Guest Post by Willis Eschenbach [Updated, see end of article]
One of the claimed dangers of a few degrees warming of the Earth is increasing drought. Drought is a very difficult thing to fight, because it is hard to manufacture water. So this is a frightening possibility.
I have long claimed that “a warmer world is a wetter world”. I have said this without any actual data, based solely on the following logic.:
Increased temperature —> increased evaporation —> increased precipitation.
Today I graphed the numbers for the US precipitation. I used the USHCN state-by-state precipitation database, which also includes area-averaged values for regions of the US, and for the US itself.
First, here is the change in precipitation in the US since 1895:
Figure 1. Annual precipitation in the US. PHOTO SOURCE
Since the both the US and the globe have warmed since 1895 it seems that a warmer US is a wetter US. However, precipitation is spotty and unevenly distributed. One area can be very wet while a nearby area is dry, so what about the precipitation in each of the states?
The USHCN database contains state data. Since there are drier states and wetter states, I looked at the percentage increase in precipitation rather than the absolute change in precipitation. Here are the state-by-state results:
Figure 2. State by state changes in precipitation, 1895-2009. Values are change per century divided by average annual rainfall.
One of the things that AGW supporters have been saying would result from warming is that the desert belts would move poleward. These are the great belts that circle the earth at about 30° North and 30° South latitude. The North American belt encompasses the Southwestern US (Southern California, Arizona, New Mexico, and Texas) and Northern Mexico. If these belts were actually moving poleward as the globe warmed over the last century, we should see decreased precipitation in the Southwestern US.
Instead, all of the southwestern states have increased rainfall. The main area with decreased rainfall encompasses the Rocky Mountain states in the central Northwestern US.
My conclusions? Precipitation is indeed spotty. A warmer US is indeed a wetter US. And there is no decrease in the Southwestern US data which would show that the great northern desert belt is moving polewards. So either the desert belt is not moving poleward, or the movement is offset by the overall increase in precipitation.
[UPDATE] Some commenters have correctly pointed out that I have only shown the precipitation, which doesn’t show the change in droughts. This is because droughts are a combination of soil moisture, temperature, rain, and other factors. This is measured by the Palmer Drought Severity Index (PDSI). The PDSI index values have the following meaning:
-4.0 to less (Extreme Drought)
-3.0 to -3.9 (Severe Drought)
-2.0 to -2.9 (Moderate Drought)
-1.9 to +1.9 (Near Normal)
+2.0 to +2.9 (Unusual Moist Spell)
+3.0 to +3.9 (Very Moist Spell)
+4.0 to above (Extremely Moist)
I used the USHCN database cited above to look at the state-by-state trends per century in the PDSI. Note that these are not the average PDSI values by state, which are without exception in the range -1.9 to +1.9 (near normal). Figure 3 is a histogram of the trends per century. A “histogram” shows the number of states (left scale) that have a certain trend range (bottom scale).
Figure 3. Histogram of state trends per century of the PDSI
The trend in most of the states (39 out of 48) is toward less drought (increasing PDSI). However, most of the trends (32 of 48) are between 0 and +2.0, which is not a large change. As a result, most of the trends are not statistically significant. Figure 4 shows the significant state trends:
Figure 4. Significant trends in the PDSI in the US states.
As you can see, despite the warming of the last 115 years shown in the USHCN dataset, while some of the PDSI trends have decreased, almost all of the statistically significant changes in the PDSI are positive (less drought). And few of the changes are statistically significant.
The IPCC models say that increasing warmth will lead to increasing drought, particularly in the mid-latitudes:
In a warmer future climate, most Atmosphere-Ocean General Circulation Models project increased summer dryness and winter wetness in most parts of the northern middle and high latitudes. Summer dryness indicates a greater risk of drought.
Despite these model prediction, we have seen no such increase in drought in the US. For most of the US, there has been so statistically significant change in the PDSI index showing the number and strength of droughts in most US states. And where there has been a statistically significant change, it is in the direction of reduced drought.
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DirkH (13:21:10) :
“I see the word “Disprove” occur every time a pro-AGW person writes something. Please explain how one can disprove something that has never been proven, in this case the assumption that a dustbowl will occur (the fact that some model runs indicate so is not a proof.)”
It is self-evident that no one can prove a prediction that something
will happen in the distant future. We would always have to wait for the
event. IPCC is not asking anybody to believe that something is proven –
it is saying that examining all the existing evidence and applying rather
good models we get these scenarios, we now have to make a risk
assessment and decide on action/inaction.
Then, the sceptic side retorts that the models are not good, or,
also frequently that models are not science.
But that is not enough, the temptation to come in and disprove ‘too
early’ is so strong. Willis Eschenbach: “We should see decreased
precipitation in the Southwestern US. Instead, all of the southwestern
states have increased rainfall.”
Is that not an attempt to disprove something ?
Land use changes in New England was mentioned with woodlands replacing farmland through the 1900s. I wonder if the booming ice trade of 1820s and 1830s on influenced earlier New England temperatures or moisture: “total shipments of goods from the port of Boston in 1826-1827 at three thousand tons”. http://hbswk.hbs.edu/archive/3650.html
Tens of thousands of tons of ice exported from Boston each winter until the development of air conditioning technology.
Thanks for another great post Willis. Good to see yet another IPCC myth bite the dust!
Same has happened here in the UK, with a trend of much more rain from 1961 to 2006, according to DEFRA. Link here:-
http://ukclimateprojections.defra.gov.uk/images/stories/Trends_images/T_300dpi/T_Fig2.46.png
So warmer, more CO2, more rain – it’s been plant heaven.
Regarding Dave Springer (06:51:45) :
I respect your conversation with Chris Riely, and would venture that you both know the subject better then me.
I do take issue with you when you say this…”I don’t believe in the financial motives etc, but sure, science has its sociology and we have to be sceptic about enthusiasm.”
I am not at all certain that montary dependency on grants for a pro CAGW POV results in just “enthusiasm” I feel that the climatgate e-mails clearly point this out, as well as many other points made on the corruption of climate research and peer review by Lindzen, Spencer, McIntyre, and many others. The light and dark side of human nature is invariable accross all religions, races, creeds and political perspectives, and the dark side is not properly defined as “enthusiasm”.
I am glad you do not discount the earlier studies done which support the strong benefits of C02 in regard to plant growth. Have you read any critiques of the paper you quoted from. For Instance has Idso at C02 Science reviewed it? BTW, at CO2 science there are numerous other “recent” studies as well as :real world “observations” which support the view expressed by
Chris Riley (08:49:01) : (Therefore I agree with his comment)
“Any discussion that attempts to infer a link between increases in CO2 and decreases in the food supply as a result of (computer projections of) drought, that does not take into account the positive externalities of CO2 emissions is simply not science. It is propaganda.”
If the world currently needed 20% more water to grow the same amount of food we would likely have complete economic collapse and numerous, perhaps worldwide wars.
It is such a shame that we are not developing the energy resources we need that could make true envirementalism affordable.
DirkH (13:21:10) :
“…The whole business of the pro-AGW people is making wild guesses and then saying: “Now disprove the things that i have just said…”
Spot on Dirk! What climate science has failed to understand is that no matter how many billions of cash you spent trying to prove the theory of CAGW, it just requires one piece of observational evidence to falsify it.
There are so many pieces of evidence that now totally conflict with CAGW that it is now dead. I fear we are in for a long and painful funeral.
Why would you use a Gaussian filter?
It isn’t a valid technique when Mann uses it.
It isn’t a valid technique when Britta uses it.
It isn’t a valid technique when anybody uses it.
It isn’t a valid technique.
Use a normal running 10 year average if you want, and stop to the average line 10 years before the end of your data.
Don’t claim to show us a smoothed average that continues up to the last datapoint.
Willis,
While I don’t subscribe to the dire predictions of the alarmists, I do not see how the pattern on the map is at odds with the prediction that the “desert belts would move poleward”. In fact the move of the desert belts poleward would require the current belts to show more precipitation (which the map does) along with a drop in precipitation in the region north of the current belts (which the map also shows).
Again, I don’t buy into the alarmist rhetoric, but at the same time I can’t ignore the contradiction in the argument being presented.
Could the answer be that the prediction is actually that the desert belts will stretch or extend poleward as opposed to moving poleward?
Dennis Nikols (10:09:05) “Physiographic regions are a much better way to look at these things […] I think the take home message is you can’t predict or model forward what you don’t understand.”
Agree wholeheartedly – So Step 1: Develop understanding…
Lake Eyre, Australia inflows:
http://www.k26.com/eyre/LE-inflows-1885-2004.jpg
Compare with 25.6 year wave (grey) here:
http://www.sfu.ca/~plv/LunarHarmonicSpectrum.png
Similar patterns occur in coastal British Columbia, Canada precipitation:
http://www.sfu.ca/~plv/CCLR1LPPT1.png
In fact, the pattern loosely matches global precipitation south of 55N – i.e. 55N-90S (very-loosely representing non-Arctic drainage – [when KNMI Climate Explorer starts taking physiographically-outlined coordinate-inputs, I’ll refine…])
However, we shouldn’t make the foolish mistake of simply extrapolating. There are a few layers of complexity…
I am digging at the roots here:
http://www.sfu.ca/~plv/VolcanoStratosphereSLAM.htm
Earlier on I found correlations with solar system variables, but then I became aware of confounding of solar system dynamic variables with lunisolar tidal variables and switched focus.
(Certainly the solar system has some role in influencing the relationship between Earth & Moon, but that’s a level higher in the causation chain and not necessarily of immediate concern in understanding lunisolar effects on the terrestrial hydrologic cycle.)
Strongly Suggested:
Let’s not trivialize the hydrologic cycle by inventing ridiculous (to be clear & blunt) claims that it shows a simple bivariate correlation with some global temperature index (…but certainly the hydrologic cycle needs to be front & centre in the climate discussion at this stage and I acknowledge the role of inflammatory comments in stimulating blog discussion, even if not necessarily the tactic I would choose …but many voices in the choir – many roles to be played… and more than one timescale to think about). It should be added that a discussion of precipitation is incomplete without a seasonal (particularly growing season) breakdown (including a look beyond averages at the nature of variability – many more discussions & blog posts to be had on important subjects – can’t squeeze all into one…)
Important Question:
What I want to know from any physicists participating in the discussion:
When will the next nutation obliquity phase reversal occur?
The last time one occurred, there was a major drought (the dirty 30s).
One of the major keys to better understanding of the hydrologic cycle lies in the study of parallels between Earth orientation parameter (EOP) variations and the lunisolar harmonic spectrum. I base this comment on many analyses, most of which I have not publicized.
tommy (10:12:41) “Norwegian weather […] During this years unusually cold winter we also had the driest months in over 100 years in some areas of this country.”
Caution: My understanding is that the Norwegian winter precipitation patterns share features with those of coastal British Columbia, Canada. The relationship between precipitation and temperature flips over between summer & winter here. The keys to understanding: the roles of the freezing point and arctic outflow winds. (Related: There is certainly a relationship between precipitation and inflow into the Arctic basin.) I have not studied the Norwegian summer patterns, but now you’ve got me curious to see what can be learned from a comparison (since Norwegian summers are not so drought-prone as those of western North America – could be informative about hazards of working with annual northern hemisphere averages…)
Ed Murphy (09:22:23) “Water vapor that has little dust to cling to produces less clouds/rain. That all changes dramatically with a decent size eruption.”
Bear in mind the other factors, like temperature. If a major stratosphere-class eruption cools the planet, you’re going to see LESS inflow into the Arctic basin (since inflow there is related to temperature – bear in mind that the freezing point is critical in temperature-precipitation relations). Seasons, geography, physiography, ….
As sarcastic, it comes across; as worthwhile and clever, not so much.
A while back someone reported on the greening of the desert above the sahara, this was due the warming making it damper, in the article. The simple logic is something we need to cherish, it could also be called “common sense” this seems to be a by product of unobtanium in the green world. I find it depressing that we have to suffer under the green tyranny of eco laws, what dumbo banned incadesent lamps? then to compound the felony promote CFL glow worms? no research behind this travesty just thought it was good for us, the cat converter in our cars and the paint thinner and alcahol masquerading as real gas???? the technology changes but the solution stays the same, biofuel, another really daft idea, did no one think it through, plus what effect on older fuel systems? you need different “O” rings for ethanol, the normal ones break up, I am told this happens at over 10%. this is the failing of the MSM, they were zippy when Nixon was in the frame but now?????
This is another bit of evidence that global warming does not cause droughts. Ian Plimer discusses this a number of times in his book “Heaven and Earth.” There are extensive ice core records that show much more dust in the ice during cold periods and ice ages due to desertification. Warm periods show much less dust in the ice.
I believe this misconception that warming causes droughts comes from people associating droughts with hot dry periods in the summer. The warmists deliberately use such weather to further their claims and “forget” to remind people that their vaunted models predict that the warming actually should occur during winter nights. The geological evidence shows droughts are more common in cold periods
Willis re: what you tried to “disprove”… maybe you should ask DocWatt in #3.
MattB:
Does DocWatt speak for Willis? Thought not.
I was thinking an isohyet map having contour lines of equal precipitation would be interesting as well.
I have issue with the way the CSIRO and BoM “sell” their statistics to the public in Australia. I have probably covered this before on WUWT, certainly on JoNova, but given that it relates to rainfall it seems appropriate to link the offending report again.
The following is a link to the annual roundup on climate for 2009 at BoM:
http://www.bom.gov.au/announcements/media_releases/climate/change/20100105.shtml
There is the usual alarmism on this being the warmest year/decade/millenium or whatever, but scroll down to the rainfall section titled:
“Another drier than average year in the southeast mainland”
Notice the qualifier at the end of the sentance? Most people will register the first half of the sentance and think… ah yes, another dry one. Fact of the matter is that it was wetter than average (for 1960-1990) and that the decadal average has been creeping upwards over the last 110 years.
Check the graph below (at the linked report). The ten-year-average bars distract the eye to give a false horizon, but the average rainfall has erratically crept upwards over the period.
In Australia the main problem is that certain areas tend to be experiencing less rainfall (the SW of Western Australia for example) while the increased rainfalls are up in the tropics where it is less useful to the majority of the population. This is an entirely different question, of course.
Still it bugs me enormously that a tax-payer funded institution like the BoM deliberately word-smiths its reports to support AGW arguments.
Mr. Eschenbach,
You should continue to bother! Your posts and responses are informative, always supported by public-domain data and typically contrary to many of the current climate paradigms. It is people like you that expose people of the ecological-religion and faith-based-science factions for what they are NOT. The ecological-religion, faith-based-science crowd is clearly not interested in real climate science. Although, I am still in doubt about their underlying motive(s), their actions can be easily characterized as; the spreading of mis-information, fear and alarmism. They appear to have a situational-ethics-like compass at the core of their loose interpretations of data. By starting with carefully selected data, they then craft scary future senarios at the end of a trail of seemingly logical steps. They are good story tellers, I guess. On second thought, what is the primary motive of any major religion in regards to public policy? I would have to say it would be to “spread the good news”, “convert the masses” and increase the size of the congregation.
So like it or not, Mr. Eschenbach, you and others on the website are the antidote to our current-day climate-opiate. Keep up the good work.
“There is no discernible • trend in average
precipitation since 1951, in contrast to
trends observed in extreme precipitation
events”
“It is unlikely that a systematic change
has occurred in either the frequency or
area coverage of severe drought over the
contiguous United States from the midtwentieth
century to the present”
This is what the CCSP report 2008 has to say about precipitation and drought trends since mid 20th century.
Great work Willis!
In the past 10 years I have made 30 or more field trips into the Great Sandy Desert of NW Australia. Originally part believing AGW, I soon came to the conclusion that this was a crock. The flora and fauna here was fantastically diverse, and the dune vegetation was better than my well watered garden on the coast, including what was thriving even on top of the dunes. Rainfall here is very spasmodic but is increasing over the last 20 years or more. Temperature in this desert is hot, (bounded by Marble Bar, Telfer and Balgo in the East) and it can be dry for longer than a year but can make up for it in a week when affected by a passing tropical cyclone. In Broome we have had 3 x 100 year rainfall events since 1970. The average temperature here has not increased by more than the ‘margin of error’ over the period of data collection since the 19th century.
Better hot than cold.
mikael pihlström (11:47:28)
Mikael, there is nothing that can disprove a projection of a SW USA dustbowl 90 years from now.
There is also nothing that can disprove a projection of alien spaceships demolishing New York City ninety years from now.
This is a recurring problem with the AGW hypothesis, that it does not make falsifiable predictions.
Not sure what your point is here, though …
w.
mikael pihlström (14:07:49)
Scientific claims assuredly can be disproven (usually called “falsified”). However, you can’t falsify future events.
If you had quoted my entire statement, it would be clear to everyone that I was referring to past events, not future events, viz:
The warming of the globe occurred in the past century, and the AGW claim was that this warming would make the desert belts move polewards. In the US, we haven’t seen that. I postulate two possible reasons it hasn’t happened.
Science advances by falsification … but for a theory like AGW to be testable, it has to make falsifiable predictions. AGW makes very few such predictions.
One of these few falsifiable predictions is the poleward movement of the desert belts in response to AGW. I don’t claim to have falsified that claim. I do claim that in the USHCN data there is no sign of movement of the desert belts in the SW USA over the 20th century …
w.
Duncan (15:51:26)
I love your style, science by assertion, as though repeating something over and over makes it true. Nowhere do you say what might be wrong with using a Gaussian filter, I mean, explanations are so last week. Then there is the crude attempt at “guilt by association” by mentioning Michael Mann and Keith Briffa …
Sorry, I’m not impressed.
I use Gaussian smoothing because it reveals the slower changes in the data by smoothing out the high frequency changes. It is a perfectly valid technique that has been used for that purpose for many, many years.
I run it out to the end because the way I do it, the error at the ends is both measurable and quite small. I wrote a paper on this, it’s available here. In it, I demonstrate that the method that I use to deal with the ends is far superior to the bogus method used by Michael Mann. I also show how to calculate the end errors, and show their size in a sample dataset.
In future, if you say something like “Willis, why do you use Gaussian smoothing, and how do you handle the end effects”, you won’t come off looking like you forgot to take your meds … and I’ll say “Hey, Duncan, thanks for asking, here’s the answer.”
Area Man (16:24:15)
Area Man, the thing you are missing is that the SW USA is at the north edge of the ~ 30°N desert belt. In this area the belt forms the Sonora Desert, which stretches southwards from the SW US for hundreds and hundreds of miles into Northern Mexico.
If the desert belt moves northward, the SW US would move from being at the top edge of the Sonoran Desert to being more in the middle of the Sonoran Desert … and I guarantee you, the middle of the Sonoran Desert is much, much drier than Arizona and New Mexico.
This would show up in the record as the SW US becoming drier, which doesn’t appear to be happening.
w.
Now Bulldust – my issue is that these sort of articles, which actually say just about nothing, are written to be intentionally interpreted by the hungry masses as “This disproves AGW”. My reference to DocWatt is to point out that this article is taken as such by that poster. It is an incitement to frenzied climate ignorance.
However the reality is that IPCC 2007 says “Increasing temperatures tend to increase evaporation which leads to more precipitation (IPCC, 2007). As average global temperatures have risen, average global precipitation has also increased.” So Willis’ line is actually the IPCC line. http://www.epa.gov/climatechange/science/recentpsc.html
I for one would like to see sources for “One of the claimed dangers of a few degrees warming of the Earth is increasing drought.” as I doubt it is as blanket a statement are presented, rather a localised issue with local ramifications.
As Willis points out – higher temps = higher evaporation, which also means that higher rainfall does not necessarily mean more water available to crops. Annual rainfall also does little to look at cropping cycles and seasonal droughts, again with significant issues for agriculture management.
Willis, what do you think of the snowstorms this past winter?
Willis… “This would show up in the record as the SW US becoming drier, which doesn’t appear to be happening.” hmm it really appears to me again you are trying to disprove something here, by producing graphs that concur with the IPCC? Maybe you should update your article above to say “Willis Eschenbach agrees with IPCC records for rainfall over USA”.