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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Here is some good data:
http://www.esd.ornl.gov/projects/qen/nerc130k.html
The Younger Dryas and Older Dryas do have “dry” in them for good reason.
Cold climate = dry.
Short term drops in temperature in Summer time though, cause a jump in rainfall.
The complete opposite happens in winter, when it takes a temperature uiplift
to force an increase in precipitation.
Such that when looking at England and Wales rainfall since 1766, generally the colder years are wetter, and hotter are years dry.
But some years above 10.0 deg. C., are amongst the wettest. It all depends on when the temperature spikes and notches occur relative to the seasons.
Longer periods of colder climate regimes do always go dry, and deserts expand.
I consider that what the warmist are thinking is that with increased temperature, there won’t be any precipitation as a result of there being a higher temperature all the time, regardless.
A Kinda sorta Venus scenario …
But what they —the warmist— neglect to consider is that the Earth is farther away from the Sun, and therefore is very much less affected over all by solar radiation in the way they would have the rest of us believe.
By dint of just the changing of the seasons alone, we aren’t so nearly affected as they would think, even by our own influences.
Dear Willis: Common sense prevails though it would not reach the MSM. Your wise, and elementary, reasoning about the WATER CYCLE tell us that something is rotten in the educational area, perhaps because of blindly following UNICEF (binding agreements?) regarding educational curricula, I don´t know but perhaps the “prophet of evil” most malevolous climatic theories are corrupting our kids´minds (actually grand kids) with all that environmental and “save the planet” crap.
BTW Glaciers grow with increasing humidity…
Didn´t you know buddy that Ice, is made out of water?, so:
No water=No Ice.
I tackled this <a href="http://sonicfrog.net/?p=2841"back in Feb when we had the Global Warming caused blizzards. Remember the lame rational to support that was that we were getting more storms and blizzards because Global Warming = an increase in precipitation. A blogger was using the EPA’s stats to show that North America had become wetter over the last century. OK, but then I decided to follow the link for more info. Low and behold, this was on the next EPA page.
I’m glad someone else has followed up on this. But Willis, really, you could have just come to me and I would have saved you all the time and research! 🙂
Mike aka Sonicfrog.
not willing to believe there can be such a deviation between South Dakota and Colorado.
I’m willing to bet there is an element of quality of record keeping that is involved.
Like the time the attendant goes on vacation and has their relative take the measurements while they are out of town. “Uncle bob” had better things to do.
TWW (04:26:30) :
willis’s map is based on 1895 to 2009 change. so, you know what the comparisons are with.
when the TV folks talk and newspaper folks write, there is not even a reference year. it is just based on whatever will make the news interesting to watch/read.
as for the “professors” announcement, it is based on god knows what reference years…. they are just geared towards trying to get some grant money.
During the last century many areas have changed land uses.
It wouldn’t surprise me if the increased rainfall in the northeastern US is related to more tree cover. Early in the century this area was largely agricultural. There was appreciable sheep grazing of the hills and hay exports to transport folks in new york city.
On another note, I wonder if cosmic ray intensity will correlate better with rainfall than temperature trends. The indian monsoon has a perodicity with the 22 year hale cycle
http://cdaw.gsfc.nasa.gov/publications/ilws_goa2006/178_Hiremath.pdf
what is the color for california?
Note to self – remember to close your links. Here is my original post from Feb.
http://sonicfrog.net/?p=2841
Indians of the Amazon jungle have a rain producing device.
Here, how to make one (to send it as a gift to AL-aka “La Gorda”(the fat one) black sorceress:
http://www.ehow.com/how_15892_make-rain-stick.html
You can download, also, a Virtual version for your Iphone:
http://www.apple.com/es/itunes/affiliates/download/?id=287335465
LOL!
@ur momisuglyDavid A
Great post. An EXTREMELY important point !!
The science of Botany was well developed long before the politicization of climate science. Science done prior to this politicization cannot be reasonably challenged on the basis of political bias. I quote the abstract of a paper published in 1983 that addresses the question of the direct effects of CO2 concentration on agricultural productivity and water use efficiency.
“About 430 observations of the yields of 37 plant species grown with CO2 enrichment increased agricultural weight yields by 36%. Additional analysis of 81 experiments which had controlled CO2 concentrations showed that yields will probably increase by 33% with a doubling of CO2 concentration. Another 46 observations of the effects of CO2 enrichment on transpiration were extracted and averaged. These data showed that a doubling of CO2 could reduce transpiration by 34%, which combined with the yield increase, indicates that water use efficiency may double.”(with a doubling of CO@ur momisugly concentration)
Kimball,B.A. and Idso, S.B. 1983. “Increasing atmospheric CO2 : effects on crop yield, water use and climate. Agric. Water Manag., 7:55-72
This link shows time lapse photography of the effect of CO2 concentration on plant growth
http://www.co2science.org/education/truthalerts/v13/cowpea.php
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 there is one important lesson we should have learned in the twentieth century, it is that policies that are based upon propaganda rather than facts are extremely dangerous.
Look we have the great MattB (05:00:48) : with us, he’s come to defend the indefensible LOL.
Here is a really interesting paper which clearly demonstrates the periodicity of rainfall with the solar cycle in the US. Seems there is a lag with the TSI.
http://www.greatglobalwarmingswindle.com/pdf/Gamma%20Rays%20and%20Climate%20-%20Perry,%20Charles.pdf
Even in the chart presented by willis we can see the 22 year hale cycle in the original posting. Landscheidt could predict el ninos and the US midwest droughts by using solar observations. i don’t understand why wattsupwith doesn’t look at his approaches as he is the only person with a track record of successful predictions around appreciable rainfall change trends.
What David said.
David Becker, Ph.D. (04:18:08) :
“It is curious that one of the states that had the largest decrease in rainfall (Wyoming) abuts one that had one of the largest increases (South Dakota). It makes no sense that the rain stops at the border. I wonder if the data is corrupted. Did the measuring techniques change over time (and space?)”
Dust in the atmosphere is generally reckoned to be a sign of dryness and desertification. The Vostok ice core record shows that dust tends to be at its highest toward the end of ice ages and at a minimum during the warm inter-glacials. (http://en.wikipedia.org/wiki/Ice_age). In other words, the data shows that warmer periods have less desertification.
If Earth started getting no volcanoes I just bet ya’ the desert would begin spreading towards the poles in a big time hurry. Water vapor that has little dust to cling to produces less clouds/rain. That all changes dramatically with a decent size eruption.
But if its colossal enough it can also lead to our extinction… those things that protect life on this rock… eruptions.
willis, your main point about the lack of a drying trend in the US is a good one.
As an exercise, though, I do wonder, though, whether “increased temperature = increased evaporation = increased precipitation” is necessarily correct. Evaporation is a function of temperature and of the humidity of the air into which it evaporates. The humidity of the air is a function of how well the precipitation cycle (mostly the Hadley-Walker aspect) works.
The precipitation cycle depends on how well each leg works. If the cooling/sinking leg does not work so well with increased CO2 then perhaps the upper troposphere becomes “clogged” with relatively warm air, which inhibits the formation/size of rain clouds.
Something to ponder.
David
Drought trend (100+ years)
http://ncwatch.typepad.com/.a/6a00d83451e28a69e201347fb8e733970c-pi
Models, not science, behind the Europe-wide ban on air traffic. Sound familiar?
http://online.wsj.com/article/SB10001424052748704246804575191181799721308.html?mod=WSJEUROPE_hps_LEFTTopStories
Adjacent regions/area having diametrically opposing rainfall data comes with the territory. Simply watch a time sequence of intrumental or tree ring data and the reason why is readily apparent. There are places which share common borderline inclusion with more than 1 region. The patterns repeat often enough, and the dry vs wet centers are offset enough to make for regions/states that appear in stark contrast over time.
That being said, we live in a time where data has not been properly taken, stored or reported.
Like the missing M in METAR, the reset button is now M as in Mandatory.
It’s going to be a long time before confidence is restored in climate records.
Work done prior to the politicisation of climate data is at a premium.
” sphaerica (04:44:07) :
Sometimes simple logic is overly simplistic.
…
Meanwhile other regions (like the southwest U.S.) will see more evaporation, with that water precipitating elsewhere, like in the northeast U.S. For regions that are already under stress for water, this is very bad news.”
Your first line is certainly correct.
Regarding the last para, you might want to consult your local meteorologist.
I know.. AlGore hasnt actually invented the Jet Stream, yet.
Still…..
We know from western history that during the Roman warm period north Africa was the bread basket of the empire. We also know that during the Medieval warm period the US southwest supported corn crops that allowed the Anasazi to flourish.
From this it would appear that warmer climates are wetter in the northern hemisphere desert belts. I suspect that similar patterns could be inferred from palynological records in the southern hemisphere (northern too).
This begs the question of why the climate models predict otherwise.
Chris Riley (08:49:01) :,
Very good point. Add to this the possibility that the “heat in the pipeline” is actually the fuel used to increase the biomass fertilized by human CO2 emissions. The net is a small increase in temperatures while feeding millions (if not billions) more humans.
The perfect negative feedback.
David Becker, Ph.D. (04:18:08)
David, the data is aggregated by the USHCN on a state-by-state basis, so the changes will be on a state-line basis. I was curious about this as well. The South Dakota data could be corrupted, as it contains a fairly large single-year jump. I have no independent way to verify it, but it may be bad.
w.