WASHINGTON • Global warming is heating the Arctic at a record pace, driving broad environmental changes across the planet, including extreme storms in the mid-latitudes, a major US scientific report said.
Persistent heat records have rattled the fragile Arctic for each of the past five years, a record-long warming streak, said the 2018 Arctic Report Card released by the National Oceanic and Atmospheric Administration (Noaa) on Tuesday.
The mounting heat in the north is upsetting typical weather patterns, a trend that "coincides" with severe winter storms in the eastern United States and an extreme cold snap in Europe in March, it said.
"Continued warming of the Arctic atmosphere and ocean are driving broad change in the environmental system in predicted and also unexpected ways," warned the report.
"New and rapidly emerging threats are taking form and highlighting the level of uncertainty in the breadth of environmental change that is to come."
It said Arctic air temperatures for the past five years, from 2014 to this year, "have exceeded all previous records since 1900", when record-keeping began.
This warming trend "is unlike any other period on record", said the peer-reviewed report compiled by 81 scientists working for governments and aca-demia in 12 countries.
During the latest period studied - October 2017 through September 2018 - average annual temperature in the Arctic was 1.7 deg C higher than the 1981-2010 average.
"The year 2018 was the second warmest year on record in the Arctic since 1900 (after 2016)," it said.
The Arctic also saw the second lowest overall sea-ice coverage and the lowest recorded winter ice in the Bering Sea.
The Arctic continues to heat up at twice the rate of the rest of the planet, but the effects are far from isolated and are now spilling over into the mid-latitudes.
That is because a warmer Arctic reduces the north-south temperature difference, which provides the main fuel for the polar jet stream - or a river of strong wind - at levels where jet aircraft fly, Noaa said.
In this warming environment, the jet stream has become wavier, a pattern that "allows warm air to penetrate farther north and cold air to plunge farther south, compared with when the jet is strong and relatively straight", said the report.
Scientists now see evidence that this changing jet-stream may be sparking extreme storms.
"Notable extreme weather events coincident with deep waves in the jet-stream include the heatwave at the North Pole in autumn last year, a swarm of severe winter storms in the eastern United States this year, and the extreme cold outbreak in Europe in March this year, known as the Beast from the East."