NOTE: Images in this archived article have been removed.
Decadal surface-air temperature (°C) via average of datasets maintained by the HadCRU, NOAA and NASA.
“Global Warming Has Accelerated In Past 15 Years, New Study Of Oceans Confirms,” as we reported back in March. And “Greenland Ice Melt Up Nearly Five-Fold Since Mid-1990s, Antarctica’s Ice Loss Up 50% In Past Decade,” as we reported last November. Another study that month found “sea level rising 60% faster than projected.”
And yet much of the media believes climate change isn’t what gets measured and reported by scientists, but is somehow a dialectic or a debate between scientists and deniers. So while 2010 was the hottest year on record and the 2000s the hottest decade on record, we are subject to nonsensically framed stories like this one from CBS, headlined “Controversy over U.N. report on climate change as warming appears to slow.”
The drama-driven junkies of the MSM apparently think that the most newsworthy thing in the once-every-several-years literature review by hundreds of the world’s leading scientists is that people who make a living denying climate science … wait for it … deny climate science. That CBS story actually begins, “Climatologists and climate-change deniers agree on at least one thing this week: everyone is awaiting the landmark U.N. report on climate change that will be presented at next week’s meeting of the Intergovernmental Panel on Climate Change (IPCC).” Stop the presses! No, please, stop the damn presses already if you are an editor or reporter who thinks deniers deserve equal billing with scientists.
Because the media keeps making the same faux pas about the faux pause, scientists and science writers have had to debunk it repeatedly. Anyone in the media who insists on buying into the false dialectic MUST read the new piece at Real Climate by climatologist Stefan Rahmstorf, the Mother Jones piece by Chris Mooney, this piece by Tamino, and almost anything at Skeptical Science (such as this or this). Also, Peter Sinclair has a great video on this.
Let me extract the key points and figures. Back in July, scientist Dana Nuccitellisummarized a new study, “Distinctive climate signals in reanalysis of global ocean heat content“:
- Completely contrary to the popular contrarian myth, global warming has accelerated, with more overall global warming in the past 15 years than the prior 15 years. This is because about 90% of overall global warming goes into heating the oceans, and the oceans have been warming dramatically.
- As suspected, much of the ‘missing heat’ Kevin Trenberth previously talked about has been found in the deep oceans. Consistent with the results of Nuccitelli et al. (2012), this study finds that 30% of the ocean warming over the past decade has occurred in the deeper oceans below 700 meters, which they note is unprecedented over at least the past half century.
- Some recent studies have concluded based on the slowed global surface warming over the past decade that the sensitivity of the climate to the increased greenhouse effect is somewhat lower than the IPCC best estimate. Those studies are fundamentally flawed because they do not account for the warming of the deep oceans.
- The slowed surface air warming over the past decade has lulled many people into a false and unwarranted sense of security.
For more on the myth of a low climate sensitivity (or the myth that climate sensitivity is the same as projected future warming), see this post. In reality, the best science says that the Earth’s actual sensitivity to carbon pollution isprobably on the high side.
The bottom line is provided by Rahmstorf at RealClimate:
The heat content of the oceans is growing and growing. That means that the greenhouse effect has not taken a pause and the cold sun is not noticeably slowing global warming….The increase in the amount of heat in the oceans amounts to 17 x 1022 Joules over the last 30 years. That is so much energy it is equivalent to exploding a Hiroshima bomb every second in the ocean for thirty years.
Before discussing the explosive ocean heat data, Tamino and Rahmstorf make an important point about recent warming. Here is the plot of the NASA temperature data:
“Since 1975, global average surface air temperature has increased at a rate of 0.17 deg.C/decade,” Tamino notes. “But the rate of increase hasn’t been perfectly constant over that entire time span. As a matter of fact, there’s a 15-year time span during which the rate is notably different. Fifteen whole years!!!”
Rahmstorf replied to one journalist who asked whether there’s a real slowdown or “Do the IPCC authors feel pressured to write about it just because skeptics are making so much noise about it?”
You’d have to ask them but it is quite possible. I think a lot of the interest in this topic in the science community has been triggered by the public debate about it. If you look at the 15-year period up to 2006, the warming trend was almost twice as high as normal (namely 0.3 °C per decade) but nobody cared (you can see a graph with this trend line here [or above]. We published a paper in Science in 2007 where we noted this large trend, and as the first explanation for it we named natural variability. There is a certain asymmetry in that 15 years of high trend don’t raise much interest, whilst 15 years of low trend do. The reason is that interest groups strongly push the latter.
What’s surprising is not that deniers and confusionists keep pushing their denial and confusion — that is, after all, their job — but that much of the mainstream media keeps buying what they are selling.
Let’s return to the speed up in ocean heat content:
Change in heat content in upper 2000 meters (6500 feet) of world’s oceans. Source: NOAA
Rahmstorf, who is Head of Earth System Analysis at the Potsdam Institute for Climate Impact Research, explains:
The amount of heat stored in the oceans is one of the most important diagnostics for global warming, because about 90% of the additional heat is stored there (you can read more about this in the last IPCC report from 2007). The atmosphere stores only about 2% because of its small heat capacity. The surface (including the continental ice masses) can only absorb heat slowly because it is a poor heat conductor. Thus, heat absorbed by the oceans accounts for almost all of the planet’s radiative imbalance.
Here’s a graphic illustration of that via Skeptical Science:
A visual depiction of how much global warming heat is going into the various components of the climate system for the period 1993 to 2003, calculated fromIPCC AR4 5.2.2.3
What does that mean for our understanding of climate change? Again, here’s Rahmstorf:
If the oceans are warming up, this implies that the Earth must absorb more solar energy than it emits longwave radiation into space. This is the only possible heat source. That’s simply the first law of thermodynamics, conservation of energy. This conservation law is why physicists are so interested in looking at the energy balance of anything. Because we understand the energy balance of our Earth, we also know that global warming is caused by greenhouse gases – which have caused the largest imbalance in the radiative energy budget over the last century.If the greenhouse effect (that checks the exit of longwave radiation from Earth into space) or the amount of absorbed sunlight diminished, one would see a slowing in the heat uptake of the oceans. The measurements show that this is not the case.
Rahmstorf also notes that “Completely independently of this oceanographic data, a simple correlation analysis (Foster and Rahmstorf ERL 2011) showed that the flatter warming trend of the last 10 years was mostly a result of natural variability, namely the recently more frequent appearance of cold La Niña events in the tropical Pacific and a small contribution from decreasing solar activity.”
You can see the effect of La Niña “directly in the following figure, without any statistical analysis”:
As you can see, “both the red El Niño years and the blue La Niña years are getting warmer, but given that we have lately experienced a cluster of La Niña years the overall warming trend over the last ten years is slower.” This is thenoise “associated with natural variability, not a change in the signal of global warming.”
And, as it turns out, just last month a major study published in Nature confirmed that “the slowing rise in global temperatures during recent years has been a result of prevalent La Niña periods in the tropical Pacific.” The abstract of that study explains:
Our results show that the current hiatus is part of natural climate variability tied specifically to a La Niña like decadal cooling.
Thus there are, as Rahmstorf notes, “at least three independent lines of evidence that confirm we are not dealing with a slowdown in the global warming trend, but rather with progressive global warming with superimposed natural variability.”
And let’s not forget another key indicator of accelerating warming — the accelerating melting of the great ice sheets as documented in the most comprehensive analysis of satellite altimetry, interferometry, and gravimetry data sets to date:
Warming of the whole globe (as opposed to the thin surface layer) has sped up. When the rate of surface warming returns to the trendline, I wonder if the media will report that global warming has accelerated.
