Arctic sea ice is melting so fast most of it could be gone in 30 years.
A new analysis using complex computer models of weather and climate says conditions that had been forecast by the end of the century could occur much sooner.
The ice is important because the white surface reflects sunlight back into space. When ice is replaced by dark water, sunlight can warm the water and increase warming of the planet.
The new report appears in Friday's edition of the journal Geophysical Research Letters.