Friday, December 01, 2006

Global Warming Update

Bob Seitz headshot by Robert N. Seitz

Last January I ran off a shirttail calculation estimating the weight of carbon dioxide in the Earth's atmosphere (280 gigatonnes), and compared it with the weight of methane trapped in the world's permafrost (also 280 gigatonnes). While methane has 22 times the global warming effects of carbon dioxide, it has a half-life in the atmosphere of only about 8 years. If this outgassing of AlCan and Siberian tundras took place completely but slowly, it would release something like 280 gigatonnes of methane that would convert to CO2 over a period of decades. But what I didn't consider was the fact that a tonne (metric ton) of methane, with a molecular weight of 14, would oxidize to a little over three metric tones of CO2, with a molecular weight of 44. So the 280 gigatonnes of methane would become 880 gigatonnes of CO2, or about 3 times the 280 gigatonnes of CO2 in the Earth's atmosphere today. That's not good news. That would quadruple the amount of CO2 in the Earth's atmosphere. I also mentioned the lesser possibility that the methane clathrates ("methane ice" deposits at the bottom of the world's oceans contain about 10,000 gigatonnes of methane, and that would convert to about 31,500 gigatonnes of CO2, and that this is thought to have occurred during the Mesozoic/Cenozoic Thermal Maximum that killed off the dinosaurs about 55,000,000 years ago. That wouldn't be the best prognosis for humanity, but at least it didn't transform the world into a searing hell like Venus.

It's important to be aware that the outgassing of methane hasn't yet been included in existing climate simulations, or at least in the forecasts that we're hearing right now.

That was the good news. Now for the bad news.

It has just been announced that the rate of rise of atmospheric CO2 has more than 2.5-folded since 1990…. the fourth consecutive year of two-parts-per-million growth. Last year, 7.85 gigatonnes of CO2 was added to the atmosphere compared to 6.87 gigatonnes in 2000.

A month ago, several news sites reported that in the latest annual report on climate change, issued last spring, it was erroneously concluded that methane release into the atmosphere had slowed down. In fact, it has continued to increase, but this fact was learned too late to correct it in the report. Now, in a display of "media Alzheimer's disease" the same media are reporting the incorrect earlier message that the methane release rate has fallen.

In the meantime, the rate of methane release from Arctic permafrost is rapidly accelerating.

To clothe methane release rates in numbers, suppose that methane is being released at the rate of 0.1% a year. At that rate, it would take 1,000 years for all the world's permafrost to outgas. Since there's an estimated 280 billion tones of methane locked up in the world's tundras, 0.1% a year would translate into a release rate of 280 million tones of methane a year. Given that methane has 22 times the greenhouse effect of CO2, this rate of release would equate to about 6 gigatonnes of CO2a year in terms of greenhouse effects, or about 3/4that of last year's CO2release. (Note that after 8 years, half of the integrated total of 2.24 gigatonnes (= 1.12 gigatonnes) of methane released over the 8-year half-life of this atmospheric methane would have converted to 3.15/22 tonnes of CO2, raising the global CO2burden by 3.5 gigatonnes of 8 years. This would still be small compared to the 64 gigatonnes of CO2 added to atmosphere from other sources. )

Clearly, even an outgassing rate of only 0.1% a year isn't happening yet, or the effects would be more evident. However, we might expect that the warmer the Arctic gets, the faster the permafrost will outgas.

What's so alarming about the outgassing of permafrost is the fact that it would be a case of global warming feeding upon itself. Although our burning of fossil fuels would have initiated this process, outgassing of methane could, possibly, continue to elevate CO2levels even if we cut our fossil fuels emissions to zero.

This last summer, for the first time, a passage opened up through the sea ice all the way to the North Pole. This was a fluke, but it appears to be a harbinger of things to come.

Kerry Williams has brought up an interesting point, and has buttressed his case with computations. His calculations indicate that climate change is coming on too rapidly to permit trees to migrate toward the poles as fast as the global-warming-induced changes in their habitats. This could lead to an ecological crisis in which oxygen renewal might take a hit.

My personal prognosis-one that I try not to think about-is that we will pass the "tipping point" if we haven't already passed it, at which runaway global warming occurs no matter what we do. Conservation can help us reduce our fossil fuel demands somewhat, but some fuel guzzlers like 18-wheel transfer trucks are probably already about as efficient as they can currently be made, and our civilization depends upon our ability to haul freight. Even if we can reduce our CO2output to some 20th-century level, CO2would continue to rise.

I suspect that sometime within the next decade, there's going to be panic in the streets over this. Venture capitalists are already pouring money into solar power startups. Semiconductor-grade silicon is currently a bottleneck in solar cell production, and the prices of solar cells have risen rather than fallen over the past two years, due in part to Germany's subsidization of solar power and to California's "million solar rooftops"program. In the meantime, solar technology is in a state of ferment. (The best investment plays might lie in supporting technologies such as batteries, power inverters, or mounting hardware.) Within ten years, we might have high-efficiency, low cost solar rooftops that are natural looking and are fashionably accepted within the neighborhood. Production of vehicle fuels might be another application of solar power. For countries that have extensive electrical grids, solar arrays may take hold in central power systems in sun-belt regions rather than in the form of distributed rooftop power.

Another promising area is battery research. Long-lived rechargeable batteries that store a kilowatt-hour per kilogram may be in the offing. These are being suggested for hybrid vehicles that can plug into the wall for recharging. (Some amateurs are beefing up the lead-acid batteries in their Priuses for short around-town jaunts on electric power only, with plug-in recharging back home.) A typical home uses about 40 kilowatt-hours of energy a day, although careful design can reduce that number. At that rate, 100 kilograms of batteries could probably provide for a household.

Wind power offers promise along coastlines and in mountainous areas.

Biodiesel generated from cellulose waste requires some further bioengineering of microbes, but that might become a way to generate vehicle fuels. (I suspect that some combination of ethanol and biodiesel generation may be the wave of the future rather than hydrogen fuel cells. We already have a century of experience and infrastructure in place for the internal combustion engine. But we'll see.)

Nuclear power is an immediate short-term solution to power requirements, but one would hope that we would step on the accelerator with respect to converting to alternate energy solutions, bypassing nuclear power. In any case, it will take years to build new nuclear power plants. Meanwhile, in spite of efforts to convert to alternate energy sources, China is planning to rely almost entirely on new coal-fired power plants for its burgeoning power goals. But I suspect that this plan may be overtaken by the "pani-in-the-streets"

If the "panic in the streets" scenario occurs at some future time, I could imagine southern property falling in value, and northern property values rising, as people try to relocate themselves in anticipation of rising temperatures. Commercial installations would be shifted northward, and residential acquisitions would follow. In North America, land along the northern Pacific coast, and in Canada and Alaska would seem to me to be especially valuable.

The UK science magazine, "New Scientist"has taking the unusual step of describing the well-funded global warming disinformation program that has been mounted by Exxon, General Motors, and Ford Motor Company-a campaign that is reminiscent of the disinformation programs financed by the tobacco and dairy industries that deliberately obfuscated the dangers of smoking and dairy products during the 60's and 70's..

Some Thumbnail Calculations

An object in interplanetary space will arrive at an equilibrium temperature at which the radiation power absorbed from the sun equals the radiation power re-radiated by the object. The total radiation power absorbed from the sun by a spherical "black body"(perfect absorber) is given by πr2 times the power per unit area. For a spherical black body in the vicinity of the Earth, the power absorbed from the sun is given by the solar constant = 1,370 watts/square meter. The power re-radiated back into space will be spread over the entire surface of the sphere = 4πr2. This means that the re-radiated power density will be exactly ¼th of the power density received from the sun, or 1,370/4 w/m2 = 342.5 w/m2. Then we can plug this number into the Stefan-Boltzmann equation, Power/m.2 = 5.67 X 10-8 T4, and solve for the equilibrium temperature at which the Earth re-radiates the same amount of power/m.2 it receives from the sun. The resulting black-body equilibrium temperature is 278.8º Kelvin or 5.65º Celsius or about 40 degrees Fahrenheit. In reality, there are many complications that muddy these waters. There is cloud cover, atmospheric convection, and uneven surface and cloud top temperatures, to name just three.

Dr. Angell de la Sierra has raised the question: if CO2blocks heat radiation from the ground, why doesn't it also block the incoming radiation from the sun? I believe that this asymmetry may arise because the radiation from the sun peaks at a wavelength of about ½ micron, whereas radiation emanating from the Earth peaks in the far infrared at a wavelength of about 10 microns. The atmosphere is transparent to visible and near-infrared radiation, whereas it is, perhaps, semi-opaque in the far infrared. Dr. de la Sierra also observed that the situation must be complicated. Convection patterns would play a role. If atmospheric CO2is semi-opaque to far-infrared radiation, it can do so either by reflecting it or by absorbing it. If it reflects far-infrared radiation, then it would tend to re-radiate less radiant heat than the corresponding black body, and this would certainly have a warming effect. If atmospheric CO2is semi-opaque because it's a good absorber differential in the 5 to 15 micron range, then it would heat up. At the same time, the effective temperature of the radiating surface would tend to be low because the radiating surface would be high in the Earth's atmosphere, which is where convection enters the picture. Also (Dr. de la Sierra pointed out), atmospheric CO2might radiate from lower levels as well as higher levels, complicating the situation further.

If the Bush Administration's denial of the reality of global warming and deliberate inaction destroys humanity, it will be the greatest crime against humanity ever committed.

Time will tell.

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