More of the “extreme events” meme…
From the AGU weekly highlights
Regional models expect drier, stormier western United States
Key Points
- Statistically significant increases in western US future extreme winter precipitation
- Eight dynamically downscaled GCM simulations show generalized agreement
- Spatial pattern of changes in mean precip. is different than that of extremes
As American southwestern states struggle against ongoing drought, and the Northwest braces for a projected shift from a snow- to a rain-dominated hydrological system, climate researchers strive to provide precipitation projections that are fine grained enough to be of value to municipal water managers. Estimates derived from large general circulation models show that in a warming world, water availability in the western United States will be increasingly dictated by extreme events.
However, such large models tend to lack necessary detail for the small-scale interactions and topographic influences that dominate daily changes in local precipitation. To convert the broad predictions of global models into practical predictions, Dominguez et al. used an ensemble of regional models, set to fit within the projections of general circulation models, to estimate future winter average and extreme precipitation for the western United States.
The authors find that for the years 2038–2070, winter average precipitation in the southwestern states would be 7.5 percent below 1979–1999 levels. They also find, for the entire areal-averaged western United States, a 12.6 percent increase in the magnitude of 20-year-return-period winter storms and a 14.4 percent increase for 50-year winter storms. In some regions, like southern California and northwestern Arizona, this increase in strength of 50-year storms was pushed as high as 50 percent. Though the temporal and spatial granularity of the regional climate models is much improved over that of general circulation models, workable and useful measurements for hydrological engineering and water management design will need ever-better estimates of future rainfall patterns.
Source:
Geophysical Research Letters, doi:10.1029/2011GL0507624, 2012
Title:
“Changes in winter precipitation extremes for the western United States under a warmer climate as simulated by regional climate models ”
Authors:
- F. Dominguez, E. Rivera, and C. L. Castro
- Department of Atmospheric Sciences, University of Arizona, Tucson, Arizona, USA;
- D. P. Lettenmaier
- Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA.
Abstract:
We find a consistent and statistically significant increase in the intensity of future extreme winter precipitation events over the western United States, as simulated by an ensemble of regional climate models (RCMs) driven by IPCC AR4 global climate models (GCMs). All eight simulations analyzed in this work consistently show an increase in the intensity of extreme winter precipitation with the multi-model mean projecting an area-averaged 12.6% increase in 20-year return period and 14.4% increase in 50-year return period daily precipitation. In contrast with extreme precipitation, the multi-model ensemble shows a decrease in mean winter precipitation of approximately 7.5% in the southwestern US, while the interior west shows less statistically robust increases.
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Embroidering the narrative, part 1266.
Speaking of narrative:
“And if all others accepted the lie which the Party imposed — if all records told the same tale — then the lie passed into history and became truth. ‘Who controls the past’ ran the Party slogan, ‘controls the future: who controls the present controls the past.’ ” — George Orwell, 1984
IPCC says it all.
They might be happier if they moved to Mars or Venus, where the weather would suit them better.
Houston, this is IPCC Mars, the WeatherGrinch has landed.
“Models say…. .”
‘Nuff said.
If the IPCC AR4 GCMs do not demonstrate any skill in forecasting near term global conditions, how are any results based on these models to be of any use whatsoever?
My understanding is that the latter decades of the 20th century were unusually wet in the SW. A change to drier times would be a return to more ‘normal’ times. Unfortunately, we populated places like Colorado and New Mexico from the 70s on.
Someone correct me, if I’m wrong.
But don’t these models lack any “skill” when applied regionally?
(Not that they have any “skill” when applied globally!)
This really seems to be a “look over here” trick for the Warmists, since the models just aren’t cooperating with higher temperatures.
How sad is it to think that these guys are now most likely celebrating the occurrence of disastrous weather events.
After enlarging their ‘ensemble’ maps to a legible size, it looks like the prediction is for wetter times (blue) in most of the west, with a couple of spots drying out. WTF?
Who could care less what the climate models consistently predict? Are they any good at hindcasting the hydrological cycle of the region under analysis? If the answer is no, the next question to ask is, why does this sort of stuff get published?
Maybe California can buy all those mothballed Australian sesalination plants they built in response to the dire drought predictions of yesteryear.
Roger Pielke Sr has had some interesting history of the hydrology of the southwest. In the twelfth century there was a megadrought that lasted decades. Mother nature has tougher tricks up her sleeve than anything the models can dish out.
So the modeled precipitation will by 7.5% below what 1977-1999 levels, the modeled precipitation for that range or the observed precipitation for those years? Because the AR4 models were about that much below the observed precipitation increases when simulating 1977-1999. So it should be no surprise they are that low in 2038-2070, unless the documented diagnostic issues have been specifically addressed.
Well maybe, but that would Mann was right (I suppose it is always possible he is correct occasionally, but definitely not in regards to the MWP) and there was no MWP.
Just about every study indicates the MWP period was co-incident with higher precipitation in the US south west – more heat means more evaporation and that usually means more rainfall.
As per usual, these models ignore the historical evidence.
So bottom line: another example of grant generated BS.
Also, the usual predictions of doom and gloom take place long after most of us are in our boxes.
Hate to disappoint them on “drier”.
Century trend for California precip:
http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=pcp&month=9&year=2011&filter=12&state=4&div=0
Looks slightly wetter, but not meaningful.
Century trend for Oregon precip:
http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=pcp&month=9&year=2011&filter=12&state=35&div=0
Slightly wetter.
Century trend for Wash precip:
http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=pcp&month=9&year=2011&filter=12&state=35&div=0
Unquestionably wetter.
Odd, innit? These “experts” love to use linear extrapolation when it’s obviously wrong, but when linear extrapolation actually gives a pretty clear picture, they totally ignore it and decide the trend must run against the data.
The only consistent thing about experts is that they are 100% wrong 100% of the time.
The east to switch to a colder warmier climate with drought induced wetness.
As American southwestern states struggle against ongoing drought…
Dam California! Dam it all to hell!
What I know about the climate could be written on a postcard. So on a warming world the main temperature increase is at the poles thus the temperature gradient from the equator to the poles is reducing resulting in less wind and a more settled climate.
When a world cools the main cooling is at the poles with increasing temperature gradient resulting in increased wind and more extreme climate events.
What to believe?
Maybe I’m negative mood this bright, sunny morning in gorgeous New England, but this post is rubbing me the wrong way.
I can buy the southwest’s attention to the possibility of a long period of drought, but I haven’t heard much from the northwest’s bracing. There’s enough variability in annual snowfall that I think it would be hard to distract the population from other issues like population, highway congestion, the historic earthquake that could happen any time, the tsunami that would likely result, and just when is Mt. Ranier going to erupt next?
Hmm. I’m sort of tolerant of calling model output “data,” but I’m having trouble with the concept that comparing multiple runs produces “statistically significant” data. Ultimately it’s the algorithms expressed in the code that produce the results, and by making multiple runs to reduce the noise, what you’re left with reflects on the algorithms, not the numbers.
Ah well, being an OS software engineer, I tend to deal with deterministic code, and statistically significant performance data. Perhaps the OS folks in Redmond are a different breed. 🙂
Perhaps that’s what Joe Romm had in mind with his permanent drought in the SouthWest.
http://notalotofpeopleknowthat.wordpress.com/2012/01/07/romms-permanent-drought/
Oh, it’s not just a model, it’s a multi-model ensemble! Well, that makes all the difference…..
As the doom was gloomed long before there were models of it, is there just the faint possiblity that the models are full of confirmation biases?
As the climate is now cooling, and much more cooling is expected in the near term, can we use the modelled outputs to predict that the opposite effect, 7.5% wetter conditions in the SW, will actually be the coming experience?
What goes around come around. If the models are statistically correct, making falsifiable predictions, then Arizona can expect more rain in the years to come.
The empirical evidence contradicts the model, so some above think. No problem. We will just build a fire and hold the modellers feet to it while discussing the virtues of computational fluid dynamics.
“….As American southwestern states struggle against ongoing drought, and the Northwest braces for a projected shift from a snow- to a rain-dominated hydrological system, climate researchers strive to provide precipitation projections….”
They lost me right there. I see a shift back towards the 1960’s and 1970’s with an INCREASE in blocking by pushing the climate zones more towards the equator. The Russian heatwave of 2010 and the All-Time Snowfall Records Fall Across Western Oregon & SW Washington are examples. If you watch the jet stream over the USA every day like I have for the last couple of decades you could have seen the change for yourself.
Ten years ago, the weather for my area (North Carolina) were what I saw coming from the west. Now we see more weather coming from the south, north or even east as the jet streams forms Rossby waves
I am just a farmer/scientist with a keen interest in the weather patterns that bring the rain to my fields. I can certainly see the shift in weather patterns as part of my daily study. Correct perdiction means the differnce in making or losing money in my business. I do not have the luxury of fudging data for the “Cause”
Estimates derived from large general circulation models show that in a warming world, water availability in the western United States will be increasingly dictated by extreme events.
What do they show for a cooling world?
I agree with their model, which is equivalent to saying that the PDO is going into a negative phase, and the earth as a whole will be cooling:
http://www.appinsys.com/globalwarming/PDO.htm
local effects of negative PDO:
Northwestern North American spring time snow pack and water year (October-September) stream flow Above average with negative PDO
Winter and spring time flood risk in the Pacific Northwest – above average with negative PDO.
For the Southwest:
http://www.climas.arizona.edu/sw-climate/pdo
“Decreases in winter precipitation associated with negative PDO conditions and intensified La Niña conditions could, for example, put stress on the urban water systems of the Southwest. Even moderately drier-than-normal conditions could have serious effects in some sectors. For example, CLIMAS researchers have documented that ranching operations in the Southwest are highly sensitive to climatic conditions. Forest fire management is another area crucially influenced by climatic conditions and trends.”
Having worked with AQMD and ARB, I see this as an opportunity to depopulate California and the Southwest. This is what the regulators want anyway. AQMD wants to totally eliminate NOx emissions and is willing to shut down all businesses in the SoCal area to do just that. With no commerce, there are no jobs, and with no jobs, there is no need for people, and with no people, there is no need for water and irrigation. That will reduce the burden on the Colorado Aqueduct, and more water will flow south. Back to Nature. When do we start? OOOOps, forgot about tinsel town. They will need their own supply of water and weather modification programs to make sure they live in luxury while the region is transformed into the Green Paradise that they always wanted it to be.