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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Alan the Brit:
At November 13, 2013 at 1:52 am you ask
Yes.
Natural Variability is the range of climate behaviours (i.e. temperatures, atmospheric pressures, precipitations, wind speeds, etc. and their rates of change) which occurred in the Holocene prior to the industrial revolution.
Few of these parameters and their rates of change can be determined with accuracy and precision for times prior to the industrial revolution. However, there are no observations which indicate that any of these parameters has been outside the range of Natural Variability since the industrial revolution. Indeed, this was the importance of the Mann, Bradley & Hughes ‘Hockey Stick’: it (wrongly) seemed to suggest that since the industrial revolution global temperature has been rising to above the range of Natural Variability.
I hope that helps.
Richard
If we observe, within our miniscule time-of-observation, an event beyond 1 or 2 sigma of our expectation, then it raises the question is our period of observation causing this rarity. It is hubris if not malpractice to believe otherwise.
This thinking…when our proxy understanding of climate suggests many 6-8 sigma events within the recent Holocene.
I don’t think you’re on to something here.
“The team compared climate model predications with the Global Precipitation Climatology Project’s global observations”.
In any comparison between models and hard data, models trump reality every time. Yeah right.
The efficiency of the earth’s hydrological cycle is:
(temperature equator – temperature poles) / temperature equator (all units Kelvin)
(300 – 240) / 300 = 20% efficiency
what happens if we warm the poles 2x more than the equator? (4C as compared to 2C)
(302 – 244) / 302 = 19.2% efficiency
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.
Not quite a Marcott level paper but not far off. Certainly nothing to Marvel over.
Are they for real? 31 years of data – of which half had no increase in global temperature anyway.
Have they compared the 33 years of satellite observations against the much longer precipitation records from around the world. There are 60 year cycles in climate so they must be classing these as noise if they think 33 years is enough data to confirm their hypothesis.
Any poleward shift in amount and intensity ought to be observable in the manual records.
Yes, what the authors have found is a fingerprint. A fingerprint showing that models do not capture natural variability.
The authors have committed an error of logic. They start with the premise that models are an accurate representation of natural variability. Since observations don’t match the models, it means that humans must be affecting the observations.
There is a much simpler explanation, that Occam tells us is the more likely answer. The models are wrong. They don’t match natural variability.
This error in the models has been clearly demonstrated by their failure to predict a pause of more than 15 years. Trying to spin model error into a human fingerprint of human climate change is nonsense. It is a failure of logic on the part of the authors.
Assumption 1: CO2 is responsible for observed climate change. Unproven assumption.
Therefore 1: Assumption2: “increasing temperatures will lead to an intensification of the hydrological cycle (“thermodynamic” changes).”
Therefore 2: Assumption 3: ” 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). ”
Just thought that in passing I’d mention AMO,PDO,NAO,Enso and throw in changes in TSI, Solar magnetic field and resultant direct or indirect effect from cosmic rays. Wonder if they just might have missed something here.
son of mulder says:
November 13, 2013 at 3:17 am
Have they compared the 33 years of satellite observations against the much longer precipitation records from around the world.
Indeed! I can’t claim to fully have understood their paper, after all I’m a complete layman in atmospheric physics and I have only spent a few minutes reading the paper. But it seems to me that they are comparing 33 year linear trends over the period 1979-2012. It’s really no surprise that they can conclude that the circulation patterns have moved poleward as a general trend over that period (which includes a long warming period and following “pause”), but I think Stephen Wilde may be right that they are moving in the opposite direction again now.
Admad says: @ur momisugly November 13, 2013 at 2:50 am
“The team compared climate model predications with the Global Precipitation Climatology Project’s global observations”.
In any comparison between models and hard data, models trump reality every time. Yeah right.
>>>>>>>>>>>>>>>>>>>>>>>>>>>
Oh, they proved something alright but not what they think they proved. They just proved two or more of the following.
1. The computer model is not fit for purpose
2. The are lying to promote ‘The Cause’ and keep those grant funds flowing.
3. They are not scientists by any stretch of the imagination and should be fired immediately.
4. They are ready to join Lewandowsky on the therapist’s couch, all victims of mass hysteria.
Honestly, how do these people get grant money – I’m almost speechless.
It is sad to suggest this, but in light of the state of climate science, corrupted and in a state of disrepute, it is difficult to trust anything being put forward by scientists in relation to climate. Such is the feeling of many.
People accept the weather of yesteryear… they accept the weather of today… they accept there will be unpredictable weather in the future. They’re not interested anymore in what grant-funded scientists have to say about the climate. And this is all due to the corrupt IPCC and its associated army of climate change charlatans who call themselves scientists.
richardscourtney says:
November 13, 2013 at 2:48 am
Thank you, Richard. I feel a dim light has been switched on, everything has become perfectly blurred! Still awaiting the Wet Office’s Deep Thought to give me 6 numbers on the Lottery!
Alan 😉
I find that having Kerry A. Emanuel editing an article on climate change equivalent to have Jose Canseco editing article on use of steriods in baseball.
Alan the Brit:
Thankyou for your reply to me at November 13, 2013 at 3:57 am. I enjoyed that.
However, some onlookers may be so amused by the humour of your post that they miss the important point you make. Hence, I take the liberty of ‘spelling it out’.
Climate variability is how climate varies.
It is NOT how computer outputs vary because the computer models emulate the understandings of climate possessed by those who built the models. But climate does not constrain its behaviour to the understandings of modellers.
Natural climate variability is how climate varies in the Holocene unaffected by human activity.
Anthropogenic climate change is how climate varies in response to human activities.
One of the several errors in the paper by Marvel and Bonfils is the failure to understand that natural climate variability is only demonstrated by nature and is not indicated by outputs of climate models.
Richard
‘cannot be explained by natural variability alone’
if you do not know what causes ‘ natural variability’ in the first place theie is simply no way you can make this statemnt. Now ask them to give you a weather forcast for more than 72 hours a head worth a dam , and they will say they cannot becasue there are ‘to many unknow factors ‘
Its must be CO2 becasue we cannot think about anything else , is not a good scentffic answer .
Good example of post-normal science:
1) Start with the hypothesis that “CO2” is “what done it”,
2) Use models which are nothing more than a series of algorithms written in code by humans and consistent with (1) above.
3) State that the made-up “data” from these models supports your hypothesis.
4) Call it “natural variability” to throw off the attack dogs.
It sounds like “PhD” in this instance stands for the derogatory acronym I heard about in college–“Piled higher and Deeper”. That’s what post-normal “scientists” do.
“The authors have committed an error of logic. They start with the premise that models are an accurate representation of natural variability. Since observations don’t match the models, it means that humans must be affecting the observations.”
That’s a direct nail/head interface ferd.
FICTION writer, Margaret Atwood:
12 Nov: Huffington Post: Margaret Atwood: We Must Tackle Climate Change Together
Whatever you think of the causes — man-made (through CO2 levels created by the burning of fossil fuels), natural (as part of a solar cycle) or divine (as part of a plan to destroy the world) — Canada’s climate is changing. And Canada isn’t alone: Conditions around the world are being altered much faster than was formerly predicted…
(LOL) This is why the Pentagon — along with other government agencies — has been paying so much attention to climate modelling.
Novelists, filmmakers and other creators have been registering these changes for some time. There’s a new term, cli-fi (for climate fiction, a play on sci-fi), that’s being used to describe books in which an altered climate is part of the plot…
Even recently, people have said they “don’t believe” in climate change, as if it is akin to Santa Claus or the tooth fairy. But chemistry and physics are not beliefs; they are ways of measuring the physical world. They don’t negotiate, and they don’t hand out second chances…
It’s not longer a question of green versus commerce: We really are all in it together when it comes to air, water, earth and fire. We’re in the soup. It’s a shared soup and we’ll have to work together to get out of it.
Air, water, earth and fire were once known as the four elements, and they’re still the things whose extreme fluctuations stand to affect us most — and not in a good way…
http://www.huffingtonpost.ca/margaret-atwood/atwood-climate-change_b_4256145.html
This one doesn’t smell right…Kind of like durian left in the sun.
Stopped reading at “heat-trapping gases”. Press release writer should read up on Kirchhoff’s law. Or go the full mile and use “planet-destroying gases”. Or maybe “kitten-killing gases”.
said LLNL’s lead author Kate Marvel. And then she had to get back to drawing her super hero comic.
Global precipitation variability decreased from 1940 to 2009. Dry areas became wetter while wet areas became drier.
It looks like drier regions became greener as the world warmed significantly between 1982 to 2010.
Have the rains become more variable? Not in this area, rainfall was less variable during the warmer 20th century than previously.
Drier, wetter, more floods, less floods, more heat spots, more cold spots, rain weakstrong, snow lessmore. These are the things I project to get less and more of in variable regions around the world / backyard etc.
Given that droughts and extreme flooding occurred during the Little Ice Age, what is a person supposed to believe? It is estimated that about 500,000 people drowned in a series of devastating floods in Europe alone, during the Little Ice Age. It seems a major problem with so-called climate scientists is that they are clueless about history.