An interesting way to bring Europe to its knees would be to blast a channel alongside the Panama Canal so the tropical Atlantic and Caribbean water could pass straight into the Pacific. Currently all of it, and the warm air over it, has to swirl back past Florida and aim north-east for Cornwall, as the North Atlantic Drift.

We owe our mild climate to that narrow neck of land connecting North and South America which forces all the tropical warmth, water and air, in our direction. The relatively warm winters that the UK enjoys are an anomaly for our latitude as both eastern Canada, and northern Japan, have bitterly cold winters, 20 degrees worse than us. The energy transfer is quite staggering, with the 30 million cubic metres of water that passes Florida every second increasing five-fold by the time it reaches Newfoundland. However, instead of carrying on through the Arctic Ocean, most of it sinks just north of Iceland and creeps slowly south again as deep bottom water, surfacing hundreds of years later.

This is all because the water becomes heavier as it cools, and when the surface water evaporates, it leaves the salt behind. It’s made even more saline when ice forms as only the fresh water freezes, leaving a very heavy brine that sinks in great dense waterfalls thousands of feet down through the North Atlantic, so helping to keep the surface water from the Caribbean moving north.

The importance of this heavy salt water explanation for our mild, warm winters was made into a very unrealistic film some years back, called The Day After Tomorrow. In it, fresh water diluted the salty current so it didn’t sink and it slowed down. This led to thick ice that covered North America in days, whereas in reality it would take more than a century to have a noticeable effect, though it has happened in the past.

Thirteen thousand years ago, the warming at the end of the Ice Age was abruptly halted when a large North American freshwater lake burst into the north Atlantic, so slowing the current and reducing the warm air from the south. Interestingly, we might just be seeing the start of a similar episode of cooling.

There is now more fresh water entering the Arctic from Canadian and Russian rivers, and from melting ice, up 20 per cent since 1990, and over the next century or so, the North Atlantic Drift could start to slow and then we would cool.

This is just another way that our current lifestyles will impact on generations to come as global warming can produce unexpected cold as well as heat.