Remarkable new scientific evidence has been published that suggests abrupt rises in temperature have been a feature of global climate change going back to the iceless Jurassic period over 150 million years ago. These warming events, in which the temperature rose many degrees centigrade within decades or less, were thought to be a feature of the last ice age up to 100,000 years ago and confined to Greenland and the North Atlantic. This dramatic new evidence suggests they were a feature across the globe going back millions of years.
The findings will give fresh insight into the highly politicised debate around climate science and Net Zero. It is constantly argued that the recent small rise in global temperature, which started over 200 years ago, is unprecedented, and is caused by humans burning fossil fuel. Far from being unprecedented, it seems similar changes in temperature over comparable, and often shorter, time periods were ubiquitous across paleoclimatic history stretching back to the Jurassic era.
A group of French scientists led by Slah Boulila from the Sorbonne carried out extensive research into what are known as Dansgaard-Oeschger (DO) events. These events, named after two paleoclimatologists, track 1,500 year temperature cycles when large rises suddenly occurred followed by a reversion to ice age conditions. The scientists noted warming up to 15°C within a few decades, “pointing to abrupt and severe changes in Earth’s past climate”. Scientists and green activists seeking to downplay the significance of large changes in the paleoclimatic record have suggested that oscillations of northern hemisphere ice sheets and surrounding waters played a part.
But the French scientists now say that paleoclimatic studies have shown that the 1,500-year climate cycle is no longer restricted to the North Atlantic Ocean of the last glacial period. “The 1,500-year cycle is documented in both hemispheres, in other oceans and in continents, such as in lake and river deposits, in pollen fossils, in stalagmite proxy records, and in loess-paleosol deposits,” they add. In conclusion, the scientists note that the analysed paleoclimate records of the late Jurassic “supports the global nature of DO-like event, and in particular that their potential primary cause is independent of ice sheet dynamics”.