Open thread weekend

wayne says:
May 28, 2011 at 8:41 pm
“…Not all complex physics the AGW/IPCC portrays needs to be so complex if viewed correctly while staying simple, that is if a few souls are willing to allow it to be stay simple. … Physics at the core level IS simplicity itself, it is the few dishonest people that force it to remain in complexity, that is their sole shield.”
Another great physicist is credited the the rule “everything should be made as simple as possible, but no simpler”.
In many ways, physics is simple. But in many ways it is not. You can’t reduce everything to the freshman level of Feynman’s popular texts and expect to bne able to solve all physics problems.
Classical electricity and magnetism can be simplified to
∇×E = −∂B/∂t
∇×H = J + ∂D/∂t
∇·D = ρ
∇·B = 0
F = qE + qv×B
Much of quantum mechanics can be summed up in the simple equation of Schroedinger:
iħ δ/δt ( Ψ(r,t) ) = [ -(ħ²/2m ∇²) + V(r,t) ] Ψ(r,t)
The second law of thermodynamics (which comes up often in discussions here) and be summarized with the simple equation:
S = -k Σ P(j) log (P(j))
The point is that the “simplicity” of an appropriate equation depends on the sophistication of the person using it and the situation where it is being applied. Freshman physics is a GREAT starting point for understanding any number of interesting topics, but often the topic itself demands more involved equations.
For example, Newton’s laws are great for figuring out how satellites move and behave. Unless you need to be really precise (like GPS satellites) where relativity is required to deal with the fact that time itself is different on the orbiting satellite than on the earth.

TerryS
I like your approach — using math & science to understand issues in climate science. I agree with the equation you derived
h = r * ln(2) / y
which is a standard equation in radioactive decay as well. But I would suggest two additional points
1) when you double the amount of CO2 in the atmosphere, the half-life would double, since you doubled “y” but you didn’t double “r”. But you will still get most CO2 atoms cycled thru the system in 25 years, so this is only a minor point.
2) There are two very different time-frames of interest here. One is the time a given molecule of CO2 stays in the atmosphere. This would indeed be just a few years as you derived. The more interesting question is how long would it take for the extra CO2 to be absorbed.
As long as the rate of CO2 into the atmosphere (~ 770 GT/yr) equals the rate out of the atmosphere (~770 GT/yr), then the amount in the atmosphere will not change (Whether there is 300 ppm or 600 ppm there). Presumably, for several centuries before the industrial revolution, everything was pretty much in balance.
As people add CO2 to the atmosphere, the rate into the atmosphere increases. It we indeed stopped burning fossil fuels today (which would be a disastrous choice for many reasons) , nature would still be adding ~ 770 GT/yr. The only way to actually reduce the CO2 levels would be for nature to increase the rate it removes CO2 from the atmosphere. The two most obvious choices that I can think of would be:
1) a net year-to-year gain in plant mass (ie sequestering C in the plant material). That will happen somewhat since more CO2 in the atmosphere will stimulate plants to grow a little better. OTOH, people tend to keep cutting down forests and replacing them with croplands that do not sequester as much carbon, releasing extra CO2 into the atmosphere.
2) uptake by the oceans, leading to higher CO2 levels in the water. This will certainly happen as well, since the~ equilibrium exchange that had been occurring for centuries has gotten out of balance.
These two processes cannot be modeled with the equation you derived. Understanding these processes requires knowledge of chemical equilibrium, ocean currents, how people will use land, and the response of plants to potential changes in CO2 & temperature, & precipitation.
The point is that determining the time to cycle CO2 molecules thru the atmosphere is straight-forward; determining the time to permanently remove CO2 molecules is much more involved.

Smokey says:
May 29, 2011 at 12:15 pm
“Tim Folkerts, I am shocked and horrified! You didn’t really write “CO2 atoms”, did you?☺”
I looks like I did!
But if we are keeping score, it looks like:
10 times I just said “CO2”
2 times I said “CO2 molecules”
1 time I said “CO2 atoms”
So I was correct 12/13 of the time. And if that is the worst mistake you found, then I am doing pretty well. 🙂

In view of the rejection by the EPA of challenges to their endangerment finding, why would we be surprised to find that they have a long-term stake in the IPCC’s climate models and in the continuance of the IPCC itself.
http://scienceandpublicpolicy.org/originals/the_un_states_epa.html