(CNN)Bitterly cold, frozen and inhospitable to nearly all wildlife apart from polar bears.
This is the image of the Arctic that comes to mind for many.
But in a matter of decades -- a blink of an eye in the history of this planet -- human-caused global warming has transformed the Arctic into a place that scientists say is increasingly unrecognizable.
If the Arctic is a doctor's patient, the National Oceanic and Atmospheric Administration's (NOAA) Arctic Report Card is its annual physical -- a comprehensive check-up on the health of this vast and important biome.
Today's Arctic is much hotter, greener and less icy than it was even just 15 years ago, when NOAA published its first Arctic Report Card.
And with near-record high surface temperatures and near-record low sea ice observed yet again, the report card released Tuesday paints a picture of a region that is warming rapidly, at a pace far outpacing scientists' expectations.
"We thought the changes would take a lot longer, and the models were saying they would," said James Overland, an oceanographer at NOAA's Pacific Marine Environmental Laboratory, who has been a part of all 15 Arctic Report Cards and co-authored the portion on surface air temperatures in this edition. "But the rate of change we've seen in the last 20 years -- and especially the last five years -- is beyond what we thought would happen."
Here's a look at the biggest changes observed in the Arctic this year, and what they mean for the rest of the planet.
Extreme heat and dwindling ice
Scientists say the Arctic is a bellwether for the global climate.
As the planet heats up due to human emissions of greenhouse gases, the effects of that warming are felt here first -- and foreshadow the changes to come in lower latitude climates.
"Further south in the US's lower 48, we can handle a change of a couple of degrees in air temperature," Overland said. "But the potential changes in the Arctic that are triple what we see at the mid-latitudes are going to completely change what the Arctic looks like, and that will feedback to the rest of the planet."
From shrinking sea ice and melting on Greenland's ice sheet, to permafrost thaw and even shifts in species distributions, many of the changes observed across the Arctic are being driven by increased air temperatures, Overland said.
The report found that the past year was yet another abnormally hot one in most of the region.
The period between October 2019 and September 2020 was the second-hottest year in the last century for the Arctic, with surface temperatures 1.9 degrees Celsius (3.42 degrees Fahrenheit) warmer than the 1981 to 2010 average. Only 2016 saw higher temperatures than this past year.
The extreme warmth was especially pronounced in Siberia, which saw sweltering temperatures 3 to 5 degrees Celsius (5.4 to 9 degrees Fahrenheit) above average during winter and spring.
Since 2000, the Arctic has warmed more than twice as fast as the rest of the planet, the report says.
All of this extra heat has taken a toll on another critical part of the Arctic ecosystem -- its sea ice.
In addition to serving as a vital habitat for polar bears and walruses, the Arctic's sea ice is a key part of the planet's air-conditioning system, reflecting the sun's energy back into space and keeping temperatures around the North Pole cool.
But last year saw another near-record-low sea ice extent, another sign that this air conditioner is breaking down, scientists say.
Sea ice freezes in winter and melts during summer, and this year's summer minimum extent was the second-lowest ever observed in the 42-year satellite record, according to the report.
The trend of declines in the sea ice's winter maximum extent also continued this year, with March 2020's extent coming in as the 11th-lowest on record.
The 14 years from 2007 to 2020 have all seen the 14 lowest extents on record, and sea ice extents have declined by about 13% per decade since 1979.
It is now no longer a question of "if" we will see an ice-free Arctic in the new few decades -- it is "when," said Walt Meier, a senior research scientist at the National Snow and Ice Data Center and a co-author of the sea ice section of this year's Arctic Report Card.
"For me being about 50-years-old, I thought (an ice-free Arctic in summer) would be something my grandchildren would probably live to see," Meier said. "But now, if I have a reasonably average lifespan, then I'll probably live to see it, which is really stark in my view in terms of how fast things have changed."
A greener, less snowy Arctic
Snow still covers much of the Arctic for up to nine months out of the year. But that too is changing, as warming leads to declines in both the area of land and length of time that it is buried in snow.
The snow cover extent in June 2020 over the Eurasian Arctic was the lowest in the 54-year record, and the North American part of the region saw its 10th-lowest extent.
That snow cover also melted much earlier in parts of the region, especially in Siberia, which saw record heatwaves in 2020.
Though the report found that the duration of snow cover was roughly normal over much of the Arctic, snow cover over huge swaths of Siberia melted as much as a month early, owing to temperatures that were more than 5 degrees Celsius above average.
Another effect of a warmer climate is that the Arctic is growing greener.