over and over.

So far I've only talked about carbon dioxide emissions. There are lots of other problems we should tackle, too! But presumably many of these are just symptoms of some deeper underlying problem. What is this deeper problem? I've been trying to figure that out for years. Is there any way to summarize what's going on, or it is just a big complicated mess?

Here's my attempt at a quick summary: the human race makes big decisions based on an economic model that ignores many negative externalities.

A 'negative externality' is, very roughly, a way in which my actions impose a cost on you, for which I don't pay any price.

For example: suppose I live in a high-rise apartment and my toilet breaks. Instead of fixing it, I realize that I can just use a bucket — and throw its contents out the window! Whee! If society has no mechanism for dealing with people like me, I pay no price for doing this. But you, down there, will be very unhappy.

This isn't just theoretical. Once upon a time in Europe there were few private toilets, and people would shout "gardyloo!" before throwing their waste down to the streets below. In retrospect that seems disgusting, but many of the big problems that afflict us now can be seen as the result of equally disgusting externalities. For example:

One could go on; I haven't even bothered to mention many well-known forms of air and water pollution. The Acid Rain Program in the United States is an example of how people eliminated an externality: they imposed a cap-and-trade system on sulfur dioxide pollution.

Externalities often arise when we treat some resource as essentially infinite — for example fish, or clean water, or clean air. We thus impose no cost for using it. This is fine at first. But because this resource is free, we use more and more — until it no longer makes sense to act as if we have an infinite amount. As a physicist would say, the approximation breaks down, and we enter a new regime.

This is happening all over the place now. We have reached the point where we need to treat most resources as finite and take this into account in our economic decisions. We can't afford so many externalities. It is irrational to let them go on.

But what can you do about this? Or what can I do?

We can do the things anyone can do. Educate ourselves. Educate our friends. Vote. Conserve energy. Don't throw buckets of crap out of apartment windows.

But what can we do that maximizes our effectiveness by taking advantage of our special skills?

Starting now, a large portion of This Week's Finds will be the continuing story of my attempts to answer this question. I want to answer it for myself. I'm not sure what I should do. But since I'm a scientist, I'll pose the question a bit more broadly, to make it a bit more interesting.

How scientists can help save the planet — that's what I want to know.

In the new This Week's Finds, you can often find the source for a claim by clicking on the nearest available link. This includes the figures. Four of the graphs in this issue were produced by Robert A. Rohde and more information about them can be found at Global Warming Art.

For more discussion go to my blog, Azimuth.

Certainty of death. Small chance of success. What are we waiting for? - Gimli

© 2010 John Baez