“I wonder whether in this situation it makes sense to remain within the European Union,” said Italian foreign minister Roberto Maroni two weeks ago, in a crude attempt to blackmail other EU countries into taking more of Italy’s illegal immigrants. But the time may come when Italy’s northern neighbours will be quite happy to see Italy leave the Union. In fact, they may even close their borders with all the EU’s Mediterranean members.

The current fuss has arisen because Italy, the closest EU country to Tunisia, was hit by a wave of Tunisian “refugees” after the recent revolution there. They are not really fleeing from persecution and repression: the revolution largely ended that. They are economic migrants taking advantage of the fact that the chaotic new regime, unlike the Ben Ali dictatorship, no longer patrols the beaches to stop them from leaving for Italy.

Ben Ali had an unwritten deal with several EU countries to control the migrant flow in return for financial and diplomatic support. Since his regime collapsed in January, an estimated 25,000 Tunisian “refugees” have flooded into Italy, mostly in boats that dump them on the shores of the nearby Italian island of Lampedusa.

This is profoundly unpopular in Italy, a country with a severe allergy to immigrants from the wrong parts of the planet. Prime Minister Silvio Berlusconi, who is currently fighting charges of bribery, abuse of power, and paying for sex with underage girls, is certainly not going to defy that popular mood.

Indeed, Berlusconi is on record as saying that Milan “seems like an African city” because of the number of foreigners in the streets. (Actually, only four percent of Italy’s population are non-citizen foreign residents, and more than half of them are European.) So when Lampedusa was inundated with Tunisians, Berlusconi came up with a sneaky way of getting rid of them.

Most of the “refugees” from Tunisia would rather be in France anyway, because many of them have relatives there and most of them speak some French. So Berlusconi’s government just made it easy for them to go to France.

Early this month Italy began issuing six-month temporary residence certificates to the Tunisian refugees. Once they were Italian residents, however temporary, they were legally free to go anywhere else in the “Schengen” group of countries, an area with no internal border controls that includes almost all of Western and Northern Europe except the United Kingdom. Most of the Tunisian refugees immediately headed for France.

Which is why, last Saturday (April 16), the French authorities began stopping the trains that normally cross the border from Italy into France without any identity checks. The Italian government responded with feigned outrage, but the French message was clear: you can’t dump your refugees on us, no matter what the Schengen Treaty says.

Now fast-forward 30 years, and assume that the average global temperature is two degrees Celsius higher than it was in 1990. That’s a reasonable assumption if there is not a drastic cut in global greenhouse gas emissions in the next 10 years.

“Global average temperature” is a number that combines cooler temperatures over the two-thirds of the planet that is covered by oceans and considerably higher ones over the one-third that is land, so in Italy it will be three or three-and-a-half degrees hotter. And Italy, like all the countries on both sides of the Mediterranean, is in the sub-tropics, which will suffer a major loss of rainfall in a warmer world.

Less rainfall and much higher summer temperatures mean that less food can be grown, and few of the sub-tropical countries will be able to feed their own populations any more. Countries like Italy are rich enough to import food to cover any local crop failures now, but they may not be able to when simultaneous crop failures all around the sub-tropics drive export prices sky-high.

This is a scenario in which not tens of thousands but millions of people are fleeing the drought-stricken countries of North Africa, trying to get into Europe. But it’s also a scenario in which millions of Italians, Spanish, Greeks, and citizens of other EU members in the Mediterranean take advantage of the Schengen rules on free movement to move somewhere cooler that still has enough food. Like France, for example.

Will France (and Germany and Poland and Sweden) let all these “climate refugees” from the Mediterranean countries in? Not very likely, is it? And are strategists in the more northerly EU countries aware that this problem is coming their way? Of course they are.

Nobody is going to discuss this scenario in front of the children now, but you can see what happened to the Italian trains trying to cross into France last weekend as a dress-rehearsal for the future. Not an inevitable future, nor one that will be upon us the day after tomorrow, but an ugly and quite probable future nevertheless. And similar things would be happening along all the other borders where the sub-tropics meet the temperate zone.