View from Trefonen

In my first blog in this series I mentioned the Gulf Stream and its relationship with the warming and cooling of the North European climate. It is thought by many climate historians that the cooling effect of the Gulf Stream weakening has happened before, in fairly recent times, during the early part of the Holocene. After the last ice age ended, around 15,000 years ago, there was a period of rapid warming. Ice sheets retreated, sea levels rose – and the Gulf Stream currents, overwhelmed by the melting of the Laurentide ice sheet over Canada, switched off. Almost immediately, in climate terms, global temperatures fell sharply, leading to what is known as the Younger Dryas event, about 12,800 years ago. Ice sheets that had been in retreat across northern Europe re-formed, and global warming went into reverse – for a while. Then the warming trend reanimated and the period we call the Holocene began, usually dated from about 10,000 years ago. Climate change is so unpredictable, by its v

 In the last few days I have seen various mentions in the news of a report on the state of the system of currents that form the Gulf Stream, which keeps northern Europe warmer than its latitude would normally allow. As I understand it, when a lot of fresh water pours into the North Atlantic, usually as a result of the melting of ice sheets in North America, the salinity of the ocean is reduced and the currents drop lower, rather than staying near the surface. As a result of global warming, there has been a lot of quite rapid melting of glaciers in Canada, and the current system is becoming unstable. If it collapses completely the warming effect of the Gulf Stream would stop, bringing about (fairly swiftly, probably over a couple of decades) abrupt cooling of north-western Europe. A New York Times news item this morning explains: ‘… a crucial ocean circulation system in the Atlantic Ocean, which helps stabilize the climate in Europe, is now starting to slow down. While the [IPCC] co