Guest post by Willis Eschenbach
There’s a new study out from NOAA called “Probable maximum precipitation (PMP) and climate change”, paywalled of course, which claims that global warming will lead to a 20%-30% increase in “probable maximum precipitation”. The abstract says:
Probable Maximum Precipitation (PMP) is the greatest accumulation of precipitation for a given duration meteorologically possible for an area. Climate change effects on PMP are analyzed, in particular, maximization of moisture and persistent upward motion, using both climate model simulations and conceptual models of relevant meteorological systems. Climate model simulations indicate a substantial future increase in mean and maximum water vapor concentrations. For the RCP8.5 scenario, the changes in maximum values for the continental United States are approximately 20–30% by 2071–2100. The magnitudes of the maximum water vapor changes follow temperature changes with an approximate Clausius-Clapeyron relationship. Model-simulated changes in maximum vertical and horizontal winds are too small to offset water vapor changes. Thus, our conclusion is that the most scientifically sound projection is that PMP values will increase in the future due to higher levels of atmospheric moisture content and consequent higher levels of moisture transport into storms.
When I heard that number, a 20%-30% increase in maximum rainfalls, my urban legend detector starting ringing like crazy.
Figure 1. The authors’ guess at how much more rain will be falling by the end of the century.
So … why did my urban legend detector go off from this claim? It has to do with energy.
The press release quotes the authors as saying:
“We have high confidence that the most extreme rainfalls will become even more intense, as it is virtually certain that the atmosphere will provide more water to fuel these events,” said Kenneth Kunkel, Ph.D., senior research professor at CICS-NC and lead author of the paper.
Now, the increase in maximum rainfall is said by the authors to be due to the increase in water vapor in the air. It’s unclear if the 30% increase in maximum rainfall will be matched by a corresponding overall increase in rainfall. However, it is highly unlikely that an increase in water vapor will only increase maximum rainfall events. The authors themselves say that their projections show “a substantial future increase in mean and maximum water vapor concentrations”.
So to be conservative, let’s cut the 30% increase in maximum water vapor down to a 20% increase in mean water vapor, and see what that looks like.
I want to determine how much energy we’re talking about here. Suppose the rainfall were to go up (on average) by about 20% globally. Right now, the globally averaged rainfall is on the order of a metre of rain over the entire surface per year, a bit more or less depending on who is measuring. Twenty percent of that is 200 mm. So we need to evaporate an additional 200 mm over every square metre of surface to produce the stated increase in rain.
It takes 2260 joules of energy to evaporate a gram of water. For each square metre we need to evaporate 200 mm, or 200 kg of water. To evaporate that much water takes 4.52e+8 (452,000,000) joules of energy.
Now, a joule is a watt-second. We need 4.52e+8 joules of energy every year to evaporate the additional water, which is 4.52e+8 watt-seconds per year. Dividing that by the number of seconds in a year (3.16e+7) gives us the change in constant 24/7 watts needed to evaporate that much water. Remember, this is an increase in the constant watts of energy striking every square metre of the planet.
And that number, dear friends, the amount of additional energy needed to increase global evaporation and thus rainfall) by 20%, turns out to be 14.3 W/m2. That’s about the amount of energy increase from three doublings of CO2. Yes, CO2 would have to go from the current ~400 ppmv to about 3,200 ppmv to provide that much extra forcing …
So my urban legend detector is still working fine. There’s nowhere near enough energy available to power that claimed jump in rainfall.
Now, I could leave it there, since the energy necessary to make their claims possible doesn’t exist. But in order to confirm that finding, my plan of further inquiry was to see whether either the intensity of rainfall events or the mean rainfall has changed over the last century. People are always claiming that we don’t have any controls for our experiments when we study nature. But nature provides its own experiments. To start with, we have the warming since 1900. On land, according the Berkeley Earth Surface Temperature data, the temperature has gone up about a degree over that time … but did the rainfall go up as well?
Figure 2. Global precipitation over the land, in mm/day. Data Source 1901-2009: CRU TS 3.10.01 (land)
OK … no increase at all in global rainfall, neither in the monthly means nor in the maximums. So no support for their claims there.
So how about local maximum rainfall events? Are those going up?
For this, we can turn to the temperature and precipitation records of England. For the Central England region, we have daily temperatures and daily precipitation records since 1931. Since 1931, the average Central England Temperature (CET) record has gone up by just under one full degree. So we should see any thermal effect on the maximum rainfall. With that 1°C temperature rise as the backdrop, here’s the maximum central England daily rainfalls, month by month, for the last eighty years.
Figure 3. Maximum daily rainfall, 1931-2012, Central England. Data Source Photo Source
Here, we find the same thing. There is no evidence of any increase in maximum rainfall events, despite a 1° temperature rise.
Hmmm …
The part I really don’t like in all of this is that once again, all of their claims are built on computer models. But what I don’t find is any serious testing of their whiz-bang models against things like the global or the CET temperature and rainfall records. In fact, I don’t see any indication in any venue that any computer models are worth a bucket of warm spit when it comes to rainfall. Computer models are known to perform horribly at hindcasting rainfall, they do no better than chance.
So once again, we’re back in the land of Models All The Way Down. I gotta confess, this kind of thing is getting old. NOAA and NASA appear to be falling further and further behind reality, still churning out useless studies based on useless models.
Just one more waste of taxpayers money.
w.
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John Parsons AKA atarsinc
Willis, Thanks for addressing my questions. I know you are much more knowledgable on the subject than I, but I don’t learn much unless I’m willing to ask stupid questions.
I think you ( and a few others here) are failing to consider that CO2 has effects far higher in the atmosphere than water vapor. I question your idea that the additional heat leaves the atmosphere as quickly as you describe. My understanding is that it will leave, but only after establishing some form of equillibrium. That can take a very long time.
You used the example of the UK to reinforce your argument. If you would have used the US during the same time, you would have refuted your own argument. That was my point.
You say, “… note that on the map in Figure 1, it shows these increases will happen everywhere. I’d already investigated the global question in Figure 2 and the associated discussion, showing no increase in either mean or maximum rainfall despite global warming.” Willis, you showed land only values. An old sailor like yourself knows that ain’t everwhere.
Willis, my remark that the argument “doesn’t fly” says nothing about your “motives”. I don’t doubt your sincerity.
I’ll try to contact the author’s of the study and see what they have to say about your…dare I say it, model.
Respectfully, JP
Another brilliant essay, Willis. And yet more overwhelming evidence that some scientists at NOAA suffer from an genetic defect which deprives them of all empirical instincts. They can survive only in a bubble of unvalidated models.
John Parsons AKA atarsinc
Ill Tempered Klavier says:
April 6, 2013 at 9:24 pm
ITV, Thanks for the response. You say, “Since 4.52e+8 joules is the additional energy needed to evaporate the amount of water required to yield a 20% increase in precipitation for one year, each year that continues needs that amount of additional energy from somewhere.”
I (and several others here) are not convinced that’s correct. It would be, if nothing was preventing the heat from quickly leaving the system. But the atmosphere does put restraints on the heat leaving. I think one would need to find out how and when the system returns to equilibrium.
I look forward to you addressing Nick Stokes’ point, as many here seem to believe that Willis’ model oversimplifies that issue.
Sincerely, JP
Nick Stokes:
Did I miss the part where they built a stainless steel shell around the outer atmosphere?
Really? There’s no heat sink in the upper atmosphere? Thermal energy doesn’t radiate away from there? Do you actually hear yourself???? So outer space is no longer a heat sink?
John Parsons AKA atarsinc
Lars P. says:
April 7, 2013 at 2:08 pm
“Bear in mind that the water cycle is net energy transfer from the surface to the higher atmosphere. the net energy transfer through radiation inside the atmosphere is much lower, a think that warmista keep on ignoring.”
True, but you still have that energy in the atmosphere.
How about people stop calling each other “warmistas” and ” deniers”. What does that add to the conversation? JP
Nick writes “No dispute there. But OLR can’t increase by 15.6 watts, unless the air becomes extraordinarily hot. There’s no other heat sink up there. That heat has to come back down.”
Has to come back down? Really? Is that the only option? What about… Gets radiated away from the earth along with the rest of the sun’s energy that was absorbed that day?
John Parsons AKA atarsinc
TimTheToolMan says:
April 7, 2013 at 3:29 pm
Tim, you say, ” What about… Gets radiated away from the earth along with the rest of the sun’s energy that was absorbed that day?”
There’s your problem Tim. A portion of the energy the Earth recieves each day IS NOT radiated back out of the atmosphere “that day”. There is an imbalance between the incoming and outgoing radiation. This imbalance is measurable. Just like the oceans, the atmosphere needs time to equilibrate a perturbation. This is at the heart of why I believe Willis’ model is overly simplistic. JP
Excellent article, as usual. Willis says:
“There is no evidence of any increase in maximum rainfall events, despite a 1° temperature rise.”
A 1ºC rise is substantial. Which makes me question how accurate the temperature record really is. A 1º rise would surely cause significantly more precipitation, no?
And atarsinc claims that CO2 lingers in the atmosphere for a long time, but numerous peer reviewed studies show short [≈5 yr] persistence.
John Parsons AKA atarsinc
Vince Causey says:
April 7, 2013 at 7:36 am
Vince, you say that the energy “…remains within the climate system…”, and thus leads to “an absurdity”. It would if ALL the energy stayed for an indefinitely long time. But, only a portion does. What portion is beyond my knowledge, but Willis’ argument suffers from the equal but opposite assumption: the energy all leaves within a a very brief period. JP
MikeB,Nick Stokes, WernerBrozek etc.
It’s not as simple as all that. to Increase precipitation from 1m (ave) per annum to 1.2m per annum on average requires the evaporation and transport of 20% more water to the Troposphere AND the energy required to raise the humidity to the required level. To sustain a 20% increase in flux of water through the troposphere, that energy needs to be continuously supplied. The Models actually (partially) account for the evaporation (That is for the present levels of evaporation), but according to Will Kininmonth not enough. The models do not account for the energy loss of conversion of heat energy to potential, kinetic, or electrical (Lightning) for that matter. This loss constitutes a large negative feedback.
The IPCCs presumed energy increase from a doubling of CO2 is 3.7W / M2 – remember that this is after FEEDBACK so you can’t get out of the argument by saying the water vapour increases the energy – THE IPCC estimate is After Feedbacks and we need an after feedback value to compare with it.
The paper purports that a forcing of 3.7W/M2 could increase precipitation 30%, and Willis sets out to prove this is energetically impossible.
Willis has correctly shown that even a 20% increase in precipitation (alone) takes about 14.3 W / M2 to create, I say it’s more because just evaporating the water doesn’t supply any energy to get it to 3Km high. The AVAILABLE energy to do this is 3.7W per Meter squared (by the IPCC) which includes all recycling of energy to the surface by the water vapour.
You are correct to say a small proportion of that energy is “Recycled” (which would reduce the number a little – but doing so would give you a BEFORE Feedback forcing) but that’s not how the IPCC does it, they use Net forcing AFTER feedbacks not before, so Willis’s number represents a forcing after feedbacks which can be directly compared with the IPCCs after feedback available energy estimate.
14.3/3.7 is 3.8 – Therefore the 3.7W/M2 available energy is only sufficient to drive 20/3.8 or a 5.2% rise in the flux of water through the hydrological cycle (Assuming no other losses). And as was pointed out, if all the energy is consumed in cycling water, nothing is left over to heat the planet!.
He thus proves the Hypothesis that a doubling of CO2 can produce 20-30% more precipitation is wrong
There is a central mistake in climate science – Conservation requires that we account all the inputs and output of energy to/from the system – when you make a claim such as this you must remember that you need to do work in many places, the CO2 Energy needs to provide the energy to provide the extra rainfall, heat the atmosphere, produce the extra air velocities and energy for lightning in those superstorms we are all warned about . You can’t have it all in 3.7W/m2 (which is all the extra energy available) conservation demands it.
PS Heat energy is radiated to space but the fraction converted to kinetic energy is expended into the earth’s gravitational system (moving the earth relative to the sun), or damps or speeds the earths rotation a fraction. It’s Lost as heat then, disappeared into the motion of the planets and once it’s out we need to put it back
John Parsons AKA atarsinc
dbstealey says:
April 7, 2013 at 4:32 pm
D.B., I’m made no comment on th residency time of CO2. I said CO2 is found at much higher altitudes than water vapor.
But since your 5 yr residency figure seemed so far out of whack with most current knowledge, I took a look at your source. Of the 36 studies, ALL were over twenty years old. Most were thirty years old or older. Many were from the sixties and seventies. Just being old doesn’t mean there wrong, but in this area of Science they just didn’t have the investigative and measurement capabilities to make accurate predictions.
Compare the more up-to-date studies, you’ll see what I mean. JP
Jim D says:
April 7, 2013 at 11:35 am
I hadn’t even looked at the C-C part of their calculations. However, I doubt very much if we’ll see a global 20% increase in water vapor. As Forest Mims III pointed out upstream, we haven’t seen much change in that at all.
Part of the problem is that the ocean isn’t going to get 3° warmer without the addition of huge amounts of energy. This is because climate sensitivity is inversely proportional to temperature—it takes more and more energy to gain each additional degree.
And in the range of temperatures where the natural heat engine we call the climate runs, the price for one more degree is very, very steep. This is not, as people often assume, merely due to the fact that radiation goes up as the fourth power of temperature.
An additional part of this is from what is called “negative feedback”, but is better characterized as “parasitic loss”. As with all heat engines, parasitic losses increase as some power of ∆T, the difference between the hot and cold ends of the heat engine.
Finally, and most importantly, there are a number of self-organized, emergent phenomena which come into existence to cool off any surface hot spots, particularly in the tropics, the hot end of the natural climate heat engine. These include thunderstorms, the El Nino/La Nina pump to move hot water to the poles, dust devils to carry excess surface heat aloft, cyclones, and the Rayleigh-Benard circulation of the uppermost ocean and lower atmosphere.
Regarding the increase in humidity, I suppose I should write a post about how thunderstorms act as a natural de-humidifiers. But in any case, yes, you could easily have 20% more total precipitable water in the air without a 20% increase in rain. It depends on the temperature of the air. By the same token, you could have more rain with the same humidity.
Finally, the biggest variable in evaporation rates is the wind. While the C-C equations rule regarding energy at the water surface, evaporation varies linearly with the wind. This is one way tropical thunderstorms keep going. The squall wind at the base of the storm jacks the evaporation rates through the roof, reducing the air density and keeping the thunderstorm alive.
Best regards,
w.
atarsinc says:
April 7, 2013 at 2:49 pm
Thanks, John. On my planet the only stupid questions are the ones you don’t ask.
When the thunderstorms take the heat from the surface up to say 15,000 feet, the air pressure is only about half what it is at the surface. This means you’ve just cut the CO2 effect in half.
Much more importantly, you’re way above the most important greenhouse gas, water vapor. Because of the combination of these two effects, the energy in the air is much freer to radiate out to space.
Many people don’t realize that 75% or so of the downwelling longwave radiation striking the surface comes from the bottom hundred meters or so (330′) of the atmosphere. That’s how effective the water vapor and the CO2 are at absorbing longwave radiation. By moving as latent heat from the surface to the inside of the cloud, and as sensible heat only when shielded by the cloud, the interaction with the GHGs in the bottom of the troposphere is avoided almost entirely.
And as a result, where it does emerge high in the troposphere is much more free to radiate energy away to space.
All the best,
w.
atarsinc says:
April 7, 2013 at 4:38 pm
Ah, I see I’ve not been clear enough. My argument is not that it “leaves within a very brief period”. I don’t think you could even measure that.
I say that once the energy moves from the surface to the upper troposphere, little of it returns to evaporate more water at the surface.
Does some return? Sure, that’s the deal with the greenhouse effect.
But because it’s moved way up to the top of the troposphere, and heat doesn’t mix downwards very well, and it’s freer to radiate to space up there, and at theoretical best you’d only expect to get less than half back down in a perfect situation … you’re not going to get a whole lot all the way back to the surface to evaporate more water.
w.
atarsinc says:
April 7, 2013 at 4:58 pm
John, you’re conflating half-life (or e-folding time) with molecular residence time in the atmosphere. The former is the time it takes a pulse to decay to half it’s initial value. The latter is how long the typical CO2 molecule stays in the air.
The latter, residence time, is on the order of 5-8 years, depending on what figures you use.
The former, the half-life or e-folding time, is the subject of much debate, none of which is on-topic in this thread.
All the best,
w.
atarsinc says:
“I’m made no comment on th residency time of CO2.”
But you did, John:
“There is an imbalance between the incoming and outgoing radiation. This imbalance is measurable. Just like the oceans, the atmosphere needs time to equilibrate a perturbation. This is at the heart of why I believe Willis’ model is overly simplistic… I question your idea that the additional heat leaves the atmosphere as quickly as you describe. My understanding is that it will leave, but only after establishing some form of equillibrium. That can take a very long time…”
Those statements concern CO2 residency time.
Also, what does it matter if a study is twenty years old? My point was that all the papers [with the lone exception of the IPCC] are in agreement that CO2 has a much shorter residency time than the doomsayers admit. If they admitted that CO2 does not linger in the atmosphere for very long, their “carbon” scare starts to fall apart.
Finally, I would be interested in your response to Willis’ 5:40 pm comment above. It seems to me that situation would reduce the effect of CO2 by a considerable amount. It would also go a long way toward explaining this.
Willis, you are predicting warming without increased rainfall. This is a good recipe for lower relative humidity, less clouds, and an arid climate. I hope you are wrong on that, but I would say that there are parts of the world vulnerable to this turn of events. As I mentioned, I believe the sun has enough energy to evaporate an extra 14 W/m2 of latent heat, and this is not connected to the CO2 at all.
Jim D says:
April 7, 2013 at 7:35 pm
Jim, you are making claims about my predictions without quoting my words. This is a good recipe for misunderstandings. I can defend my own ideas, but I can’t defend your interpretation of them. I don’t recall either predicting warming, or predicting that it would occur without increased rainfall. What I said was that a 20% increase in global rainfall wasn’t gonna happen.
Quote my words that you think are wrong, Jim. Otherwise, no one (including myself) knows what you’re talking about.
w.
atarsinc write “This imbalance is measurable.”
Or so we thought. Perhaps you can let Trenberth know where that energy is hiding then?
CodeTech says: April 7, 2013 at 3:18 pm
Nick Stokes:
“Really? There’s no heat sink in the upper atmosphere? Thermal energy doesn’t radiate away from there? Do you actually hear yourself????”
Do you actually read? Even what you quote? I said “There’s no other heat sink”.
John Parsons AKA atarsinc
Willis, Thanks for your response. But, more importantly your clarifications. You’re a good teacher.
I sometimes find myself assigning the thoughts of commenters that agree with you; to you, yourself. Your clarifications make that error obvious. After all, the title of your article was, “Improbable…” not “Impossible”.
Because you said:
“…within about fifteen minutes of leaving the surface, a parcel of air leaving the surface [sic] is transported to the top of the atmosphere. [Did you mean top of the troposphere? Can a parcel of air actually move to the TOA?] So yes, they can move that fast.”
I was pleased to see you clarify that by saying,
“Ah, I see I’ve not been clear enough. My argument is not that it ‘leaves within a very brief period’. I don’t think you could even measure that.”
That makes more sense to me.
Others here should note that you said this:
“But because it’s moved way up to the top of the troposphere, and heat doesn’t mix downwards very well, and it’s freer to radiate to space up there, and at theoretical best you’d only expect to get less than half back down in a perfect situation … you’re not going to get a whole lot all the way back to the surface to evaporate more water.”
This addresses what some of us were trying to point out (e.g. Nick and others). Actually, “less than half” could have a very large impact on your calculation. Particularly when a couple of other 2 or 3 percentage factors that you conceded are added to the equation.
Willis, regarding the CO2, you are correct that I was conflating e-folding and molecular residency; but, in my defense, so was/were the author(s) of the link D.B. cited. When I see an author who cites literature that’s largely from 30 to 40 years ago (the most recent being 22 years old) in a field where new information is expanding so rapidly; and that author(s) present(s) literally none of the large number of more recent studies, my B.S. detector starts going off.
I want to study your comments in depth. There”s a lot of interesting stuff there, and I’m not conversant at your level of knowledge on atmospheric physics. You’ll excuse me if I say your comments seem much more profound than the post.
I often try to communicate with the authors(s) of studies that are criticized at such a fundamental level. I’ll attempt to do that here and will let you know if I get a response.
Thanks again for taking the time to address some of my questions. JP
John Parsons AKA atarsinc
dbstealey says:
April 7, 2013 at 6:27 pm
atarsinc says:
‘I made no comment on the residency time of CO2.’
“But you did, John…”
Where in that statement do you see any reference to residency time of CO2?
If I told you a story about my dog digging in the rose garden, would you say I was “commenting on fur”?
Geez!
John (atarsinc),
I would like to apologize if I came across too strongly in my prior comments. I am so fed up with the usual alarmists’ digging in of their heels, that I overlook the relatively few commentators who have a genuine desire to learn and understand. It is difficult for most folks to overcome the 24/7/365 rain of alarmist climate propaganda. Those truly willing to learn have my respect.
Do a search in the WUWT archives for “Eschenbach”. You will find Willis’ articles. You can’t go wrong, and you will find a point of view that you won’t see in the mainstream media. When ‘everyone’ believes something to be true, without verifiable evidence [such as the widespread belief that CO2=CAGW], the probability is that the majority ‘consensus’ is wrong. Knowledge is power. You can learn things here that the average person does not know. Make good use of that knowledge, it will put you head and shoulders above the crowd.
TimTheToolMan says:
April 7, 2013 at 8:24 pm
atarsinc write “This imbalance is measurable.”
Or so we thought. Perhaps you can let Trenberth know where that energy is hiding then?
If three horses go into the barn at night, and two come back out in the morning; you don’t need to know which stall the horse in the barn is in to know there’s two in the pasture. JP
D.B., Thanks for the kind thoughts. I’ll take your advice. I totally concur with your sentiments regarding the media. They haven’t a clue.
Just to be clear, I’m of the opinion that AGW is a real phenomenon that absolutely needs to be investigated very seriously. To claim that Science knows with certainty that the effects of AGW will be Catastrophic is ridiculous.
Best Wishes, JP