Persistent warming in the Arctic is pushing the region into “uncharted territory” and increasingly affecting the continental United States, scientists said Tuesday.

“We’re seeing this continued increase of warmth pervading across the entire Arctic system,” said Emily Osborne, an official with the National Oceanic and Atmospheric Administration, who presented the agency’s annual assessment of the state of the region, the “Arctic Report Card.”

The Arctic has been warmer over the last five years than at any time since records began in 1900, the report found, and the region is warming at twice the rate as the rest of the planet.

Dr. Osborne, the lead editor of the report and manager of NOAA’s Arctic Research Program, said the Arctic was undergoing its “most unprecedented transition in human history.”

In 2018, “warming air and ocean temperatures continued to drive broad long-term change across the polar region, pushing the Arctic into uncharted territory,” she said at a meeting of the American Geophysical Union in Washington.

The rising air temperatures are having profound effects on sea ice, and on life on land and in the ocean, scientists said. The impacts can be felt far beyond the region, especially since the changing Arctic climate may be influencing extreme weather events around the world.

The new edition of the report does not present a radical break with past installments, but it shows that troublesome trends wrought by climate change are intensifying. Air temperatures in the Arctic in 2018 will be the second-warmest ever recorded, the report said, behind only 2016.

Susan M. Natali, an Arctic scientist at Woods Hole Research Center in Massachusetts who was not involved in the research, said the report was another warning going unheeded. “Every time you see a report, things get worse, and we’re still not taking any action,” she said. “It adds support that these changes are happening, that they are observable.”

The warmer Arctic air causes the jet stream to become “sluggish and unusually wavy,” the researchers said. That has possible connections to extreme weather events elsewhere on the globe, including last winter’s severe storms in the United States and a bitter cold spell in Europe known as the “Beast From the East.”

The jet stream normally acts as a kind of atmospheric spinning lasso that encircles and contains the cold air near the pole; a weaker, wavering jet stream can allow Arctic blasts to travel south in winter and can stall weather systems in the summer, among other effects.

“On the East Coast of the United States where the other part of the wave comes down,” Dr. Osborne said, “you have these Arctic air temperatures that are surging over into the lower latitudes and causing these crazy winter storms.”

The rapid warming in the upper north, known as Arctic amplification, is tied to many factors, including the simple fact that snow and ice reflect a lot of sunlight, while open water, which is darker, absorbs more heat. As sea ice melts, less ice and more open water create a “feedback loop” of more melting that leads to progressively less ice and more open water.