News Section
Stories from Climate Central's Science Journalists and Content Partners

Temperature Plateau Likely Due to Deep Ocean Warming

By Fiona Harvey, The Guardian

A recent slowdown in the upward march of global temperatures is likely to be the result of the slow warming of the deep oceans, British scientists said on Monday.

Oceans are some of the Earth's biggest absorbers of heat, which can be seen in effects such as sea level rise, caused by the expansion of large bodies of water as they warm. The absorption goes on over long periods, as heat from the surface is gradually circulated to the lower reaches of the seas.

Temperature in the northern hemisphere since the year 1000.
Click image to enlarge. Credit: IPCC

Temperatures around the world have been broadly static over the past five years, though they were still significantly above historic norms, and the years from 2000 to 2012 comprise most of the 14 hottest years ever recorded. The scientists said the evidence still clearly pointed to a continuation of global warming in the coming decades as greenhouse gases in the atmosphere contribute to climate change.

This summer's heatwave, the most prolonged period of hot weather in the UK for years, has not yet been taken into account in their measurements.

Peter Stott of the Met Office said computer-generated climate models all showed that periods of slower warming were to be expected as part of the natural variation of the climate cycle, and did not contradict predictions. Given that variation, current temperatures are within expectations.

As well as the heating of the deep oceans, other factors have played a significant part in slowing temperature rises. These have included the solar minimum — when the sun is less active and generating slightly less heat, as occurred in 2008/2009 — and a series of small volcanic eruptions, including that of Iceland's Eyjafjallajökull volcano in 2010. Ash from volcanoes reflects light back into space, and major eruptions in the past have had a severe, albeit temporary, cooling effect.

Despite the slowdown in warming, by 2060 the world is still likely to have experienced average temperatures of more than 2°C (3.6°F) above pre-industrial levels — a threshold that scientists regard as the limit of safety, beyond which climate change impacts are likely to become catastrophic. Professor Rowan Sutton, director of climate research at the National Center for Atmospheric Research at Reading University, said the current pause would only delay reaching this point by five to 10 years.

BEST land-only surface temperature data (green) with linear trends applied to the timeframes 1973 to 1980, 1980-1988, 1988-1995, 1995-2001, 1998-2005, 2002-2010 (blue), and 1973-2010 (red).

The "pause" in the rise of global temperatures has been seized on by climate sceptics, however, who have interpreted it as proof that the science of climate change is mistaken. But despite the slowdown in warming, the warmest years on record were 1998, 2005 and 2010, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).

Professor Sutton said more research was needed on the effects of warming on the deep oceans, as observations of deep ocean temperatures have only been carried out in detail over the past decade and more are needed. Higher temperatures could not only have a devastating effect on marine life, he said, but could also contribute to increases in sea levels as sea water expands.

The Met Office warned early in the summer that the UK could be in for a decade of "washout" summers, like those of the past six years, because of the effect of climate change on global weather systems, partly as a result of changes in wind patterns caused by the melting Arctic.

But no sooner had the meteorologists made their prediction than the weather bucked this trend, with a shift in the Atlantic's jet stream air circulation system giving rise to high-pressure weather fronts and a long period of settled sunny weather.

Reprinted with permission from The Guardian

Related Content
Heidi Cullen’s Senate Testimony on Climate Science 
Why Global Warming Slowed in the 2000’s: Another Possible Explanation 
The Heat is On: U.S. Temperature Trends 
The Keeling Curve (Graphic)


By Eric Peterson (Front Royal, VA 22630)
on July 23rd, 2013

This article is biased, bordering on ridiculous.  There is an unexplained lull in warming and the deep ocean is mostly unmeasured.  We don’t know why it has not warmed more.  We also do not know why it warmed more in the 90’s but strong El Nino with release of prior heat gain from high solar activity is part of the reason.  The Mann hockey stick shown in the first chart has superseded including by the IPCC.

From the wikipedia page on The Hockey Stick Illusion which has the image above on its front cover:  “Since its release, the book has received a mixture of positive and negative reviews; The Guardian referred to it as “Montford’s entertaining conspiracy yarn”,[2] while The Spectator described it as a “a detailed and brilliant piece of science writing”[1] and The Sunday Telegraph described it as “a remarkable scientific detective story”.[3]”

Reply to this comment

By Fred (College Park/GA/30349)
on July 24th, 2013

When the warming “deep” oceans begin to heat & release the methane gases burried down there in bubbles the size of Texas, we’ll ask the skeptics then.

Reply to this comment

By rollin
on July 24th, 2013

Increases in coal burning, forest burning and other carbon particulate producers as well as increased SOx may have further reduced sunlight. There seems to be little effort to monitor the black carbon and SOx in the atmosphere. Locally (temperate region) the temps are up this past decade followed by shifts in bird and plant populations along with generally lower snow and ice formation.

Reply to this comment

By hank
on July 24th, 2013

I have to agree strongly with Eric Peterson’s comment. I think it was Kevin Trenberth that first floated the idea of deep ocean warming back in march as a ploy to evade discussing the uncertainty caused by the pause in warming. Since then, it has been mostly blogs that support the AGW meme that have repeated this story and now 4 months later it is stated as fact in many quarters, really? That’s not how science works. Honest Climate scientist have admitted that there is a lot of uncertainty regarding the pause in warming and have postulated that climate sensitivity is obviously less than models have been showing up until now.
Finally, rational and critical thinkers see this “Deep Ocean” thing as more of an evasion by alarmists than anything else and it adds greatly to the mistrust that much of the public feels towards the whole Global Warming/ Climate Change movement and alarmists scientists that support it. It’s really damaging the cause but no one seems to get that point.

Reply to this comment

By John Ward (Gainesville)
on July 24th, 2013

Why on earth would “rational and critical thinkers see this “Deep Ocean” thing as more of an evasion by alarmists than anything else”? What is your evidence that this conclusion is not accurate?  There is plenty of research that concludes it is: Meehl et al. 2011; Levitius et al. 2012; Nuticelli et al. 2012;  Balmaseda et al. 2013; Guemas et al. 2013. Do you know of any that shows the ocean isn’t continuing to warm? Science works by doing research and publishing it in peer-reviewed climate journals. When numerous studies confirm a conclusion and none offer contrary evidence, this would seem to be the view that rational and critical thinkers would be likely to accept. The NOAA website includes graphs of ocean temperatures: The third one at this URL combines the five year temperature averages for 0-700 meters and 0-2000 meters. This clearly shows the ocean has continued to warm and, since 1996, the temperature has risen faster when the lower depths have been averaged in.

Reply to this comment

By John Ward (Gainesville)
on July 24th, 2013

You will be pleased to know that the accuracy of the hockey stick used to illustrate the above article was confirmed by the most comprehensive study ever done of temperatures over this period by 78 researchers from 24 countries, who worked for seven years, with the assistance of colleagues, to produce their results.

They determined that “[t]here were no globally synchronous multi-decadal hot or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age,” but rather “a long-term cooling trend, which ended late in the nineteenth century.” The superposition of the new information over Mann’s 1999 graph was not an illustration in the research paper, but it uses that information. The graph in the paper extended back 2000 years, and both graphs can be seen here:

Since the article is behind a pay wall, I am linking you to a discussion of it, where you will also find three of the illustrations from the research paper.

Reply to this comment

By Eric Peterson (Front Royal, VA 22630)
on July 25th, 2013

John, thanks for the update, I had not seen that. 

Prior to Mann publishing the hockey stick shown above, there was published evidence of a global MWP, e.g. Here’s a 2001 summary from after the hockey stick was created: Also there is supporting evidence from global sea level rises during the Medieval period with about 1/4 meter (+/- 1/4 meter) positive deviation from the Little Ice Age Here’s a more recent paper on sea level:

From what I can see that new paper has not been fully reviewed and absorbed into the consensus.  I would treat it with skepticism until its underlying data and methods can be fully reviewed.

Regarding your reply to Hank, the temperatures you refer to are from the updated Levitus model.  That model has many climate assumptions in it that underlie the calculation of the missing temperature data.  It lacks a lot of temperature measurements in the deep ocean.  It should not be referred to as a “graph of ocean temperatures” but as a model of ocean temperatures, subject to better future measurements.

Reply to this comment

By John Ward (Gainesville)
on July 25th, 2013

Here is a blog with a collection of links to feedback on the new paper—and an outspoken, running commentary. The first one, in Real Climate, is by a contributor to the study and gives some good background.

Reply to this comment

By Camburn (ND)
on July 26th, 2013

What it truly amazing in regards to the “deep sea heat”, is there is no physical mechanism to get it there.

And yet….some seem to think joules can jump 700M through water….........uh huhhhhhhh.

Reply to this comment

By jeff (New Orleans, LA)
on August 15th, 2013

What I find interesting, especially after seeing the “skeptics vs realists” view of the global warming is that in order to “prove ” global warming,  the so called “realists” focus on a small data sample over 40 years and call it “warming.” These “realists” mock the “skeptics” and say they ignore the science. Who’s ignoring the science?  When you look back over several hundred years we see warming and cooling periods. It’s a cycle.  During the height of the Roman Empire, tax records show that people were growing grapes and paying taxes on their harvest in places that today are too cold to support a vineyard.  At the time of the birth of our nation, Earth was experiencing a cool down. These so called “realists” want to argue facts, but only the facts that are convenient to them.  I don’t think there were too many gas guzzling SUVs running around in either case.  Why is it so hard for you “realists” to accept these facts? Sorry… it’s cyclic. Move on.

Reply to this comment

By Richard Kiefer (Arvada, CO., 80005)
on February 25th, 2014

I am not sophisticated enough to argue the point, but looking at the charts on global Temperature (Global Land Temperature Anomaly, the “hockey stick”), draw a line between the highest temperatures in the chart (1973 - 2009), and they continue steadily upwards, draw a line between then lowest temperatures, and they continue steadily upwards, and the same is true if you draw a line through the middle of the mass, or about average, and the result is the same.

Cherry-picked points have been picked to supposedly show temperature decreases within each span (perhaps coincidentally synchronous with sunspots), making it appear that there are steps within each cycle where the temperature seems to decline -  but the direction of each step is still upward from then last.  The temperature of each step has continued to rise (through 2010, at least) and the graph suggests _ until there is further information -  that it will continue to do so.

Now, If all that heat and CO2 emissions that we are producing aren’t heating up the air and Earth’s surface that much, what are they doing?   They are melting all the world’s ice BEFORE raising the air, sea and ground temperatures.   That heat required to change ice to water (or water to steam) is known as “latent heat,” and its effects are known to all scientists.   Because of the Earth’s size, however, those changes are not readily apparent, but they are coming.      The glaciers are rapidly receding, and when they have, no one will have the last laugh.

Reply to this comment

Name (required):
Email (required):
Enter the word "climate" in the box below:

[+] View our comment guidelines.

Please note: Comment moderation is enabled. Your comment will not appear until reviewed by Climate Central staff. Thank you for your patience.