Widening tropics 'will drive deserts into Europe'

Alarming new satellite evidence of the effects of global warming comes as forecasters predict more severe hurricanes

A A A

The world's tropical zones are growing, threatening to drive the world's great deserts into southern Europe and other heavily populated areas, alarming new research suggests.

The study - based on satellite measurements over the past quarter of a century - shows that the tropics have widened by 140 miles since 1979. Scientists suspect that global warming is to blame.

Up to now the most startling evidence that the world is heating up has come from the poles where ice sheets have disintegrated, sea ice shrunk, and glaciers started racing towards the sea. But new research published in the journal Science suggests that equally dramatic changes are under way in the hottest parts of the planet.

"It's a big deal," says Professor Thomas Reicher of the University of Utah, one of the authors of the study. "The movement has taken place over both hemispheres, indicating that the tropics have been widening. This may be a totally new aspect of climate change."

Professor Reicher and colleagues at the University of Washington and Lanzhou University in China found that the giant jet streams 30,000-50,000 feet up in the atmosphere have shifted towards the poles, in the first direct satellite evidence that global warming is affecting the worldwide circulation of air.

These vast rivers of air - often hundreds of miles wide - meander from west toeast, pushing weather across the globe and marking the boundary between tropical and temperate regions to both the north and south of the Equator.

The research found that the air currents have moved about one degree latitude - equivalent to 70 miles - towards the North and South Poles, making a total widening of 140 miles.

"The jet streams mark the edge of the tropics. So, if they are moving poleward, that means that the tropics are getting wider," says Professor John Wallace, of the University of Washington.

The famous lines on the atlas marking the Tropics of Cancer and Capricorn will remain at 23.5 degrees north and south, because these mark the limits of where the sun is directly overhead at some point during the year - the official measurement of the tropics. But the study suggests that they will become irrelevant as boundaries of the tropical climatic zones.

It shows that the areas just outside the tropics, at around 30 degrees north and south - running through China, North India, the Middle East, North Africa, Florida and the US Gulf Coast, and through Australia, Southern Africa and Argentina - are warming particularly fast.

The zones immediately outside the tropics are often very dry - containing many of the world's great deserts - and these are also expected to move towards the poles as part of the tropical shift.

The scientists believe that this may explain the recent droughts in southern Europe and the south-western United States. They say that if the process continues it could move the deserts into heavily populated areas, with devastating results.

They are unable to prove that the shift is being caused by global warming, though they believe it is a likely explanation; another possible factor is the depletion of the world's ozone layer.

But the evidence that global warming is causing more severe hurricanes grew stronger last week as the annual season for them opened.

Forecasters are predicting another torrid year with some 16 named tropical storms, 10 of them hurricanes. Four are expected to hit the United States. There is estimated to be a one in three chance that New Orleans will be hit again, and insurers as far north as New York are reluctant to provide cover for the storm damage.

Two new studies last week confirmed research which indicated that rising sea temperatures, caused by global warming, are increasing the strength of hurricanes. On Wednesday Jeb Bush - the Governor of Florida and the brother of the President - met some of the scientists who had conducted the research, saying that he found their information "compelling".

Have you tried new the Independent Digital Edition apps?
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Ashdown Group: Junior Application Support Analyst - Fluent German Speaker

£25000 - £30000 per annum + benefits: Ashdown Group: A global leader operating...

Ashdown Group: Training Coordinator - Financial Services

£32000 - £38000 per annum + benefits: Ashdown Group: A highly successful, inte...

Recruitment Genius: Supply Chain Administrator

£8000 - £10800 per annum: Recruitment Genius: A Supply Chain Administrator is ...

Recruitment Genius: Client IT Account Manager

£25000 - £30000 per annum: Recruitment Genius: A Client IT Account Manager is ...

Day In a Page

No postcode? No vote

Floating voters

How living on a houseboat meant I didn't officially 'exist'
Louis Theroux's affable Englishman routine begins to wear thin

By Reason of Insanity

Louis Theroux's affable Englishman routine begins to wear thin
Power dressing is back – but no shoulderpads!

Power dressing is back

But banish all thoughts of Eighties shoulderpads
Spanish stone-age cave paintings 'under threat' after being re-opened to the public

Spanish stone-age cave paintings in Altamira 'under threat'

Caves were re-opened to the public
'I was the bookies’ favourite to be first to leave the Cabinet'

Vince Cable interview

'I was the bookies’ favourite to be first to leave the Cabinet'
Election 2015: How many of the Government's coalition agreement promises have been kept?

Promises, promises

But how many coalition agreement pledges have been kept?
The Gaza fisherman who built his own reef - and was shot dead there by an Israeli gunboat

The death of a Gaza fisherman

He built his own reef, and was fatally shot there by an Israeli gunboat
Saudi Arabia's airstrikes in Yemen are fuelling the Gulf's fire

Saudi airstrikes are fuelling the Gulf's fire

Arab intervention in Yemen risks entrenching Sunni-Shia divide and handing a victory to Isis, says Patrick Cockburn
Zayn Malik's departure from One Direction shows the perils of fame in the age of social media

The only direction Zayn could go

We wince at the anguish of One Direction's fans, but Malik's departure shows the perils of fame in the age of social media
Young Magician of the Year 2015: Meet the schoolgirl from Newcastle who has her heart set on being the competition's first female winner

Spells like teen spirit

A 16-year-old from Newcastle has set her heart on being the first female to win Young Magician of the Year. Jonathan Owen meets her
Jonathan Anderson: If fashion is a cycle, this young man knows just how to ride it

If fashion is a cycle, this young man knows just how to ride it

British designer Jonathan Anderson is putting his stamp on venerable house Loewe
Number plates scheme could provide a licence to offend in the land of the free

Licence to offend in the land of the free

Cash-strapped states have hit on a way of making money out of drivers that may be in collision with the First Amendment, says Rupert Cornwell
From farm to fork: Meet the Cornish fishermen, vegetable-growers and butchers causing a stir in London's top restaurants

From farm to fork in Cornwall

One man is bringing together Cornwall's most accomplished growers, fishermen and butchers with London's best chefs to put the finest, freshest produce on the plates of some of the country’s best restaurants
Robert Parker interview: The world's top wine critic on tasting 10,000 bottles a year, absurd drinking notes and New World wannabes

Robert Parker interview

The world's top wine critic on tasting 10,000 bottles a year, absurd drinking notes and New World wannabes
Don't believe the stereotype - or should you?

Don't believe the stereotype - or should you?

We exaggerate regional traits and turn them into jokes - and those on the receiving end are in on it too, says DJ Taylor