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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Willis, if it is not going to warm, the whole thing about increased rainfall is moot. No one suggests the rainfall will increase without warming. It was stated as a consequence of warming. You should have started with saying why you don’t think it will warm, and the rainfall conclusion would have followed.
JP writes “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”
Except if its dark and you mistake a cow walking past the barn for a horse going in, you’re going to be forever wondering about how many horses you have and where they all are.
The point is more about the measurements themselves, and less about aportioning the energy resulting from those measurements to locations.
Tim, I agree. “The point is more about the measurements themselves, and less about aportioning [sic] the energy resulting from those measurements to locations.”
The problem for your argument is that YOU brought up “locations” (“where that energy is hiding”), not me.
But once again, Tim, I completely agree that we need to be able to strengthen our confidence in the measurements. If they were tightly constrained, a good portion of the entire argument would be settled. JP
Willis,
” We’re talking orders of magnitude, and you want to point out a few percent?”
You calculated 14.3 W/m^2 was required, the source I supplied showed that 8.5 W/m^2 was supplied by GHG forcing from the aggressive scenerio alone. That is hardly orders of magnitude, and well within the range when supplemented by water vapor feedback. Keep in mind that the direct effects of CO2 alone result in a climate sensitivity of only about 1 degree C. With models averaging 3 degrees C and some as high as 6 degrees C, they have a lot of water vapor feedback. It is the usage of an aggressive scenerio and the usage of climate models without disclosure, discussion and accounting for their known correlated diagnostic issues that are responsible for what I agree are improbably results. So the issue is not that they don’t get within range of your 14.3 W/m^2 figure, they do, the issue is how they get there.
Nick Stokes
Outer space is an essentially infinite heat sink. What @&#^% difference does it make if there’s “ANOTHER” one?????? Do you actually think your original comment, OR this attempt to belittle me and explain it, demonstrates that you understand logic?
CodeTech says: April 8, 2013 at 2:04 am
“Outer space is an essentially infinite heat sink. What @&#^% difference does it make if there’s “ANOTHER” one?????? “
Well, since you can’t or won’t go back and read the original, here’s more of what I said:
“But OLR can’t increase by 15.6 watts, unless the air becomes extraordinarily hot. There’s no other heat sink up there.”
What is OLR? Is that the problem? It means Outgoing Longwave Radiation….
And in fact OLR can barely increase at all. It can only have a small temporary imbalance with incoming solar. Essentially all that 15.6 W/m2 has to go back down.
Nick Stokes says: April 8, 2013 at 2:36 am
It seems the link got messed, though it’s easily found. Else try Outgoing Longwave Radiation.
Nick, you actually believe what you’re typing, don’t you?
Sigh.
Why is the simplicity of this so evident to everyone else, and yet so lost on you?
JP writes “The problem for your argument is that YOU brought up “locations” (“where that energy is hiding”), not me.”
You can place the emphasis on that point whereever you like, perhaps its time to remember the original point though. You have stated that there is a radiative imbalance. That’s one set of measurements.Another set of measurements shows no energy accumulating. Well, nowhere near as much as the radiative imbalance would imply at any rate.
Which ones do we believe?
Analyses like Willis’ take a broader view of the numbers that are put forward. A view that includes actual atmospheric process and not arguments based on numbers alone with no appreciation of where they came from and what they might mean.
Nick writes “And in fact OLR can barely increase at all. It can only have a small temporary imbalance with incoming solar. Essentially all that 15.6 W/m2 has to go back down.”
There is no change in the amount of outgoing energy. If there is more water vapour then that’s at the expense of energy simply passing as radiation through the atmosphere. Explain why it must go back down.
‘Nick Stokes says:
April 7, 2013 at 2:03 pm
Alan D McIntire says: April 7, 2013 at 1:12 pm
“If rainfall increases 20%, that 78 watts would have to increase by 20%, or by 15.6 watts.”
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’
A 20% increase in rainfall would require an additional 15 or so watts be transferred from the surface to the upper atmosphere.
We’d only get an additional 3.7 watts from a doubling of CO2, therefore a doubling of CO2 will NOT result in an addditional 20% increase in rainfall and an additional 15 or so watts transferred from the surface to the atmosphere. That was the whole point of Willis Eschenbach’s article!
Willis, slightly OT, ignore if you wish. You made this statement above as part of a response to altarsinc using his reference of 15K ft; “
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.
Does that mean all altitudes greater than 100m have less-than-or-equal-to 25% of the downwelling longwave radiation? The average height of land mass is .8km, per Wiki, putting it well above the potential for DW LWR. Since land is 30% of the planet, and DW LWR isn’t supposed to work well on water, where the hell is the potential for GHG warming?
‘ atarsinc says:
April 6, 2013 at 8:14 pm
Mike McMillan says:
April 6, 2013 at 6:54 pm
“Net net, it leaves most of its original energy up in the clouds, a one-way transport of heat away from the surface.”
Mike, that seems right, but you’re still dumping the heat into the lower troposphere. You know, that part of the atmosphere where weather happens. JP’
That part of the atmosphere where weather happens is also where ALL of the positive greenhouse effect happens.
Consider: The higher the lapse rate, the higher the greenhouse effect. With NO lapse rate, outgoing radiation at each level of the atmosphere would be at the same temperature- there’d be NO greenhouse effect.- Water vapor transfers heat from the surface to higher in the troposphere, reducing the lapse rate and reducing the greenhouse effect.
http://okfirst.mesonet.org/train/meteorology/VertStructure.html
“The stratosphere is marked by a temperature inversion from about 11-12 km to 50 km above sea level.
Because warmer air lies above cooler air in this region, there are few overturning air currents and, thus, the stratosphere is a region of little mixing. ” Note there’s no positive lapse rate- in fact there’s a slight temperature INVERSION- only a small fraction of the atmosphere is above the troposphere- and this small fraction would cause a slight ANTI-greenhouse effect due to that negative temperature lapse rate.
TimTheToolMan says: April 8, 2013 at 4:17 am
“If there is more water vapour then that’s at the expense of energy simply passing as radiation through the atmosphere. Explain why it must go back down.”
The surface won’t radiate less unless it cools. Nor will the lower atmosphere.
My point is simply that very little extra energy is required to maintain higher rainfall. Heat disappears as LH on evaporation, and is conveyed aloft, but it doesn’t “leave town” as Willis says. It reverts to sensible heat on condensation, and can’t just be lost. OLR can’t increase, because it has to generally match arriving sunlight. It has nowhere to go but down, and in fact the only new sink for heat is the greater evaporation at the surface. That heat will be recycled.
John (atarsinc).
The imbalance is not measurable – its calculable, but I feel one of the problems which leads to the high sensitivity estimate is the plethora of losses that are unaccounted in these models, such as kinetic energy of raindrops, wind driven by thermal differences( and lightning through electrostatic accumulation from relative motion of different materials. The small losses add up, and I dont think there is a reliable estimate of them. So indeed there might be an imbalance positive or negative at any moment, but what is it, and what is it caused by, and how much of that gap is accounted for by these small losses. After that is accounted how much driving energy is left to cause warming?
For example if we concede that global warming causes bigger storms, the the corrolary of that is that the losses will increase and the sensitivity must therefore be lowered ( essentially the additional energy used to drive the superstorm cant be used to perform warming because the superstorm radiated it to space, and threw it against the surface as rain, wind, thunder and lightning) Things that use energy generally take that energy away from warming so I dont believe you can have increased storminess without reducing sensitivity.
Its the same with evaporative cooling.
Nick Stokes says:
April 8, 2013 at 6:46 am
… OLR can’t increase, because it has to generally match arriving sunlight. It has nowhere to go but down…
———
Right, I get that the system stabilizes at equilibrium. But in my view, when we reach this point in our reasoning where we’ve arrived at a dubious step in the expected process, it’s time to go back and question the premises. What I mean is, the heat that we’re thinking of that’s been released on condensation up in the atmosphere isn’t aware of the energy budget; it’s dodgy to think that it’s going to magically just migrate downward to oblige our energy budget calculations. By what mechanism would it do this? Why? No, at this point I’d be more inclined to go back and say the initial premise was probably wrong somehow, that we’d see a 20-30% PMP increase.
Outgoing radiation does NOT have to match incoming radiation, contrary to what Nick Stokes says. In fact, outgoing radiation FAR exceeds incoming radiation each night, and is less than incoming radiation each day.
Alan D McIntire says:
April 8, 2013 at 8:56 am
Outgoing radiation does NOT have to match incoming radiation, contrary to what Nick Stokes says. In fact, outgoing radiation FAR exceeds incoming radiation each night, and is less than incoming radiation each day.
———–
Darn it. I always get stung this way when I’m not paying close attention. ~blush~
thanks Alan.
I think by now that Willis Eschenbach, who isn’t stupid, must realise that he is wrong in respect of energy being required each year.
It is always a good test of character to observe what people do when they know that they are wrong. Do they bluff it out like Pachauri? Do they make an appeal to the scientific illiterate knowing that uniformed commentators will support them like they support their local football team?
For example
OK, when it’s night on one side of the planet it is daytime on the other. So at what time of day does outgoing radiation exceed incoming radiation?
For equilibrium outgoing radiation must balance the incoming radiation ( in the long term). This is called the ‘radiation balance’ and it exists at the top of the atmosphere (TOA). If the Earth/atmosphere system were to emit more radiation than it received then it would grow colder and colder. If it emitted less than it received then ithe Earth would get hotter and hotter. OK so far? So the Earth must be in energy balance – energy in equals energy out.
NO, it is not perpetual motion, it is called ‘Conservation of Energy’ – also known as the 1st Law of Thermodynamics. Energy cannot be created or destroyed. So once the energy is in the system it stays there (unless it is radiated to space – which it cannot do because of the Radiation Balance- see above). Is this too hard for people? Because it is basic stuff.
Just to clarify, I do not think that this NOAA paper has any merit. On the contrary, it is typical of those all papers which have no purpose or justification other than that they receive government funding.
Nevertheless, the energy argument is not the best objection to it. It is simply wrong!
atarsinc says:
April 7, 2013 at 3:22 pm
True, but you still have that energy in the atmosphere.
The energy goes from warm to cold. Net energy flux from the surface to the atmosphere and not from atmosphere to surface:
http://en.wikipedia.org/wiki/File:Breakdown_of_the_incoming_solar_energy.svg
Why don’t you think it to the end atarsinc?
It would create a net energy transfer from atmosphere to surface if it would have a “hot spot” which it does not.
It would eventually slow down the flux from surface to higher atmosphere if it would raise the temperature (decrease the temperature gradient)
Which is not happening.
It simply goes out of the system:
http://theinconvenientskeptic.com/2012/08/temperature-dependence-of-the-earths-outgoing-energy/
The Earth average temperature varies in a Year by 3.5°C, much more then what we talk about here, and the Earth is getting rid very easily of it.
How about people stop calling each other “warmistas” and ” deniers”. What does that add to the conversation? JP
Hm, don’t you realise that warmistas is totally different to denier? Denier was chosen to insult skeptics as an analogy to holocaust denier.
I see warmistas just as a naming as if the opposite to contrarian or skeptic?
Do you find it insulting? Appologies if so. (Maybe you can explain me why, but you must not).
Does CAGW-theory supporters sounds better? (I think there was a discussion about this some time ago, need to check what people agreed to… ) “CAGW-theory supporters” and “CAGW-theory skeptics” sounds acceptable to me.
MikeB says:
April 8, 2013 at 11:22 am
For equilibrium outgoing radiation must balance the incoming radiation ( in the long term). This is called the ‘radiation balance’ and it exists at the top of the atmosphere (TOA). If the Earth/atmosphere system were to emit more radiation than it received then it would grow colder and colder. If it emitted less than it received then ithe Earth would get hotter and hotter. OK so far? So the Earth must be in energy balance – energy in equals energy out.
Depending what one calls “long term”?
There are huge imbalances between what the Earth receives in energy and what goes out during the Year.
The Earth receives during the North Hemisphere winter about 6% more energy from the Sun then in the North Hemisphere summer due to the elliptic orbit, however the outgoing longwave radiation is higher during the North Hemisphere summer, quite the contrary to the incoming energy – see the graph here:
http://theinconvenientskeptic.com/2012/08/temperature-dependence-of-the-earths-outgoing-energy/
Lars P. says:
April 8, 2013 at 12:43 pm
Uhm, appologies, right link with Global OLR is here:
http://theinconvenientskeptic.com/wp-content/uploads/2012/06/Global-99-now.png
MikeB, maybe on your planet, but on THIS planet outgoing radiation is whatever it needs to be to maintain equilibrium, whether day or night does not matter. Relative to the sky the sun is an extremely small point in the sky, the entire rest of the sky is available to radiate energy to. That’s ANY energy, whether or not the radiator is hot or not so hot, because the rest of the sky is only slightly above absolute zero.
Willis is not wrong, you simply claiming it does not make it so.
Heat loss to space is demonstrated empirically, so if your thought experiment or model doesn’t show that it should be so then your thought experiment or model is wrong.
Honestly, some people need to stop following the dead-end logical fallacy of “greenhouses” and stop trying to trace the ping-pong ball antics of individual photons bouncing off of CO2 and just LOOK out the window. The atmosphere is nothing even remotely close to static, it’s constantly in motion, constantly absorbing energy from the sun, moving it around, then emitting it back to space whether on the dayside or nightside. The average temperature is more a function of atmospheric mass than composition, which is why it has proven to be so remarkably stable over the last few billion years.
Lars, I agree. However, how long does it take for the system to achieve equilibrium? I don’t know that answer. I do know that for some forcings in the paleo record it’s measured in millennia. JP
CodeTech says:
April 8, 2013 at 1:19 pm
“The average temperature is more a function of atmospheric mass than composition, which is why it has proven to be so remarkably stable over the last few billion years.”
“…stable over the last few billion years.” That statement is not just false. It’s ridiculous. JP