Image copyright EPA Image caption Fire that triggered the Siberian fire was found in seclusion in the Arctic region
A Siberian forest fire has burned since at least 4,000 years ago, a US-based organisation says.
The Ice Floe Centre said it would go on and study the same spot in the Altai region, Russia, to learn about past Arctic climate patterns.
It identified the site after creating infrared images showing the forest in flames.
The fire destroyed 20,000 square miles of tree tops in August and September. The Baltic Sea and the Siberian tundra were coated in smoke.
The Altai region was under the influence of the Arctic Oscillation , a major climate oscillation that has been stable for more than half a century and affects weather around the globe.
Energetic combustion from a heated lake glacier spread warm air to 1,000km (600 miles) away, creating the Siberian fire.
Dating the fire is impossible because of the mystery surrounding it.
While its source was found to be inaccessible, the Altai region has almost five million lakes . The region relies heavily on the lakes for irrigation, a source of income and energy.
Image copyright NASA Image caption An infrared image of Siberian forest on 28 August in tinder dry condition
Little research has been carried out on ecology or climate change in the area.
Bill Armitage, chief executive of the Ice Floe Centre, said: “It’s now a hot topic, but until we’ve looked at the exact site where the fire started, no one can say with certainty if it’s happening now or even before.”
The study will begin later this year, he said.