LIVERMORE, Calif. — The rain in Spain may lie mainly on the plain, but the location and intensity of that rain is changing not only in Spain but around the globe.
A new study by Lawrence Livermore National Laboratory scientists shows that observed changes in global (ocean and land) precipitation are directly affected by human activities and cannot be explained by natural variability alone. The research appears in the Nov. 11 online edition of the Proceedings of the National Academy of Sciences.
Emissions of heat-trapping and ozone-depleting gases affect the distribution of precipitation through two mechanisms. Increasing temperatures are expected to make wet regions wetter and dry regions drier (thermodynamic changes); and changes in atmospheric circulation patterns will push storm tracks and subtropical dry zones toward the poles.
“Both these changes are occurring simultaneously in global precipitation and this behavior cannot be explained by natural variability alone,” said LLNL’s lead author Kate Marvel. “External influences such as the increase in greenhouse gases are responsible for the changes.”
The team compared climate model predications with the Global Precipitation Climatology Project’s global observations, which span from 1979-2012, and found that natural variability (such as El Niños and La Niñas) does not account for the changes in global precipitation patterns. While natural fluctuations in climate can lead to either intensification or poleward shifts in precipitation, it is very rare for the two effects to occur together naturally.
“In combination, manmade increases in greenhouse gases and stratospheric ozone depletion are expected to lead to both an intensification and redistribution of global precipitation,” said Céline Bonfils, the other LLNL author. “The fact that we see both of these effects simultaneously in the observations is strong evidence that humans are affecting global precipitation.”
Marvel and Bonfils identified a fingerprint pattern that characterizes the simultaneous response of precipitation location and intensity to external forcing.
“Most previous work has focused on either thermodynamic or dynamic changes in isolation. By looking at both, we were able to identify a pattern of precipitation change that fits with what is expected from human-caused climate change,” Marvel said.
By focusing on the underlying mechanisms that drive changes in global precipitation and by restricting the analysis to the large scales where there is confidence in the models’ ability to reproduce the current climate, “we have shown that the changes observed in the satellite era are externally forced and likely to be from man,” Bonfils said.
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Identifying external influences on global precipitation
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Edited by Kerry A. Emanuel, Massachusetts Institute of Technology, Cambridge, MA, and approved October 18, 2013 (received for review July 30, 2013)
Significance
This study provides evidence that human activities are affecting precipitation over land and oceans. Anthropogenic increases in greenhouse gases and stratospheric ozone depletion are expected to lead to a latitudinal intensification and redistribution of global precipitation. However, detecting these mechanisms in the observational record is complicated by strong climate noise and model errors. We establish that the changes in land and ocean precipitation predicted by theory are indeed present in the observational record, that these changes are unlikely to arise purely due to natural climate variability, and that external influences, probably anthropogenic in origin, are responsible.
Abstract
Changes in global (ocean and land) precipitation are among the most important and least well-understood consequences of climate change. Increasing greenhouse gas concentrations are thought to affect the zonal-mean distribution of precipitation through two basic mechanisms. First, increasing temperatures will lead to an intensification of the hydrological cycle (“thermodynamic” changes). Second, changes in atmospheric circulation patterns will lead to poleward displacement of the storm tracks and subtropical dry zones and to a widening of the tropical belt (“dynamic” changes). We demonstrate that both these changes are occurring simultaneously in global precipitation, that this behavior cannot be explained by internal variability alone, and that external influences are responsible for the observed precipitation changes. Whereas existing model experiments are not of sufficient length to differentiate between natural and anthropogenic forcing terms at the 95% confidence level, we present evidence that the observed trends result from human activities.
paper: http://www.pnas.org/content/early/2013/11/05/1314382110.full.pdf
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However, detecting these mechanisms in the observational record is complicated by…..
…no rise in temperature for the past 17 years
Lawrence Livermore is conducting climate research? NASA was bad enough. Is there any government agency NOT doing climate research? The madness has to stop.
Changes in global (ocean and land) precipitation are among the most important and least well-understood consequences of climate change.
On a scale of not-understood-at-all to completely-understood, where would least-well-understood be found? Is it above or below kinda-well-understood? Is it between plain-old-understood and not-so-well-understood? Is it close to we-think-we-understand-it-but-not-sure-understood?
Just curious.
As can be seen, just a small change in temperature leads to a marked reduction in the efficiency of the heat engine that drives earth’s weather. This loss of efficiency means that “intensification of the hydrological cycle” is physically impossible.
As such, the paper is a work of science fiction. It proposes a violation of the 2nd law of thermodynamics.
Well, much as I completely agree with your basic argument, with nonlinear hydrodynamics, not physically impossible, especially not transiently. Even if the mean temperatures don’t change at all, the system fluctuates as it self-organizes into different chaotic/turbulent patterns. The range of fluctuation is (empirically) large as evidenced by a glance at the hurricane record. Furthermore, the fluctuations are not “random” but are strongly correlated with in particular ENSO activity — warming or cooling in the Pacific seems to at least partially dictate the pattern and intensity of Atlantic storms.
As your calculation shows, the ideal efficiency would only make a tiny change even for temperature changes on the order of 1% (which is huge, several times what has been observed over the last 160 years), but this heat engine doesn’t run anywhere near its peak efficiency, and a reorganization of the engine could easily either intensify or weaken storms (independent of any given temperature change, so certainly WITH a given temperature change). To the extent that the paper discusses observations, its statements may or may not be correct — I’m guessing that it is grasping at data straws in a data set too small to arrive at any meaningful conclusions. Its arguments, I agree, are not particularly sensible.
This is especially true at the present. If anything, the evidence accumulating over the last few years is that both the total number of storms and the total energy of storms is in a surprising deficit throughout the Atlantic basin. Although there have been a very few large storms (e.g. tornadoes), there have been fewer storms and fewer large storms. This year’s Atlantic hurricane season was downright boring for a hurricane watcher — which is a good thing for all the inhabitants of coastal property. It was the wussiest season in over 50 years. We continue to extend the longest stretch in recorded history without a category three or better hurricane making landfall in the US — a record that began some two years ago so we are extending it by YEARS over the previous record, and there is little chance of a category 3 storm happening at all before perhaps August or September of next year, so we are nearly certain to extend the record by eight more months.
This actually is evidence of reduced efficiency of storms, but it is difficult to conclude from this that global warming is responsible (following your more correct but still flawed argument). It is more likely related to the near-neutral ENSO conditions and to a general COOLING of the Atlantic over the last decade compared to the decades preceding it. Bob Tisdale would probably have less anecdotal data on this, but I look at the tropical weather SST maps for the Atlantic at least several times a week throughout hurricane season, and my eyeballs tell me that the subtropical Atlantic has been a bit cooler at peak for the last few years — it gets hot, but not AS hot as it used to get. That and wind shear seem to be preventing storms from forming.
This is where your argument gets tricky. Hurricanes don’t form due to the temperature difference between the poles and the equator. They form because of the temperature difference between warm waters on the surface of the ocean and the troposphere. If the upper troposphere and stratosphere are “calm” with comparatively light winds, defects that are always present in the wind pattern at the surface self-organize due to coriolis forces and transport warm, wet air laden with latent heat upwards, creating low pressure centers and the characteristic coriolis-twisted inflow. As the moisture laden air rises it cools, releasing its heat as rain precipitates out, and the plume of warm out generates an anticyclonic outflow pattern up high. As long as the outflow and inflow remain aligned vertically and the ocean remains much warmer than the outflow, there is plenty of temperature differential and the hurricane will strengthen. If upper-level winds push the outflow laterally off to the side of the inflow (shear) this essentially bends the “chimney” (eye) of the hurricane over, and can completely disrupt it, essentially choking the engine. This year shear was high all over the Atlantic, and although I watched many promising young storms (“regions with the potential for development”) nucleate here and there, the conditions were doubly unfavorable for growth — high shear, comparatively cool sea surface temperatures. Where they did form over seas that were plenty warm enough for a good hurricane, shear kept all but a handful from making it to the tropical storm category, and I think there was only one or two storms that made it to category 1 hurricane status (far from land, briefly).
So what you should be looking at is not temperature difference between poles and equator, but temperature difference between the surface of the sea and the upper troposphere. The former may well vary, and if the globe is warming sea surface temperatures will warm as well, which will without question increase the potential for large, violent tropical storms. The temperature of the upper troposphere in the classical picture of AGW will actually decrease — the argument is that more GHGs push the tropopause up without changing the DALR, so that the radiative region is cooler and less heat is lost from the atmosphere, forcing more heat to be lost by direct radiation from the surface itself — so that actually, their argument is not science fiction at all. CO_2 driven AGW would indeed both warm sea surfaces and cool the tropopause and thus increase the efficiency of hurricanes, if it is not accompanied by persistent increases in upper level shear (or other factors, a decrease in tropical waves that nucleate the storms) that confound the simple prediction.
Tornadoes are a different matter, as they generally are associated with cold air moving over warm air, and hence are indeed associated with comparatively sharp lateral temperature differences. They are rare where temperatures are uniformly warm or cold, but often accompany a cold front moving over a warm weather pattern, especially in the spring. Frequency and strength depend a lot more on the local temperature change, not on the absolute temperature. A decrease in tornado frequency in the US might be a signal that temperatures and circulation patterns are more uniform, less rapidly varying. I suspect this is tied a lot more into things like the PDO phase and the behavior of the NAO — things that affect the probability of arctic cold fronts proceeding southeast across the US to overrun warmer weather already stationary there — than to “AGW” per se, but perhaps one could tell some sort of story otherwise.
The problem here is that correlation is not causality, either way. A lack of Atlantic hurricanes doesn’t disprove AGW any more than a surplus proves it. Arguments linking hurricane frequency and strength to AGW are not science fiction, but they are oversimplified — otherwise we could use hurricane frequency for the last couple of years in the Atlantic basin as a thermometer for mean SSTs and conclude that the basin is actively COOLING. I suspect that the correlations found in the study are profoundly weak because numerous other studies have looked for simple first order correlation between GASTA and storm intensity and frequency (e.g. the Pielke’s) and found nothing of the sort, if anything a weakly negative correlation. So now they are resorting to look for second order effects — some sort of coincidence between storm frequency and storm latitude — and they find a correlation, but one (completely unsurprisingly) too small to be statistically significant.
This is data dredging. If one looks at all sorts of multivariate combinations, sooner or later you’ll find one that is above random chance even when the individual variables are not visibly correlated.
The paper should almost certainly not have been accepted. If the direct correlation is already absent at levels that are statistically significant, looking for multivariate correlations is a most chancy enterprise, and reporting a statistically insignificant result as “proof” (given the wording above) seems rather hyperbolic.
rgb
markcjf: “Yet again we seem to have pseudo-science masquerading as real science. Or am I being harsh?’
A little. If you decide that the proper relation of philosophy and experiment is that experiment validates philosophy, then this is just proper. Start with the philosophy, if the experiment fails to refute it, the philosophy is more strongly proven.[1] But you call that pseudoscience, then the vast bulk of science is in such a condition.
More properly, in my stridently unhumble opinion, this is first order myth making. That speaking beyond the data is to speak beyond what has been shown by experiment. I don’t want to go so far as to state that the bulk of scientists that do this are the guilty party in this as this is what they were trained to do. But if not a given scientist, then they were snookered out of money for the failure of an education they received. In either case, if we’re speaking beyond what the experiments and data show, then we’re not using the experiments and data in the first place. And may as well save the time and expense fussing about it by just writing pure and honestly presented philosophy position papers.
[1] http://en.wikipedia.org/wiki/Raven_paradox
Can these people explain how human activity affected the Sahara desert between 12,000 B.C. and 6,000 B.C.?
@ferd berple
your remarks are spot on!
Just another bit of dross for the publications scoreboard.
What an absurd waste of research dollars. Everything wrong with this has been well-stated above.
GIGO. These two should learn about atmospheric circulation and weather first…
How can people who do not understand our complex climate conclude that any aspect of it cannot be explained by natural variability alone?
Thirsty says:
November 13, 2013 at 6:44 am
Lawrence Livermore is conducting climate research? NASA was bad enough. Is there any government agency NOT doing climate research? The madness has to stop
>>>>>>>>>>>>>>>>
Unfortunately 195 governments including the USA signed the UNFCCC, the United Nations Framework Convention on Climate Change. The USA ratified this treaty on March 21 1994 per the United Nations.
http://unfccc.int/essential_background/convention/status_of_ratification/items/2631.php
This is the broad framework treaty that includes The Kyoto Protocol.
In other words 195 governments are committed to shoving this crap down the throats of their people.
As many of us keep saying It was ALWAYS political and the CO2 as the climate control knob was mandated by $%#& TREATY. There is nothing scientific about it. Once it was so mandated no work would be funded to actually look at anything but CO2 as the major factor controlling climate.
Circular reasoning at its finest.
So models do actually make predictions, then? That’s good news. How about the prediction for warming in lock step with CO2 increases & for a tropical tropospheric hot spot?
Lawrence Todd says:
November 13, 2013 at 4:25 am
I find that having Kerry A. Emanuel editing an article on climate change…
That sounded warning bells for me, as well. It is, in his usual breathless style, a press release where absolute certainty has replaced scientific language and caution.
Briefly skimming the linked PDF threw up the name Ben Santer, another of the usual “Team” suspects.
I’d recommend reading the paper itself, however, as the language is much more circumspect. None of the claims in the press release are stated as certain in the paper. That is the problem, not that potential team-members are trying to prove a theory rather than test it.
Pielke Sr. and others have a bit to say about local human impacts on locally experienced climate conditions including rainfall.
“we present evidence that the observed trends result from human activities.”
But they don’t. They present evidence that the observed trends are not replicated by the models that have been shown, time and time again, to be incomplete and erroneous.
The claims are outrageous.
Gail Combs: “As many of us keep saying It was ALWAYS political and the CO2 as the climate control knob was mandated by $%#& TREATY.”
Once upon a time they used to put a stop to such things: http://en.wikipedia.org/wiki/Indiana_Pi_Bill
This is what happens when you divert science funding away from the real sciences and into • Climastrology. Lawrence Livermore simply followed the money, damned nuclear weapons safety and terrorism.
LLNL is now responding to the national threat of more or less rain in the USA and proposes what exactly??? What the heck do they propose we do about it? What if they are wrong? See Australia’s mothballed desalination plants as a lesson in humility in the face of nature.
This paper boils down to “we can’t think of anything else so it must be our demon gases.”
Have there been any actual OBSERVED changes in precipitation to date?
Dear Thirsty.
Yes, Gail Combs is quite correct and there is not too much to add to her statement. But, I will add a footnote to say that every nook and cranny of government is involved in this mess. It is what governments do – except in the reign of Regan, governments don’t shrink – they GROW.
And to grow requires $$$$$$. And in today’s economic climate (hah!) governments can’t directly tax people and then remain in office. so, they are looking for ANY means to tax people indirectly. Climate change was a gift-wrapped treasure chest for government and they ALL (all 195) recognized it instantly – even before the so-called science was settled.
Open your eyes – governments WANT catastrophic climate change. Nay! Governments NEED it. They will make climate change true because they must. Our current fearless leader is not stupid. He is not naïve. In fact, we would be naïve to think he is. He is a POLITICIAN with an agenda and he will exploit every opportunity to further that agenda. Ditto the U.N. and all the other signatory governments Gail Combs mentioned
We will all do well to recognise that the science DOES NOT MATTER to our politicians except in two ways: 1) they can use their own scientists or those they fund to support the pre-conceived conclusions in their effort to expand their powers and influence, and 2) they can use the indirect taxes they levy using the findings of “government experts” to continue to grow the government by creating more departments, agencies, divisions and bureaus which will conduct research along the correct lines so they can circle back to item No. 1.
In other words, because governments WANT/NEED this, they will use every department at their disposal to support it. Other scientists are not “government scientists” so they can be labeled as “on the take” paid-for shills for “big oil”…… As we will undoubtedly see in the pending SCOTUS case,people have a deference to the government because governments are perceived as being disinterested and, consequently, unbiased in a particular issue. That includes the courts. Why else do you think the average Joe on the street is not utterly relieved to learn that the sky is likely not going to fall on his head? Why are such people angered when you challenge the orthodoxy? Because “government experts” are reliable. They landed people on the moon after all.
So, don’t despise Obama for being ignorant about the science – he isn’t. Rather, despise him for being a politician which he IS. It is a calculated power game – in other words, politics. Plain and simple. Learn that, and you will be less surprised to find out how pervasive a force it is in every facet of our governments.
MattN says:
November 13, 2013 at 9:57 am
Have there been any actual OBSERVED changes in precipitation to date?
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not really
http://www.climatedata.info/Precipitation/Precipitation/global_files/BIGwprc-02a-observed_precipitation_ipcc_-_3.12.gif.gif
“… model experiments…” … “… evidence… .”
Yes, indeed, Gail Combs (at 3:28am today), they are either:
1. Lying
2. Very stupid AND/OR
3. Psychotic
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lol, Stephen Richards (at 6:06am today), no doubt.
I would say that this (posted immediately below) has more truth in it and was a FAR better investment of time and money, than the above paper (yes, yes, of course, that wouldn’t be saying much and this was, indeed, a fine film…. but you get my point, I hope):
(Trivia: of course, this little bit of climatology wasn’t completely honest, either…. that’s not Audrey Hepburn singing….. it’s Julie Andrews)
Well…the warming has stalled, they need a new angle, I reckon they’ll need to better than this!
They apparently can’t see the forest for all the trees. More correctly lack of trees, not one mention of the biotic pump and how the impact of deforestation and land use changes along coastal and adjacent inland regions play a large, and historic role in the very subject they supposedly studied.