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NOAA: 2012 One of Globe’s 10 Hottest on Record

Last year was one of the globe’s 10 warmest years on record, with numerous milestones set that indicate that global warming is continuing, despite a plateau in the short-term trend in global average surface temperatures, according to a new climate report released on Tuesday. The report, which amounts to a 260-page checkup of the health of the climate system, details sweeping changes that took place last year in the Arctic, with records set for the lowest sea ice extent in the satellite era, lowest June snow cover in the Northern Hemisphere, warmest permafrost temperatures in northern Alaska, and most widespread melting of the Greenland ice sheet.

Surface temperature departures from average in 2012.
Click image to enlarge. Credit: NOAA.

More than 97 percent of the vast Greenland ice sheet showed some form of melt during the summer of 2012, which was four times greater than the 1981-2010 average melt extent, the report said. Preliminary information shows that 2012 may be the 22nd straight year in which Arctic glaciers lost more ice than they gained, known as “negative glacier mass balance.”

Melting glaciers and warming oceans are causing sea level to increase, and global average sea level hit a record high in 2012 as well. According to Jessica Blunden of the National Oceanic and Atmospheric Administration (NOAA), ice melt has recently been contributing about twice as much to sea level rise as seawater expansion due to warming ocean temperatures.

The "State of the Climate" report, published in the Bulletin of the American Meteorological Society, was compiled by 384 scientists from 52 countries and underwent scientific peer review. This edition marks the 23rd straight year that scientists have issued a report.

“Many of the events that made 2012 such an interesting year are part of the long-term trends we see in a changing and varying climate — carbon levels are climbing, sea levels are rising, Arctic sea ice is melting, and our planet as a whole is becoming a warmer place,” said Kathryn Sullivan, the acting NOAA administrator, during a conference call with reporters.

Sullivan said the report provides evidence in support of the Obama administration’s efforts to mitigate and adapt to climate change. The White House has directed the Environmental Protection Agency to draw up regulations that would curb greenhouse gas emissions from existing and new coal-fired power plants, among other steps.

Sea level in 2012 compared to the 1993-2012 average based on AVISO satellite data.
Click image to enlarge. Credit: NOAA.

The report offers comprehensive evidence of how the climate system is changing, but does not draw conclusions about what is driving these changes. However, other studies have linked many trends, from the sharp decline in Arctic sea ice to global sea level rise, to manmade emissions of greenhouse gases from the burning of fossil fuels, such as coal and oil. The amount of carbon dioxide, which is the main long-term global warming pollutant, in the air hit record high levels in 2012, crossing the symbolic threshold of 400 parts per million at some Arctic observatories. Earlier in 2013, the 400 ppm mark was exceeded at other observatories, including Mauna Loa, Hawaii.

Tom Karl, who leads NOAA’s National Climatic Data Center in Asheville, N.C., said the climate indicators detailed in the study all show a coherent picture that is consistent with what would be expected in a warming world. He cited a cooling trend in the stratosphere, which was record cold during 2012, which is consistent with the effects of greenhouse gases on the earth’s atmosphere, since they warm lower layers of the atmosphere while helping to cool the upper layers.

While global average surface temperatures have not increased much during the past decade, Karl said natural variability in the climate system, such as a spate of La Niña events in the Pacific Ocean, have helped influence temperature trends on such short timescales. “When we look at the records, the prevalence of La Niñas since 2000 have contributed to colder ocean temperatures, and obviously that affects the atmosphere as well, and our global temperature numbers,” Karl said.

He said that during the decade ending in 2012, global temperatures decreased slightly, after warming during the previous decade. “There is considerable variability” in decadal trends, Karl said, cautioning against reading too much into them. The longer-term trends over 30 to 50 years all show a significant increase in global average surface temperatures, he said.

Map shows the sea ice extent on September 16, 2012, along with the extent of the previous record low (yellow line) and the mid-September median extent (black line).
Click image to enlarge. Credit: NOAA.

Even with the temporary slowdown in temperature trends, the report details an environment that is clearly undergoing rapid changes. No one seems to have told other elements of the climate system that surface temperatures have not risen much in recent years, largely because the Earth is still taking in much more heat from the sun than it is letting out, and high average temperatures are having many cascading effects.

“It’s really important to take a look at the broad spectrum of measurements that we have available,” Karl said. “You don’t see records every year but you do see a consistent picture . . . one of a generally warmer world,” Karl said.

For example, in recent years, ocean heat content has significantly increased, especially in the deep ocean, below 2,300 feet. Meanwhile, in the Arctic the past six years have seen the lowest sea ice extents on record, with 2012 dropping to 18 percent below the previous record low level, which occurred in 2007.

Jackie Richter-Menge, a research civil engineer at the Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory in New Hampshire, said the Arctic has been warming twice as fast as the rest of the globe, on average. “Overall, we see the Arctic continues to be a region where we have some of the most compelling evidence” of warming temperatures, she said.

Richter-Menge said changes are cascading throughout the Arctic system, with less sea ice leading to higher Arctic Ocean sea surface temperatures, which in turn has helped the Arctic become greener, with more productive vegetation in the far north.

In contrast, in Antarctica, sea ice extent reached a record high in September of 2012. Studies have shown that this trend is actually consistent with the impacts from global warming, along with the influence of the thinning of the ozone layer, which has altered upper atmospheric air circulation.

Related Content
Carbon Dioxide Passes 400 PPM Milestone, NOAA Finds
It's Official: Arctic Sea Ice Shatters Record Low
Accelerated Warming Driving Arctic Into New Volatile State
Antarctic Sea Ice Grows as Result of Warming
Visualizing 2012's Record Arctic Sea Ice Melt
Science Made Simple: Take the Dog For a Walk
Temperature Plateau Likely Due to Deep Ocean Warming


By Rudy Haugeneder (Victoria, BC, Canada)
on August 6th, 2013

Climate Change is happening faster than science expected and may just be taking a tiny half lull right now before jumping into hyperdrive that is not quite “the Day After” but not that far behind. It is Nature’s right, once she decides to act, to go into methane-spewing hyperdrive.

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By Eric Peterson (Front Royal, VA 22630)
on August 8th, 2013

Most likely the current lull in warming will continue for decades.  It’s hard to predict solar activity beyond the next cycle, but if it continues to be low, we will see some actual cooling.  The big drop in solar activity only took place around 2008 and we have yet to feel the effects of that due to thermal inertia from the oceans.  Just like the rise in atmospheric temperature due to manmade CO2 comes in spurts (the largest being in the 1990’s), the drop from low solar activity will come in spurts.  We could see substantially colder temperatures in a decade or two, and that doesn’t even count the possibility of a large tropical volcano which could happen at anytime and cause a few years of extreme cold.

From the article: “Overall, we see the Arctic continues to be a region where we have some of the most compelling evidence”

Alaska has cooled for a decade, part of a pattern with warming in eastern Siberia and cooling in central Siberia, and warming in northern Europe.  The weather varies far more than the warming from CO2.  This summer was one of the coldest ever measured in the Arctic: see

There is clearly very little risk from the current 1C per century of global warming nor the associated 1 inch per decade sea level rise.  The temperature risk is mostly on the downside.

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By HTuttle (Manhattan, NY, NY)
on August 8th, 2013

Likely just lagging indicators of prior warming that will lag behind again at the plateau. Do those ever enter into calculations at all?

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By Lauren Anderson (Provo, UT 84604)
on August 8th, 2013

Eric Peterson makes a good point about natural climate variability being rather larger than any detectable anthropogenic signal so far.  It is clear the planet is warmer than it was a century ago though it is difficult to attribute it to any specific cause as yet.  It also seems apparent that short term trends may not be very meaningful.  I would revise Peterson’s prediction about the current lull in warming likely continuing for decades.  Based on the inability of any of the global climate models to predict the current lull, I would say we don’t have precise enough tools to predict whether the lull will continue or not.

Though I agree with his risk assessment, based on the fact that the measured temperature rise and sea level rise of the last century appears to be rather insignificant and appears to be decelerating slightly in the last decade or so, I would note that the measured global sea level trend from 2002-2011 is 1.7 ± 0.3mm per year, or about 1 inch per 15 years, 50% less than the 1 inch per year Peterson stated.  This is from the GRACE satellites and tide gauge measurements.

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By Dave (Basking Ridge, NJ 07920)
on August 9th, 2013

I’ll just pick up the SLR point from some comments. The mean rate of sea level rise is currently 3.3 mm/yr starting from 1993 as measured by altimetry – not 1 inch per 15 years or 1.7mm/yr (Lauren) or 1 inch per decade or 2.5 mm/yr (Eric).

There can be short term variations in sea level due to natural variability. For instance from mid 2010 to mid 2011, global mean sea level (GMSL) dropped by about 5 mm making 2011 an especially low year or marked dip in the record. This drop was determined by gravimetric measurements provided by the GRACE pair of satellites to be due to the effects of large amounts of net water transport from the ocean to various land masses and related to ENSO. Hence a rate of sea level rise which is estimated by the arithmetic difference in the end points 2002 to (particularly) 2011 will of course be lower than the overall mean which instead provides a much more accurate and representative indication. This type of biased data selection and selective interpretation is no more representative of the actual general trend in sea level rise than would one that was instead based on the period from 2011 to 2013 when GMSL instead rose dramatically by about 2cm or at least three times the rate of the general trend since 1993 - and when obviously some of that excess land water variously found its way back into the oceans…


@CC: Nice report, although it would also be nice to be able to read the scales on these figures which here, and enlarged, are below legibility limits.

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By Eric Peterson (Front Royal, VA 22630)
on August 12th, 2013

Thanks for the reply Lauren.  The sea level measurements are a bit controversial because there can be many feet of sea level variation across the Pacific ocean due to wind patterns.  So it is quite difficult to measure an inch in a decade when the natural rise and fall can be 10 inches or more in one season.  So while I think your estimate may be better than mine, I wouldn’t put a lot of confidence in any estimate.

I agree that we cannot predict what will happen regarding a lull or a resumption of warming (or even possible cooling).

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By John Elish (Cartersville ,Ga. 30120)
on August 14th, 2013

The earth has survived many ups and downs in climate temperature and sea level. This whole global warming myth is just that. The earth will survive.  Man will not destroy the earth, that God has created.

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By Tom Moran (Milford, CT 06460)
on September 26th, 2013

Satellite altimetry is not my specialty so I’m asking for help on this topic….if the measurements have a margin of error in centimeters how do we refine to millimeters?  If plate tectonics is moving land at centimeters per year how do we recalibrate to compensensate for horizontal and vertical plate movements? Thank you.

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