Saturday, March 24, 2007

Al Gore and the fever analogy

A number of bloggers have called Al Gore to task for using the metaphor of a baby having a fever to suggest appropriate action to global warming.

I admit that “fever” is a poor analogy, because far too many fevers are of benign origin. A more appropriate analogy would be hyperpyrexia, or malignant hyperthermia, a condition that is virtually always fatal if left untreated. Like global warming, malignant hyperthermia is not well understood, and can occur suddenly, and the response of those ignorant of it will be to repeat the GWB mantra “no one could have predicted…” (I think malignant hyperthermia relates to insufficient basal NO, and insufficient mitochondria leading to (in the case of acute respiratory distress syndrome (for example), excessive expression of iNOS) inhibition of mitochondria leading to excessive mitochondrial potential and expression of uncoupling protein and collapse of ATP levels with the mitochondrial potential being uselessly dissipated as heat, but that is a story for another blog.)

The “problem”, is that by calling global warming a “fever” (a misdiagnosis by a lay person (Al Gore)), other lay people (non-atmospheric scientists and those who don’t understand global warming) think it is benign, like most "fevers". Al Gore should have likened global warming to malignant hyperthermia. A condition that at one time was nearly always fatal in a hospital setting. Now, with better understanding and sufficiently prompt and vigorous supportive treatments, malignant hyperthermia is only about 5% fatal.

Perhaps if we act vigorously and in the proper way(s), global warming will only have a 5% fatality rate. Unfortunately, if we proceed as if “no one has predicted” any bad consequences, by the time those consequences become obvious, it will be too late.

CO2 in the atmosphere right now, is higher than it has been in the last 10 million years. At which time Greenland had very little ice. Under present conditions, Greenland is unstable and will melt. The only question is when, not if. When Greenland melts, sea level will go up 7 meters.

Current “models” of how fast Greenland is going to melt are woefully inadequate. Sort of like the “models” of hyperthermia 100 years ago. That was before the understanding of how medications lowered fevers:

Before the understanding that sometimes fevers accompanied heart failure:

When ice sheets melt, they do so catastrophically. They don’t just sit there and slowly melt like an ice cube (the only model that is understood, and so is the only model that can be used).

I have been doing a lot of research on global warming and have looked into ice melting dynamics.

The models are extremely conservative. What that means is that they only "model" stuff they understand well. If it isn't "understood", it simply gets left out of the model.

What is left out of the ice melting models are the non-linear things that can greatly accelerate the movement of ice into the ocean. These are simply ignored. Not because they are thought to be unimportant, but because it is not known how to model them.

I will discuss several of them. One of the biggies comes from the fact that water is denser than ice. Ice sheets are only stable because they are below freezing from the top, all the way to the bedrock that they sit on. The center of the Earth is hot, and heat only flows down a temperature gradient. So there is a heat flux at the bottom of the ice, from the bedrock into the ice. That heat can only go somewhere if the somewhere it is going is colder than where it is. If the heat can't go anywhere, it accumulates, and the temperature goes up until the ice melts.

When ice melts, the water it becomes is denser, so it sinks to the bottom, and the ice floats in it. If the water layer at the bottom of the ice gets thick enough, you don't have an ice sheet any more, you have a river covered with ice. The ice may be 3,000 meters thick but if the water layer is "deep enough", the whole shebang will flow to the sea.

What keeps the ice frozen, is the heat flux during the winter when the top is very cold, -40 or so. The heat from the Earth flows down the temperature gradient and is radiated off into space. So at the base of the ice, the temperature is near freezing or below, and it gets progressively colder as you go up, until at the very top there are seasonal fluctuations.

What happens when there is melting water at the top? Small amounts can run off. If there is more, what happens? Because water is denser, the pressure at the bottom of a column of water is higher than ice of the same thickness. The ice deforms, the water flows down. All the way down, until it meets ice that is colder than the freezing point of water, then the water freezes, depositing its heat of melting and raising the temperature of that ice to the freezing point.

But that disrupts the temperature gradient that is transporting heat from the base to the surface. If there is no gradient, geothermal heat can’t go any where. So the temperature of the ice sheet goes up. As ice gets closer to the melting point, its mechanical strength goes down. It is less able to withstand shear and stay as a solid mass.

So what happens is that the ice sheet gets warmer, but doesn’t change much in appearance. Until the warming reaches a critical point where the ice isn’t strong enough to support its own weight. Then it starts to move. When the ice is moved by gravity, its gravitational energy is dissipated as heat at the base where there is relative motion. This is why ice is slippery. Frictional energy dissipated at the surface causes melting and a film of water that lubricates the interface. When the base is at the melting point, any additional energy causes melting, and there is no temperature gradient for the heat to flow away to, for the water to freeze again.

It is likely that the melting of Greenland will occur in catastrophic events. It won’t really “melt”, what will happen is that large masses of ice will flow into the sea. That will raise sea level abruptly. How abruptly? Good question. What is going to slow it down? Once it starts to flow, and has a sufficient film of water to lubricate the flow, not much. We could see large chunks of Greenland slip into the sea, 10’s of percent of the Greenland ice mass. 10% of Greenland would raise global sea level by about 2 feet. If that ice flowed into the Atlantic in a week, the rise in the Atlantic would be more than that, and then it would subside. Would there be big waves? I don’t know, I don’t think so, but a transient of 10 feet wouldn’t surprise me. It might be like a 10 foot storm surge that lasts for a month or two. Flooding everything on the coast of the Atlantic. The ice would likely make the Atlantic impassible until it melted. Then the light fresh melt water could well shut down the ocean circulation.

If CO2 continues to be added to the atmosphere, it could get to levels that haven’t been seen since dinosaurs roamed the Earth. There was no ice at the poles then. When the West Antarctic ice sheet melts, that will also add about 7 meters to sea level. When the East Antarctic ice sheet melts, that will add about 60.

Something like 1/3 of humans live below 100 meters altitude. When sea level goes up, where are they going to move to?

Al Gore is trying to tread a very fine line, portray what might happen in a “sound bite” that is short enough that the media will put it on the news, simple enough that some people will understand it, and yet somehow connects to global warming and the need to do something.

1 comment:

Hylda said...

This can't have effect in actual fact, that's exactly what I believe.