Heat energy in the top 2,300 feet (700 meters) of the ocean in 2013 compared to the 1993-2013 average. Orange and blue areas show where the upper ocean’s heat storage rose or fell by as much as 5 gigajoules per square meter.

CREDIT: NOAA, Larry Belcher, John Lyman

The planet kept warming at an unhealthy pace last year, according to a report by hundreds of the world’s top scientists led by researchers at the National Oceanic and Atmospheric Administration (NOAA).

Tom Karl, director of NOAA’s National Climatic Data Center, said that the planetary vital signs documented in this report, “State of the Climate in 2013,” reveal “The planet is changing more rapidly … than in any time of modern civilization.”

One of the most important findings is that “upper ocean heat content has increased significantly over the past two decades”:

Heat content in the global ocean down to 700 meters (2300 feet) has risen in the past two decades. Via NOAA.

As NOAA explains, the reason ocean heat content is rising is that “Increasing concentrations of greenhouse gases are preventing heat radiated from Earth’s surface from escaping into space as freely as it used to; most of the excess heat is being stored in the upper ocean.” Why is this so important to our understanding of global warming?

Recent studies estimate that warming of the upper oceans accounts for about 63 percent of the total increase in the amount of stored heat in the climate system from 1971 to 2010, and warming from 700 meters to the ocean floor adds about another 30 percent.

So the place where climate scientists predicted the overwhelming majority of the heat trapped by human emissions would end up is precisely where there has been rapid warming in the past 20 years.

And in case you were wondering what total ocean heat content has looked like in recent decades, NOAA has the chart for you:

Global ocean heat over the past half century (down to 2000 meters) . Via NOAA.

Here are the highlights of the “State of the Climate in 2013” (emphasis in original):

• Greenhouse gases continued to climb: Major greenhouse gas concentrations, including carbon dioxide (CO2), methane and nitrous oxide, continued to rise during 2013, once again reaching historic high values. Atmospheric CO2 concentrations increased by 2.8 ppm in 2013, reaching a global average of 395.3 ppm for the year. At the Mauna Loa Observatory in Hawaii, the daily concentration of CO2 exceeded 400 ppm on May 9 for the first time since measurements began at the site in 1958. This milestone follows observational sites in the Arctic that observed this CO2 threshold of 400 ppm in spring 2012.
• Warm temperature trends continued near the Earth’s surface: Four major independent datasets show 2013 was among the warmest years on record, ranking between second and sixth depending upon the dataset used. In the Southern Hemisphere, Australia observed its warmest year on record, while Argentina had its second warmest and New Zealand its third warmest.
• Sea surface temperatures increased: Four independent datasets indicate that the globally averaged sea surface temperature for 2013 was among the 10 warmest on record. El Niño Southern Oscillation (ENSO)-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific. The North Pacific was record warm for 2013.
• Sea level continued to rise: Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 ± 0.4 mm per year over the past two decades.
• The Arctic continued to warm; sea ice extent remained low: The Arctic observed its seventh warmest year since records began in the early 20th century. Record high temperatures were measured at 20-meter depth at permafrost stations in Alaska. Arctic sea ice extent was the sixth lowest since satellite observations began in 1979. All seven lowest sea ice extents on record have occurred in the past seven years.

NOAA Administrator Dr. Kathryn Sullivan summed the report up this way, “These findings reinforce what scientists for decades have observed: that our planet is becoming a warmer place.”