Arguments
What has global warming done since 1998?
What the science says...
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Every part of the Earth's climate system has continued warming since 1998, with 2015 shattering temperature records. |
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Climate Myth...
It hasn't warmed since 1998
For the years 1998-2005, temperature did not increase. This period coincides with society's continued pumping of more CO2 into the atmosphere. (Bob Carter)
Even if we ignore long term trends and just look at the record-breakers, 2015, 2014, 2010, and 2005 were hotter than 1998.
The myth of no warming since 1998 was based on the satellite record estimates of the temperature of the atmosphere. However, as discussed in the video below by Peter Sinclair, even that argument is no longer accurate. The satellites show warming since 1998 too.
There's also a tendency for some people just to concentrate on atmospheric or surface air temperatures when there are other, more useful, indicators that can give us a better idea how rapidly the world is warming. More than 90% of global warming heat goes into warming the oceans, while less than 3% goes into increasing the atmospheric and surface air temperature. Records show that the Earth has been warming at a steady rate before and since 1998 and there is no sign of it slowing any time soon (Figure 1).
Figure 1: Land, atmosphere, and ice heating (red), 0-700 meter ocean heat content (OHC) increase (light blue), 700-2,000 meter OHC increase (dark blue). From Nuccitelli et al. (2012).
Even if we focus exclusively on global surface temperatures, Cowtan & Way (2013) shows that when we account for temperatures across the entire globe (including the Arctic, which is the part of the planet warming fastest), the global surface warming trend for 1997–2015 is approximately 0.14°C per decade.
Ultimately, every part of the Earth's climate system is warming, and has continued warming since 1998.
Last updated on 22 March 2016 by dana1981. View Archives
@Riccardo - thanks for that - I was told it HAD been published - that was certainly the claim by the Cox supporter and Cox himself posted a link to it on the Drum (ABC) (as per mine above) to the paper as if it "were" published - typical of his dissembling approach. But you are correct - I can find no reference to it in any of the indexes for this journal. That in itself is telling enough as it is now almost 2 years since it was submitted. In my own days (long past) of publishing in the field of Atomic Physics it could sometimes take 12 months or so from submission to publication. But two years suggests there are some issues with acceptance. I should have checked this before.
But I'm not sure your other comment is entirely fair. I agree any physics is absent and I accept Dikran's comments on the poor statistics (as I'm not the expert there) but I'm not sure you can claim that their only conclusion is that local temperatures are sensitive to nearby ocean. Perhaps I've misread it but I gathered they were looking (purportedly) at Australian temperature data and using that as basis to dispute local warming (i.e. saying they can show a statsitically valid trend based on the Chow test that it may be flattening)
@Dikran - thanks for your comprehensive statistical refutation - I'm afraid I don't have the statistical expertise that you do - If asked I would have thought sum-of-squares errors was a fair anough approach (which is what you would expect in econometrics). But would you elaborate further? I understand what you mean about physical processes - as climate/temperature outcomes are a function of many different factors each with their own cycles and forcings and ENSO of course being a big one. But given that temperature data (what they are analysing) is ultimately data that is averaged over many sources why isn't it by definition normally distributed?
I'm sorry if I'm being a little dense - is it because each of the "drivers" has it's own statistical/natural "noise" and this creates a non-gaussian distribution of noise when the (average) temperature data is considered?
Do you know of anyone who has looked at the data after tyrying to remove the effects of ENSO etc?
I very much take your point about the "multiple hypothesis testing problem" - some thing I wasn't familiar with before but based on your explanation and a bit of my own secondary research can see how "false positives" might abound in an area like this. Are there any simple tests that can be used to identify the likelihood of this?
I do find their comments about breakpoints to be not unreasonable - although I note they make no real statement about what possible physical processes may be causing them.
Perhaps the most compelling argument (against this paper) is actually that they offer no fundamental physical reason behind their so called flattening.
If I were to have a stab at trying to understand what is going on here based on the statistical arguments you have presented I might have speculated that you can get large maxima and minima in any data that is the physical outcome of many cyclical processes that operate on different periods merely because from time to time the cyclical maxima co-incide in time. The danger is then that you "cherry" pick these points. You have to remove these other cycles to get out any linear drivers underneath the data. I think that is sort of what you are arguing?
Regardless - thanks all for your responses. Any more welcome but at least I feel now that we can point out not only that Mr Cox is on shaky ground - but also why.
Cheers
Tamino at Open Mind has looked at these issues in these two threads:
http://tamino.wordpress.com/2011/01/20/how-fast-is-earth-warming/
http://tamino.wordpress.com/2011/01/06/sharper-focus/
Thanks - while these links don't explicitly address Cox's paper and the statisticaly validity (or otherwise) of their approach they do remove the effects Dikram was pointing out.
The challenge then to Cox and Stockwell would be to analyse again based on this and see if they could still find the break points. On a visual inspection of the graphs in the links I suspect not.
Please ignore #101 - I must have hit submit when I meant to hit preview
Another way of looking at it, cyclical data is easily confusable with data containing a step change, but how likely is it to see a cyclic pattern in Gaussian white noise? A lot less likely than in data with autocorrelation or cyclical noise.
You are not being at all dense, the central limit theorem is hardly stats 101!
I checked the archive at the Journal of Forecasting, it hasn't been published yet.
For the multiple hypothesis testing issue, there are standard methods to deal with this, but they are generally overly optimistic or pessimistic. What I would do is generate a large number of model runs using a GCM where the only forcing was from CO2 and see how many produced a non-significant trend at some point during a 40 year period via the models internal variability. The forty year period is chosen since worries about global warming began to gain acceptance in the early 70s, the test is "at some point" because we are asking if cherry picking is the issue, so the "skeptics" would make the claim as soon as such a period ocurred.
Easterling and Wehner (who Stockwell and Cox claim to refute) did almost that, in that they looked at model output and found that decadal periods of little or no warming were reproduced by the models (although opf course the models can't predict when they will happen). This means that the observed trend since 1995/8 is completely consistent with model output. Easterling and Wehners' result shows that cherry picking is a possibility; it isn't necessarily deliberate cherry picking, but the skeptics have never performed an analysis that shows the ressult is robsut to the multiple hypothesis testing issues.
For the removal of ENSO, see the Fawcett and Jones paper mentioned in the intermediate version of this article. If you just look at the data:
you can see there isn't much evidence of a step change in 1997 if you account for ENSO.
The real problem with the paper is the straw man of a linear centennial trend. AGW theory doesn't suggest a linear centennial trend is reasonable, so showing a model with a break-point is statistically superior to something that AGW theory does not predict is hardly evidence against AGW.
I also remember some comment about solar forcing being better correllated with temperatures than are CO2 concentrations, and conclude that CO2 radiative forcing is not significant (or words to that effect). However, that is another straw man, the mainstream position on AGW does not say that co2 radiative forcing is dominant on a centennial scale (and that solar forcing is responsible for much of the warming of the 20th century). This is both a straw man and a false dichotomy, it isn't one thing or the other, but a combination of both. Reviewers at the Journal of Forecasting might not be suifficiently familiar with the climatology to spot that one.
What I am basically arguing is that statistics should be used to gain knowledge of the data generating process (in this case climate physics). If you ingore what is already known about the data generating process and adopt a "null hypothesis" (e.g. linear centennial trend) that is known a-priori to be incorrect, then statistical methods are likely to be deeply misleading. It is a really good idea for statisticians to collaborate with climatologists, as together they have a better combination of climate science and statistical expertise than either has on their own. This paper, like McShane and Whyner (sp?) and Fildes and Kourentzes, is an example of what happens when statisticians look at climate data without fully immersing themselves in the climatology or getting their conclusions peer-reviewed by climatologists.
I think this just about knocks it on the head - it's good to have such a clear, albeit somewhat arcane and technical, discussion. In summary I would argue this paper can be safely dismissed because
#1) After two years it hasn't been published - suggesting a problem with its acceptance
#2) It has been submitted to a forecasting journal which, whilst reputable and purports to cover climate forecasting, does so as only as one out of a long list of forecasting topics which are predominantly economic and social in nature (in other words it's light on hard science) - which means there is actually very little climate science expertise within the journal
#3) It contains no physics or science arguments what-so-ever as to what may actually be the mechanisms it purports to reveal or forecast.
The above 3 really make it clear it is hardly a paper about climate in the first place
#4) It's approach is statistically invalid since the test it applies assumes a gaussian noise distribution in the data when that is not the case (due to the multiple impacts of noise from cyclical drivers of climate of different periods and variabilities)
#5) It's approach is invalid on the physics of climate because of the above
#6) It's invalid on the physics anyway since it is established beyond reasonable doubt that increased atmospheric levels of CO2 produce an increased green house effect
#6) It's approach is statistically invalid because of the multiple hypothesis testing problem - i.e. it is highly likely to generate false positives in the statistical analysis of the data - especially when it ignore the underlying physics - in other words the so-called linear trend they forecast is likely to be plain wrong
#7) It fails to remove the effects of things like ENSO and volcanos from the data in order to analyse the temperature effects of increasing CO2 in the atmosphere - particularly egregious when the ENSO of 1997/98 was known to be one of the largest ever
#8) It actually fundamentally fails to address the central tenet of AGW - that increasing levels of human generated atmospheric CO2 are contributing to a warming of the planet independent of other (natural) factors sufficient to cause substantial climate change that will most likely be deleterious.
have I missed any?
If they want to come back on any of that all they have to do is re-analyse the data accounting for ENSO etc (as per your graph) and then show that a linear trend is still valid and is not a false positive - and of course get that accepted in peer review.
If they were honest scientists that's what they'd do.
I hope I get the chance to put that to them :)
I wish they could show such a thing - I'd love to discover AGW isn't a real problem! I wish it wasn't! But wishing doesn't make it so and good scientists don't fall for the "is/ought" fallacy.
So I am betting they won't and can't.
They would have to do more than just remove ENSO, even after that is done, a linear trend model over a complete century still isn't a reasonable model, given what we know about climate of the 20th century, so it would still be a straw man.
If they wanted to demonstrate that there really was a step change in 1997 that was evidence against AGW, they would have to limit the analysis to the period where mainstream science actually says CO2 radiative forcing was dominant (e.g. approximately 1970 onwards). For any test, the null hypothesis ought not to be known to be false apriori.
If they wanted to show it wasn't just ENSO they would also have to use data that had been adjusted for ENSO. As it is well known that ENSO affecte climate (especially Australian climate), showing ENSO is responsible is nothing new.
If the want to say it is PDO, this is more of an oscillation that modulates ENSO, so a step change model isn't really appropriate anyway.
I don't think there is evidence that the analysis isn't honest, just naive (from the climatology perspective) and lacking in self-skepticism.
As for your comment about "honesty" - I agree the paper shows no dishonesty. But I don't think it is "naive".
If you had been following Mr Cox's tactics on the ABC and other blogs you might question whether he is always entirely forthright in his approach.
He is actually a lawyer - not a trained scientist.
He wrote an article once on Drum (http://www.abc.net.au/unleashed/44734.html) about how there had been a challenge to the Australia/New Zealand tempetarure data, implying some sort of conspiracy on the part of BOM people in New Zealand. He made it out as if this was independent challenge from credible sources. What he failed to disclose directly in the article was that he was actually one of the prime architects of the challenge (in his capacity as secretary of the Climate Sceptics)- which didn't come from reputable client scientists at all.
He also published the link to his "paper" on Drum in response to a challenge to submit a piece of peer reviewed science that invalidated AGW. Somehow he conveniently neglected to mention that it hadn't actually been published.
In other words he has an avowed political agenda - it not simply a naive approach or lack of self-scepticism
What evidence can you present for your claim that natural variability 'has a tendency to average out over longer timescales'? Given that we have geophyiscal evidence of massive natural shifts over millions of years, your claim sounds spurious and without merit.
The regular causes of short-term variability (ENSO) do not cause long-term swings. The changes you're talking about "over millions of years" are not caused by short-term (11y or 25-50y) solar cycles.
There's an echo 'faster than they can repackage and rebrand' that seems to start in an editorial in Investor's Business Daily on July 28. Based, of all things, on the Monnett investigation charade.
I get all my climate science news from investment tip sheets, don't you? But FauxNews sure picked it right up.
It was less than a week after the Monnett story broke that permits for drilling the Arctic started moving forward. Beneficiaries - Shell Oil. Here's one environmental blogger that sees this as more than a 'coincidence.'
That noted climatologist James Taylor had a July 27 editorial in Forbes touting Spencer's paper.
Here's the system works:
- Do bad science, get good press. Repeat. Ignore rebuttals.
- Do good science, nobody pays attention.
See the Ocean Cooling corrected again for more discussion.
Done. See Tracking Earths Energy and any of the many sensitivity threads, for example here.
But average temperature (actually temperature anomaly, in comparison to a standard base period) is important because it is a directly observable change. But more important than the year-to-year, month-to-month anomalies is the temperature trend. Since the mid-70's that trend is up.
Spencer describes the 3rd order polynomial fit to the data as being "for entertainment purposes only, and should not be construed as having any predictive value whatsoever.".
It may not have any predictive value, but it does show in hindsight that it has warmed since 1998. Many thanks for debunking this one for us Roy! ;o)
I checked around and all of the skeptic websites have their rehashing of an article that seems to have originated in the daily mail. From what I understand, that's a pretty cruddy source, but using a link below, I went to Curry's own website and it sounds like this is what she's saying:
This quote is from the daily mail article:
In fact, Prof Curry said, the project’s research data show there has been no increase in world temperatures since the end of the Nineties – a fact confirmed by a new analysis that The Mail on Sunday has obtained.
‘There is no scientific basis for saying that warming hasn’t stopped,’ she said. ‘To say that there is detracts from the credibility of the data, which is very unfortunate.’
Read more: http://www.dailymail.co.uk/sciencetech/article-2055191/Scientists-said-climate-change-sceptics-proved-wrong-accused-hiding-truth-colleague.html#ixzz1cIFa5qrh
Here is a blog from Judith Curry, climate etc. I don't know much about it, but the most recent post goes into detail about a conversation she had with Muller and a second post clarifying her comments and what happened in the daily mail interview.
http://judithcurry.com/
I went and re-checked the article linked on the home page about the skeptic myth that it hasn't warmed since 1998. It says it hasn't been updated for a while. I get that Muller released his data and leaked his summaries before the data had been peer reviewed and Curry makes a number of comments saying she wished he hadn't done that and that he did it on his own. I get her critique hasn't been peer-reviewed either.
A number of the articles referenced a site called wood for trees that has a simple app that lets you access the BEST data and make simple plots. I know nothing about its accuracy or validity, but you can use it to check various date ranges.
http://www.woodfortrees.org/plot/best/from:2002/plot/best/from:2002/trend
I'm curious if anyone has any better info on this argument and if there is any agreement or counter argument related to Curry's declaration that the BEST data set shows that warming has stopped over the last 10-12 years?
Also, please don't hear me saying that in and of itself proves anything about anything. I'm not "going anywhere" with this quote and from reading Curry's blog, she says it doesn't prove or disprove global warming. But it does call into question many of the models and most specifically, it makes Muller look like a bit of a dodo for the way he presented his data and his initial denial of the data then later retractment and admission supposedly of what the data says.
Thanks for any thoughts,
Rick
[DB] Thanks for taking the time to voice your concerns. Tom Curtis has already addressed most of them below, but let me focus on Wood For Trees.
http://www.woodfortrees.org/ is a website run by Paul Clark, a British software developer. Paul has loaded into the website all the publicly-available temperature datasets, including BEST. As such, it is an invaluable tool for quickly comparing temperature trends over varying timeframes. Many climate scientists use Wood For Trees for quick comparisons for the public to turn to for answers to questions.
It's not a panacea for research, as the pros still work directly with the datasets directly, but it is a valuable tool.
As for the rest, I'll close by saying that anyone who agrees that a time series of only a decade isn't scientifically significant AND who also says that over the same time a scientifically significant long-term trend has stopped is speaking out of both sides of their mouths. The two positions are mutually exclusive.
1) The trend over the chosen period is positive;
2) That the last two data points are almost certainly flawed - so much so that the real scandal here is why where they included? (See below);
3) That if you exclude the flawed data, the trend rises to a level comparable to the trend in various satellite products;
4) That if you do not cherry pick the start point and use a full decades data (rather than artificially truncating it at less than a decade, as Curry did), the trend matches the trend since 1975 at a hefty 0.27 degrees C per decade:
Finally, Tamino shows that the minimum time period with a statistically significant slope terminating in early 2010 (the end of the BEST data excluding the two faulty values) is approximately 16 years. That is the minimum period over which the level of statistical significance is sufficient to determine the sign of the slope. And over that period, the trend is positive, and very much the same as the trend since 1975:
Finally, I referred to the last two data points being flawed. Tamino shows the huge rise in uncertainty for those two points, but it was Nick Stokes that discovered why. It turns out the data for those last two months comes from just 47 stations, compared to the 14,488 stations for the preceding months. What is worse, all of those stations are in Antarctica.
Given the low number of samples, and biased distribution, there is no scientific justification for including the last two samples in their finished product. This is one genuine issue with the BEST product, but as the faulty data points bias the end points low, don't expect to here it raised by so called "climate change skeptics", for whom the predetermined outcome has always been more important than scientific integrity.
I also get [DB]'s comment about a very short period of time not indicating anything about the longer term trend, and Curry makes that exact comment as well. But Tamino sure goes off on her and presents some pretty compelling analysis saying she was way off base in her critique of Muller. It is pretty odd, however, that Muller was wrong about his own data. I don't know Tamino, but when two of the folks who did the data set both say the same thing, it seems odd that they're both wrong.
My last thought, I read through Tamino's post and all the comments. A number of folks offered that what she said was "technically accurate" (i.e. there's no scientific evidence than global warming hasn't stopped", but that her statement is meaningless. But at least from what I read, she said she made that comment to shut up Muller who she said made some comments saying the BEST data set proved AGW was true and that skeptics were totally wrong. I get reminded occasionally by my advisors about the limits of what the data I'm analyzing says and what I can and can't claim about it. If one takes her comment as chastising Muller for over-speaking, it doesn't have the connotation Tamino goes after and then, all of Tamino's analysis ends up demonstrating her exact point which is that small of a period cannot be used to prove anything.
It was late when I read through her blog so I don't remember what she said she was responding to from Muller, but that's what I remember her saying started this whole thing, some statement from him she said was way overblown, so she wanted to restate it technically accurately and say let the data speak for itself.
Odd because that is incorrect. Read the BEST FAQ under 'has global warming stopped?'
the decadal fluctuations are too large to allow us to make decisive conclusions about long term trends based on close examination of periods as short as 13 to 15 years.
There is no evidence of a change in trend on that long a time scale. Muller said it correctly; it's Curry and others who are deliberately spreading disinformation.
#120: "a fact confirmed by a new analysis"
There is no 'new analysis'; there is just a deliberately cherrypicked graph. Based on that kind of science, consider this: It was cooler today than it was in July; is that evidence that global warming stopped?
‘We see no evidence of it [global warming] having slowed down,’ he told BBC Radio 4’s Today programme. There was, he added, ‘no levelling off’.
Read more: http://www.dailymail.co.uk/sciencetech/article-2055191/Scientists-said-climate-change-sceptics-proved-wrong-accused-hiding-truth-colleague.html#ixzz1cOGjgBRy
Curry's argument was much like Tamino's argument against her, that the statement from Muller was a stupid statement and meaningless. He could have simply said that short term trends don't matter due to decadal fluctuations, but he didn't. It seems like she called him on a statement of his that was not careful and that she saw as misleading.
Help me with this if you can Tom or Muon, if Tamino said Curry screwed up bad for making her statement that there is no evidence global warming hasn't stopped, wouldn't the exact same argument apply to Muller's statement? And since he made it first, isn't it more logical to see her statement as a correction of his?
The second thing Muller said that seemed pretty crazy stupid was the comment in the WSJ article, ‘there were good reasons for doubt until now’.
Read more: http://www.dailymail.co.uk/sciencetech/article-2055191/Scientists-said-climate-change-sceptics-proved-wrong-accused-hiding-truth-colleague.html#ixzz1cOIS0rEw
Curry said she critiqued him in part because of this comment. The site you referenced Muon makes the following statement at the end of the FAQ:
Our study addressed only one area of the concerns: was the temperature rise on land improperly affected by the four key biases (station quality, homogenization, urban heat island, and station selection)? The answer turned out to be no – but they were questions worthy of investigation. Berkeley Earth has not addressed issues of the tree ring and proxy data, climate model accuracy, or human attribution.
Why would answering this one question mean that there was no longer any basis for skepticism? The insinuation that there used to be a basis for skepticism but the only possible reason was potential inaccuracy in the temperature data is pretty silly and Curry called him on it.
It seems like he has backed way off his strong interpretational statements of what the data means and is going back to what Curry said earlier, let the data speak for itself and let the project be simply about trying to make the cleanest and most accurate, publically available set of temperature data available.
The "good reasons for doubt" comment is a different issue. Reasons for doubting what? AGW? The surface temperature record? Frankly Muller is exaggerating the importance of the BEST results regardless of what specifically he was talking about, but exaggerating the importance of BEST is nothing new for Muller. BEST shouldn't have been necessary to accept the accuracy of the surface temp record to begin with.
Regardless, Curry's statements were ill-conceived and inaccurate, as the new post discusses.
In a word, no.
First off, let's lose the double negatives and translate Curry's statement: 'There is evidence that global warming stopped.' This, as shown by tamino, is clearly false. For a change in trend (warming stopped) to be considered as evidence, it must be statistically significant - or else it is just more than likely noise.
Muller's statement: "We see no evidence of it [global warming] having slowed down." That's consistent with the statement made in the FAQ and the requirement that evidence be statistically significant. All else (including this spin job by some very frantic denialists) is noise.
Further discussion of this Curry/Muller question should go to this new thread.
On Curry's statement vs. Muller's, this is logic 101.
Curry says "A is proven to be true." (i.e. A = the globe has been cooling).
Muller says "There is no evidence of A."
Muller's statement is not the opposite but equal of Curry's.
Curry's statement is false not because A is false, but because there is no valid evidence to support her statement A.
Muller's statement is true not because A is either true or false, but rather because it is a statement about the evidence, not about proposition A itself.
Do you see the difference?
Seriously? You actually posted that comment?
Please take the time to click on the "Intermediate" tab above, read that poast in its entirety, understand it, and then get back to commenting.
Or do you only use the statistically absurd definition of warming in which only the maximum is relevant to the trend when trying to deny global warming?
[Source]
So, if I understand correctly, for global warming to be seen to be stopped, we would have to see steady temperatures in both the atmosphere and the oceans. Just one of these is not sufficient.
Is this correct?
No.
To have some confidence (one can never "know") that warming has stopped you would need to see 17 consecutive years in which you see no trend (mind you, that's not 17 years of no warming each year, but instead no trend in that span of 17 years) in both the atmosphere and the oceans.
One would hope that in that same period you would also see an halt in the melting of glaciers and arctic ice and other indicators of a warming world.
The chances that "global warming has stopped" is extremely unlikely. Where real science is operating right now is a matter of how much warming we're going to see from the expected increases in atmospheric CO2. Is the IPCC central estimate of 3.0C for 2XCO2 correct? Is it slightly lower? 2.5C? Or is it actually higher? ~4.0C?
The difference between climate sensitivity of 2.5C and 4.5C has major implications for what human society needs to do to address the situation.
What exactly do you mean by the phrase "global warming has stopped"? More specifically, what exactly do you mean by "global warming"?
There are many measures of the temperature of the planet:
- near-surface air temperatures over land (i.e., typical weather station data)
- tropospheric temperatures from satellites or radiosondes
- sea surface temperatures
- deeper ocean temperatures
At any time, one or more of these can decrease for a period, even if overall heat content is still rising. Examples would be the redistribution of heat related to ENSO.
At any time, there may be temporary decreases in one or more of these, due to such factors as volcanic eruptions, anthropogenic aerosols, solar output, etc.
The effect of the top-of-atmosphere radiation imbalance caused by increased atmospheric CO2 leads to increased energy retention somewhere in the earth-atmosphere system, but it doesn't mean that every temperature, everywhere is constantly increasing.
The implication of most "global warming has stopped" statements from deniers is to claim "global heating due to CO2 has stopped", in an attempt to discredit the strong science that tells us the effects of adding CO2 to the atmosphere. This implication is unjustified, misleading, deceptive, disingenuous, illogical, specious, unfounded, unscientific [insert favourite synonym here].
To make an analogy, the "global warming has stopped" claims are pretty much equivalent to claiming that the furnace in my house has stopped heating because I opened a window on a cold winter day and one room's temperature has dropped. The furnace is still pumping just as much heat into the system, and temporary, localized effects that show cooling don't change what the furnace is doing. You don't conclude the furnace is broken, when you know that the temporary/local cooling is caused by the open window.
The effects of a volcanic eruption can be seen in a short-term temperature record.
The effects of ENSO can be seen in a short-term temperature record.
The effects of a short-term change in solar output can be seen in a short-term temperature record.
The effects of a slow, steady imbalance due to rising atmospheric CO2 cannot be seen in a short-term temperature record, and that means that short-term records also cannot show that the effect isn't there. It is an obfuscation by deniers to pretend that short-term variations in an global temperature record disprove greenhouse gas theory. To detect that slow, steady signal in the noise, you need longer records. Long enough to be statistically significant.
Not much sign of "global warming" stopping there is there? What do you figure will happen to temperature records in the next El Nino? Now perhaps you think that El Nino event will suddenly stop, but then perhaps you note that 2011 was hottest ever year with a La Nina event.
Yes, I should have included the 17 year thing. That's fine. I just wanted to know what would qualify as an end (or pause) of warming.
135.Rob Honeycutt
I am not discussing the probabilities of things or the validity of the foundational science. I am just wondering what I need to see in the data for the skeptics to have a point when they say "warming has ended".
136 Bob Loblaw
By the phrase "global warming has stopped" I mean "the total heat content of the global environment is no longer increasing".
137 scaddenp
Thank you for the graph. I will look at the paper.
everyone:
I am not posting any comments or questions to this website in order to convince anyone of anything. I just want to get a better understanding of the proper response to many of the skeptic's positions.
So, I have learned that the last decade's supposed pause in rising temperatures really isn't a pause. There is still a trend going up. The heat content of the environment is still going up. In order for the skeptics to be able to say "see, it stopped" we would have to see steady temperatures in both land and air for at least 17 years.
All of this is fine. I don't have any arguments with any of it.
I will move on to learn more about other topics on the website.
So, when there is a slowdown in surface temperature, it's not because the Earth is retaining less heat energy, it's because the heat energy is moving around in places where we can't adequately measure it.
OK, so to further discuss this, if you are viewing the deniers positions (I intentionally use denier instead of putting "skeptic" in scare quotes)
- choosing one metric (e.g. surface air temperatures) is wrong, because that is not a complete representation of the system. When you say "both land an air", that is still not complete, as it ignores deeper oceans.
- there is still a disconnect between the concepts of "total heat content" and the changes in heat content due to atmospheric CO2 increases. Total heat content depends on more than just CO2 forcing. It is not unexpected to see total heat content decrease if other forcing factors besides CO2 push things that way. To pretend that this disproves the warming effect of increasing CO2 is to ignore the sound science that tells us that other factors do play a role. This is a major inconsistency in the deniers positions: on the one hand, they argue that climate science ignores factors other than CO2 (they don't); while on the other hand they make an argument that doesn't make sense unless you do ignore other factors. (I think I should write this up and contribute it to the Contradictions page.)
To deal with this latter issue (other factors affecting heat content will temporarily obscure the slow change forced by CO2, you have two common ways of dealing with it:
1) take data over a long enough time that the short-term fluctuations cancel out (that's where the 17+ years argument comes in)
2) account for the short-term effects and remove them from the measurements, so that the long-term trend is easier to see. That were studies like Foster and Rahmstorf (as discussed on Tamino's blog come in.
Crap...I said "land and air" and i should have said "oceans and air"....sorry.
The oceans are by far the largest reservoir of heat on the planet. They cover over 70% of the Earth's surface and over 90% of global warming is going into the oceans. If we consider the ocean depths down to 2000 metres, then global warming has not slowed down at all, just global surface temperatures. It's just that all that heat is building up below the surface layers of the ocean.
Basically what the recent Foster & Rahmstorf paper found is that when you eliminate the natural variability, the man-made global warming signal emerges.
We have some posts coming up that put this all into perspective.
30 years is about enough time to blot out most of the natural variability in global temperatures. Longer will be needed for regional and subregional temperatures as the signal to noise ratio is smaller the smaller the region you consider (because the spatial averaging reduces variability just as temporal averaging does).
You will always be able to cherry pick some data that seems to suggest a lack of warming, but it is just that, a cherry pick.
If you really want to understand the climate of the British Isles, I suggest you read this book on the topic.
It hasn't stalled. See the Foster and Rahmstorf thread.
"The resultant adjusted data show clearly, both visually and when subjected to statistical analysis, that the rate of global warming due to other factors (most likely these are exclusively anthropogenic) has been remarkably steady during the 32 years from 1979 through 2010. There is no indication of any slowdown or acceleration of global warming, beyond the variability induced by these known natural factors."
It would be helpful if, as scaddenp suggests, you provided the source of these assertions: '___ says temperature increase appears to have stalled.'
http://www.dailymail.co.uk/sciencetech/article-2093264/Forget-global-warming--Cycle-25-need-worry-NASA-scientists-right-Thames-freezing-again.html
I understand that CRU is NOT dismissing the past or future affects of CO2. The interesting statement is just that temps have remained level for the last 15 years.
I have not been able to find the actual paper by CRU, so perhaps the newspaper is misrepresenting CRU's statements. Does anyone have the original paper?
Yes, The Daily Mail claims that NASA and the CRU said something... but they're (-snip-). Disagree? Then cite the spokesperson for NASA and/or CRU who said these things.
[DB] Please refrain from such verbiage without more of a definitive proof offered.
It was the Met office and CRU.
It wasn't a NASA paper, but rather NASA researchers are used in other parts of the story.