Tuesday, January 15, 2019

Gavin Explains It All

Well, Eli is retired so he is outsourcing to Gavin Schmidt who,explained it all in a series of tweets with the BlackPhysicists Tweeter.  They actually, between them had a real conversation of value, which Eli here unrolls.  Below the BlackPhysicists are in italic.  Gavin does the rest.  The sequence started with.

 @BlackPhysicists  Today our #iteachphysics topic is tools and pedagogy for teaching #weather and #climate physics. One goal of today's #iteachphysics chat is how do physics teachers include in the usual #physics curriculum, absent a specialized course, enough background and foundational knowledge to make our students better consumers of, explainers of #weather and #climate physics

I’d say to start with thermodynamics. Heat, density, convection and then Clausius-clapyeron. Condensation/evaporation and conservation of mass/energy, you have most of the principles. Coriolis rounds it off.

@BlackPhysicists In general #physics we do not spend a whole lot of time on classical #thermodynamics, but thermodynamics is essential in understanding #weather phenomena. See hurricanes described as a Carnot cycle in @PhysicsToday 



 It doesn’t need to be all-in thermo, more just the concepts. PV=nRT, buoyancy, condensation...




@BlackPhysicists  In almost every broadcast meteorologist's report we hear the term "weather model." What are weather models, exactly, and how do they work?




Here is another great animation of a weather model that includes atmospheric composition of aerosols (particulates): 






And here is an excellent primer for climate models

@BlackPhysicists There are enough wildfires and volcano eruptions happening at one time to effect #weather on a large scale?

Good Q. Small volcanoes and fires add to the background climate for sure. Impacts on weather forecasts are more subtle, but by changing where solar/IR energy is absorbed/reflected they can affect temp gradients and hence dynamics.

@BlackPhysicists What do you think re: best practices to teach probability & stochasticity, parameterization & estimation, error and bias?

 More Chaos theory/Lorentz attractor etc. Parameterisation and emergence are trickier but there are some @TEDTalks on that. 


I generally don’t find that numerical analysis as taught is particularly useful though.

 Dust can affect hurricane development (at least it has been hypothesized to). And smoke/aerosols impact air quality directly - something weather models are increasingly predicting as well.

@BlackPhysicists  In fact the group at @NCASNews led by @vernon_morris is expert on dust from the Sahel leading to African Easterly Waves and Western Hemisphere hurricanes. I think in this presentation there a slide showing North American hurricane tracks emanating from the Senegal, Gambia area.

 @BlackPhysicists Switching gears to #climate physics, in your experience do students have difficulty understanding the difference between weather and climate? This seems to be a major problem in TV punditry and probably most public discourse on weather and climate.

Actually no. Once explained - lots of good metaphors available - ppl generally get it. The ‘confusion’ one sees in punditry is fake - a position taken for rhetorical effect rather than any real misunderstanding.

Here’s a good metaphor. Climate is the clothes in your closet, weather is what you are wearing right now. The weather is constrained by the climate (you can’t wear clothes you don’t have), and the closet can change over time (new purchases/gifts), sometimes abruptly!

 @BlackPhysicists What are the basic equations from #physics of a good climate model? What are the dichotomies (false or otherwise) between ‘weather’ models and ‘climate’ models?

Atmospheric physics is basically the same - slightly different levels of truncation (spatial resolution etc) since climate models have to run longer and with more components (oceans, sea ice, composition, biosphere (to some extent)). But major difference in conservation properties and ingestion of observations.

For a weather model, continual updating with observations means small businesses imbalances don’t matter much. But climate models don’t ingest obs like this so small biases can build (model ‘drift’). Conservation is key.  Other issues are the diagnostics one is interested in. With weather, you want the specific trajectory of storms/fronts etc, with climate you want the statistical description (how many storms/what tracks) because that is where the skill is.

Actually, understanding the notion of skill is key for both kinds of model - how can you judge if a model is useful despite it not being perfect?

 @BlackPhysicists  @RogerAPielkeSr offers a lot of great resources in both #weather and #climate. One defn he's offered: Definition 1:Weather is separated by climate just by averaging time period; e.g. a 30 year time average temperature we call "climate" 

That’s been true historically, but that’s a little arbitrary and not fundamental. I would prefer a distinction based on forecasts of specific trajectories vs statistics of trajectories. An example might help.

@BlackPhysicists Right, it is possible, even necessary, to draw a distinction between a time average and more detailed statistics, even as basic as the meaning of standard deviation. That is an important point I think that's lost in a lot intro measurement in #physics 

Take Mt Pinatubo eruption. A very large forcing on the climate system, which had detectable impacts on rainfall, temperature, wind patterns. It didn’t extend the predictability of weather forecasts, however the statistical impacts were predicted skillfully by climate models.

Those climate forecasts were for 1, 2, 3 years out. Much shorter than the ‘30 year’ period you mentioned. The issue is one of signal and noise. For slow changes in forcings (or none), 30 years is a good period to average out a lot of internal variability. But for a big signal (like Pinatubo), the climate impacts easily exceed the ‘noise’ of the weather. Same with the seasons! (Note ‘noise’ here isn’t pejorative- one person’s noise is another’s signal after all). Bottom line, there is no longer single time period that separates weather and climate.

@BlackPhysicists I think a key bridge to build in the #physics curriculum is micro- meso- scale physics of how these things, aerosols, dust, etc affect #weather and #climate. That and the spectral decomposition of light and its effects 

How do you bridge weather models' that are built on 1st principle physics (continuity, Navier-Stokes, advection-diffusion of energy) to climate models? The latter isn't just long-time simulations of the former on meaningful grids and timesteps?

This is of course intended to be a counter-positional question 🤓 #

They aren’t different in principle. But all these models need to have a scale (in time/space) below which they are not resolving the ‘true’ equations. For weather models that scale is a little smaller than for climate models, but for both it’s getting smaller over time.

@BlackPhysicists And that is an important point that I think a lot of people don't get about computational physics, i.e., that pushing computational limits possibly/likely will reveal new physics just like increasing resolution, repetition rate etc of measurement does 

@BlackPhysicists Jan 12 More #iteachphysics @ClimateOfGavin you've been a great help today. Before we end, there are 2 related concepts sea surface temperature and ocean heat content. How can we best explain to students the difference between the two?

More Sea surface temperature is a diagnostic of what’s happening at the surface (duh!). It’s the field that has the direct connection to the atmosphere (via radiation, evap etc.). It is changes in SST that allow for the planet to requilibirate to any change in radiative forcing.

But ocean heat content changes writ large are tied to the planetary imbalance (how much more energy are we bringing in than losing to space). It was predicted in the 1980s that if the predictions of global warming were right for the right reasons, the signal would be in the OHC

Some discussions of that here in the light of recent updates and discussions:

@BlackPhysicists If you have time, could you give your take home message from the @NatureClimate paper that was in the news this week.



@BlackPhysicists I think I meant this report, which is more from an IPCC report at not the @NatureClimate paper. 

It's kind of covered in the @RealClimate piece I tweeted earlier. As non-climatic artifacts are removed from the OHC analyses and more data is being ingested from Argo etc, the predictions from GCMs are being nicely validated.



Saturday, December 29, 2018

Eli Explains It All: Or Why Just About Everybunny Gets Energy Thermal Energy Transfer Between the Surface and the Atmosphere Wrong


Everybunny who has been hanging about the Climateball Court for the Christmas Dinner Playoffs has heard the bit about how heat transfer from the surface to the atmosphere by radiation is small compared to that by convection.

Eli posted an elegant explanation of why that was, well to be nice, complete bollocks, but thinking about it again the Bunny has come up with a simple one that you could explain even to your obstreperous uncle next big family dinner.  Well.....maybe.

Perhaps we start with the usual figure



and the usual argument, that the heat flow into the atmosphere by evaporation and sensible heat is 104 W/m2 is massive while radiation only accounts for 398 - 342 W/m2 which is a minuscule 56 W/m2.  Limited sarcasm about minuscule.

There is a major problem with this.

It assumes that there is a difference between thermal energy that has entered the atmosphere from evaporation and sensible heat and thermal energy that entered the atmosphere by radiation.  

Nope

Let Eli reduce this to jelly beans.

If three bunnies put black jelly beans into a well shaken jar can anybunny tell Eli which one donated the black jelly bean he took out and is munching on?


Wednesday, December 26, 2018

I'll take Bashkirtsev's can't-lose side of the bet with James Annan

James Annan is low-key:


The bet - final outcome

You may be wondering what had happened with this. As you will recall, some time ago I arranged a bet with two Russian solar scientists who had predicted that the world was going to cool down. The terms of the bet were very simple, we would compare the global mean average surface temperature between 1998-2003 and 2012-17 (according to NCDC), and if the latter period was warmer, I would win $10,000 from them, and if it was cooler, they would win the same amount. See here and here for some of the news coverage at the time.

The results were in a while ago, and of course I won easily.....

So this should be the point at which I ask my blog readers for ideas as to what to spend the $10,000 on. I was hoping to do something that would be climatically and environmentally beneficial, perhaps something that might garner a bit of publicity and make a larger contribution. But they are refusing to pay. More precisely, Bashkirtsev is refusing to pay, and Mashnich is refusing to even reply to email. With impressive chutzpah, Bashkirtsev proposed we should arrange a follow-up bet which he would promise to honour. Of course I'd be happy to consider such a thing, once the first bet is settled. But it looks unlikely that this is going to happen.


Clearly, James was out-maneuvered, and that's why I prefer Bashkirtsev's position. You make a bet with someone honorable, and if he loses, he pays, while if terms come out wrong for you, then you refuse to pay and instead offer him a new chance to lose his money. Repeat as needed.

I'll take a bet that gives me a one-in-a-million chance of winning and zero chance of losing. Bashkirtsev, I salute you!

More seriously, Nature magazine covered the original bet and should cover the resolution. Better yet, they should fly James to Russia and do an ambush video of the two Russians. Or fly ME there, I'll pretend to be James and scream WHERE'S MY MONEY, DENIALISTS??? WHERE'S MY MONEY?!!!

As a side note, I've criticized my own bets with David Evans as being over-complicated, but we did address this issue via an escalating series of bet amounts over three time periods, so there's that. And David seems honorable to me, however wrong wrong wrong, dangerously wrong, he may be on climate.

Another side note, here's a blog on climate betting: http://ohbwaa.blogspot.com/. I kind of think the moment has passed due to denialists being mostly unwilling to pony up (I've probably challenged over a dozen, and I know many others have done the same), but good for this blogger for publicizing it.

Sunday, November 18, 2018

My take - The Carbon Tax Is Dead, Long Live the Carbon Tax?

While I'm inventing traditions, how about a new one that a blog post riffing off another blog post should directly steal the headline?

So I'm riffing off of William's post regarding the lab experiment in Washington State, with a revenue-neutral carbon tax in 2016 failing (William appears to obliquely refer to this one), and now a revenue-generating carbon tax in 2018 also failing.

For the audience of climate bloggers and their readers, I'll put the most relevant-to-them point first rather than bury it like I usually do: scientists and engineers seem to treat scientific and engineering challenges as legitimate while political challenges are somehow illegitimate combinations of incompetence and corruption. As a once (and apparently, now again) small-pond politician, I'll just say the political challenges of climate change would be easy if you could provide perfect long term and short term localized forecasts, and provide a no-cost engineering solution to the problem. These are all human problems.

Political challenges are as mind-bendingly difficult. Neither William nor Tyler Cowen are announcing magic solutions that will win political contests, so maybe that's a recognition on their part that the challenge is real.

Not that I have a magic solution either. I think Churchill's sayings about democracy being the worst government type except for all the other types, and that Americans can be counted on to do the right thing after exhausting all other options, might apply to Washingtonians. Maybe third time's the charm for Washington State, and some impure compromise between the two prior initiatives can succeed.

And speaking of impurity, there's the fossil fuel companies. Yes, the public has moral agency and protecting democracy is ultimately up to them, but fossil fuel companies throwing sand in their eyes and buying out their representatives isn't helping. They more than deserve their share of blame, especially as they hypocritically claim to support a carbon tax and then do their best to stop one from happening.

I'll end with a only half-joking suggestion: "Tax Carbon, Not Trucks, Beer, or Harleys". Set up a carbon tax, and stop taxing cars, trucks, beer, and motorcycles. The government gets to keep the extra tax revenue after making up for the lost tax revenue from those other sources.

Saturday, November 17, 2018

Eli Explains It All: No Atmospheric CO2 Is Not Saturated


One of the evergreens, besides the one that more CO2 is needed to grow more lettuce, is that the effect of CO2 in the atmosphere is saturated.

Part of the TL:DR to this is actually interesting and in the optional reading below, but the short of it is that the role CO2 plays in the atmosphere is to radiate a considerable amount of energy to space.  This is needed to balance the energy coming in from the sun.

In the atmosphere the higher you go the colder it gets till you hit the tropopause.

The amount of energy that can be radiated to space by COdepends on the fourth power of the temperature at the level it is radiated to space from

The effective level the CO2 can radiate to space from rises linearly with the increase in concentration. 

Until the effective radiative level is above the tropopause, adding more COslows the emission to space and thus the surface has to warm in response.

Eli has written on this before.  If you look at the emission spectrum from way up high the sharp spike in the middle of the CO2 band is where the concentration is so high that radiation cannot be emitted to space except high up in the stratosphere.


Everywhere else in the CO2 band emission is occurring in the troposphere (you can tell by looking at the temperatures, and you can tell by looking at the emission) and adding CO2 will decrease the amount of emission in the CO2 band.

Now the interesting stuff.  The optical density in the CO2 band below the effective radiative altitude is so high that any emission in that region is absorbed, at the surface in the first kilometer, on line center in the first 10 m.  The temperature in the first 10 m is essentially that at the surface.  That means emission from collisionally excited CO2 will be strong, with roughly half going back to the ground.  Increase CO2 and the backradiation will increase proportionally because there is more CO2.

That means by definition that much of the greenhouse gas effect on surface temperature is local to a few meters above the surface.

Worse, the stronger low lying backradiation slows down convection although it will speed up evaporation.

This is actually all buried in the computer code outputs from radiation transfer models, less so from gcms which don't slice and dice the layers so finely, but it is something to think about

Call it Our Party Housecleaning. Or just somewhat-moderating our hypocrisy. Take your pick

I'd like to suggest a new tradition in the period immediately following an election - to choose this time to go after the ugly flaws on one's own side of the political house.

I've written in the past that - during a campaign - I'm not going to highlight the flaws in the candidate I support. I wouldn't deny those flaws if pressed, but I'm not going to bring them up. In this increased partisan environment, I've extended that to the Democratic Party in general, although particular bad guys among the Democrats can overcome that bar.

Now that it's over though, time to at least acknowledge that cleanup is needed. A good example of an ugly flaw is Bob Menendez, the re-elected Democratic Senator in New Jersey and a likely corruption magnet. Keeping that seat Democratic to increase the odds of a Senate takeover was worth it to me. So once you're sworn in, Senator, please resign, and let the Democratic governor appoint an ethical Democratic replacement.

The chance of that request being listened to is pitiful, but we should make it regardless, and be prepared to support a Democratic primary challenger six years from now.

Another example of ugliness on the Democratic side:



The Planetary Society is correct, this is a Democratic Party War on Science campaign ad. I almost blogged about Culberson during the campaign - like him, I'm a space science nut, and very little of the political support for space extends far beyond the scientifically dubious boondoggle of government-supported, human spaceflight. My attitude was that I wanted Culberson to win if Rs kept control of the House, but if it made a difference in control of the House then I didn't. Had I known about this ad then I probably would have (should have) said something.

Fletcher didn't make this ad, it was by Michael Bloomberg's Independence USA PAC, and they should be ashamed for attacking science. Stick to attacking Culberson on earth-bound issues issues instead.

And then there's the gray area which is Keith Ellison and the domestic violence allegations against him that came up around the same time as the Kavanaugh disaster. There are two ex-girlfriends who say he abused them, which is a hell of a lot of smoke, although it's not 19 women either. The more recent accuser pretty much destroyed her credibility IMO by repeatedly talking about a video of the abuse and then refused to produce it, even in edited form or even for a private viewing by investigators. The earlier one appeared to have credibility problems too.

Personally, if I were in Minnesota I would've voted against Ellison in the Democratic primary and, with the limited information I had, voted for him in the general. I don't need to be certain beyond a reasonable doubt that Ellison was an abuser in order to support the Republican, but I'd want more than I had, given the damage the Republican Attorney General would do. And we need to watch Ellison very carefully moving forward.

As for Bill Clinton, please go away.

Saturday, November 10, 2018

Where I stopped resisiting Vox's call to resist - it's a matter of distance

I wasn't thrilled reading the title and intro to Yglesias' article, "House Democrats must resist Trump’s infrastructure trap":


President Donald Trump’s infrastructure trap is back, and for the new House Democratic majority to succeed, they need to escape it.

It’s forgotten now, but in the transition winter of 2016-’17, a shockingly large and diverse set of congressional Democrats — from both the progressive and moderate wings of the party and including some key leaders — spent enormous time and energy making friendly noises toward Trump and suggesting that the result of his election should be some kind of bipartisan infrastructure deal.

....Trump rapidly fell into the clutches of congressional Republicans’ hard-right agenda. He continued to tout vaporware infrastructure plans, only to eventually come up with a scheme to make grants stingier and privatize some airports, which went nowhere.

But with Democrats now running the House of Representatives, infrastructure is back. And Trumpworld figures, looking at the polls, maybe Trump and the Democrats should come together around a random debt-financed increase in infrastructure spending that lets Trump regain his reputation as a dealmaker and lets Democrats say they accomplished something.

....Since Trump is not very subtle, his team even explicitly told a group of Washington Post reporters that the infrastructure dangle is a trap designed to weaken Democrats’ political position. But in case anyone doesn’t get the message: This is a trap designed to weaken Democrats’ political position.

....Democrats of course can’t categorically rule out the possibility of doing a legislative deal with him. But you also don't trade away the rule of law and the basic integrity of the American government for the sake of some pork barrel spending.

Then it got better:

....Democrats also can’t afford to let Trump tour the country complaining that all Democrats want to do is investigate him while he is trying to fix the country’s infrastructure.

....This requires Democrats to come up with a plan that is striking and visionary enough that normal people stand a chance of actually hearing about and understanding it. But it needs to also be genuinely transformative in a way that would make it legitimately worth doing on the off-chance that Trump somehow decides to agree to it. ....[T]he country (and the world) really does need a transformative infrastructure plan. If Trump is desperate enough for a deal, maybe he’d go for it.

But the key is to put ideas on the table that would genuinely alarm the conservative movement — and, more important, the corporate interests who stand behind it — and force Trump to make a serious choice about breaking with the plutocrats who prop up his regime or clearly standing in the way of an infrastructure transformation.

That means massive investments in clean energy generation and transmission, municipal broadband, a serious revival of airline competition, and competitive grants to states for carbon-cutting transportation programs.

....priority No. 1 for that congressional resistance should be developing a strategy to counter Trump on infrastructure.

The key here is long distance power transmission. Yglesias argues for forcing Trump to break with his backers. I'm all in favor of forcing bad people to reveal the vile positions through symbolic votes,  but I don't think forcing Trump to break with plutocrats is a realistic path to get actual policy change. OTOH, long distance transmission puts jobs in red and purple states and helps expand the market renewable energy sources in those states, and the less-ideological/more-pragmatic conservatives in those states kind of like that profit motive. Given that power transmission could even theoretically be used by massive nuclear power plants, that constituency could also provide a minor amount of support.

Clean transportation is another potential area of cooperation - there are some advantages to purple areas and profit-seeking corporate interests, but long distance transmission is a real opportunity and a very important need.

Final note - while a deal may help Trump's image, it won't improve the economic fundamentals in time for the November 2020 election. Speaking as someone involved in receipt of the Obama stimulus for water projects, it will take more than two years for real expenditures to happen, and a deal is months away from happening.

Wednesday, November 07, 2018

Eli Explains It All: How Back Radiation Warms the Oceans

There appears to be a limited but vital audience for this newish series, Eli Explains It All, so once more the Bunny Brings Enlightenment.  An everygreen amongst the ignorati is that backradiation can't heat the ocean because it is all absorbed in the first millimeter or less.

And indeed this is true, the distance that IR light radiated from greenhouse molecules penetrates into water is a few wavelengths.  That distance is called the skin depth and it is not without consequence in some interesting and amusing ways as St. Jackson has taught us (well some of us).

Yet, as Einstein teaches us, the world is not malicious, but it is subtle, and the reason why heating the surface warms the ocean is closely related to why increasing greenhouse gases warm the Earth.

Eli will now explain.  Others have done so, Real Climate for one, but the Bunny has another simple picture that USAns can use on their uncs in a couple of weeks.

Start with the observation that sunlight is absorbed in the first few meters of the oceans.  How deep depends, of course, on what other kind of crap is there, bio and anthro, but for arguments sake a few meters.  That warms the top few meters, but the surface, that skin layer cools by evaporation.  Heat from the mixing layer will move by convection to the cooler skin layer.

Now comes the elegant part, back radiation warms the skin layer.  That means back radiation decreases the temperature difference between the skin layer and the mixing layer, Since convection depends on temperature difference, the rate of heat loss from the mixing layer decreases.  Thus the mixing layer will be warmer than it would be without back radiation and the extra warmth will be carried into the deeper ocean by conduction and currents.

Greenhouse gas warming of the surface thus acts as a control valve regulating the heating of the oceans by the sun.  The same thought about how greenhouse gases regulate the emission of heat from the Earth into space was expressed many years ago by John Tyndall
[T]he atmosphere admits of the entrance of the solar heat, but checks its exit; and the result is a tendency to accumulate heat at the surface of the planet.
To which Eli would add
The ocean surface  admits of the entrance of the solar heat, but infrared surface warming checks its exit; and the result is a tendency to accumulate heat in the oceans.