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The ​“engine” behind the sta­bil­ity of the con­di­tions that have helped Mediterranean farm­ers grow their crops for cen­turies is under­go­ing a major change.

Spain and Italy are among the first places to expe­ri­ence a new and unpre­dictable cli­mate phe­nom­e­non that is rapidly extend­ing across the Mediterranean basin.

What is hap­pen­ing is con­nected to the ongo­ing weak­en­ing of the pow­er­ful ocean cur­rents in the Atlantic, which bring huge amounts of warm water from south­ern and mid­dle lat­i­tudes to the European coast.

According to new research, the effects of the weak­en­ing Atlantic Meridional Overturning Circulation (AMOC) on the world’s cli­mate are huge and will impact at least three con­ti­nents.

The study authored by the German cli­ma­tol­o­gist Niklas Boers and pub­lished in Nature warns that the AMOC is reach­ing a crit­i­cal tran­si­tion, a tip­ping point beyond which even stronger cli­mate effects are to be expected.

“Looking at the evi­dence of the AMOC weak­en­ing is rel­e­vant because it tells us that we face a dif­fer­ence which is shrink­ing between tem­per­a­tures among waters in the trop­i­cal areas and those in the north­ern polar region,” Gianmaria Sannino, an oceanog­ra­pher and direc­tor of the cli­mate mod­el­ing and impact lab­o­ra­tory at the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), told Olive Oil Times.

AMOC is dri­ven by tem­per­a­ture. The cold north­ern region of the ocean attracts the warmer waters, cre­at­ing a stream that has played a piv­otal role in reg­u­lat­ing Earth’s cli­mate for mil­len­nia.

“It is the engine of cli­mate on Earth since oceans are the most rel­e­vant cli­mate reg­u­la­tor,” Sannino said. ​“Ninety-three per­cent of the heat pro­duced by global warm­ing is found in the oceans.”

“While changes in the atmos­phere often come abruptly and impact pop­u­la­tions and crops, and are eas­ily vis­i­ble, those in the oceans are harder to see, build up slowly and bring huge con­se­quences to the whole sys­tem for much longer peri­ods of time,” he added.

The new study con­firmed the find­ings of sev­eral pre­vi­ous ones regard­ing how major changes in the AMOC could bring about a more rapid rise in sea lev­els on the east coast of the United States, per­sis­tent droughts in West Africa and sub­stan­tial cool­ing of north­ern Europe.

While many other effects are to be expected, the first region to feel the change will be the Mediterranean basin.

“What cli­ma­tol­o­gists have dis­cov­ered is that south­ern Europe is a very spe­cific cli­matic hotspot, where cli­mate change effects are espe­cially evi­dent and hap­pen before than else­where,” Sannino said.

The basin and its agri­cul­ture have long enjoyed the mod­er­at­ing pres­ence of the Mediterranean Sea.

“Rome has the same lat­i­tude as Boston, but the cli­mate is sharply dif­fer­ent because Rome is in the mid­dle of a very big lake,” Sannino said. ​“This dif­fer­ence will be lost because of all the energy we released in the atmos­phere and in the oceans since the pre-indus­trial era.”

Regional cli­mate data, which informed the United Nations’ Intergovernmental Panel on Climate Change (IPCC) report, show that the Azores High, a high-pres­sure weather sys­tem that influ­ences the cli­mate of Europe and North Africa, is almost gone as a result of the weak­en­ing AMOC.

During sum­mer, the Azores High keeps the cooler north­ern air masses sep­a­rate from the hot African cir­cu­la­tion, cre­at­ing mod­er­ately warm sea­sons that favor agri­cul­ture and farm­ing.

“It is weak­en­ing. It is almost gone, and this causes the two masses, cool and warm, to clash over south­ern Europe with the con­se­quent extreme weather events we are more and more often wit­ness­ing,” Sannino said.

If noth­ing will be done to reduce global emis­sions and cur­tail the effects of cli­mate change, cli­ma­tol­o­gists expect tem­per­a­tures in the Mediterranean basin to rise up to 5 ºC by the end of the cen­tury, well above the expected global pro­jec­tions.

Spain and Italy, the world’s two largest olive oil pro­duc­ers, are at the fore­front of this change. Droughts and deser­ti­fi­ca­tion already threaten their agri­cul­tural sec­tors and are expected to become even worse.

“The heat­waves we had this sum­mer are just the begin­ning,” Sannino said. ​“If we cur­rently con­sider these heat­waves abnor­mal since they hap­pen every few years, by the end of the cen­tury we will have heat­waves that will not last a few days, but for sev­eral weeks. They will be hot­ter and will occur in a sum­mer that will have an early begin­ning and a late end­ing.”

Longer, hot­ter and drier sum­mers will have a pro­found impact on olive grow­ing. Already, hot­ter and drier springs in Andalusia, the world’s largest olive oil-pro­duc­ing region by a large mar­gin, are lead­ing to ear­lier flow­er­ing in olive trees and increased dam­age from heat stress events.

Additionally, a 2020 study con­ducted by researchers in Israel demon­strated that higher-than-usual tem­per­a­tures affected olive fruit growth and weight, oil accu­mu­la­tion in the fruit and its chem­i­cal com­po­si­tion.

A sep­a­rate study in Andalusia showed that hot­ter and drier con­di­tions in the south­ern Spanish region could sub­stan­tially decrease the abil­ity of seven endemic vari­eties, includ­ing the prodi­gious Picual, to grow nat­u­rally there.

Francesco Muschitiello, a geo­g­ra­pher spe­cial­iz­ing in pale­o­cli­ma­tol­ogy at the University of Cambridge, told Business Insider that ​“a shut­down of the AMOC is the eas­i­est, most effi­cient way to dis­rupt the cli­mate sys­tem.”

“Ninety-five per­cent of the time, when we talk about rapid cli­mate change, it’s asso­ci­ated with AMOC,” he added.

According to Boers, as quoted by Business Insider, ​“it typ­i­cally took a few hun­dred to a few thou­sand years for the AMOC to go back to the strong mode.”

“If the AMOC were to col­lapse to the weak mode at some point in the future, it would indeed be very hard to bring it back to the strong mode,” he added.

Climatic con­di­tions will keep chang­ing over the next decades and that will require farm­ers to adopt new efforts in order to guar­an­tee their yields and income.

“Precision and tech­no­log­i­cal agri­cul­ture means increas­ingly will be needed,” Sannino said. ​“We will have to focus on the sus­tain­able man­age­ment of the water resources, irri­ga­tion and so on.”

“More than any other sec­tor, agri­cul­ture is affected by cli­mate change and at the same time, it is one of the most rel­e­vant con­trib­u­tors to the causes of the change itself,” he added. ​“The world needs a smarter and more sus­tain­able agri­cul­ture to face a weather becom­ing more unpre­dictable.”

• Nature
• Business Insider
• The New York Times