Arguments
New research suggests global warming is accelerating
Posted on 5 June 2015 by John Abraham
As humans emit more greenhouse gases like carbon dioxide into the atmosphere, the Earth continues to warm. When I use the term “warm”, I mean there is an increase in thermal energy (heat) contained in the oceans and atmosphere of this planet.
We can measure warming by measuring temperatures; however, obtaining an accurate reading of the Earth’s temperature is complicated. Temperatures change with seasons, with locations, and there are natural long term variations that move heat around. So, we don’t expect temperatures just to continue increasing at all locations and at all times. We do expect the long term trend to be upwards, however, and that is what we’ve observed.
But if you follow the conversation about global warming, and particularly if you listen to cable news or online bloggers, you might have heard that there has been a hiatus or a halt to global warming. I’ve written before on this site that there is no halt, there never has been one. However there has been a vigorous debate about whether the increase in lower atmosphere temperatures has slowed down.
A new paper, “Possible artifacts of data biases in the recent global surface warming hiatus” just published today in Science deals with this issue. In particular, the lead researcher Dr. Thomas Karl and his colleagues investigate the quality of the near-surface temperature records and ask whether they really show a slowdown.
Dr. Thomas R. Karl. Photograph: Eric Bridiers/U.S. Missions.
The scientists make a number of improvements upon existing information. First, they focus on ocean surface temperature measurements from floating buoys and from ship-board sensors. We know that temperatures measured by ship sensors are often warmer than temperatures measured by buoys, in part because of the heat generated by the ship engine. A more thorough accounting of this effect has been implemented in the Extended Reconstructed Sea Surface Temperature data set version 4. This accounting is utilized in the paper.
Second, there has been a historical change in how ships measure surface temperatures. Decades ago, temperatures were mainly measured by insulated buckets. Around the time of World War 2, there was a change from insulated buckets to temperature sensors contained within ship hulls. The ship hull sensors recorded warmer water temperatures compared to the bucket method. A more thorough handling of the changes from buckets to ship hull sensors was also included in the new paper.
Finally, the new study used more recent estimates of the land temperatures. The new estimates combine multiple temperature databases into a single integrated whole.
The end result is that the temperature trends over the past 17 or so years has continued to increase with no halt. In fact, it has increased at approximately the same rate as it had for the prior five decades. But the authors went further by trying to cherry-pick the start and end dates. For instance, they stacked the cards against themselves by purposefully picking a very hot year to start the analysis and a cool year to terminate the study (1998 and 2012, respectively). Even this cherry-picked duration showed a warming trend. Furthermore, the warming trend was significant.
I asked lead author Dr. Karl for his comments on the significance of the paper and he told me,
I sincerely hope that SKS will dig deeper into this new paper because it has been getting hammered in the (denial) blogosphere for the last couple of days. We need some serious pushback against that onslaught!
Jen.
Well, as I understand it the Karl et al paper incorporates some very small adjustments to past and current temperature, which are primarily based upon recent work identifying errors in cross-calibrating sea temperatures from different sampling techniques.
And when those minor corrections are made, the so-called 'hiatus' vanishes. Which demonstrates that it was never a robust feature of the data. In fact the recent low trend was on the same order of magnitude as previous short term high trend variations (see Rahmstorf et al 2007). Those variations quite rightly weren't regarded as invalidating our basic understanding of climate, but rather as short term variations around longer term climate trends. Interesting, and such variations have inspired some very interesting work on solar variations and volcanic loading, but they didn't overturn the science.
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It's fascinating how the pseudo-skeptics ignore such short term high trend variations while harping on short term low trend variations - IMO quite a bit of wishful thinking and confirmation bias there.
I fully expect a lot of denialist shouting in this regard, as losing the shade of a (ill-considered and statistically unjustifiable) claim to recent low trends means the weakness of their claims will once again be dragged into the sunlight. That's been the pattern with any number of recent works that clearly convey just how much we're changing the climate. Climate denialists make the most noise when their nonsense is threatened.
The Los Angeles Times gave Judith Curry its main quote for "mainstream scientists" about this paper. She said:
"“I don't find this analysis at all convincing,” said Judith Curry, a climatologist at Georgia Tech who argues that natural variability in climate cycles dominates the impact of industrial emissions and other human actions. “While I'm sure this latest analysis from NOAA will be regarded as politically useful for the Obama administration, I don't regard it as a particularly useful contribution to our scientific understanding of what is going on."
Being a denier has gotten her the lead in the press. (The Los Angeles Times is a left leaning paper). Only the author is quoted in support of the paper. I do not see her finding fault with the data, she only criticizes the conclusion.
Jenna,
There really isn't much that SkS can do to support a new paper. Their results will have to be reviewed by their peers. If the results stand up in a year or two then we will know they are on the right track.
michael sweet @3.
The Los Angeles Times article is a bit messy but says "The new findings ... drew criticism from people on both sides of the rancorous debate over man-made climate change." Curry is followed by the "mainstream" comment of NASA's William Patzert whose quote ends “But the hiatus is history and it was real.” Presumably this is the criticism from the "mainstream" side of the alleged climate debate.
Of course, the thing with Curry is that she requires decades of hiatus or the Stadium Wave she is so fond of becomes a very silly call (as if it wasn't all ready).
I sent an email to the reporter suggesting he use Gavin Schmidt, Ken Trenberth or Michael Mann as the "mainstream" scientist. Reporters never ask James Hansen for quotes for articles like this, he is considered too extreme. They only use extreme views from the "lukewarmers".
Realclimate (Dr. Schmidt) has a post on this topic. It says the new research is nothing special and just adds to past knowledge. The "hiatus" falls off because it was never a robust result in the first place.
I didn't see a link to the Science paper by Karl et al. in the original post. Here's a link to the PDF version of the paper: Karl et al. 2015.
This comment reported in a piece in The Weekend Australian (June 6 2015) perhaps gives a more measured assessment of the paper than do some others.
"Head of climate monitoring at Britain’s Met Office, Peter Stott, said the results of the NOAA study still showed the warming trend across the past 15 years had been slower than in the previous 15 years and more study was needed to understand the role of natural variability".
I certainly concur with the last eleven words of the quote
@ ryland #7: Speaking of statements made by Peter Stott...
Both his statements seem eminently sensible as both imply that, as yet. all is not fully understood. I'm a scientist too although my PhD is in the field of molecular biology not climate science. In my own field advances are so rapid that what seems certain today is often shown not to be quite so certain tomorrow. I don't know whether climate science has the same pace of advancement but statements such as those by Dr Stott fit well with my own perceptions of how science should be conducted
ryland @7.
I can't agree that the Weekend Australian piece gives "a more measured assessment of the paper than do some others." Stott's comment is a useful addition and the first comment from UCL's Mark Maslin is helpful in putting the denialist blather in context. But the item then jumps face-first into the gutter with input from numpty denialist David Whitehouse, one of the Gentlemen Who Prefer Fantasy. Giving that bunch column space without full warning-warning for the reader is grossly irresponsible.
As for the pace of scientific advance, note the tense of 11-word statement you concur with:-)
My sentence construction is less precise than I had thought. I didn't say "the Weekend Australian piece gives a more measured assessment of the paper" I said "the comment reported in The Weekend Australian perhps gives a more measured assessment " which is not at all the same thing. As for the use of the past rather than the present tense by Dr Stott I did not think I should alter what appears to be a direct quote but to respond to you I think the present tense might be more apposite
My guess (and it is only a guess) is that ryland is imagining a further phrase after Stotts 11 words, something along the lines of
I says this because this seems to be a common response to this paper; the idea that we should "do nothing until we know everything"
However, I'm certain that Dr Stott would not agree. He knows that natural variability is the length of the dogs leash
Phil @1. As you say it is only a guess. I too can only guess at what Dr Stott meant by his reported comment, which I took at face value. I had no thought of "before" anything and have no idea why you thought I might have done. And surely serious efforts to mitigate climate change are already happening. Aren't they?
@Ryland #13:
Here's a summary of where the world is at with respect to mitigating manmade climate change:
ryland @11.
To be fair, I did mis-read your comment @7, reading it as "the comment reported" (as you managed to do yourself @11) which to me means 'all the comment reported'. But that is not what you wrote - you actually wrote "This comment reported", which can only mean this one comment.
There is a more substantial quote from Peter Stott on Karl et al (2015) here along with those from a number of other climatologists.
ryland @7, the last 15 years (2000-2014) includes near its tail one of the largest La Nina events on record (2011/2012) and corresponds with reduction of solar insolation from near record high levels to levels that have been compared with the maunder minimum. The 15 years prior to that (1985-1999) start with reduced temperatures due to the tail end effect of the El Chichon volcanic eruption, and finish with the strongest or second strongest El Nino on record. It is, therefore, hardly a mystery that the trend in the former is lower than the trend in the later.
Further, the primary source of temperature variability between the two periods is well known, with nearly all of the variability to be found in ENSO and volcanic eruptions. ENSO variations alone can account fully for the apparent slowdown in global temperature increase in the early twentieth century. This can be seen by plotting seperately the temperature trends for El Nino, neutral and La Nina years. Further study of natural variability is required to show whether or not the underlying warming due to anthropogenic factors has accelerated over that period, or remained steady. Also of interest is the influence of the PDO, which may result in a more sustained period before reversion to prior projected temperatures (ie, a strong PDO influence may result in temperatures increasing at the prior trend, but offset low due to the PDO for a period).
Given this, Stott's statement is not a particularly perspicacious response to the Karl et al paper. Indeed, it struck me on reading as rather platitudinous.
The latest in a long string of similar attempts. Each contradicts all that came before, making a mockery of "the science." The only difference: this one was accompanied by a huge media blitz.
"But this situation is nothing new, as so much of the considerable effort devoted to “explaining” the hiatus has been enacted independently, with little or no attempt to reconcile methods or results with anything that’s come before. If all the various explanations offered over the last 5 years or so were to be combined into one grand scheme, the upward trend would be so extreme as to break the thermometer. Any hope of establishing a correlation would be lost in the opposite direction: too much, rather than too little warming."
From "The Unsettled Science of Climate Change":
http://www.amazon.com/dp/B00YOARTPQ
Victorag. This seems to be a piece of pure sloganeering without the slightest supporting evidence. Indeed, rather than look at what is interesting about surface temperatures and climate, it appears to be just political pandering.
Perhaps you could explain why you apparently find the statement convincing? What I would like to see is what definition of "pause" is being used, (it is very ill-defined) and what "contradictory" papers are being published in line with this definition. Without examples of this contradictory science, it is hard to evaluate your comment. I struggle to see anything going one which make a "mockery" of science as I understand and practice it. And by the way, it would be probably best if you post links to papers that you have actually read and found contradictory rather than what some political hack has told you about them.
Your link is "interesting". Looks to be self-published ebook-only by someone using "Polar Vortex" as a pseudonym. Now why would that be? Someone shy of showing their credentials in climate science?
OK... the title says there is a suggestion of acceleration. I've read through here and the Guardian link, and all I see is
"The end result is that the temperature trends over the past 17 or so years has continued to increase with no halt. In fact, it has increased at approximately the same rate as it had for the prior five decades."
Is there somewhere else that it says accelerating?
I think it is/will be doing just that, but I don't think I see it here. I reserve the right to be wrong, but... ?
bjchip: "Considering all the short-term factors identified by the scientific community that acted to slow the rate of global warming over the past two decades (volcanoes, ocean heat uptake, solar decreases, predominance of La Niñas, etc.) it is likely the temperature increase would have accelerated in comparison to the late 20th Century increases."
Basically, if the surface warming trend has continued to rise at the same rate for the past ~50 years, but the various 'internal variability' factors listed in the quotation above have all been 'applying downward pressure' on the trend for the past ~17 years, then global warming (i.e. the enhanced greenhouse effect due to human greenhouse gas emissions) must have accelerated over that time period to counteract those other factors and keep the trend steady.