Sunday, March 21, 2010

Hope & Fear: Climate Change Fact and Fiction

There's a lot of talk about hope and fear. Do we need to be saved?
Saved from what? From people telling us what to do? From cops and robber?
From catastrophic climate?

My personal belief is that's there's no right answer to the questions of strong or weak government, or to the questions of personal liberty vs. obligations to the state. I believe that societal questions have no right or wrong answers because we can't predict the future and we can not retro-actively determine the cause of a certain effect when the size of the system is as large as the earth.

The questions of climate change are quite complicated as well. The processes between the earth's atmosphere and its surface are non-linear and extraordinarily complex. I think that it's so complex that's it may be irreducibly complex, and by that, I mean that the only way to figure out what will happen is to let it happen, i.e. there is no way to accurately model the interplay between the earth's atmosphere and its surface.

If there was no life on the planet, the model would be non-linear & quite complex, though maybe we could model it to some extent. But with life processes, the non-linear processes are of a different degree. There are biological feedback mechanisms that make cloud-formation feedback look like middle-school mathematics.

I don't want to take a particular side on the debate surrounding global climate change, but what I want to do is calm the waters. I'd like to differentiate between global climate change and catastrophic climate change. (By catastrophic climate change, I mean the idea that human CO2 emissions will cause the earth's climate to radically change inducing billions of people to have to find new places to live.)

I'd like to set a tone that is without the hope or fear seen so often in newspapers, TV and the web.

I am not afraid of catastrophic climate change because of the following basic physics principles:
1) The forcing function for the effect of CO2 in the atmosphere is logarithmic
This means that the change in the forcing function is the same for a change from 200 ppm CO2 to 400 ppm as would the the change from 400 ppm to 800 ppm of CO2.

2) Total radiation is proportional to T^4 (temperature to the fourth power.)
In the IPCC report, they approximate the change in the radiative forcing function with a linear increase in temperature.

So, here's some simple math:

The earth receives light from the sun at an average power of 1366 Watts per meter squared. This number varies between 1412 W/m2 in the Northern Winter and 1321 W/m2 in the Northern Summer. In order to compare this number with the IPCC's definition of radiative forcing, I believe that there is a difference of (1-alpha)/4. The (1-alpha) corrects for the actual amount of sunlight absorbed by the earth, and the 1/4 factor converts the circular area(pi*r^2) of sunlight hitting the earth with the surface area (4*pi*r^2) used in the definition of GHG forcing function.
The CO2 forcing function looks like:
delta Radiative Forcing (in units of W/m2) = 5.35 * ln (C/Co)
where C is the current concentration of CO2 in ppm and Co is a set value of 280 ppm.
The current value of delta RF is roughly 1.66 W/m2.
That's on the order of 0.6% of the equivalent total radiative forcing from the sun. Even if the amount of CO2 in the atmosphere were to double to 560 ppm. The change in radiative forcing would only be 3.7 W/m2, which is still only ~1.4% of the total equivalent sunlight absorbed the earth.

To first order, I get a temperature change of ~1.2 deg C for a CO2 doubling. This ignores secondary effects (which definitely can be important), but I think that it points out that it will take a while before we get to large increases in temperature (~5 deg C.)

Since we have some time before drastic action is required, I suggest that more research be done in the area of understanding the actions of proposals to change the status quo.

For example, how many people will be saved by a policy and how many will die because of the policy? People will die under the status quo and people will die under any new policy. The question is: will there be any net saving of life? For example, will warmer weather save lives in the winter? Will a new policy cause economic difficulty such that more people will starve than under current policy?

Since we have some time, I'd like to really know what the net effect is of the various policies I've seen presented in IPCC reports.

Ultimately, the 7 billion people living on this planet will need to come to some agreement about what level to cap greenhouse gas emissions, and we can make a more informed decision if we have the data in front of us to determine which policy can save the more lives.

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