by Judith Curry

The ‘pause’ has gone mainstream, with an article by Justin Gillis in the NYTimes.

NYTimes published the following article: What to Make of a Warming Plateau. Excerpts:

The rise in the surface temperature of earth has been markedly slower over the last 15 years than in the 20 years before that. And that lull in warming has occurred even as greenhouse gases have accumulated in the atmosphere at a record pace.

The slowdown is a bit of a mystery to climate scientists. True, the basic theory that predicts a warming of the planet in response to human emissions does not suggest that warming should be smooth and continuous. To the contrary, in a climate system still dominated by natural variability, there is every reason to think the warming will proceed in fits and starts.

But given how much is riding on the scientific forecast, the practitioners of climate science would like to understand exactly what is going on. They admit that they do not, even though some potential mechanisms of the slowdown have been suggested. The situation highlights important gaps in our knowledge of the climate system, some of which cannot be closed until we get better measurements from high in space and from deep in the ocean.

What to make of it all?

So the real question is where all that heat is going, if not to warm the surface. And a prime suspect is the deep ocean.

The deep-ocean theory is one of a half-dozen explanations that have been proffered for the warming plateau. Perhaps the answer will turn out to be some mix of all of them. And in any event, computer forecasts of climate change suggest that pauses in warming lasting a couple of decades should not surprise us.

Now, here is a crucial piece of background: It turns out we had an earlier plateau in global warming, from roughly the 1950s to the 1970s, and scientists do not fully understand that one either. A lot of evidence suggests that sunlight-blocking pollution from dirty factories may have played a role, as did natural variability in ocean circulation. The pollution was ultimately reduced by stronger clean-air laws in the West.

What happened when the mid-20th-century lull came to an end? You guessed it: an extremely rapid warming of the planet.

So, if past is prologue, this current plateau will end at some point, too, and a new era of rapid global warming will begin.

Joe Romm

Joe Romm counters with an article entitled: Climate Scientists Ring Alarm Bell, NY Time Hits Snooze Button. Excerpts:

The Times piece focuses on the recent seeming slowdown in one indicator of global warming — surface air temperatures — and uses some especially inartful language to describe it.

The headline is “What to Make of a Warming Plateau.” I’m sure that the super-sophisticated word-smiths at the Times (who filed this story under “science/earth”) are aware that “in geology and earth science” a plateau is “an area of highland, usually consisting of relatively flat terrain.”

Memo to Times: We ain’t at a flat highpoint. We aren’t anywhere near the highpoint and we’re not even close to flat on any scale of time relevant to human civilization.

It’s pretty hard to find any evidence of “quiet” in this country (between superstorm Sandy and record-smashing heat) or up in the Arctic (where the ice is disintegrating decades ahead of schedule, which appears to be driving more extreme weather) or in the deep ocean

Washington Post

Romm refers to a recent op-ed in the Washington Post written by Michael Oppenheimer and Kevin Trenberth, entitled Climate science tells us the alarm bells are ringing, which is written in response to Lamar Smith’s recent op-ed. Excerpts:

Legions of studies support the view that, left unabated, this warming will produce dangerous effects….

Man-made heat-trapping gases are warming our planet and leading to increases in extreme weather events. Droughts are becoming longer and deeper in many areas. The risk of wildfires is increasing. The year 2012, the hottest on record for the United States, illustrated this risk with severe, widespread drought accompanied by extensive wildfires….

We know a lot, more than enough to recognize that the alarm bells are ringing.

Increases in heat waves and record high temperatures; record lows in Arctic sea ice; more severe rainstorms, droughts and wildfires; and coastal communities threatened by rising seas all offer a preview of the new normal in a warmer world.

Much has been made of a short-term reduction in the rate of atmospheric warming. But “global” warming requires looking at the entire planet. While the increase in atmospheric temperature has slowed, ocean warming rose dramatically after 2000. Excess heat is being trapped in Earth’s climate system, and observations of the Global Climate Observing System and others are increasingly able to locate it. Simplistic interpretations of cherry-picked data hide the realities.

Joe Romm states:

In this tale of two city newspapers, who is right? You won’t be surprised that I side with the climate scientists.

JC comment: I’ve always wondered why Michael Oppenheimer, a political scientist, gets to be called a climate scientist, whereby Freeman Dyson, a famous physicist does not. They are both from Princeton, both have studied the climate change problem, but neither has published primary research on climate change detection and attribution.

Mark Steyn

Mark Steyn, nemesis of Michael Mann, has an entertaining take on Justin Gillis’ article and the pause:

Fortunately, Times man Justin Gillis has an explanation for the forlorn droop on Dr Mann’s hockey stick – or at any rate for the previous cooling trend:

Now, here is a crucial piece of background: It turns out we had an earlier plateau in global warming, from roughly the 1950s to the 1970s, and scientists do not fully understand that one either. A lot of evidence suggests that sunlight-blocking pollution from dirty factories may have played a role, as did natural variability in ocean circulation. The pollution was ultimately reduced by stronger clean-air laws in the West.

So environmental laws led to the global warming of the Eighties and Nineties? Great! Whether today’s cooling is a blip in the global warming trend of the Nineties, or the Nineties warming was a blip in the global cooling trend of the Fifties, I cannot say. But either way it doesn’t look like a hockey blade.

Spinning the pause

Different people have used different graphics to depict the pause.

Here is David Rose’s infamous figure:

Here is Tamino’s figure (used by Romm):

Here is the figure from HadCRUT4 used in my recent testimony:

Justin Gillis states:

As you might imagine, those dismissive of climate-change concerns have made much of this warming plateau. They typically argue that “global warming stopped 15 years ago” or some similar statement, and then assert that this disproves the whole notion that greenhouse gases are causing warming.

Rarely do they mention that most of the warmest years in the historical record have occurred recently. Moreover, their claim depends on careful selection of the starting and ending points. The starting point is almost always 1998, a particularly warm year because of a strong El Niño weather pattern.

Bishop Hill and WUWT take issue with the accusation of starting at 1998, a particularly warm El Nino year. From WUWT:

It can be shown that the plateau may extend further back than that, and that nature still rules the climate system, more so than man. I’m not sure why Gillis thinks 15 years is the number people use starting at 1998, I don’t know of anyone making that claim recently. Even CRU’s Phil Jones admitted in a BBC interview that there had been no “statistically significant” warming since 1995, a point also brought up in 2008 by Dr. Richard Lindzen at WUWT when he said: “Why bother with the arguments about an El Nino anomaly in 1998?”

More importantly, the kickoff point for this most recent discussion by The Mail’s David Rose started 16 years ago, in 1997. The 15 year/1998 choice seems like a purposeful misdirection by Gillis. Using 1997 as preferred by Rose, we are fast approaching Dr. Ben Santer’s 17 year test, and if we use Jones and Lindzen’s 1995 start point, we’ve passed it. What will Gillis say then?

Sociology

This brings us to some sociology of climate change science. The primary issue in the public debate surrounding climate change is currently the pause in surface temperatures. People care about surface temperature since people live on the surface and obtain their food and water resources from the surface (hence the troposphere and ocean below 700 m are less relevant). Further, the main type of adverse impacts in terms of extreme weather events that can be attributed to AGW are heat waves. The IPCC has made the increase in global average surface temperature an icon of AGW.

In terms of the policy debate, the pause has the following implications:

In 2006, James Hansen famously stated that ‘we have 10 years to act.’ The pause gives us some breathing room to figure out which policies make sense and for the technologies to come on line. The urgency for addressing AGW is regarded as proportional to climate sensitivity; if equilibrium climate sensitivity is below 2C, then AGW is less compelling as a primary driver for global energy policy.

The public debate about the pause is being conducted primarily in the MSM, op-eds, congressional testimony, and yes the blogosphere. Few journal articles have been published that explicitly tackle the pause; in any event the publication cycle occurs much more slowly than the public debate.

Re the MSM, the UK has led the way, primarily in the Mail (David Rose) and the Guardian, but also with the recent article in the Economist (see my previous post UK MSM on climate sensitivity). The U.S. MSM has come on strong particularly in the last month, with substantial ink from the WaPo and the NYTimes. The recent congressional testimony by John Christy and myself have influenced the dialogue, including the recent op-ed by Lamar Smith.

The blogosphere has really played the dominant role behind much of what is being reported by the MSM. Let me provide an example. Recall the figure prepared by Ed Hawkins, that compares CMIP5 simulations with observations:

In my previous post Spinning the climate model – observation comparison, I wrote that I spotted a link to Ed Hawkins blog in a post by Roger Pielke Jr that referenced a tweet by Hawkins, which then sent me to Hawkins’ blog where I spotted the above diagram.

I really liked this diagram, and I included it in my congressional testimony that was originally written for hearing on March 5 that was rescheduled and eventually held on April 25. On March 13, I received emails from David Rose (Mail) and John Parker (Economist) regarding articles on climate sensitivity that they were preparing. I was very busy at the time, and sent each of them the relevant pages from my forthcoming congressional testimony that included Ed Hawkins’ figure. Both articles used Hawkins’ figure:

I know that my testimony led David Rose to use Hawkins’ diagram; I suspect the same for the Economist article (either directly or via Rose’s article).

So why am I relating this particular story? A mainstream climate scientist, Hawkins, posts an unpublished diagram on a relatively obscure blog (8 Feb). RP Jr picks this up from a tweet, which he posts on his blog (15 Feb), JC posts Hawkins’ figure at CE (22 Feb). Makes it into the MSM on 16 March. Subsequently goes viral. Included in the U.S. Congressional Record on April 25.

(Note: Ed Hawkins has a recent blog post on this topic, Comparing Global Temperature Observations and Simulations, Again)

This to me is a fascinating example of the ‘power’ of the climate blogosphere. The few mainstream scientists that are active in the climate blogosphere seem better at picking up the pulse of the public debate on climate change. Further, the climate blogosphere is pulling technically educated people from other fields: e.g. Steve McIntyre, Tamino, Lucia, Nic Lewis, etc. who are more focused on issues of the greatest relevance to the public debate on climate change.

For an interesting take on the ‘power’ of the climate blogosphere, see also this recent essay by Pointman entitled How to run a really bad infowar campaign.