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A warming pause?

Filed under: — stefan @ 6 October 2009 - (Español)

The blogosphere (and not only that) has been full of the “global warming is taking a break” meme lately. Although we have discussed this topic repeatedly, it is perhaps worthwhile reiterating two key points about the alleged pause here.

(1) This discussion focuses on just a short time period – starting 1998 or later – covering at most 11 years. Even under conditions of anthropogenic global warming (which would contribute a temperature rise of about 0.2 ºC over this period) a flat period or even cooling trend over such a short time span is nothing special and has happened repeatedly before (see 1987-1996). That simply is due to the fact that short-term natural variability has a similar magnitude (i.e. ~0.2 ºC) and can thus compensate for the anthropogenic effects. Of course, the warming trend keeps going up whilst natural variability just oscillates irregularly up and down, so over longer periods the warming trend wins and natural variability cancels out.

(2) It is highly questionable whether this “pause” is even real. It does show up to some extent (no cooling, but reduced 10-year warming trend) in the Hadley Center data, but it does not show in the GISS data, see Figure 1. There, the past ten 10-year trends (i.e. 1990-1999, 1991-2000 and so on) have all been between 0.17 and 0.34 ºC per decade, close to or above the expected anthropogenic trend, with the most recent one (1999-2008) equal to 0.19 ºC per decade – just as predicted by IPCC as response to anthropogenic forcing.

GISS temperature trends

Figure 1. Global temperature according to NASA GISS data since 1980. The red line shows annual data, the larger red square a preliminary value for 2009, based on January-August. The green line shows the 25-year linear trend (0.19 ºC per decade). The blue lines show the two most recent ten-year trends (0.18 ºC per decade for 1998-2007, 0.19 ºC per decade for 1999-2008) and illustrate that these recent decadal trends are entirely consistent with the long-term trend and IPCC predictions. Even the highly “cherry-picked” 11-year period starting with the warm 1998 and ending with the cold 2008 still shows a warming trend of 0.11 ºC per decade (which may surprise some lay people who tend to connect the end points, rather than include all ten data points into a proper trend calculation).


Why do these two surface temperature data sets differ over recent years? We analysed this a while ago here, and the reason is the “hole in the Arctic” in the Hadley data, just where recent warming has been greatest.

Mean temperature difference between the periods  2004-2008 and 1999-2003
Figure 2. The animated graph shows the temperature difference between the two 5-year periods 1999-2003 and 2004-2008. The largest warming has occurred over the Arctic in the past decade and is missing in the Hadley data.

If we want to relate global temperature to global forcings like greenhouse gases, we’d better not have a “hole” in our data set. That’s because global temperature follows a simple planetary heat budget, determined by the balance of what comes in and what goes out. But if data coverage is not really global, the heat budget is not closed. One would have to account for the heat flow across the boundary of the “hole”, i.e. in and out of the Arctic, and the whole thing becomes ill-determined (because we don’t know how much that is). Hence the GISS data are clearly more useful in this respect, and the supposed pause in warming turns out to be just an artifact of the “Arctic hole” in the Hadley data – we don’t even need to refer to natural variability to explain it.

Imagine you want to check whether the balance in your accounts is consistent with your income and spendings – and you find your bank accounts contain less money than you expected, so there is a puzzling shortfall. But then you realise you forgot one of your bank accounts when doing the sums – and voila, that is where the missing money is, so there is no shortfall after all. That missing bank account in the Hadley data is the Arctic – and we’ve shown that this is where the “missing warming” actually is, which is why there is no shortfall in the GISS data, and it is pointless to look for explanations for a warming pause.

It is noteworthy in this context that despite the record low in the brightness of the sun over the past three years (it’s been at its faintest since beginning of satellite measurements in the 1970s), a number of warming records have been broken during this time. March 2008 saw the warmest global land temperature of any March ever recorded in the past 130 years. June and August 2009 saw the warmest land and ocean temperatures in the Southern Hemisphere ever recorded for those months. The global ocean surface temperatures in 2009 broke all previous records for three consecutive months: June, July and August. The years 2007, 2008 and 2009 had the lowest summer Arctic sea ice cover ever recorded, and in 2008 for the first time in living memory the Northwest Passage and the Northeast Passage were simultaneously ice-free. This feat was repeated in 2009. Every single year of this century (2001-2008) has been warmer than all years of the 20th Century except 1998 (which sticks out well above the trend line due to a strong El Niño event).

The bottom line is: the observed warming over the last decade is 100% consistent with the expected anthropogenic warming trend of 0.2 ºC per decade, superimposed with short-term natural variability. It is no different in this respect from the two decades before. And with an El Niño developing in the Pacific right now, we wouldn’t be surprised if more temperature records were to be broken over the coming year or so.

Update: We were told there is a new paper by Simmons et al. in press with JGR that supports our analysis about the Hadley vs GISS trends (sorry, access to subscribers only).

Update: AP has just published an interesting story titled Statisticians reject global cooling, for which they “gave temperature data to four independent statisticians and asked them to look for trends, without telling them what the numbers represented”.


456 Responses to “A warming pause?”

  1. 201
    Mark says:

    200: Absolutely.

    Bob bob, even though there is not butter on every square mm of my bread, that slice of bread is 100% buttered.

    And that is the measure of sea ice extent.

  2. 202
    Mark says:

    “Mark, but if a couple of grams of butter melted and spread on its own (lets assume on a non-absorbing surface), wouldn’t its extent be far less than 500 grams doing the same thing?”

    Rod, who said anything about spreading the 500g?

    Talking merely about extent of butter, a couple of grammes can be spread over a much greater area than the top of the tub containing 500g.

    Therefore, if you were to look merely at the raw “how much area does this cover” (as you wish to maintain) you would come to the conclusion that a couple of grammes of butter was more butter than 500g.

    Are you seriously saying that is wrong?

    No.

    So extent is not equal to volume.

    You have to know the depth too.

  3. 203
    Mark says:

    Krog, 190 if the postulate #6 from Hank is correct, then there’s no need to actually answer your question: answering doesn’t make your original query any more published.

  4. 204
    Patrick 027 says:

    “for example, ice sheet growth following continental drift, then followed by …”

    Bad example – obviously the time scale for continental drift is not short, even compared to chemical weathering.

    My other point was that internal variability could conceivably redistribute or change clouds, humidity, temperature distributions, relative to top-of-atmosphere insolation and relative to surface types and relative to each other, so as to cause changes not just in regional radiative fluxes but on the global short-time average, and do so in such a way as to cause a net gain or loss in heat. It is entirely possible, however, that this does nothing to help sustain anomalous conditions if the anomalous conditions did not originally involve a global average temperature change. Anyway, there is ultimately a tendency for the system to get pulled back from anomalous conditions… (to be continued.)

  5. 205

    OT, but this looks to be potentially a pretty significant paleo study:

    http://www.sciencedaily.com/releases/2009/10/091008152242.htm

  6. 206
    CM says:

    “It is noteworthy in this context that despite the record low in the brightness of the sun over the past three years…”

    Do you mean solar radiation instead of ‘brightness’? Aren’t they different measures? Has anyone argued that climate might have been altered by changes in sun ‘brightness’?

  7. 207
    Hank Roberts says:

    CM, did you click the link behind the words? Why quibble over definitions? That leads only to long digression.

    Brightness is in the eye, or instrument, of the beholder.

    http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant

    It’s hypertext — words that are clickable links refer to the paper.

  8. 208
    CM says:

    Hi, CM (#206), I also go by ‘CM’ and have come to comment here rather frequently over the past year. If you’re going to stick around, I’d like to ask you to please consider using a different tag, or there’ll be lots of confusion.

  9. 209
    David Horton says:

    #177 ‘Jim Eager (148), saying “we began burning fossil carbon fuels on an industrial scale in 1750″ is quite a stretch. While that is when the first coal was mined in the U.S. industrial scale use came almost 100 years later”. Well, maybe, but the industrial revolution didn’t begin in America.

  10. 210
    Lynn Vincentnathan says:

    I was just thinking how this sort of resembles stock market charts. The advice they always give is to invest for the long haul, bec the overall trend is up….until, of course, global warming finally pushes the stock market and the economy itself into a never-ending nose-dive, esp if we do nada to mitigate it.

  11. 211

    #190 Krog

    Then my apologies. Certainly it is difficult to read inflection and tone in the written word. At the same time, going to the IPCC site might seem daunting, but you were given a link to a PDF and a reference to a single page. That is easy to look at.

    ‘Simple’ is a relative term of course but the page 4 in the report is pretty straight forward. The positive forcing of Co2 is about 1.6 W/m2 and the other GHG’s are around 1 W/m2.

    Of course there are other effects that are positive and some negatives. Total positive estimated forcing around 1.6 W/m2.

    That is about 1.6 above natural cycle by my estimations. And yes, there are error bars too.

    It’s a challenge to figure it out the communications are getting better, but it is still a challenge.

  12. 212
    Jim Steele says:

    Hank, Again I am not sure what you are asking for. My reference to increased southern hemisphere was linked to a graph produced by Cryosphere. Why didn’t the url http://arctic.atmos.uiuc.edu/cryosphere” point you” to the source. Or did you visit their website and you are now suggesting their data is wrong or just opinion?

    regards the Skeptical Science article referenced by dhogaza. I agree with the the context of the article that the proof of a continued global warming trend must be measured in terms of heat content. I was surprised to see his graph of a continued uptrend that was rather sharp. His data was based on a couple of estimations that were published but I have seen other published articles stating very different trends.

    I confess that I have only read the abstracts and have not purchased any of these articles but in the paper “Ocean heat content and Earth’s radiation imbalance” by David H. Douglassa and Robert S. Knox the abstract reads “Earth’s radiation imbalance is determined from ocean heat content data and compared with results of direct measurements. Distinct time intervals of alternating positive and negative values are found: 1960–mid-1970s (−0.15), mid-1970s–2000 (+0.15), 2001–present (−0.2 W/m2), and are consistent with prior reports. These climate shifts limit climate predictability..”

    They are stating that there is a drop in heat content since 2001. Do people have links to the full article of this paper and the Skeptical Science reference so I can compare how these diverging measures of heat content were determined?

  13. 213
    Jim Steele says:

    Martin. I agree that your distinction makes the most sense. I hope in the future people are careful to distinguish between forced and unforced natural variation.

    Regards your final comment “BTW I don’t think you’re being quite realistic about the kind of effect a quiet Sun could produce. The numbers I’ve seen are a few tenths of a degree max, meaning at best a postponement of the ongoing warming (at 0.2 degrees/decade!), hardly cooling.”

    You may want to call it unrealistic, and perhaps it is, but still I think it is a valid hypothesis. It is simply based on correlations of temperatures and observed solar minimums. Given our present state of solar knowledge, calculations based on incomplete assumptions may be much less reliable than simple historic correlations, and thus those calculations may be equally unrealistic. We have gathered an immense body of solar data, but still the consensus was that this year we would witness one of the greatest sunspot years. But now we see we are in a major minimum approaching the Dalton and Maunder, and the observations completely contradict the scientific consensus.

  14. 214
    Paul Hanlon says:

    There’s another logical explanation for the current cooling, and that is that we are entering, or have entered the cool phase of the PDO cycle.
    Looking at a long term chart of temperatures, and overlaying it with a graph of the PDO cycles shows a very strong correlation between the two.
    We seem to have had three warm phases and two cool phases of the PDO, and if this cooling phase is typical, it will likely end around 2030, with temperatures about 0.8degC warmer than they were in 1880, and CO2 levels at around 420ppm.
    The fact that temperatures will be higher means that there is some forcing at play, but given that we will have had an even amount of cold and warm cycles, will that not mean that the forcings are less “forceful” than current thinking?

  15. 215
    matthew says:

    very surprising article given all the attention that has been given to the idea the last decade has seen the world cooling.

    please explain how the ten year trend lines were calculated. Your average denier will look at the graph and say that you are ignoring the last couple of years.

  16. 216
    nick says:

    So why hasn’t the jan-aug 2009 figure been included in the 10 year trend line? Perhaps it is because it is below the trend, and so tilts the line?

  17. 217
    dhogaza says:

    please explain how the ten year trend lines were calculated. Your average denier will look at the graph and say that you are ignoring the last couple of years.

    It appears to end in 2008. 2009 isn’t over yet. Which “last couple of years” do you think have been ignored?

  18. 218
    KiwiCM says:

    Sorry CM, am now using a different name.
    Hank, thanks for the response (#207). Someone on a forum I frequent (where digression is a specialty!) has questioned why the word ‘brightness’ was used. He states that ‘Visual brightness is a distinct and different measure from irradiance’. So I thought I’d ask if there was any reason for choosing ‘brightness’. From your response it appears there was no reason behind it. That’s all I was after, wasn’t attempting to say anyone was wrong or being misleading.

  19. 219
    John Mashey says:

    re: #215 matthew
    So, please try post #138 an look at Figs 1 & 4.
    Those trendlines were computed using Excel SLOPE, using all the data up that point, an plotting the SLOPE at the *endpoint* of the period.

    Think of it is a plot of something like akin to a first derivative, and you need to pick exactly the right short intervals to get a negative first derivative, and if you use 30-year SLOPEs, you have to go back to 1975-ish to get even slightly negative slopes.

    To get flat temperatures, SLOPES have to stabilize at 0, to actually get cooling, they have to go negative.

  20. 220
    Jim Eager says:

    Rod @177, it is not a stretch at all, you are merely being US-centric. The Industrial Revolution, which started in England, not in its colonies, is generally accepted as beginning circa 1750.

    Do you have any other nits to pick?

  21. 221
    sidd says:

    Mr. Steele: Re ocean heat content (OHC)

    I refer you to the papers by Murphy et al. and Schuckmann et al (I really like the Murphy paper) referred to earlier on this thread. They demonstrate quite clearly that OHC is increasing. I quote from the Murphy paper:

    “Since 1950, only about 10 +/- 7 % of the of the forcing by greenhouse gases and solar radiation has gone into heating the Earth, primarily the oceans. About 20 +/- 9% has been balanced by increased outgoing radiation. About 20% of the forcing by greenhouse gases and solar radiation has been offset by volcanic aerosols. The remainder, about 50% has been balanced by the direct and indirect effects of anthropogenic aerosols.”

    And I note that para 40 refers to realclimate.org

    The oceans are absorbing heat at the rate of 1e22J/yr.

  22. 222
    Patrick 027 says:

    Jim Steele – “Given our present state of solar knowledge, calculations based on” … “We have gathered an immense body of solar data, but still the consensus was that this year we would witness one of the greatest sunspot years. But now we see we are in a major minimum approaching the Dalton and Maunder, and the observations completely contradict the scientific consensus.”

    My impression is that it is a lot easier to project the effects of solar, CO2, volcanic, etc, forcing on Earth’s climate than to forecast the internal variability of the sun.

    You have to be careful with those historical correlations, by the way. Some people might think that the correlation between temperature and CO2 is ‘The’ evidence for cause and effect. It is not; physics predicted such a relationship before it was ever observed. Physics also predicts a relatiohnship for solar forcing and climate, but aside from efficacy variations (see another recent comment of mine (~ week ago, try search)), the effect of the same magnitude of forcing would be the same change in climate, all other things being equal. Maybe there is some way in which climate is more sensitive to solar forcing, but there could also be some way in which it is less sensitive, … and the burden of proof is on that which is yet unsubstantiated; also, there may be evidence (?) against such sensitivity enhancement (or that would place an upper limit on it).

    Back to the correlation studies. We know that CO2 (along with glaciation itself and some other things) was likely a positive feedback in glacial-interglacial variations because there is no evidence of an externally-driven CO2 forcing, there is a lag time between climate and CO2 changes suggesting that climate acted on CO2 (although this may not be the case for temperature at some locations ??), there is strong persistent correlation of CO2 and climate, and orbital forcing seems a likely external forcing, and we know that CO2 is a greenhouse gas that would tend to cause global warming when increased or the reverse if reduced (as supported by further study of these time periods (how do you explain the full extent of the climate change) as well as other time periods in the distant past, the 20th century and afterward, other planets, and the physics).

    Correlation studies can be useful but you have to be careful about how you do it – simply looking at the amount of variation at different frequencies and ascribing all the variation in some band of frequencies to a forcing with a frequency within that band is likely to overestimate the amount of variation that can be attributed to such a forcing.

    —-

    so about the internal variability – vertical heat transport through the ocean can cause global surface and tropospheric temperature changes without radiative forcing. ENSO in particular is not just about horizontal rearrangements in temperature but also, in El Nino, about a pool of warm water spreading over a colder mass of water. There is a global average temperature increase with El Nino. The radiation feedback from the temperature increase …

    (note – this is the feedback that is often not identified as a climate feedback because, I would guess, it is so basic that it is taken as a given (not that it isn’t studied and calculated appropriately). This may lead to some confusion – when we say that the net feedback is positive, this does not include the radiative feedback directly to the temperature change with optical properties held fixed; if that were included, having any stable climate requires that the total feedback be negative. But it should be apparent that climatologists mean that the net feedback besides the – what I think we can call the blackbody radiation feedback (or maybe the Planck function feedback) – is not meant to be included – otherwise, it wouldn’t make sense to identify a climate sensitivity with zero feedback as being anything besides constant increase or decrease.)

    (Actually there is a temperature feedback wherein optical properties are temperature dependent for a given composition and physical phase, but that’s generally a small effect that can be ignored; the radiative feedbacks that are generally called feedbacks are due to changes in composition and physical state.)

    is a negative feedback that will then tend to cause the Climate system to lose heat. However, this is slowed (but not stopped) by positive feedbacks such as the water vapor feedback. It is not necessarily the same as the response to a non-ESNO global warming because of different spatial-temporal distributions, but … I have to take a break now.

  23. 223
    Hank Roberts says:

    Jim Steele: are you saying you found the material for your questions _at_ the Cryosphere site, or are you working from another site that mentioned it?

    When you have something mentioning a particular paper, look that up in Google Scholar, then look at citing papers and see what others have made of it in the actual journals.

    But also, the site-limited search approach can be useful (for any website):

    http://www.google.com/search?q=site%3Arealclimate.org+douglass+knox

    From there you can narrow your search, for example by searching for
    [
    which finds inline comments, for example this one summing up Douglass:

    http://www.realclimate.org/?comments_popup=595#comment-98036

  24. 224
    Rod B says:

    #209, The (1st) Industrial Revolution in Britain started in the late 1700s though it was birthing before 1750. None-the-less its growth was rather slow and I still don’t think one can see “industrial scale” fossil fuel use until (beginning) mid-1800s.

  25. 225
    Rod B says:

    #220, I admitted it is a nit, and, no, I have no others. As a helpful suggestion (at no charge) though, I would offer that even nits should not be grossly misstated. They’re red meat for other skeptics not as objective as me.

  26. 226
    CTG says:

    Re 150 John Mashey

    “Here’s a wish, for anyone out there that still writes serious code: it woudl be nice to have an interactive view of Figure 1 (which had both temperature and slopes), and had a slider bar that was the number of years.”

    Okay, I have written a Java applet that does that. It shows all the trends of whatever length you pick in the slider – essentially a visualisation of Robert Grumbine’s analysis. It shows quite nicely why shorter trends don’t mean that much.

    So, does somebody want to host it? Gavin?

  27. 227
    Rod B says:

    Mark, et al, I didn’t say extent equals volume. I said (asked) it was proportional/related to volume. If your saying the 500 gram tub of butter does not spread at all then I agree its volume is much greater but extent much smaller than the spread out 2 grams. But I think the analogy does not apply to sea ice. Clearly on the forming side, sea ice is not going to form and build a big mesa-type structure with lots of volume but without any sea ice formation a meter or two from the precipice boundary of the ice mesa. It seems the volume will increase as the extent increases and vice versa. There is the possibility that melting might form a mesa, but I think that is so odd and the probability so remote to not even count.

  28. 228
    dhogaza says:

    regards the Skeptical Science article referenced by dhogaza. I agree with the the context of the article that the proof of a continued global warming trend must be measured in terms of heat content. I was surprised to see his graph of a continued uptrend that was rather sharp. His data was based on a couple of estimations that were published but I have seen other published articles stating very different trends.

    Where, and how recent? Out-of-date Argo shallow-depth stuff later shown to be wrong, or what?

    Generally, the more recent a paper, the more likely it is that it’s incorporating more recent information on correcting calibration errors, etc.

  29. 229
    dhogaza says:

    Given our present state of solar knowledge, calculations based on incomplete assumptions may be much less reliable than simple historic correlations, and thus those calculations may be equally unrealistic. We have gathered an immense body of solar data, but still the consensus was that this year we would witness one of the greatest sunspot years. But now we see we are in a major minimum approaching the Dalton and Maunder, and the observations completely contradict the scientific consensus.

    And yet, September’s nearly as warm as September 1998 during a huge El Niño …

    If we’re to ponder the Maunder, we’re going to be pondering why it’s so much warmer this time ’round.

    Why do you think it would be?

  30. 230
    dhogaza says:

    So why hasn’t the jan-aug 2009 figure been included in the 10 year trend line? Perhaps it is because it is below the trend, and so tilts the line?

    Perhaps because they’re plotting annual data, and 2009 isn’t done yet?

  31. 231
    dhogaza says:

    But now we see we are in a major minimum approaching the Dalton and Maunder, and the observations completely contradict the scientific consensus.

    Oh, and BTW, regarding the solar cycle stuff, it’s pretty much out in the open that it’s not well understood and whatever predictions are made are pretty much WAGs. That’s the real scientific consensus.

    But even if the sun went cold tonight, out, snuffed, no energy output …

    You do realize that wouldn’t affect the fact that CO2 warms the planet or the feedback amplifications that follow?

    All these “it’s the sun, stupid!” miss exactly what they accuse climate scientists of missing – there are multiple factors that impact climate.

    You’re sounding more and more like an outright denialist the more you post.

  32. 232
    William T says:

    Rod (177) Don’t forget that Europe was essentially deforested by the 18th century (all those sailing ships; charcoal for forges; wood for heating; etc). That’s one reason why coal mining took off in Britain and elsewhere about that time.

  33. 233
    Patrick 027 says:

    So, including the blackbody/Planck function feedback, the climate is generally stable; to a first approximation, unforced variation tends to decay back to an equilibrium state. However, the equilibrium state could be described as a strange attractor – within limits, there are positive, negative, and ‘sideways’ feedbacks such that conditions fluctuate, but outside certain limits, the likelihood of an unforced fluctuation generally decays with greater magnitude. Also, it should be mentioned that the characteristics of these fluctuations – not the specific trajectory which never exactly repeats, but the patterns/textures that will appear similar among different sufficiently long time periods within the same long-term climate, are part of that climate, and can change with climate change.

    Unforced variations may change the global average surface and tropospheric temperatures by redistributing heat away or into those levels, to or from, for example (and necessarily if for significant time periods) the deep ocean. Radiative ‘thermal relaxation’ will tend to cause such a variation to decay with time, which interestingly implies that a time period dominated by El Ninos could actually produce some global cooling, as the surface warm water cools without compensating warming of deep water, which may resurface. Assuming finite climate sensitivity to forcing and similar feedbacks to unforced variation, this will tend to be slowed but not stopped by positive feedbacks such as water vapor (just as positive feedbacks would tend to enlarge climate sensitivity to forcing, but not to infinity, assuming all other feedbacks combined are not a net positive larger than the blackbody/planck function feedback).

    However, it isn’t obviously true that the global average feedbacks will be the same as they would to forced climate change, and it is possible to imagine that they are different;

    likewise internal variability without a global average change (after subtracting average seasonal and/or diurnal variations, etc, for the longer-time scale climatic state, depending on the time scales being dealt with) could concievably result in some global average radiative feedback (or for that matter, drive a net vertical transport of heat into or out of the ocean); this could happen because the radiative effects of local temperature variations depend on local clouds and humidity and any spatially-temporally varying greenhouse gases (and surface LW emissivity, though for some purposes that is approximated as being near 100 % and doesn’t generally vary much), the radiative effects of clouds and humidity depend on other clouds and humidity above or below, and temperature at the surface and in the atmosphere, and incident solar radiation and the angle of the sun, and the albedo of the underlying surface, etc. – and so on, and internal variability may involve some rearrangments that are of a different shape than the response to an external climate forcing.

    (BUT I’m not claiming to know any specifics beyond that; there may be arguments for expecting such differences to be limited – ie how likely or possible is it that all clouds would happend to be concentrated at high latitudes in winter, or that the poles would get warmer than the equator (obliquity as it is) – these things would require something quite exotic and unearthly. There will be physical-caused tendencies for clouds, temperature, humidity, surface type, etc, to correlate in various ways.)

    (Interesting point – if nothing else changed, keeping the average surface temperature the same while reducing variations in space and time would reduce average LW emission (by a small amount) and thus tend to cause a global average positive radiative feedback (by a small amount – in so far as the radiation emitted from the surface is concerned (setting the greenhouse effect aside), I estimated that the global annual average emitted radiation is the same as the radiation that would be emitted from a surface that is only about 1 K warmer than the average surface temperature, so it’s actually not that big of an effect).)

    But these feedbacks wouldn’t necessarily do anything to prolong the anomalous state and might in some cases act to reverse it.

    Anyway, the evidence is not in favor of a large part of the warming of the last century being caused by internal variability, even of the sort with global average radiative feedbacks. – In case you were wondering.

  34. 234
  35. 235
    Martin Vermeer says:

    Jim Steele: by 2030 we will have a transient warming of over 1C due to CO2 and its feedbacks alone… do you know the size of the LIA cooling?
    About Douglass and Knox, this is very fresh paper… you’ll have to wait how it holds up, but it contradicts the findings of others… read, e.g., here:
    http://earthobservatory.nasa.gov/Features/OceanCooling/ and refs therein.
    When you’re in this business, you get a certain feeling about what papers are worth, and I have this dark brown feeling about, e.g., the company Prof. Douglass keeps and the places he publishes: see http://www.pas.rochester.edu/~douglass/recent-publications.html No, it doesn’t prove anything. But life is short and it has been a useful heuristic for me.

  36. 236
    llewelly says:

    Stefan, I’m looking at http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts.txt and the global temperature anomalies given in that file are about 0.1 C greater than the points on your graph. What’s your baseline?

  37. 237

    #190 Krog

    Important of course to consider water (H2O) which accounts for about half the forcing (and is a variable gas). H2O can vary dramatically and is not well mixed in the atmosphere.

    The additional CO2, CH4, N2O and CFC’s tipped the balance. Now the oceans are warming and more moisture is evaporating and trending up, which is a critical feedback. The industrial GHG’s may have tipped the scale, but H2O, combined with the atmospheric lifetime of CO2 combines to create a positive feedback that, at this point, has risk written all over it.

    Once the cycle tips positive (which it has), it may be very hard, or possibly impossible to return to a manageable balance (equilibrium or reducing forcing). In the mean time, special interests are protecting their profit potentials not realizing that doing so has the potential to strongly degrade the entire global economy (monetary, biological, chemical) as it pertains to reliance of the human system and important species, in which case any profits they are chasing become increasingly meaningless anyway.

    The onus of action is on limiting CO2 to reduce potential future impacts and further exacerbation of the forcing feedbacks, while simultaneously working on other mitigation and adaptation strategies.

    If you want to see where this all can go, review this page (it’s a short read):

    http://www.ossfoundation.us/projects/environment/global-warming/summary-docs/2009-may-leading-edge

  38. 238
  39. 239

    #214 Paul Hanlon

    I don’t believe we know enough about the PDO to predict that it will remain cool for 30 years.

    Plus there is strong positive bias in the system (the combined effects of human caused GHG’s and albedo) which further complicates the potentials.

    In my opinion, anyone stating we will be in a negative PDO for 30 years is merely guessing.

    I sure wouldn’t bet on it ending in 2030.

    In reality, we don’t know when it will return to positive and for how long… unless of course someone can add to this and show where we now have a better handle on PDO fluctuation???

    Anyone?

  40. 240
    Mark says:

    John P, something to clear up:

    Water vapour is quite well mixed, if constrained mainly to the troposphere if you consider its value by RH.

    Water vapour is quite variable if you consider its value by columnar weight.

    I bring this up because there was another discussion about the 80%RH figure in climate models and someone thought that this was a parameter just put in to make the model work, rather than an output.

    Water vapour’s effect as a GHG is based on total water content, not RH. So John is talking about total H2O content which is variable, not RH which is much less so.

  41. 241

    #215 matthew

    Why might you, or anyone else, care about a couple of years (any couple of years) in the context of the clear long term climate trend:

    http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif

    The last couple of years are inside natural variation, therefore they are not a part of the trend of the signal, but rather a result of the noise of natural variation.

    http://www.ossfoundation.us/projects/environment/global-warming/natural-variability

    We have the attribution on the signal.

    http://www.ossfoundation.us/projects/environment/global-warming/myths/images/climate-forcing/Radiative_Forcing_Components_IPCC_AR4.png/image_view_fullscreen

    So why do people keep insisting that the noise is more important than the signal?

    Why are you even bringing it up? Do you think natural variation is overriding the anthropogenic effect in the long term climate trend?

  42. 242
  43. 243
    Mark says:

    “http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif

    The last couple of years are inside natural variation, therefore they are not a part of the trend of the signal, but rather a result of the noise of natural variation.”

    In fact, one should say that AGW is only really proven wrong when the temperature line gets to the level of the 1900’s.

    After all, you don’t decide that you’re looking at a simple harmonic oscillator because you see values going up quicker then slowing down (but still going up), do you.

    You wait for a cycle before saying there IS a cycle.

    At least if you’re a scientist you do.

  44. 244
    Mark says:

    RodB

    “Mark, et al, I didn’t say extent equals volume. I said (asked) it was proportional/related to volume. ”

    But it doesn’t.

    The proportion of butter spread on my slice of bread this morning to go on as eggy soldiers was much lower than the proportion of open butter surface on the tub of 500g of butter I took my spread from.

    If surface area was related to volume, this means the more surface area, the less volume.

    You aren’t saying that this is true.

    Are you?

    If you want to spread the 500g of butter and compare it to how far a couple of grammes spread, then to do the same area only comparison with ice records, you have to go back in time and spread all the ice from 1980 etc so that it is as thick as the ice is today.

    Got a handy time machine? And a really BIG shovel?

  45. 245
    Mark says:

    Rod, you’re trying to say that this equation I learned when I was about 8 is wrong:

    V=W x L X D

    and is instead

    V=W x L

    It isn’t.

    And you can’t say “but they are proportional” because that requires a constant of proportionality.

    DEPTH IS NOT A CONSTANT.

  46. 246
    G. Karst says:

    I think it would be more helpful if someone were to define “flat temperatures”. If one defines flat temperatures as an anomaly of 0.0 for 30 yrs, then the world will never see “flat temperatures”. What is a realistic expectation of flat temperatures… 0.0 +/- ?? for X number of years?

  47. 247
    David Miller says:

    Regarding #226

    CTG, contact me (riley_4_prez … d.sparks.net). Let me know what you need and I can probably provide it.

  48. 248
    G. Karst says:

    Mark:

    You seem to be saying that one dimension (depth) is more important than the other two (area). In general, ice volume varies with ice extent (ice melts from it’s edges, top, bottom and all around). There are papers that support this basic premise. You need to find them.

  49. 249
    Mark says:

    G Karst, a question that can only be answered by the negative:

    A six sided dice rolled 30 times will not show 0.0 difference from the calculated mean (3.5) in the mean values rolled. Neither if you rolled 100 times. Or a thousand.

    All you can say is “we are confident to [a certain confidence level] that this is a fair dice”.

    Perhaps it would be more helpful to explain what science you think will make the temperature flat and then ascertain what would show that that science is taking effect. And then give a confidence level to which you have found or rejected your science.

  50. 250
    Jim Eager says:

    Rod @224, Newcomen invented his coal-fired steam engine in 1712 and it was widely employed to pump water from British coal and tin mines, which sounds like a purely industrial application to me, even if of limited scope. Watt’s improved steam engine was introduced in 1775, which rapidly enabled steam power to displace water power in industrial manufacturing on a wide scale well before the mid-1800s.

    I will agree that neither of these events support the oft-cited 1750 date, but the application and spread of steam power was in fact rapid and widespread, and pretty much all sources agree that it had reached critical mass by the 1830s-1840s with the adaptation of steam power to produce rotary motion. Use of fossil carbon fuels got it’s next significant boost with the 1858 introduction of the Bessemer process for making steel, btw.


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