Normally 6°C wouldn’t be very warm – but in the Norwegian islands of Svalbard it’s a sultry modern summer, unlike anything seen for at least 1,800 years. That’s what sediments taken from an Arctic lake have told William D’Andrea from Columbia University in New York and a US team. It’s even warmer than a medieval warm period when parts of the northern half of the planet were as hot as, or hotter, than today. And while the record they’ve made reflects just this one site, it adds to the picture showing how unique today’s climate is. It’s also another step towards understanding how climate has changed through history, William told me.
Climate dynamics are extremely complex, and cooling in some locations can happen at the same time as warming in others, or increased precipitation in some places along with drought in other places,” he said. “These are the fingerprints we are trying to map and understand by generating such reconstructions.”
The fingerprints slowly become clearer as scientists collect more historical records, often as tubes of ice drilled from glaciers, or of mud and rock drilled from sea and lake beds. The tubes, or cores, cut through layers of mud or ice built up year after year. Scientists can then use fossils and chemicals to date and work out what conditions were like when they were laid down.