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Leading climate scientists on Thursday issued their annual physical of Earth, comparing the planet in 2013 to a patient that's only getting worse and highlighting problems with key vital signs: from record warmth in Australia and China to sea levels that continue to rise and Arctic sea ice in continued decline.

The vital signs reflect "the largest changes that we've been able to witness in the historical record," said Tom Karl, director of the National Climatic Data Center, part of the National Oceanic and Atmospheric Administration. "The planet is changing more rapidly … than in any time of modern civilization."

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The report, titled the "State of the Climate in 2013", was led by the NOAA and incorporated input from 425 researchers around the world.

Karl compared Earth to someone trying to maintain their ideal weight but instead constantly adding a couple more pounds. That's not good for the patient, he said at a press conference, and "the trend is continuing."

That view was echoed by Michael Prather, who didn't work on the report but has been an author on six recent reports by the U.N. Intergovernmental Panel on Climate Change.

"You wouldn't view this as the patient has turned around," said Prather, an earth system science professor at the University of California, Irvine. "The planet is warming, there's still a lot of energy going into the ocean, we're still out of balance."

Among the 2013 vital signs highlighted by NOAA:

  • All major greenhouse gas emissions increased to new records.
  • Air temperature was among the warmest on record, with 2013 ranking between second and sixth depending upon the dataset used. Australia saw its warmest overall year, China its warmest Summer.
  • Sea surface temperatures were among the 10 warmest on record.
  • Sea level continued to rise by about an eighth of an inch each year.
  • The Arctic continued to warm.

Particular attention was given to the Arctic, where summer sea ice is declining by 14 percent per decade. Moreover, warm temperatures in Alaska that have led to record melt of permafrost.

"We're seeing very rapid declines in these very important climate indicators," said Martin Jeffries, who studies Arctic issues for the U.S. Office of Naval Research.

Fairbanks saw 36 days of temperatures above 80 degrees Fahrenheit, he noted, significant because "there's not a lot of air conditioning in Alaska."

Still, 2013 did not set a new global record for air temperature –- that's still held by 2010.

That fact has led some naysayers to question if warming is even an issue, or at least not as dire as experts say.

Prather acknowledged that the air temperature, which IPCC projections say should have jumped up, has been a mystery. "Does it make me lose sleep? No. Does it make me curious? Yes."

One theory is that more warmth is being absorbed by the oceans, instead of being added to the atmosphere.

And Prather is still convinced warming projections are on target because two other indicators –- sea level rise and more heat going into the oceans –- are "doing what we expect."