NOAA study: Human-caused climate change a major factor in more frequent Mediterranean droughts
Winter precipitation trends in the Mediterranean region for the period 1902 – 2010.
High Resolution (Credit: NOAA)
Wintertime droughts are increasingly common in the Mediterranean region, and human-caused climate change is partly responsible, according to a new analysis by NOAA scientists and colleagues at the Cooperative Institute for Research in Environmental Sciences (CIRES). In the last 20 years, 10 of the driest 12 winters have taken place in the lands surrounding the Mediterranean Sea.
“The magnitude and frequency of the drying that has occurred is too great to be explained by natural variability alone,” said Martin Hoerling, Ph.D. of NOAA’s Earth System Research Laboratory in Boulder, Colo., lead author of a paper published online in the Journal of Climate this month. “This is not encouraging news for a region that already experiences water stress, because it implies natural variability alone is unlikely to return the region’s climate to normal.”
The Mediterranean region accumulates most of its precipitation during the winter, and Hoerling’s team uncovered a pattern of increasing wintertime dryness that stretched from Gibraltar to the Middle East. Scientists used observations and climate models to investigate several possible culprits, including natural variability, a cyclical climate pattern called the North Atlantic Oscillation (NAO), and climate change caused by greenhouse gases released into the atmosphere during fossil fuel use and other human activities.
Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010, the team found. This means that other processes, none specifically identified in the new investigation, also have contributed to increasing drought frequency in the region.
The team also found agreement between the observed increase in winter droughts and in the projections of climate models that include known increases in greenhouse gases. Both observations and model simulations show a sudden shift to drier conditions in the Mediterranean beginning in the 1970s. The analysis began with the year 1902, the first year of a recorded rainfall dataset.
Reds and oranges highlight lands around the Mediterranean that experienced significantly drier winters during 1971-2010 than the comparison period of 1902-2010.
High Resolution (Credit: NOAA)
In this analysis, sea surface temperature patterns emerged as the primary reason for the relationship between climate change and Mediterranean drought. In recent decades, greenhouse-induced climate change has caused somewhat greater warming of the tropical oceans compared to other ocean regions. That pattern acts to drive drought-conducive weather patterns around the Mediterranean. The timing of ocean temperature changes coincides closely with the timing of increased droughts, the scientists found.
The Mediterranean has long been identified as a “hot spot” for substantial impact from climate change in the latter decades of this century because of water scarcity in the region, a rapidly increasing population, and climate modeling that projects increased risk of drought.
“The question has been whether this projected drying has already begun to occur in winter, the most important season for water resources,” Hoerling said. “The answer is yes.”
Climate is a global phenomenon with global impacts on food prices and water security, and NOAA researchers are engaged in understanding changes in climate across many regions of the world. In the Mediterranean, winter drought has emerged as a new normal that could threaten food security. Lessons learned from studying climate in that region may also be relevant for the U.S. West Coast, which has a similar climate to the Mediterranean region of Europe and North Africa.
NOAA’s mission is to understand and predict changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us on Facebook, Twitter and our other social media channels.
“Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010, the team found.”
Oh, how I would love to hear this explained in detail!
Living in Germany and working in Italy all I can say is that NOAA is in never never land, Italy has had this week rains that caused billions of $ of damage,and more to come, Northern Germany has had rain nearly every day for years, friends in Denmark say the sun is in NOAALAND because it is not shinning in Denmark.
Those 36mm less rain in the middle of the Libyan desert appear particularly suspect, alongside Tunisia’s border-confined blessing.
I surmise there are many little devils in many of the paper’s little details (those start years for example) to render the whole exercise meaningless as usual. Note that the reddish bit by Italy’s “neck” is the same place affected by the recent flash floods. Who knows what’s the meaning of “winter”? (Rhetorical question)
Because we know that climate does NOT EVER change naturally over a period of more than 100 years.
If they really did their homework, they’d discover that it was actually a side effect of all the bombs going off on the eastern side of the sea since the 60’s.
“Sometime during the past 6,000 years, the southern boundary of the Sahara desert moved 500 kilometers south” “Without including the vegetation as a variable (rather than a fixed parameter), the models were not able to show the region’s transformation from a fertile expanse of vegetation 6,000 years ago to an arid stretch of mostly sand and mountains today.”
A couple of quotes off a webpage I found having remembered that the Sahara was supposed to not be desert about 6000 years ago. The models may be correct so far as a trend but it does not mean that CO2 must be the culprit. Basically our understanding is still very limited.
The above quotes taken from http://eltahir.mit.edu/news/climate-change-6000-years-ago-sahara-desert-explained
Apparently the National Geographic had not gotten the message:
Sahara Desert Greening Due to Climate Change? James Owen, National Geographic News July 31, 2009
Once Lush Sahara Dried Up Over Millennia, Study Says, James Owen, National Geographic News, May 8, 2008
So is yes climate is changing – it is getting drier . . . and it is getting wetter! And it did so before the major increase in fossil fuel CO2.
George Tetley says:
October 28, 2011 at 10:21 am
Living in Germany and working in Italy all I can say is that NOAA is in never never land, Italy has had this week rains that caused billions of $ of damage,and more to come, Northern Germany has had rain nearly every day for years, friends in Denmark say the sun is in NOAALAND because it is not shinning in Denmark.
——————
George, if you look at the graph, you can see that the last two winters are shown as wetter than normal. But as always, it is the trend that matters.
“Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010, the team found.”
An explanation would of this obviously alarmist statement be good, but I doubt if that will ever be forthcoming ……… Unless, of course, after a decade long, grant funded, research grant. ‘Climate science’ never changes – it’s all about generating scare stories by grant addicted individuals.
In southern Spain, the winters of 2009/10 and 2010/11 were amongst the wettest of all time and for the first time all the the country’s dams were full. Just another one of those inconvenient facts in ‘climate science’.
Did the researchers look at the NAO? It is clear from many surveys that a negative NAO (as in the period 1950-1970) gives more wet air in the Mediterranean, while the opposite happens for a (strong) positive NAO. The year 1972 shows a sudden shift to a positive NAO, which was leading over the period 1972-current, which makes the Mediterranean countries a lot drier in winter. See:
http://www.ldeo.columbia.edu/res/pi/NAO/ and
http://en.wikipedia.org/wiki/File:Winter-NAO-Index.svg
Thus that “man-made” climate change is the cause of the reduced rainfall should be taken with a lot of salt…
Forty years ago, I’m pretty sure Dr. Hoerling would have said that the significantly wetter winters during 1958-1970 were evidence that the magnitude and frequency of the wetting that had occurred was too great to be explained by natural variability alone.
These sort of stories always remind me of a classic episode of Jungle Jim…
The rainfall patterns in the Mediterranean Region follow the ocean surface temperature patterns. This should be obvious, since the rainfall comes from ocean evaporation. However, there is no connection between ocean surface temperatures and atmospheric carbon dioxide concentration.
Evaporation depends on surface temperature and wind speed. (http://oaflux.whoi.edu/publications.html). The wind direction determines where the rainfall will end up. The average ocean latent heat flux, or evaporation at low and mid latitudes is over 100 W.m-2 or 8.6 MJ.m-2 per day. This evaporation is roughly linear in wind speed. So try 100 ±50 W.m-2 for wind speeds of 8 ±4 m.s-1. This means that the short term variation in the ocean latent heat flux is at least 4 MJ.m-2 per day.
Now, full summer sun is about 25 MJ.m-2 per day. About half of the solar flux is absorbed in the first 50 cm level of the ocean. That is over 10 MJ.m-2 per day. The daily temperature variation in top few meters of the ocean is about 1 C. The heat capacity of the ocean is about 1 MJ.m-3.
Over the last 200 years, the increase in atmospheric CO2 concentration has been ~100 ppm. This has produced a ~1.7 W.m-2 increase in the downward long wave IR (LWIR) radiation coupled into the ocean for ‘ clear sky’ conditions. This is 0.15 MJ.m-2 per day. The penetration depth of this LWIR flux into the ocean is less than 100 micron. That is about the width of a human hair.
Look at the numbers:
Daily solar flux (full summer sun) coupled into the first 50 cm ocean layer >10 MJ.m-2
Variation in wind driven evaporation: >±4 MJ.m-2
Increase in downward flux from CO2: 0.15 MJ.m-2
The oceans just don’t respond to these small changes in LWIR flux. It just evaporates!
Note: There is no such thing as climate equilibrium. The change in CO2 flux has to be added to the short term ocean flux balance where it disappears into the noise of the wind driven evaporation.
So stop this global warming causes everything nonsense.
Ferdinand
Did the researchers look at the NAO?
Obviously not.
http://virakkraft.com/Inverted%20NAO-Mediterranean%20droughts.png
Hmm like to see that graph against AMO. The Atlantic is switching to colder so one might expect winter droughts to decrease sharply :D:D
“In the last 20 years, 10 of the driest 12 winters have taken place in the lands surrounding the Mediterranean Sea”
And if there was a 30 year natural cycle during that period, does that affect the study?
Is there data about the atmospheric absolute water content trends?
I predict that the amount of water vapour has been rising, aerosol numbers falling, while cloud extent has been decreasing. In ’72 I was flying over the Med and we go back there every few years. It is _covered_ in oil sheen.
More oil, fewer aerosols, less cloud, less rain, more water vapour. A couple of Latham and Salter’s cloud ships parked a few miles west of Cyprus might produce some beneficial results.
JF
“This is not encouraging news for a region that already experiences water stress, because it implies natural variability alone is unlikely to return the region’s climate to normal.”
And where does it say what the “normal” climate in the region is?
Carved on the back of Moses’s Tablet of Stone, perhaps?
I’d like to see the details of this paper where they reveal the “missing link” that actually shows greenhouse gases are causing this to happen.
I’m just a poor old country boy, but this sure looks like they might be confusing correlation with causation.
Farming in Rhodesia (now Zimbabwe) in the 1970s on granite sandveld soils we planted our corn in marginal wetlands to increase yields in dry years. To forecast the coming summer season we took note of the el nino/ la nina cycle, the South African Cape winter rainfall, the advice of our agronomist and gut feeling. Rhodesia was known as the breadbasket of Southern Africa but Zimbabwe is now in ruins. NOAA should pay attention to Will Alexanders papers on African droughts these can be found at NZ climate science
Seems these researches no nothing about the climate regarding the AO, NAO, AMO, PDO and ENSO or the cherry picking continues and other factors are conviently ignored.
There has been a major switch in the climate in the NH since 2007 and that means more -ve AO, -ve NAO, -ve PDO and -ve ENSO (ie La Nina). It shouldn’t be too long in future with increasing cloud albedo that the AMO follows and becomes -ve too.
As already at least partly mentioned, the simple observation of how the NAO behaves explains the situation.
http://upload.wikimedia.org/wikipedia/commons/0/08/Nao_indices_comparison.jpg
+ve NAO
http://eo.ucar.edu/spotlight/nao/images/figure2a.jpg
-ve NAO
http://eo.ucar.edu/spotlight/nao/images/figure2b.jpg
These images above say it all really.
WHOA!! They used a “baseline” of only 8 years??!!?? WUWT??? Quick, while it lasts, would someone please add the NOAA logo to the wiki with the humorous photo of a modern day buffoon? http://en.wikipedia.org/w/index.php?title=Jester&oldid=457440048#Modern_usage
**Whatever happened to “10 years isn’t long enough to establish a climate trend?”
**Whatever happened to “15 years isn’t long enough to establish a climate trend?”
**Isn’t the latest peer reviewed paper “It takes 17 years or longer to extablish a climate trend?”
**How about we pick a baseline of about 1945 thru 1953? (significantly drier than the baseline they used)
**How do they explain the extreme and unusual WETNESS of the 8 years starting at about 1960 thru 1968?
**I’d love to see how these people explain the Dust Bowl years in the USA and Canada.
**Whatever happened to “increased aerosols over the past decade has counteracted the continuing trend of global warming?”
**Increased aerosols also supposedly means increased cloud nuclie and increased rain, right? So how does that square with Med. drought?
**Whatever happened to “global warming causes greater evaporation?” As all of those lands border ocean, greater evaporation ought to be causing greater rainfall in the ocean adjacent areas.
**Whatever happened to “increased ocean temps have caused greater snowfall over Antarctica, thus accounting for the overall increase in ice?”
All the contradictions just keep piling up when it comes to “climate science.”
Sahara getting Greener…
http://news.bbc.co.uk/2/hi/8150415.stm
“…Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010, the team found. This means that other processes, none specifically identified in the new investigation, also have contributed to increasing drought frequency in the region…”
So half of the dryness by GHG, and the other half by “other processes”.
And naturally, they won’t talk about the other processes.
If their statement were re-worded, they’d get this: “…Other, un-named processes explained roughly half the increased dryness of 1902-2010, the team found…”, then nobody would have paid attention to it.
“The magnitude and frequency of the drying that has occurred is too great to be explained by natural variability alone,”
Given that currently climate science cannot explain past climate change, this seems simply assertion not science. We don’t know the mechanisms for the changes observed just within the Holocene, let alone before, yet we know this *can’t* be natural.
What would they say were we slipping into the next glacial period? The range for “natural variability” is very large, yet it is discounted out of hand.
lgl says:
October 28, 2011 at 11:30 am
Wow! That is quite a correlation! At first glance looks like that the NAO explains 90% (or more) of the rainfall in the Mediterranean. Not much left for the influence of CO2/AGW/ACC…