Why it matters to be rational, and how you can tell we aren’t, part II

In Part I I discussed avian flu as the near-term threat I think we're not taking seriously enough. Here I'm going to talk about global warming, the long-term threat.

I'll start with a doomsday scenario. It is not a particularly original one—I think it was the basis for this crappy movie—but I think it serves as a good way to illustrate why global warming is such a very severe worry.

I'm sure everyone knows the Gulf Stream, the warm ocean current that keeps the northeastern United States and the U.K. more temperate than their latitudes would predict. Well, the Gulf Stream is part of a worldwide system of ocean currents known as the Ocean Conveyor.

For a variety of reasons, North Atlantic waters are relatively salty compared with other parts of the world ocean. Salty water is denser than fresh water. Cold water is denser than warm water. When the warm, salty waters of the North Atlantic release heat to the atmosphere, they become colder and begin to sink.

In the seas that ring the northern fringe of the Atlantic—the Labrador, Irminger, and Greenland Seas—the ocean releases large amounts of heat to the atmosphere and then a great volume of cold, salty water sinks to the abyss. This water flows slowly at great depths into the South Atlantic and eventually throughout the world’s oceans.

Thus, the North Atlantic is the source of the deep limb of the Ocean Conveyor. The plunge of this great mass of cold, salty water propels the global ocean’s conveyor-like circulation system. It also helps draw warm, salty tropical surface waters northward to replace the sinking waters. This process is called “thermohaline circulation,” from the Greek words “thermos” (heat) and “halos” (salt).

If cold, salty North Atlantic waters did not sink, a primary force driving global ocean circulation could slacken and cease. Existing currents could weaken or be redirected. The resulting reorganization of the ocean’s circulation would reconfigure Earth’s climate patterns.

Computer models simulating ocean-atmosphere climate dynamics indicate that the North Atlantic region would cool 3° to 5° Celsius if Conveyor circulation were totally disrupted. It would produce winters twice as cold as the worst winters on record in the eastern United States in the past century. In addition, previous Conveyor shutdowns have been linked with widespread droughts throughout the globe.

It is crucial to remember two points: 1) If thermohaline circulation shuts down and induces a climate transition, severe winters in the North Atlantic region would likely persist for decades to centuries—until conditions reached another threshold at which thermohaline circulation might resume. 2) Abrupt regional cooling may occur even as the earth, on average, continues to warm.
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Signs of a possible slowdown already exist. A 2001 report in Nature indicates that the flow of cold, dense water from the Norwegian and Greenland Seas into the North Atlantic has diminished by at least 20 percent since 1950.

So, less salty, cold, sinking water in the North Atlantic could totally fuck us. What could give us less salty water? How about a whole lot of freshwater ice going into the sea up there, say from the Greenland ice sheet?

The amount of ice flowing into the sea from large glaciers in southern Greenland has almost doubled in the last 10 years, possibly requiring scientists to increase estimates of how much the world's oceans could rise under the influence of global warming, according to a study being published today in the journal Science.

The study said there was evidence that the rise in flows would soon spread to glaciers farther north in Greenland, which is covered with an ancient ice sheet nearly two miles thick in places, and which holds enough water to raise global sea levels 20 feet or more should it all flow into the ocean.

But surely we would have time to adjust, right?

Fossil evidence clearly demonstrates that Earth's climate can shift gears within a decade, establishing new and different patterns that can persist for decades to centuries.

Right. Crap.

Of course, we don't know how close we are to this happening. If it happens in the next two decades, we're screwed. If it happens in a century, it could offset global warming for those of us in the northeast U.S., while mostly screwing more tropical people.

This shutdown of the Ocean Conveyor is only one of three major problems that could be triggered by global warming pretty soon.

There are three specific events that these scientists describe as especially worrisome and potentially imminent, although the time frames are a matter of dispute: widespread coral bleaching that could damage the world's fisheries within three decades; dramatic sea level rise by the end of the century that would take tens of thousands of years to reverse; and, within 200 years, a shutdown of the ocean current that moderates temperatures in northern Europe.

The debate has been intensifying because Earth is warming much faster than some researchers had predicted. James E. Hansen, who directs NASA's Goddard Institute of Space Studies, last week confirmed that 2005 was the warmest year on record, surpassing 1998. Earth's average temperature has risen nearly 1 degree Fahrenheit over the past 30 years, he noted, and another increase of about 4 degrees over the next century would "imply changes that constitute practically a different planet."

"It's not something you can adapt to," Hansen said in an interview. "We can't let it go on another 10 years like this. We've got to do something."

James Hansen has been trying to warn us about this for twenty years, incidentally. He was the first to brief Congress on the subject in the late 1980s, and has been a hero in overcoming a scientist's traditional reluctance to take dramatic public stands. He's gotten plenty of shit for it, too. A great American.

Princeton University geosciences and international affairs professor Michael Oppenheimer, who also advises the advocacy group Environmental Defense, said one of the greatest dangers lies in the disintegration of the Greenland or West Antarctic ice sheets, which together hold about 20 percent of the fresh water on the planet. If either of the two sheets disintegrates, sea level could rise nearly 20 feet in the course of a couple of centuries, swamping the southern third of Florida and Manhattan up to the middle of Greenwich Village.

Not two months after that article ran, this report hit the papers.

The Antarctic ice sheet is losing as much as 36 cubic miles of ice a year in a trend that scientists link to global warming, according to a new paper that provides the first evidence that the sheet's total mass is shrinking significantly.
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It is one of a slew of scientific papers in recent weeks that have sought to gauge the impact of climate change on the world's oceans and lakes. Just last month two researchers reported that Greenland's glaciers are melting into the sea twice as fast as previously believed, and a separate paper in Science today predicts that by the end of this century lakes and streams on one-fourth of the African continent could be drying up because of higher temperatures.

(As long as we're on the subject of bad stuff happening because of global warming: polar bears are drowning because of melting ice, and beetles formerly held in check by cold winters are devastating the great northern forests. And a big hurricane destroyed one of our major cities.)

I am heartened that the problem is getting major attention in the media now. The problem is, it is getting virtually zero attention from either political party. That, in turn, is because politicians have quite correctly deduced that global warming motivates just about nobody's vote. (The Democrats, for example, seem to be pushing an energy plan made up of some combination of ethanol, a pander to Midwestern corn farmers, and liquefied coal, a pander to Western coal states. Usually the coal thing is accompanied by some sop to the idea of carbon sequestration, a technology that doesn't exist yet. It makes me want to throw things.)

Why don't voters care? I am sure SG can explain the phenomenon better than I can in terms of economic modeling of behavior, but let me try to compare terrorism (which has seriously motivated votes in at least the last few election cycles) to global warming (which hasn't). Terrorism is for the most part extremely unlikely, and probably (in an opinion I am pulling from my ass) September 11 will stand for a long time as its worst ever blow. But September 11's damage was obvious, instantaneous, and traumatic, and provoked fear of far greater harm that could come without warning. Global warming, on the other hand, is 100% likely (it is already underway), and if left unchecked its damage will almost certainly dwarf September 11. Yet even if the entire world's climate shifts over a decade, in human terms that change will still feel gradual, indirect, and to some extent manageable. A few hundred to a few thousand more people may die of heatstroke alone each year in this country with a relatively small rise in temperature—in other words a September 11 maybe every couple of years—but we will not take notice.

If we assessed our risks rationally, in other words, all deaths being equal, we would make global warming one of our top priorities. Because we don't, our president can drum up fear over the possibility of Iran getting nuclear arms, which is unlikely to be a serious existential problem for us anytime in the foreseeable future.

I would start proposing some solutions but a) this has already gone on far too long, and b) I think you'd do better to listen to better-informed people than me. Once we can get the technology working, I think our best medium-term bet for reducing our emissions may be pebble-bed nuclear plants. One better-informed plan can be found here. A well-informed critique of it can be found here, and another, general vision is here.


Tags: global warming, Ocean Conveyor, Greenland ice, Antarctic ice, rationality, risk, thermohaline, James Hansen, sea level rise, environment, terrorism, pebble-bed nuclear



UPDATE (July 11, 2006): We have since learned that nuclear is not a viable option. Basically, there just isn't enough rich uranium ore around.