Mother Jones news has an “alarming” article called “Our Coming Mega-Drought” in which they say “…virtually all of the world except for China and Russia will experience increased drought by 2030 and severe drought by 2060” and they cite these computer model maps at left.
Yes, it looks pretty bad. But the thing about models, is that they are very sensitive to starting conditions, and like we’ve learned with temperature measurement errors worldwide, so are there errors with precipitation measurement. Rain gauges are easily influenced by wind, and wind eddies. So things like buildings, shrubbery, trees, and station moves can all have an impact. Pierre Gosselin at No Tricks Zone has a good summary of issue related to precipitation measurement which I present below.
======================================================
Huge Global Precipitation Deficits Due To Woefully Inaccurate Measurement Techniques!
By P Gosselin on 24. Oktober 2010
NOAA 8 inch rain gage. Source: http://www.crh.noaa.gov/iwx/?n=coop_station
German Weather Service meteorologist Christoph Hartmann writes what I think is a surprising essay on measuring precipitation, and the errors in doing so. Indeed Hartmann says precipitation may be understated by up to 50%, or much more at some locations.
As Hartmann explains, measuring precipitation is by no means an exact science, and results have to be taken with a lump of salt.
There are many sources of errors, and in his essay here he looks at just two main sources: wind and instrumentation.
But first, let’s take a look at how precipitation is measured. In his previous essay he described two types of precipitation measuring gages. In Germany precipitation is measured with the unit of liters/m², e.g. 25.4 liters is an inch of rain.
Two methods of measuring precipitation
Hartman explains that precipitation is generally measured by a rain gage with a known opening area, for example 200 cm² in Germany, which is positioned 1 meter above the ground surface. The gage funnel catches the precipitation and leads it to either
1) a graduated measuring tube or a
2) an optical drop counter
Optical rain gage (drop counting). Source: atmos.washington.edu
With the measuring tube system, the tube is graduated and the amount of precipitation can be simply read off. With the optical rain gage (drop counter), the amount of precipitation is derived from the number of drops. If the precipitation is snow or ice, then the measuring tube or optical gage are brought inside and the captured precipitation is melted and measured.
Hartmann explains that the biggest sources of error are wind-related. This is easily seen when measuring snowfall. Just before a snowflake falls into the gage, air turbulence sucks it back out tosses it overboard. Just taking a look around after a blizzard, it’s easy to imagine how difficult it is to measure snowfall. Places exposed to wind are barren, while other places are covered by meter-deep snowdrifts. How much snow really fell?
Hartmann says measurement errors of up 400% can occur over time when measuring powdery snowfall in alpine, polar or windy areas.
One way to reduce error is to place the instrument in a wind-protected area. By measuring the wind speed, it is then possible to adjust precipitation measurements. But Hartmann writes:
Wind effects lead to an under-estimation of the actual fallen precipitation. The level of deviation depends on the speed of the wind and the type of precipitation.
Because wind speeds are factored into precipitation measurements, climatological precipitation trends without taking changes in wind speeds into account should always be deduced very carefully.
The second problem encountered arise from the two above described measurement instruments, especially with the optical rain gage, writes Hartmann. With frozen precipitation, the gages are heated up in order to melt the precipitation. But this involves evaporation. And under torrential rains, the optical gage becomes much less accurate. The result, writes Hartmann:
Under equal precipitation amounts, the optical gage measures less precipitation than the measuring tube, both in summer and in winter.
So if two different stations use different instruments, them they will show different precipitation amounts even when the actual precipitation is the same. In summary, Hartmann writes his stunning conclusion:
In total these two sources of errors lead to a precipitation deficit of 5 to 15% for liquid precipitation, and between 20 and 50% for solid [frozen] precipitation. In very windy locations, the deficits are substantially more.
Because instruments measure less precipitation than what actually falls, it means we have a worldwide precipitation deficit solely because of the measurement method.
What does it all mean? Are many of the reported droughts solely the product of faulty readings? And we all thought that the network of temperature measurement stations was a mess. This is a huge open floodgate to potential climatological data manipulation and bogus assertions. See here for example: motherjones – the coming mega-drought (h/t NTZ reader DirkH).
A warmer world is a wetter world so lets generate some more water vapor (you know that REAL GHG!). A lot more CO2 will probably be ineffective in warming the world but it won’t hurt either as plants can use it.
Messages of doom, disaster and downfall is all they can produce.
Is there no notion that their models are crap?
Don’t they know how stupid it is to make any long term prediction about our weather or climate?
This is tiresome to say at least.
My backyard measurements (2 gauges- drip counter and graduated measuring tube) are sometimes way out from the nearby airbase rain fall measurements (6km distant).
Rain patterns, like thunderstorms, upset a region’s rain measurements.
So how correct really are official rain recordings in catchment areas?
My own measurements also show over thirteen years averaged rainfall by the month is decreasing, and also a three year cycle (using excel “19 moving average” – graph 2 at http://tonyf.customer.netspace.net.au/weather&rainfall/rainfall_since_1999.htm)
I seem to remember a recent WUWT blog where the Australian weather service adjusted the historical precipitation chart down. http://wattsupwiththat.com/2010/10/15/bom-disappears-rainfall-data-no-trend-becomes-downtrend/ I suspect intentional human error may be another leading factor in missing precipitation.
Mother Jones trying to replace Nature? National Geographic?Weekly World News?
What next-“Nostradamus’ predictions given to Bat Boy?” sorry if I sound a bit cynical.
I recall they were on the “next Ice Age ” bandwagon….
Unfirtunately I don’t read German, so can’t tell if the point I’m about to make was covered or not.
There is another very common type of rain guage that is mentioned in this post. That is the tipping bucket rain gauge. All stations on our network (located in South Island New Zealand) use the tipping bucket type. I believe that they are subject to the same types of errors discussed here, but also to another error that overstates the rainfall in some circumstances.
I have installed a cheap chinese made weather station at home, just for my own interest, and happened to notice a strange situation recently. We were experiencing very strong pre frontal winds with gusts exceeding 70 kmh. It hadn’t started to rain yet, but the rain guage started showing readings. I went out to the weather station to see what was happening, and discovered that at certain wind speeds the rain gauge would vibrate and operate the tipping bucket. Thus rain was being recorded when none was actually falling. It may also explain why our remote weather stations at work sometimes show rain in the prefrontal conditions earlier than we were expecting.
Or, in the case of a local rain guage, it was broken most of the year while funds were not available to fix it.
In another case, it was not properly supported by the computer controls, so it would fill up because the automatic dump mechanism didn’t work.
The motherjones H/T must go to thegoodlocust; i found it in Tips&Notes and posted it in Pierre’s blog:
“thegoodlocust says:
October 24, 2010 at 9:34 am
Here is an amusingly idiotic article from Mother Jones:[…]”
And it’s really amusing; the guy starts rather good, even identifies the study as a modeling study, but ends with “This will happen in the next 20 years if we don’t act now”, completely forgetting that it’s all computer conjecture. People are so easily fooled when a computer is involved. I should exploit that more myself…
Mother Jones news has an “alarming” article called “Our Coming Mega-Drought” in which they say “…virtually all of the world except for China and Russia will experience increased drought by 2030 and severe drought by 2060”
Hmm… Mother Jones news and the only two countries that won’t experience increased drought are or were both communist….
I participate in the CoCoRaHS rain Gauge Network. While working on my Master’s degree I did a short study on gauge accuracy and precision. There are 4″ dia gauges with a graduated cylinder for the reading. My results mirrored the links above for high winds. Much of the under reporting I saw was due to splash out of the rain hitting the funnel. This was confirmed with a high speed video camera. Given similar measuring methods the precision was +/- 1%, however if I removed the funnel and just used the 4″ dia tube during high wind situations, the difference was 20% to 80% more collection in the open tube.
Like everything in science, you must know the limits of your measurement system before making assessments no less model inputs for the data.
I have this Charlie Brown feeling of …
AAAAARgh !! Can’t anybody do this stuff right ?
Aw sheesh. Bring Back Al Gore and his floods… I am sure we can cope with that a lot easier. It looks like we have a choice — nay a cornucopia of disasters from which to chose — so we may as well choose those that favor us… Even the reverse revolving hurricanes would likely be better…
Phil R says:
October 24, 2010 at 6:18 pm
“Hmm… Mother Jones news and the only two countries that won’t experience increased drought are or were both communist….”
You mean communism helps? That’s good news. The social democrats, Greens and Communists in Germany could form the next government here in Germany if elections were held now. So we should be save from drought.
Every dark cloud has a silver lining…
But, but, but… There was a research result reported here a few months back that we would all die of heat stroke because the temps would be high and we would be unable to cool by sweating due to 100% humidity. At 100% humidity the merest shade of cooling (e.g. when the sun goes down) and it is raining. So how do droughts happen? It couldn’t be that the alarmists are making up whatever BS they think will ‘sell’, could it? Nah!
CCSP, 2008: Reanalysis of Historical Climate Data for Key Atmospheric Features
“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 type of predication is garbage. Even without the issues of initial conditions based on measurement systems the science is flawed. The “proposed” warming will dramatically increase the amount of evaporation from the oceans. While patterns could shift if global warming really did happen, the amount of total rainfall would increase globally.
A quick look at the map shows that the expectation is that the jet streams would stop functioning and somehow the Gulf of Mexico would stop sending vast amount of humid air into the central United States. It appears that he used every scenario that causes drought and simply amplified them.
John Kehr
The Inconvenient Skeptic
Ron House says on October 24, 2010 at 6:37 pm
Well, what will happen is that the moisture will precipitate out but it will evaporate again before hitting the ground, so there will be more droughts while there will also be an acceleration of the hydrological system so that there is tons more moisture in the atmosphere.
Simple, isn’t it?
It’s worse than we thought. Climate change is now laws of physics change.
Do these idiots really expect anyone to believe that the water cycle is going to cease working virtually all over the globe? Oh wait. They published it in Mother Jones news. Of course they’ll believe it.
CERTAINTIES?
UNCERTAINTIES?
Then there is this:
As someone noted, rain is a very local phenomenon. I have seen it raining heavily a mile from my house, but upon reaching my driveway find my yard still parched and dry. So it would seem reasonable at least where I live that the variance of any one station would be so ridiculously high as to be unusable for trend analysis. Maybe where you have monsoons and large area rainfall it would work as the larger rain pattern would be (I speculate) more constant.
It seems to me that lake levels, dam water-flow, and river flow information would be more useful (if kept and accurrate enough) for determining rainfall trends related to climate. As a lake will tend to accumlate water from the same area of land over time it seems it would be a good proxy. Surely communities keep track of how much water they pull from lakes and rivers for water treatment. This would be an interesting study for someone with the time.
This equivocation in the article seems to blow up whatever predictions are made afterward…
And no hurricanes to Mother Jones is: “bad luck”. WTF?
REPLY: I was going to comment on that one, but figured I’d leave it to you if you want to expound on it. – Anthony
Phil R says:
“Hmm… Mother Jones news and the only two countries that won’t experience increased drought are or were both communist…”
Mother Jones is seriously wrong. China has been experiencing major droughts since before AGW was a twinkle in Svante Arrhenius’ daddy’s eye: click
The Gobi Desert is only about 40 km from Beijing, and it is heading their way. They’re trying to stop it. Wishful thinking, just like Mother Jones’ belief that deserts are caused by “AGW.”
My local rain gauge is the ground water level in the 5 interconnected (via gravel veins) gravel pits in our local wetlands that have no discernable outlet. My calibration is where trees that have grown in the recent but distant past lower water table and whether or not they are covered, and if so, for how long: ie, have they survived being water logged for the past year. Four inch diameter poplar and cottonwood trees have died over the past year from being submerged for more than a year. So, in my estimation, the ground water level has risen more than 2 feet. Judging by the 6 foot extent of the shoreline brown of the surrounding grass, it seems that the high water from this last winter and spring has receded to a level 2 feet above previous “normal” levels. No recent drought in my immediate neck of the woods. Last weekend, our Fall Color Tour took us to a Northern region identified October 19th as moderate drought region on the usual NOAA maps. We tramped through rivers, streams, bogs, and lakes with water upto high water marks and were briskly flowing. Campfire wood we purchased was wet and we had a dickens of a time getting it started. Now this is not a global assessment, and admittedly very regional, but the drought maps and our direct experience over the same mapped areas was markedly different. I wonder how much time drought people spend tramping through the woods? fishing the streams? eyeballing rather than relying on some remote rain gauge which may or may not be accurate? I had better close my bedroom window, I hear thunder rumbling and it is getting closer.
I use the five gallon bucket method and probably get as good accuracy. I used to use my wheelbarrow tell the bottom rotted out.
Is Mother Jones available for Vegas. They sure know how to make a safe bet. Picking 2060 is brilliant.