Has Global Warming “Stopped”?

December 31st, 2008

Posted by: Roger Pielke, Jr.

Well, it all depends on what “stopped” means.

I’ve been asked to comment on the silly debate over whether or not global warming has “stopped.” Like so much in the climate debate, the answer to this question depends upon what you want it to be, your political views, and what is meant by the word “stop.” So here are two incompatible perspectives.

1. Global Warming Has Stopped!

Evaluating this claim, linked above to the website of Senator James Inhofe (R-OK), requires some care with the English language. Specifically, we must take care with the definition of “stop.” The claim that global warming has stopped is false if “stop” means, as the first entry of the online OED defines it, “to come or bring to an end” because this definition carries with it some implications about the future. If global warming has indeed stopped (under this definition), then it would call into question all of those campaigns to “stop global warming,” as explained by Mark Lynas:

Why bother [supporting urgent action to reduce carbon emissions] if global warming has ‘stopped’, and therefore might have little or nothing to do with greenhouse gas emissions, which are clearly rising?

But have any leading scientific organizations or assessment groups suggested that global warming will not continue? No. To the contrary, scientific organizations have gone to some lengths to explain that recent global temperatures do absolutely nothing to alter the existing scientific consensus.

2. “Global Warming Has Not Stopped”

For instance, the UK Met Office explains that “Anyone who thinks global warming has stopped has their head in the sand” (PDF). Once again, we need to pay careful attention to language. If “stop” is defined according to the third entry of the online OED, then it means “to cease or cause to cease moving” with no connotation about the future. Under this definition, it is obvious that global temperatures have not increased over the past 8, 11 or 18 years (depending on your dataset and definition of increase, see below;-). But clearly, the increase has ceased for some period of time. The significance of this cessation is of course a separate issue from the fact that there has been a pause.

The UK Met Office even acknowledges this when they write:

. . . due to natural variations in climate, we expect to see ten-year periods both globally and regionally with little or no warming and other ten-year periods with very rapid warming.

So according to this explanation of what it means to “stop”, global warming can indeed “stop” for periods of ten years. Since global temperatures in 2008 are not so different than 1995, or for some datasets, 1990, the far more important question than “has global warming stopped or not?” is “When will global warming resume?”

This will bring us to the profound question of what it means to “resume”. Fortunately, instead of such word games Lucia Liljegren is tracking observed temperatures versus predictions, which turns out to be a much more interesting and productive question.

15 Responses to “Has Global Warming “Stopped”?”

  1. lucia Says:

    Hi Roger– There is broken html in the final paragraph. That article did something they usually don’t do: It gave the actual averages GMST in real units! “The 1961-90 global average mean temperature is 14.0 °C” It will be ineresting to see if the temperature really does rise to 14.4C. (Or higher.)

    Obviously, global warming has not stopped. Now

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  3. Roger Pielke, Jr. Says:

    Thanks Lucia, fixed!

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  5. Larry Sheldon Says:

    I still think “we” (definition left as an exercise) are allowing ourselves to be sucked into the wrong definitions.

    Global warming is real, it is (or was) happening–has been since the bottome of the last ice age and will (did) continue until we start (started) back down into the next. (Think it is much to early to say we need to switch to the past tense here).

    The evidence that humans have much to do with it globally is thin. (The evidence for local climate change is much better.).

    Warm is not bad. Warm is good.

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  7. lucia Says:

    Larry– Where ever we may be being sucked, Morano is posting the “global warming has stopped” meme. If Morano wanted to make a more nuanced claim, he could. So, it’s fair for Roger to point out that Morano’s meme is very very poorly supported by either evidence or language usage.

    Morano is a politician, and as such, it’s hardly shocking he over reaches and/or spins quite a bit. But it’s also fair to point out that Morano is spinning.

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  9. Paul Biggs Says:

    Morano is countering climate alarmism. I think Roger is being a bit naive with this statement: “But have any leading scientific organizations or assessment groups suggested that global warming will not continue? No. To the contrary, scientific organizations have gone to some lengths to explain that recent global temperatures do absolutely nothing to alter the existing scientific consensus.” Surprise, not! Keep the alarm rolling and those research grants coming in.

    We’ve seen the UK Met office making the unscientific statement, Phil Jones being the latest, that warming is being ‘masked.’ So warming is warming, but cooling is masked warming. Nope, warming can’t be masked. No record global average temperature predicted by the met office for 2009 in contrast to their failed prediction of a record year for 2007. Another holiday for CO2. A lack of sunspots and the start of a 20-odd years of PDO cooling don’t bode well for the global warming industry.

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  11. Paul Biggs Says:

    And, where and what is the ’scientific consensus?’ To the best of my knowledge, no one has obtained an individual signed statement from each of the 2500 IPCC participants setting out their views. Sure, we know what 50 or 60 lead authors say and we know, for example, that the consensus on the link between hurricanes and global warming existed only in Trenberth’s head, not in the literature.

    Furthermore, Pachauri recently said, “I refuse to accept that a few papers are in any way going to influence the long-term projections the IPCC has come up with.” So it seems that the IPCC isn’t set up to accept anything other than warming driven by man-made CO2.

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  13. Jim Clarke Says:

    Climatologists who believe that natural climate variations are large compared to the human influence have been predicting the current trend in global cooling since the early 1990s, citing ocean circulation cycles as the cause of both much of the observed warming and cooling over the last 110 years. They have been roundly dismissed and generally vilified because they could not completely describe how the mechanism worked.

    Now we have the proclaimation that ‘natural variability’ will ‘mask’ the warming for about 10 years, followed by rapid warming. What is the mechanism that produces this effect? I know of no natural cycles that operate on 10 year periods.

    Until the planet stopped warming and started to cool a bit, the global warming folks simple dismissed any mention of ocean induced climate cycles. Now they embrace them to explain the cooling, but refuse to acknowledge that if natural variability can cause cooling, then it must also be responsible for some of the warming. The logical inconsistancy in the AGW arguments are profound, yet whole sections of the scientific community turn a blind eye!

    Yes…on a decadal time scale…global warming has stopped. On an annual time scale, global cooling has started. That is what the data indicates. One may argue that global warming may continue at some later date, but one can not argue that it is warming now! Such arguments should be logically coherent and not comprised of arbitrary numbers seemingly pulled out of a policy hat!

    In this case, the politician is actually speaking more factually than the scientists!

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  15. tarpon Says:

    When does real science resume? And should it not be totally open science, no hidden data, no secret formulas, all, everything out in the open, available on the Internet and subject to the community.

    I think two things have reared their ugly heads in this quest for political science, the publication racket, and the grant racket. They need to both be removed from biasing science.

    How many grants have been given out with the specific purpose of trying to prove AGW, instead of doing pure science.

    I for one am appalled at what has been allowed to happen to science, all in the name of trying to prove the unprovable. Ice ages come and go, anyone want to tell me why? or how that has happened for the last 5 million years or so?

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  17. Mark Bahner Says:

    Hi Roger,

    “Under this definition, it is obvious that global temperatures have not increased over the past 8, 11 or 28 years (depending on your dataset and definition of increase, see below;-).”

    You mean 18 years (not 28), don’t you? You’re referring to 1990 to 2008, correct?


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  19. Roger Pielke, Jr. Says:

    18, yes, thanks. Now corrected!

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  21. Paul Biggs Says:

    The UK Met Office didn’t predict 10 or more years of non-warming – they predicted 2007 to beat the global average temperature record of 1998 – and they were WRONG! They are also pretty useless at predicting weather a few months or weeks in advance:


    I’m forced to conclude that their weather and climate models are pretty useless.

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  23. Adder Says:

    Interesting. So, just to be able to compare predictions with actual trends then, how would the trendlines of the datasets look like?

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  25. Roger Pielke, Jr. Says:

    Adder, see:


    Even better, see:


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  27. Adder Says:

    Ok, thanks! Lucia (26 Dec) shows the trendines, and they are very close to the predictions.

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