Wednesday, May 27, 2020

Good Intentions

To be honest, and Eli is always honest, good intentions slip away when one is sleeping through a lockdown, one day like another, and another and another and one simply stays in bed and does not visit Rabett Run muchly

However to continue where we left off, Eli has come across a a rather nice way of showing how absorption of thermal radiation in the atmosphere warms the surface.

Start with the simplest case the surface of an Earth whose atmosphere does not absorb infrared radiation. Solar energy q falling on the surface warms it until the surface can radiate an equal amount of energy. The temperature at which this happens is given by the Stefan-Boltzman equation.

Ok, this is a bit simplified, no albedo, all the energy is absorbed and none reflected and the emissivity of the surface is unity, no view factor, but that can be added back in later, here all Eli wants to do is establish the principle.

What would happen if we added two absorbing layers between the surface and space

Since the heat, the net thermal energy passing between each layer has to be the same as the heat going into the surface, q, there are three equations. At the top, the heat, being radiated to space is just the same as the heat injected at the bottom, and is given by σT24

Between the first and second layer the same amount of heat, q, is transferred. In this case, q is the net difference between the thermal energy transferred upwards as shown by the blue arrow and the backradiation from the top layer shown by the orange arrow. Note that at the top the backradiation equals the radiation emitted to space which in turn is equal to the radiation absorbed at the bottom. Conservation of energy and all that.

At the bottom, the heat transferred between the surface and the first layer is also q, but in this case the difference is between the upwards thermal radiation from the surface, σT04 and the backradiation from the first layer σT14

Three equation, add them up, and you get that 3q = σT04, solve for T0 and compare to the result with only a surface. The temperature of the surface is warmer by a factor of 31/4 or if you want numbers about 1.3.

By inspection (instructor speak for do the work) if you had N layers the surface would warm by a factor of  N1/4 while the input and output of heat from the system remains constant. 

Vacuum ovens use this principle with multiple heat shields to slow the transfer of heat from the inside to the outside and that is where Eli first came across them when he was but a little guy building his own systems. (not nearly as neat as this one). Looking closely there are about 7 layers to the cake here.

There are a lot of discussions on line of one layer energy balance models for the Earth's atmosphere which explicitly include emissivity and albedo, coming up with an effective emissivity of about 0,77 across the entire IR spectrum, but the multilayer POV puts paid to the argument that backradiation can't make the surface warmer

Sunday, May 10, 2020

VPOTUS needs to be ready for 2028, and why Eric Levitz is wrong

My February 2019 post saying "please not Bernie or Biden" for the Democratic nomination was less than completely successful in determining national politics. My subsequent support for Warren for president also didn't do so well. Now, as I'm seeing Warren ranked highest among Democratic preferences for Vice President, I'm yet again disagreeing with my fellow Democrats

The catalyst for this post was NYMag's Eric Levitz using some criteria for Biden's Veep selection that I don't think are very useful. Maybe most important is the one that he overlooked - that the VPOTUS could be needed to run for a first  term in 2028. The assumption that Biden is at most a one-term president, although possible, isn't guaranteed. Instead I'm guessing that if he wins and if things seem reasonably good in 2024, and if to public appearances he seems healthy (we won't know the reality because we tolerate complete obfuscation for presidential health) then Biden's running in 2024. The Veep chosen this summer needs to be ready to run in 2028.

While Warren's not as old as Bernie and Biden, she's up there already, and she'll be their age in 2028. There's no reason for Democrats to take on this age disadvantage. Warren will make a fine Cabinet member if Biden wins, and can consider running in 2024 if he doesn't run again, but VPOTUS should go to someone else. Worth considering also that whoever's Veep may have a reason not to run in 2028, like Biden did in 2016. Using up the Vice President slot for someone who will be 82 when she'd run for a first term in 2032 is a mistake.

So, going through Levitz's criteria, we have first, readiness to be a good president tomorrow. Well yes in general the VP should be capable of being a good president but that person doesn't have to have the same experience we'd want in the president. Barring some real bad luck, the veep will have months to years of experience serving in the Biden administration getting ready to take over. The most important thing is whether the VP helps defeat Trump, and second whether the person is good material for a future presidential campaign. Some experience is crucial, but virtually any viable Democratic VP candidate will be far more qualified than Trump was.

Second, the candidate shouldn't cost a Senate seat. I kind of agree, although I would trade a Senate seat for the presidency if the VP could really help. Still, this is probably his least objectionable criterion.

Third is that the candidate would be ready to run only in 2024, which is wrong for reasons discussed above.

Fourth is to help Biden politically, which is only wrong in that Levitz thinks the VP won't help and therefore says this criterion is unimportant compared to others. While that's generally been true in past elections, I think it's wrong as to individual states.

A popular governor in a swing state, and that's you Gretchen Whitmer, could move several percent of the vote. Levitz is wrong to dismiss her as too inexperienced. I'll agree that it would be better if she had more experience, but still she has years of state legislative experience before her two years so far as governor, and she'll get more experience as VP before becoming or running for president.

In general, choose a popular, smart, and not-too-elderly woman politician from a swing state (including Stacey Abrams and Georgia in that catergory), and Biden will do fine.