How Global Warming will make the British Winters Colder

I promised yesterday to explain how with global warming increasing at a rapid rate we might find some places, like the United Kingdom and North West Europe getting much colder than normal. It is possible (and probably likely) that global warming will leave a legacy of more and more snowy icy winters in the United Kingdom.

The important thing here is to look at the latitude of the United Kingdom. It is at the same latitude as Newfoundland and much of Siberia, which places have incredibly cold winters. Traditionally the United Kingdom has warm winters for its latitude and the reason for this is the North Atlantic Ocean Circulation System.

The ocean currents in the North Atlantic travel approximately from the Caribbean to the shores of the British Isles. In three dimensions they constitute a conveyor belt, which is partly driven by the effect of the earth’s rotation, but mostly by the greater energies created by differences in water temperatures. We call this the Gulf Stream and it warms the British Isles. If the Gulf Stream shut off the British Isles would have winters as cold as those of Newfoundland and Labrador.

The Gulf Stream operates in the Atlantic Ocean – the saltiest and coldest of the large oceans. Warm water from the tropical region of the ocean is forced north at the surface, bringing heat, like a giant heat exchanger, to the British Isles.

When the current reaches the southern part of Greenland and Western Norway it has discharged much of its heat and is saltier and therefore denser than the cold waters into which it mixes.

The current sinks (a process called overturning) and travels back at the bottom of the sea until it reaches the Caribbean, where it warms up again rises to the surface and the process continues.

All of this is perfectly consistent with the laws of physics and thermodynamics and is not scientifically controversial, as far as I know.

Now what is also not controversial is that if you mix a dense salty current (like that of the Gulf Stream as it overturns) with fresh water (which is less dense) you slow the overturning process down and possibly stop the current altogether. We do not know the precise levels of fresh water that will stop the Gulf Stream, but there is some geological evidence that the Gulf Stream has already stopped rapidly in previous eons.

Generally scientists tend to the view that stopping the Gulf Stream altogether is unlikely, but slowing it down is probable, if the climate continues to warm.

It is clear that the more freshwater you add, the more you slow down the Gulf Stream and a slowed down Gulf Stream will provide less heat to North West Europe. A stopped Gulf Stream will provide no heat at all.

How does climate change fit into this? It is established that climate change is causing more rainfall in the temperate and northern parts of the world, adding more fresh water into the sea that the sea has traditionally received. We also know that glaciers and ice reserves in the northern regions are melting, thereby bringing an additional source of fresh water to the North Atlantic.

Twelve thousand years ago (give or take the odd millennium) NASA believes that the Gulf Stream shut down because of the melting glaciers bringing so much freshwater to the North Atlantic. If it stopped today certainly several billion people in the northern hemisphere would perish. As I have said that is extremely unlikely, but if the Gulf Stream does slow down it will because global warming has melted glaciers and created more rainfall injecting more fresh water in the ocean.

In the British Isles we would experience deeper colder and bitterer winters because the Gulf Stream would bring us less heat. That is how global warming can make the winters in Britain longer harder and colder.