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.
Ferdinand Engelbeen says:
October 28, 2011 at 10:48 am
Did the researchers look at the NAO?
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From the original post: “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.”
So, the answer is, “Yes”.
The area has been slowly drying for almost 25,000 years. That being said, deforestation has undoubtedly affected, if not destroyed, watersheds throughout the region, thus aggravating both drought and flooding. These idiots need to reforest the area like America, China,Germany, Poland, and other countries that faced similar challenges have done or are doing.
Gator says:
October 28, 2011 at 10:14 am
“Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010, the team found.”
It’s simple really. The main greenhouse gas is water vapour. so, obviously, in some places around the Meditrranean there has been a reduction in rainfall from the condensed variety of this greenhouse gas.
The remainder of the change is caused by that highly selective greenhouse gas CO² which is well known to be the reason for anything else otherwise unexplained.
“The analysis began with the year 1902, the first year of a recorded rainfall dataset.”
From under developped France. The instrumental data in France start in 1952, but perhaps it’s better in Lybia…
Sorry if my english is very poor.
pat says:
October 28, 2011 at 12:51 pm
The area has been slowly drying for almost 25,000 years. That being said, deforestation has undoubtedly affected, if not destroyed, watersheds throughout the region, thus aggravating both drought and flooding. These idiots need to reforest the area like America, China,Germany, Poland, and other countries that faced similar challenges have done or are doing.
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Unfortunately the idiots here in the USA in charge of regulating farms seem to have forgotten the Dust bowl Era They are now agitating to put in place Scorched-Earth Farming
“….UC Berkeley food expert Michael Pollanz, … nicely summarized these industry rules as “sanitizing” agriculture…”
In the name of food safety, farmers in California are compelled to comply with “scorched-earth strategies” in the “quest for an antiseptic field of greens.”
,,,,,,Ponds and trees are “poisoned and bulldozed” in the name of food safety. “Farmers are told that ponds used to recycle irrigation water are unsafe. So they bulldoze the ponds and pump more groundwater, opening more of the aquifer to saltwater intrusion… .
“Vegetation buffers used to filter storm runoff and harbor pollinators are cleared. Yet, there is science indicating that removing these vegetation buffers located near field crops can render food less safe because vegetation and wetlands serve as a filter of pathogens.
UC Davis scientists found that vegetation buffers can remove as much as 98 percent of E. coli from surface water. UC Davis advisers warn that some rodents prefer cleared areas.
….The rules are based on what the large farming industry deems to be secret “super metrics” standards…. Many of the known rules are unscientific, and conflict with environmental and organic standards.
Farmers must follow them if they expect to sell their crops. These can include vast bare-dirt buffers, elimination of wildlife, and strict rules on water sources……” http://antemedius.com/content/scorched-earth-farming-foolishness
This was written in 2009. We (farmers) expect these “industry standards” to soon be enshrined in USDA/FDA regulations thanks to the new Food Safety Modernization Act of 2010.
Expect to see grass filter strips and the trees planted during the dust bowl era replaced by by bare dirt “buffer zones” and fence. I am afraid we will need another major problem before sanity rules again.
Nicias says:
October 28, 2011 at 12:58 pm
“The analysis began with the year 1902, the first year of a recorded rainfall dataset.”
From under developped France. The instrumental data in France start in 1952, but perhaps it’s better in Lybia…
Sorry if my english is very poor.
______________________________
Your English is quite good.
No doubt they used Mike Mann’s famous tree pluviometers (rain gauges)
What does “Climate is a global phenomenon” mean?
Looks like another meaningless ‘duh!’ statement to me.
Oops – spoke too soon ?
Liguria, Italy – the area around Genoa, Cinque Terre and the Italian Riveria has just been hit by devastating floods with scenes reminiscient of Toowoomba in Australia 2011 – cars flowing down streets etc.
http://genova.repubblica.it/cronaca/2011/10/26/news/maltempo_frana_investe_tir_su_a12_l_autista_rimane_intrappolato-23835418/
“Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010, the team found.” Was this really what they stated in the paper, or did they refer to one variable (temperature) explaining 50% of the variance in the dependent variable (rainfall) using a multivariate statistical method? Whatever method was used, correlation does not equal causation. I was really surprised a few years ago, when I actually read some climate science papers and realized how different the standards are for inferring causation in climate science and just about all other fields. I have read many on epidemiology relating to human health problems, and the difference between them and climate science (which use some of the same statistical methods) is remarkable. Epidemiology papers typically have long lists of potential confounders and how they were controlled for or the degree to which they might contribute to the results, possible sampling errors, diagnostics of the statistical analysis, and other critical matters. Even so, conclusions are almost always stated in terms of correlation, association, or statistical relationship, not in terms of confident statements about causality. If anything, climate science should be more tentative, because it isn’t possible to use experimental interventions to test causation as can be done in many cases in health-related research (in animal models if not in humans directly). Even more amazing is the tendency to string several correlations together to state that warming will cause, for example, millions of Mexicans to migrate to the U.S. A paper in PNAS concluded that (based on climate models, not real data) projected temperature increases would decrease crop yields and this would cause migration. There is so much uncertainty in each of these three relationships that predicting outcomes by stringing them together (remember, not beginning with actual data but with output from non-validated climate models) is ridiculous. Yet, this type of analysis has been vigorously defended by climate scientists. Strange.
‘The analysis began with the year 1902, the first year of a recorded rainfall dataset’.
What might a ‘recorded rainfall dataset’ be?
Why could it only start in 1902?
Weird, I remember reading accounts of past droughts up to seven years long in the Mediterranean area. Have we had one of those in a while?
I thought WUWT readers were smart. Haven’t you noticed the sudden increase in dodgy papers all showing that man made CO2 is wrecking the planet are coming out just in time for the COP17. They did it before Cancun and they did it before Copenhagen. The papers don’t have to be scientific nor do they need to be peer reviewed any more. They just have to show humans bad. Ban Ki Moon needs your dough and he is getting desperate. Every year that passes shows the warming( and the great scare) losing traction and the dream of untold wealth for the UN slipping away. The end is nigh I tell you. Nigh.
If I read the nifty graph accompanying the article correctly, we are agonizing over a total anomaly of +/- 2.5″ of rainfall. That would seem to be a fairly stable climate. But what do I know.
When the globe is warming the climate zones drift poleward. In the case of the Mediterranean region the dry North African conditions can spread poleward too causing increased dryness around the Mediterranean.
There were reports during the late 20th century warming spell that Mediterranean dryness would spread poleward into southern England where we were encouraged to acquire drought resistant plants for our gardens.
However since about 2000 the climate zones have been drifting back equatorward and the severity of Mediterranean dryness has been reducing as per Figure one in the article. Many sensitive plants were destroyed in the UK and Eire by recent cold outbreaks.
If human activity were the cause of the earlier poleward drift then that drift could not have reversed at a time when human emissions are higher than ever.
The evidence is quite clear that something else drives the shifts of climate zones poleward and equatorward.
“In recent decades, greenhouse-induced climate change has caused somewhat greater warming of the tropical oceans compared to other ocean regions.”
I thought that greenhouse-induced warming was supposed to have a greater effect on the higher latitudes.
David L Hagen provided a quote from National Geographic : “Scientists are now seeing signals that the Sahara desert and surrounding regions are greening due to increasing rainfall. . . .This desert-shrinking trend is supported by climate models, which predict a return to conditions that turned the Sahara into a lush savanna some 12,000 years ago. . . .“.
My question is this : did the climate models predict increased Saharan rainfall before it was observed?
If they did, then I should be able to find it in the Regional Climate Projections of the IPPC report (AR4 chapter 11):-
Executive Summary : “Annual rainfall is likely to decrease in much of Mediterranean Africa and the northern Sahara, with a greater likelihood of decreasing rainfall as the Mediterranean coast is approached. Rainfall in southern Africa is likely to decrease in much of the winter rainfall region and western margins. There is likely to be an increase in annual mean rainfall in East Africa. It is unclear how rainfall in the Sahel, the Guinean Coast and the southern Sahara will evolve.”
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Table 11.1: Regional averages of temperature and precipitation projections from a set of 21 global models in the MMD for the A1B scenario. The mean temperature and precipitation responses are first averaged for each model over all available realisations of the 1980 to 1999 period from the 20th Century Climate in Coupled Models (20C3M) simulations and the 2080 to 2099 period of A1B. Computing the difference between these two periods, the table shows the minimum, maximum, median (50%), and 25 and 75% quartile values among the 21 models, for temperature (°C) and precipitation (%) change.
…
Precipitation Response (%)
Min 25 50 75 Max
…
SAH DJF -47 -31 -18 -12 31
MAM -42 -37 -18 -10 13
So – is there support in the IPCC report for the statement that “This desert-shrinking trend is supported by climate models, which predict a return to conditions that turned the Sahara into a lush savanna some 12,000 years ago“?
No. The median prediction is an 18% decrease in precipitation over a century.
That entire sea has dried up before when the Strait of Gibraltar closed. Geologists estimate it would only take a thousand years for the sea to dessicate when the Strait closes again. So, it’s pretty dry there.
Additionally, since they claim to have an attribution figure, what is the volume of water CO2 is responsible for? What is the absolute volume of ‘missing’ water?
Additionally, can someone explain why the wording in these statements is ok for a climate scientist:
“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.”
If you haven’t identified the ‘other processes’, how did you eliminate them in attributing the dryness to carbon dioxide? Did you? If not, why do you think that’s okay?
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.
I know it’s just the press release, but did you check the adjoining seasons for your missing precipitation? What’s the annual net change in precipitation? How has winter impacted that?
Sorry about using ‘additionally’ twice in a row. I’m trying to keep track of a baseball game also. 🙂
Gail Combs
An excellent point. I am now terrified that the trees planted during the dust bowl, in the most affected regions, appear to be dying of natural age and are not being replanted (The belts are often too thin for self generation). Likewise your well deserved point on bio remediation of natural waste products. Which is encouraged by multiple other government agencies. We have a country gone insane with bureaucracies inhabited by fools with unlimited power and no education.
Julian Flood says:
October 28, 2011 at 11:40 am
“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.”
Really Julian? Covered in “Oil Sheen”? Pictures? information? I have swum, every day of every year since 1963 (even in winter) in the sea around Cyprus. There is no oil sheen and the azure blue waters are pristine! Back in the 60’s some ship captains were responsible for washing out their tanks but that is a rare occurrence nowadays with huge penalties.
Cyprus get plenty of precipitation every winter (we have had huge downpours already over the last two weeks) and it gives us great snow up on the mountains, come late January we take huge sporting advantage of. It is the lack of storage space that can affect us in the summer. The huge increase in the amount of private swimming pools and tourists has added to any water shortage. That said, new desalination plants and a huge find of gas offshore to power them has already alleviated any water shortage the island has from time to time. Not one water cut this year.
Water shortage around the coastal towns is nothing new. Simply observe the remains of the Roman/Ottoman aqueducts that used to run all the way to the mountains to supply their towns/cities!
http://blog.travelpod.com/travel-blog-entries/greekcypriot/6/1258470168/tpod.html#pbrowser/greekcypriot/6/1258470168/filename=kamares-on-the-old-limassol-road.jpg
” Mushrooming of Desalination Systems in the Middle East & Environmental Disasters Around World . INSTAL ZERO DISCHARGE SYSTEMS ( ZDS ) in Heavy Duty DESALTERS & solve all Major Environmental problems –> No Iceshelves melt, No Sea rise, No Ozone Holes, No droughts, No flooding of Cities & Low lying Islands, More icemasess near poles & Himalayas, Intencities of Hurricanes will reduce, GLOBAL COOLING —> AIRCONDITIONING OF MOTHER EARTH “
Do we have accurate precipitation data for early 20th century Med. countries? No we do not which makes any proposed trend suspicious.
Roman records indicate that desertification happened in North Africa following the destruction of the local forests to create farmland.
I’m not a climate scientist but maybe the massive increase in population over the last 100 years and consequent changes in land use would be high on my list of things to investigate.
Something that has been observed to happen repeatedly (changes in land use leading to changes in rainfall patterns) can be tested against something that is yet to be proven (higher temperatures leading to desertification). Deserts are caused by a lack of rainfall, not by ambient temperature. If heat alone caused a lack of rainfall can a climate scientist explain to me why tropical rainforests can exist at all.
Someone needs to tell them about the present trend toward floods all over the world, now that the solar cycle and PDO / AMO have shifted…
Droughts are just Sooo last panic…