Wednesday, July 11, 2012

The space alien's answer to the greenhouse gas/heatwave question

If you asked a scientifically advanced space alien whether current heat waves are worsened by our greenhouse gas emissions, it might take the complicated probabilistic approach humans have used to explain that our emissions have made the heat waves far more likely.  Or maybe it will do something easier.

Our space alien, Gort, sends out the Insta-Array of temperature sensors to get a reading, and then presses the "Ennaturalnate" button on the Climate Changeometer, instantly reverting all global greenhouse gas levels to their pre-industrial levels.  I'll leave the final answer to the non-lawyers here, but I think that all other things being equal, there would be a small but real drop in temperature within a few hours.  If one third of our warming to date is from direct effects of greenhouse gases, then Ennaturalnate should instantly drop temps in a heatwave between .25 and .5F.  Non-lawyers, is this right?  UPDATE:  per the initial comments, might take more like a week for a heat wave on land, and far longer over oceans or globally.

So that's the first and simplest answer for the news media that has so much trouble with this - if you could immediately remove all the human additions to the atmosphere, then temperatures would drop within hours, a small amount.  If the local television allows more than a five second soundbite, then you add that moreover there are feedback effects that make things significantly worse and add up over time.  And many of the climate denialists would have to agree about the near instantaneous effect, because many of them acknowledge climate forcing while making up nonsense about feedbacks being negative.  These denialists can add their caveats, but noone cares.

Just one lawyer's view of the issue.

21 comments:

Anonymous said...

" If one third of our warming to date is from direct effects of greenhouse gases, then Ennaturalnate should instantly drop temps in a heatwave between .25 and .5F. Non-lawyers, is this right?"

I'm not sure about the timescale here. If you instantly double CO2, it takes several years to get 50% of the temperature response (http://www.columbia.edu/~tas2163/Wu_etal_2012.pdf is a paper about instant doubling of CO2 in a coupled 3D atmosphere/slab ocean system, you can look at the graphs here to see one example of response time). On a short timescale, if you live near the ocean, the ocean's response time is critical, and even if you live far from the ocean there are enough teleconnections that the response will still be slower than you expect. There's a lot of thermal inertia in the system: the reason that GHGs can change the temperature is that they are adding Joules every second of the day for years on end.

Also, you wouldn't capture any circulation effects due to GHGs for a while (the above paper suggests about a year for the new patterns to really settle in, and many more years for the new magnitudes to adjust).


Oh, wait, this paper is even better: http://www.gfdl.noaa.gov/bibliography/related_files/ih1001.pdf: for an instant return to preindustrial forcing, "The response is characterized by an initial fast exponential decay with an e-folding time smaller than 5 yr, leaving behind a remnant that evolves more slowly"

-MMM

Anonymous said...

A Machiavellian Earthling might ask Gort to ramp up the CO2 to 500 ppm for a year or several, before obliging us with that drop back to 280 ppm.

It would teach a lot of the slow folk on the planet what their intellectual betters have been trying to tell them for decades.


Bernard J. Hyphen-Anonymous XVII, Esq.

[Recaptcha said "9 Direlore"]

Hank Roberts said...

The direct effect is on the apparent temperature of the sky overhead -- so how much change you'd feel locally would mostly depend on the local humidity at the time, right? Make the change on a crisp cold night and it'd be noticeable; on a humid afternoon it'd probably be lost in the clouds.

By the way, to accomplish this, just pull in the little cosmic strings that we see tangled up making carbon dioxide molecules. Implementation left as a student extra credit exercise.

Anonymous said...

Dr. Lumpus Spookytooth, phd.

yeah and you could blow up the sun and the temperature would go down further, which proves that natural effects are stronger than manmade, but none of you cares.

J Bowers said...

If only the world could agree to try an experiment: switch everything off (apart from medical and emergency services) for a day or two to see if there were any measurable responses, after scientists had made predictions as to what would happen. Maybe do it two or three times. I'm also sure there'd be a cat's chance in hell of it happening.

Anonymous said...

Dr. Lumpus Spookytooth, phd.

here is a very telling quote from the paper

"However, studies of changes in extremes that include more recent observations show that ongoing changes in temperature extremes are regionally consistent with those observed in the latter half of the twentieth century."

the statement should read studies of changes "that only include" once again, no basis of comparison here.

How is it that global warming deniers are creationists but its the carbonazis who wont look at data before 1800? That's pretty funny.

a_ray_in_dilbert_space said...

Ah, speaking of aliens, Dr. Lumpus Spunkydrawers shows up to pollute the thread.

We'd be more than happy to peruse any data you care to provide, "Herr Doktor". I'm sure it would be a novel experience for you.

J Bowers said...

"Carbonazi"? Makes a change from something on the lines of "carboncommie". PizzaHomeDelivery guys are as consistent with their insults as they are with reasons for the planet warming.

Anonymous said...

My hunch is that the area of the heatwave may have actually experienced negative net energy anomalies -
more outgoing due to the higher temps, lower humidity atop the subsidence inversion.
( Of course those factors have to counter the increase solar input )

I've got some data to analyze and will post a results link here.

Of course, even if the above hunch is correct, removing CO2 would create a still larger negative net energy anomaly.

But the point is, for short term events such as this,
surface temperatures can and do anti-correlate with net energy to space.

CW

raypierre said...

The Held paper that one of the anonymice cited is indeed the best one for this. The 5 year rapid response time is mostly determined by the thermal inertia of the ocean mixed layer. There's a shorter term even faster response (especially over midlatitude land) they don't much talk about, and that's held back by the thermal inertia of the atmosphere itself, which yields a time scale on the order of a week or two. The water vapor and probably cloud feedbacks would set in on a similar time scale, at least over land, so you wouldn't have to wait very long for them to become important. But the temperature drop would not be immediate, since the atmosphere does indeed take some time to cool down.

Would the Ennaturalator also remove anthropogenic aerosols, or just the greenhouse gases?

dbostrom said...

Break a rack of balls on a pool table with a cue ball moving at 25mph and then try the same experiment with the cue ball moving at 26mph. Show how the rack of balls can absorb the additional energy of the 26mph cue ball without any externally measurable change in behavior and-- voila!-- we can make heatwaves behave identically no matter the energy in the atmosphere.

No problem. Just make energy vanish and we're done.

Russell said...

Carbonara sequestration seems a logical sequel to the Medium Apple's super sized soda ban.

Jeffrey Davis said...

If you removed the CO2 at night, the change wouldn't be noticeable at least until the next morning, right?

EliRabett said...

No.

Roy Spencers box experiment is relevant to this

Brian said...

Seems that it would take more like a week than a few hours to see an effect. I'll update.

To answer Raypierre's question, the Ennaturalnate button can be pushed with or without the Aerosolnilatron lever engaged, so Gort can show us the result either with or without resetting aerosols.

Scrooge said...

There can't be any scientifically advanced aliens. If they were advanced they already would have developed technology that would end up killing them.

Russell said...

Sorry, Scrooge.

All the aliens within 32 light years have been bored to death by reruns of Cosmos.

Anonymous said...

"Gort ... instantly revert[s] all global greenhouse gas levels to their pre-industrial levels. "

If Gort can pull off that trick, he'll get my vote (even if he is fat)

~@:>

Aaron said...

Run the weather models with the heat in the system set to 1960 levels.

The difference between those runs and the results recited on tonight's weather is global warming.

Lower sea surface temperatures change everything. It is SST that drive the winds that, do or do not, bring rain. The difference is much more than 0.5F. The difference is the change atmospheric circulation.

It is that change in atmospheric circulation that is melting Greenland ice (look at the winds.)

Brian Dodge said...

One important structural feature of the atmosphere is the fact that approximately 1/4 of the CO2 is above the 250 mbar altitude, but practically zero water vapor (~1/1000 to 1/2000, depending on local lapse rate & humidity profiles). If the CO2 were suddenly removed, the upper layers of the troposphere would rapidly begin cooling because of the loss of CO2 back radiation from above, and large areas would fairly quickly drop below the dew point. The resulting formation of clouds would increase albedo causing further cooling; it would be like global scale eruption of many Mount Pinatubos. The recovery from this negative spike would depend on the rate that the excess water rained out. The increased vertical temperature gradient would intensify storms over the short term. As the atmosphere approached equilibrium, returning to ~60-70% RH, the warmth stored in the upper layers of the oceans would maintain an increased hydrological cycle, with a relaxation time of years - sort of like a super El Nino, but without the patterns caused by differences between Eastern and Western Pacific. The areas that got dryer after Pinatubo erupted probably wouldn't dry out as much, but areas that got wetter would get much wetter.

kT said...

I would be more interested in the effects of variable solar irradiance from a variably transmissive annular occulting disk located at Solar L1 .