Tuesday, March 28, 2017

Gravity, the Greenhouse Effect and Surface Temperature


When Eli last left the bunnies, he was pointing out how gravity explains much of the greenhouse effect, well, except for the part that you need some things in the atmosphere that absorb IR radiation from the surface.

The first is the lapse rate, the decline of temperature with altitude in the troposphere.  There are plenty of detailed derivations of the dry lapse rate on the net and a bunny can even throw in some water vapor, but the basic principle is that the atmosphere is for all thermodynamic purposes an ideal gas, and the temperature decreases with pressure, and pressure decreases with altitude because of gravity. 
The second is the decrease in density with altitude, again because pressure decreases with altitude because of gravity.  The higher you go the less stuff 
Both of these effects explain why radiative energy transfer from the ground to space slows, the higher greenhouse gas concentrations are.  
In a shortly following post the Rabett quoted pretty much the same from J.S. Sawyer, written in 1972
The chief effect of increasing carbon dioxide is that the gas which is radiating heat to space is found at a higher level in the atmosphere than before - the radiation from lower down in the atmosphere is absorbed by the extra carbon dioxide above and then reradiated to space.  In the troposphere, at least, temperature decreases with height so the effective radiating temperature of the carbon dioxide becomes lower if the amount of the gas is increased and therefore less heat is radiated to space.  Thus the additional carbon dioxide tends to act as a blanket which keeps the Earth warmer - the Earth has to get rid of the incoming radiation from the Sun, and the same amount can only be removed if the temperature of the atmosphere rises a little.
But, to be honest there was some handwaving there, namely the mechanism for heating the surface when the radiating layer moved up.  Ferren in a comment provided the link.  As shown in the figure, when the radiating level moves up because the CO2 mixing ratio increases, since the lapse rate (the slope) stays constant, the surface temperature increases and, of course, the reason the lapse rate stays constant is that it is fixed by gravity.


Anybunny who wants to deny that the greenhouse effect exists or that increasing greenhouse gas concentrations will not warm the surface is denying the law of gravity, which is pretty basic.  Given that humidity increases with temperature, they are also going to have to deny a fair bit of thermodynamics to claim that the concentration of water vapor in the atmosphere will not occur.

Monday, March 27, 2017

Maybe the Republicans will LGBTQ our health care after all

I thought after the election that Republicans' best political strategy on health care was to do what they planned on LGBTQ issues, which is (with several important exceptions) strongly condemn the Democrats for steps taken for gay rights, and then continue those steps. Examples are gays in the military, jobs protection, and gay marriage. Exceptions are in general being transphobic, and gay rights overseas. The exceptions offer some political rewards, but reversing other gains in LGBTQ rights would come at a political cost.

There was no political victory route for Republicans on healthcare, including either repeal or repeal-and-replace. It all ends in disaster for them. Now they can just grouse about Obamacare but announce we'll just have to live with it, rather than make a serious effort to do something about it over the next four years.

The next question is whether they'll actively sabotage Americans' health care in the belief it will help them politically - maybe they'll do it, but I'm not sure it'll help them.

If for some reason they actually do the right thing and work on bipartisan, incremental health care improvements, maybe they can campaign in 2018 on the basis of governance rather than emotion. Just don't hold your breath for this.

Friday, March 24, 2017

An Oldie But Goodie - J.S. Sawyer on the Greenhouse Effect and CO2

In the continuing quest to find excellent descriptions of the greenhouse effect, Eli has come across J.S. Sawyers Nature article from 1972, Man Made Carbon Dioxide and the Greenhouse Effect, which was commented on by Skeptical Science and warehoused (bunnies can read it there) by the Weasel.  Ray Pierrehumbert and David Archer included it in their climate change reader. Nevelle Nicholls wrote an appreciation of Sawyer's ground breaking work in 2007 under the title of A Warning We Ignored 35 Years Ago, unfortunately just as valid  today 45 years later.

In four pages, Sawyer summarised what was known about the role of carbon dioxide in enhancing the natural greenhouse effect leading to warming at the earth's surface, and made a remarkable 28-year prediction of the warming expected to the end of the 20th century. His prediction can now be compared with what has been observed. 
 Nicholls continues
While the IPCC (2007, ER)  assessment devotes a volume to this subject, Sawyer could only conclude, after conceding that climate variations of only a fraction of a degree can have "considerable economic importance" that "although there may be no immediate cause for alarm about the consequences of carbon dioxide in the atmosphere, there is certainly need for further study".

Perusal of the IPCC volume devoted to the impacts of climate change on natural and human systems leaves one feeling far less sanguine than Sawyer was 35 years ago.
Sawyer's description of the greenhouse effect, as well as the rest of the paper, is masterful
As carbon dioxide is one of the principal gases taking part in radiation exchange in the atmosphere and in the radiation of the Earth's heat content, a change in the content of carbon dioxide within the atmosphere is likely to influence the process.  The chief effect of increasing carbon dioxide is that the gas which is radiating heat to space is found at a higher level in the atmosphere than before - the radiation from lower down in the atmosphere is absorbed by the extra carbon dioxide above and then reradiated to space.  In the troposphere, at least, temperature decreases with height so the effective radiating temperature of the carbon dioxide becomes lower if the amount of the gas is increased and therefore less heat is radiated to space.  Thus the additional carbon dioxide tends to act as a blanket which keeps the Earth warmer - the Earth has to get rid of the incoming radiation from the Sun, and the same amount can only be removed if the temperature of the atmosphere rises a little.
He continues
An atmosphere at a higher temperature can hold more water vapour and the additional water vapour produces a similar blanketing effect to that produced by carbon dioxide.  Manabe and Wetherald calculate that an increase of 100% in the content of carbon dioxide would increase the world temperature by 1.3 C if the water content of the atmosphere remained constant, but by 2.4 C if the water vapour increased to retain the same relative humidity.  The increase of 25% of CO2, expected by the end of the century therefore corresponds to an increase of 0.6 C in world temperature, an amount somewhat greater than the climatic variations of recent centuries 
He did pretty well




Friday, March 17, 2017

The Past is Prologue to the Future - EPA Version

With Trumps, Pruitt and Co. busy dismantling EPA Eli has been showing the young bunnies postcards from the past of places like Los Angeles and their future wheresoever they are



However, this being Friday, a musical interlude is required

Thursday, March 16, 2017

What's Your Jacoby Number? - 6, 35, 67, 72, 75, 180


Jeff Jacoby has exposed himself to the Skeptical Science in an article that appeared recently in the Boston Globe.  While it's not even a winner in Climate Change Denial Bingo (Trademark Tim Lambert) Eli prefers to simply call out the numbers at Skeptical Science.

Mostly the article simply repeats old nonsense, but there is one new deceptive argument typical of those like Jacoby who know nothing and whose stock in trade is bluster about everything including climate change.  For the sake of argument Eli would like to dissect that

But for the sake of argument, say there are merely 15 variables involved in predicting global climate change, and assume that climatologists have mastered each one to a near-perfect accuracy of 95 percent. What are the odds that a climate model built on a system that simple would be reliable? Less than 50/50. (Multiplying .95 by itself 15 times yields 46.3 percent.) Is it any surprise that climate-change predictions in the real world — where the complexities are exponentially greater and the exactitude of knowledge much less — have such a poor track record?
Eli will call this the Jacoby birthday argument for it's vague relation to the old proposition of how many people do you have to have in a room to get good odds that they have the same birthday.  As everybunny knows you figure this by taking the probability that two people don't have the same birthday, eg. that the second persons birthday is one of the other 364 days and then continuing so the probability is 364/365 x 363/365 x 362/365 etc. and you find that with 23 people it's even odds that two have the same happy day.

When Ms. Not Mr. Bluster says that she knows the value of a parameter to an accuracy of 95%, what she means is that she has evidence that the actual value lies within some range of her estimate of the most likely value.  The most likely value and the range can be set by theory, by observation, by observation, by experience, aka expertise or some combination of the three.

Since at least for climate models the uncertainty in the parameters is two sided, e.g. each parameter estimate is as likely to be too small and too large.  So if you have 15 parameters that you multiply together odds are some will be a little too large and some a little too small, and in the end the result will average out to be just right (or close).

Best sets of parameters can also be inferred from comparison with observations. Climate modelers can create an ensemble of results by systematically or randomly varying the parameters of their model, observing the variation in their results and comparing with observation.

There is even a way out of the one Earth problem, ie that there is only one set of observations which is discussed in Numerical Recipes pp689  Confidence Limits on Estimated Model Parameters describing how uncertainties in parameters can be deduced as well as the best fit parameters.

Tuesday, March 14, 2017

Top 5 ENSO climate bet - in progress

I'm working on a new climate bet offer - that for 2017 or for a subsequent year that someone would like to bet with me, that year will be in the record top five years for the type of ENSO year that the particular year ends up being, whether it's El Niño, La Niña, or a moderate year. Quickly perusing the temp record suggests it would be a fairly safe (but not guaranteed) bet although I haven't really analyzed it.

I think it could in some modest way help focus attention on comparing apples to apples rather than stupid finger-pointing at La Niña years being colder than El Niños. Showing almost every year is in the top five is usefully alarming, too.

Haven't quite worked out the details, especially the best data set. Suggestions are welcome, and credible betting opponents are even more welcome.

Tuesday, March 07, 2017

Why We Will March for Science in April

We will march for what we love, the thrill of discovery, the joy of understanding, and the benefits for all.