Clues hidden deep in the trunks of ancient trees have revealed that last summer was the northern hemisphere’s hottest in 2,000 years.

Last year had already been confirmed as the world’s warmest on record by a large margin, at least since 1850, due to climate change.

But tree rings, which record temperature information far further back than even Victorian scientific records, now show just how unprecedented last year’s scorching temperatures were.

Researchers say that temperatures last June, July and August were nearly 4C warmer than the coldest summer two millennia ago.

Climate scientists have repeatedly shown that global temperatures have been rising rapidly in recent decades. According to the UN’s climate body, the last time the world was consistently this warm may have been more than 100,000 years ago.