Not quite The Day After Tomorrow

Thursday, 8 July, 2004
Leonie Joubert
Masters student in Climatology, Leonie Joubert on why future French harvests could be frozen into oblivion and southern hemisphere vineyards racked by severe droughts.

You have to credit Hollywood script-writers - they certainly know how to mill science and fable into the most extraordinary array of half-baked visual pulp fiction. Improbably explosive volcanoes, earthbound asteroids, ravenous anacondas, great white sharks with a penchant for premeditated bingeing, DNA manipulations that make Frankenstein look positively limp-wristed - give them a cue and they'll unleash it on a big screen near you.

And they've done it again. In The Day After Tomorrow, humanity cringes as brutal weather sets upon the great capitals of the world, not the least of which results in New York City disappearing into the grip of an ice age.

However, beneath the web of computer-generated scare mongering and mangled science is a thread of truth.

Take a look at the map - ever wondered why the United Kingdom and parts of west and central Europe have relatively mild climates compared with Canada, southern Russia and other countries at similar latitudes?

It's thanks to the Gulf Stream, a warm body of water, which moves north up the Atlantic Ocean from the Gulf of Mexico and along the eastern seaboard of the United States where it veers across the Atlantic, taking heat to western Europe.

Oceanographers have been watching a ticking bomb in the northern Atlantic for some decades now. With global warming bringing warmer temperatures to many parts of the globe, ice sheets have begun to melt. The concern from climate change specialists is that Greenland's retreating glaciers will flush freshwater runoff into the head of the Gulf Stream, causing a decline in salinity and stopping that north bound warm water in its tracks.

While it seems counter-intuitive to suggest that global warming could bring an ice age, this may well be the case in Britain, western Europe and parts of the US as the Gulf Stream is disrupted.

The Woods Hole Oceanographic Institute reports that waters of the northern Atlantic have become significantly less salty since the mid-1960s, 'particularly in the last decade'.

If a confounded Gulf Stream were to lead to a mini-ice age hitting those parts, it most certainly would not happen in a single day, as is suggested in The Day After Tomorrow . Rather it would take a decade or more. Neither would it result from advancing glaciers from the north, but a general freezing over of those regions.

It would also be limited to those areas impacted upon by the Gulf Stream - other areas of the planet would most likely experience warming. Increased number and severity of storms is also expected as global warming will result in greater evaporation but even the most advanced computers are unable to predict where these will strike.

Of course what this means for investment gurus is that current and approaching vintages of French wine would be worth their weight in gold once the chill sets in and later harvests are frozen into oblivion. Meanwhile southern hemisphere vineyards may not be able to step into the breach because they'll be struggling with the increased temperatures and severe droughts predicted for the next 50 years in our parts.

Further reading:

Separating the science from the fiction:
Woods Hole Oceanographic Institute: 

Weather patterns around the globe
Weather patterns around the globe

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