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2008 temperature summaries and spin

Filed under: — gavin @ 16 December 2008 - (Italian)

The great thing about complex data is that one can basically come up with any number of headlines describing it – all of which can be literally true – but that give very different impressions. Thus we are sure that you will soon read that 2008 was warmer than any year in the 20th Century (with the exception of 1998), that is was the coolest year this century (starting from 2001), and that 7 or 8 of the 9 warmest years have occurred since 2000. There will undoubtedly also be a number of claims made that aren’t true; 2008 is not the coolest year this decade (that was 2000), global warming hasn’t ‘stopped’, CO2 continues to be a greenhouse gas, and such variability is indeed predicted by climate models. Today’s post is therefore dedicated to cutting through the hype and looking at the bigger picture.

As is usual, today marks the release of the ‘meteorological year’ averages for the surface temperature records (GISTEMP, HadCRU, NCDC). This time period runs from December last year through to the end of November this year and is so-called because of the fact that it is easier to dice into seasons than the calendar year. That is, the met year consists of the average of the DJF (winter), MAM (spring), JJA (summer) and SON (autumn) periods (using the standard shorthand for the month names). This makes a little more sense than including the JF from one winter and the D from another as you do in the calendar year calculation. But since the correlation between the D-N and J-D averages is very high (r=0.997), it makes little practical difference. Annual numbers are a little more useful than monthly anomalies for determining long term trends, but are still quite noisy.

The bottom line: In the GISTEMP, HadCRU and NCDC analyses D-N 2008 were at 0.43, 0.42 and 0.47ºC above the 1951-1980 baseline (respectively). In GISTEMP both October and November came in quite warm (0.58ºC), the former edging up slightly on last month’s estimate as more data came in. This puts 2008 at #9 (or #8) in the yearly rankings, but given the uncertainty in the estimates, the real ranking could be anywhere between #6 or #15. More robustly, the most recent 5-year averages are all significantly higher than any in the last century. The last decade is by far the warmest decade globally in the record. These big picture conclusions are the same if you look at any of the data sets, though the actual numbers are slightly different (relating principally to the data extrapolation – particularly in the Arctic).

So what to make of the latest year’s data? First off, we expect that there will be oscillations in the global mean temperature. No climate model has ever shown a year-on-year increase in temperatures because of the currently expected amount of global warming. A big factor in those oscillations is ENSO – whether there is a a warm El Niño event, or a cool La Niña event makes an appreciable difference in the global mean anomalies – about 0.1 to 0.2ºC for significant events. There was a significant La Niña at the beginning of this year (and that is fully included in the D-N annual mean), and that undoubtedly played a role in this year’s relative coolness. It’s worth pointing out that 2000 also had a similarly sized La Niña but was notably cooler than this last year.

While ENSO is one factor in the annual variability, it is not the only one. There are both other sources of internal variability and external forcings. The other internal variations can be a little difficult to characterise (it isn’t as simple as just a super-position of all the climate acronyms you ever heard of NAO+SAM+PDO+AMO+MJO etc.), but the external (natural) forcings are a little easier. The two main ones are volcanic variability and solar forcing. There have been no climatically significant volcanoes since 1991, and so that is not a factor. However, we are at a solar minimum. The impacts of the solar cycle on the surface temperature record are somewhat disputed, but it might be as large as 0.1ºC from solar min to solar max, with a lag of a year or two. Thus for 2008, one might expect a deviation below trend (the difference between mean solar and solar min, and expecting the impact to not yet be fully felt) of up to 0.05ºC. Not a very big signal, and not one that would shift the rankings significantly.

There were a number of rather overheated claims earlier this year that ‘all the global warming had been erased’ by the La Niña-related anomaly. This was always ridiculous, and now that most of that anomaly has passed, we aren’t holding our breath waiting for the ‘global warming is now back’ headlines from the same sources.

Taking a longer perspective, the 30 year mean trends aren’t greatly affected by a single year (GISTEMP: 1978-2007 0.17+/-0.04ºC/dec; 1979-2008 0.16+/-0.04 – OLS trends, annual data, 95% CI, no correction for auto-correlation; identical for HadCRU); they are still solidly upwards. The match of the Hansen et al 1988 scenario B projections are similarly little affected (GISTEMP 1984-2008 0.19+/-0.05 (LO-index) 0.22+/-0.07 (Met-station index); HansenB 1984-2008 0.25+/-0.05 ºC/dec) – the projections run slightly warmer as one would expect given the slightly greater (~10%) forcing in the projection then occurred in reality. This year’s data then don’t really change our expectations much.

Finally, as we’ve discussed before, what climate models did or did not predict is available for all to see. Despite many cautions about using short-term changes to imply something about the long-term trend, these comparisons will still be made. So just for fun, here is a comparison of the observations with the model projections from 1999 to 2008 using 1999 as a baseline. The answer might be surprising for some:

1999-2008 model and data trends

You can get slightly different pictures if you pick the start year differently, and so this isn’t something profound. Picking any single year as a starting point is somewhat subjective and causes the visual aspect to vary – looking at the trends is more robust. However, this figure does show that in models, as in data, some years will be above trend, and some will be below trend. Anyone who expresses shock at this is either naive or … well, you know.

As for the next few years, our expectations are not much changed. This coming winter is predicted to be ENSO neutral, so on that basis one would expect a warmer year next year than this year (though probably not quite record breaking). Barring any large volcanic eruption, I don’t see any reason for the decadal trends to depart much from the anticipated ~0.2ºC/decade.

Update: Just FYI, the same figure as above baselined to 1990, and 1979.

393 Responses to “2008 temperature summaries and spin”

  1. 201
    Mike Lawley says:

    Gavin, With respect to comment 47, I have heard the same thing about IPCC. That many of the \scientists\ listed as members of the IPCC are not scientists and that some of the scientists listed have left the IPCC as a result of their disagreement with IPCC findings. The same source goes on to say that there is substantial disagreement among the scientists that remain members over the conclusions of IPCC studies.

    [Response: None of this is true in substance. I am aware of only two people (over 3 working groups and over the last two reports) who left the IPCC chapter they were involved in. That is not overwhelming. There is I think only one person on the IPCC author list who is also on Inhofe’s sceptics list (who hasn’t been horribly misquoted) (J. Christy). As for ‘disagreement’ where is it? Thousands of scientists reviewed the reports and were able to make as many critiques as they wanted. The basic fact is that IPCC is the mainstream – go to the AGU website and check the abstracts of last weeks meeting. Out of thousands dealing with climate, you’ll find maybe half a dozen that go against the ‘consensus’ with the vast majority trying to move beyond what’s already been found in order to tackle the remaining uncertainties. – gavin]

  2. 202
    Hank Roberts says:

    Note that Kirby writes

    “… the reported correlation of GCR flux and low cloud amount,
    measured by satellite [13, 14, 15]. Although the observations are both disputed [16, 17, 18, 19, 20, 21] and supported [22, 23, 24] …”

    and (p. 16) he’s talking about events such as crossing the galactic plane, or running into relatively dense interstellar clouds, not about local changes in our Sun over short time spans.

  3. 203
    Charles says:

    Slightly OT, but I am wondering if there has yet been any reaction to Don Easterbrook’s presentation at the just-finished AGU conference. Here’s a link to his presentation:

    I’ve read Chris Colose’s response: I’m wondering if there have been any other direct responses. I realize Dr. Easterbrook has been repeating this argument for several years, mostly at conferences. I cannot find any peer-reviewed journal articles of his which outline his ideas (is the lack of a peer-reviewed paper by him on the subject indicative of anything?), nor any other direct responses to his work in the peer-reviewed literature.

  4. 204
    davidgmills says:

    RE: Post 199

    You say: The existing data, and the lack of a GCR trend in recent decades already imply that whatever comes out of CLOUD, it’s role in attributing recent trends will be negligible, and the impact on future projections negligible.

    Where is this data? I keep hearing about it but I haven’t yet had a good source to see. I would like to take a look at it. Thanks.

  5. 205
    davidgmills says:

    RE: Post 199

    You say:

    The existing data, and the lack of a GCR trend in recent decades already imply that whatever comes out of CLOUD, it’s role in attributing recent trends will be negligible, and the impact on future projections negligible.

    I keep hearing about such data but I have yet to find a good source. Where is the data of which you speak? And what lack of GCR trend are you referring to?


  6. 206
    davidgmills says:

    RE: Post 200

    You say: “The existing data, and the lack of a GCR trend in recent decades already imply that whatever comes out of CLOUD, it’s role in attributing recent trends will be negligible, and the impact on future projections negligible.”

    I keep hearing about this data but have yet to find a good source for it. What is your source? And what do you mean by “the lack of a GCR trend in recent decades?” High solar magnetism, corresponding low cosmic radiation, and corresponding high temperatures seem like a trend to me.

  7. 207
    Andrew says:

    Re #203:

    Eastabrook claims 23 periods of global warming and cooling over the past 500 years, but erroneously focuses on just one region of the world.

    Maybe some reader don’t realize that average global temperatures for the last decade are likely greater than any decade of the past 100,000 years.

    Also, while not necessarily reflective of average global temperatures, consider that glaciers in the Alps have retreated to levels not seen for over the past 6000 years.

  8. 208
    pete best says:

    All the deniers and so called skeptics who have posted here many many times and who have been answered in a most patient and scientiic way by Gavin, Erasmus and others should explain the most prophecy (I might have overdone it a bit with that word) of climate change models and theory and hypothosis, namely that of the Arctic.

    The sea ice is acting totally out of character but not out of climate science theory, just a little faster but it is one of the strongest climate science claims and is truer (natural variability is probably helping summer sea ice melt and behaviour to) than even stated.

    The NSIDC are calling it right and the ice/water albedo affect is scientifically accurate and telling.

    Come on skeptics, give us your answer to this one and stop filling this site with endless dross that stop GISS from doing even more compelling work to demonstrate that Santa is soon going to be swimming around for most of the summer?

  9. 209
    steve says:

    re Andrew 123

    Thank you for your response. Sorry it took so long to get back to this but in my defense it is a busy time of the year. The trend of snow isn’t really what my topic was. My question was does a significant oceanic event, such as a La Nina or El Nino, effect the energy budget of the earth. Intuitively it seems it should. I was wondering if there was a study to show that it doesn’t. Perhaps this is a stupid question and everyone already knows it does and that caused the confusion?

  10. 210
    Ray Ladbury says:

    Davidgmills, There are many strands of scientific evidence indicating no trend in GCR:
    1)Single-event upset rates have not changed dramatically indicating that over the space era (which encompasses the warming epoch), there is no significant change in GCR fluxes
    2)There is no significant trend in ground-based neutron fluxes going back to the ’50s

    In addition, the “mechanism” proposed for amplifying a flux that averages 6 particles per square cm per second into a global climate signal is questionable at best. Moreover, there is the question of how such a mechanism even if operative would account for all of the other massive evidence favoring a greenhouse mechansim. One example: how does it simultaneously warm the troposphere and cool the stratosphere?

  11. 211
    Matt says:

    A few models like the NOAA CFS are now forecasting STRONG Nina conditions this winter. With subsurface temperatures now in the -4 to -5C range, this may not be far-fetched anymore.

  12. 212
    Hank Roberts says:

    > does a significant oceanic event … [affect] the energy
    > budget of the earth

    Only if you can show it changes either the incoming or outgoing energy.

    Do you find a significant change in the planet’s albedo that follows ocean cycles? Or something?

    Take a pot of ice and water on a hot stove. Measure the temperature at different points inside. Stir. Measure again.

    Did the energy balance of the system change? Significantly?

  13. 213
    steve says:

    “Do you find a significant change in the planet’s albedo that follows ocean cycles?”

    Hank, this is my question. Asking me the same question is not an answer it is mearly a reiteration of the original question. Apparently neither of us know.

  14. 214
    Julius St Swithin says:

    #208 Pete

    An alternative spin on the ice figures is that the average area of earth’s ice caps is reducing at 0.07% per annum.

  15. 215

    “[Response: Yes. Based on our understanding of climate physics, I think the likelihood of a warmer 2009 is very high. – gavin]”

    Warmer than what?

    [Response: 2008. – gavin]

    Other than increasing concentrations of CO2, what leads you to believe 2009 is going to be “warmer”, and “warmer than what?”

    I’m glad we’re having winter where I live for a change. But I’m not seeing winter disappearing magically in 9 more days.

  16. 216
    Hank Roberts says:

    Steve, I’m just another reader like you; best I can do is suggest how to look for answers while waiting to see if an expert comes along.

    Google finds some likely papers you might want to look at, just pasting in the string (they do surprisingly well with natural language questions):’s+albedo+that+follows+ocean+cycles%3F

    Seriously, look at a few of the top hits there. Question I think you may want to look into is whether there’s a persistent (ratcheting) kind of change, a “trend” — or a natural variability that would be “noisy” information.
    Scholar doesn’t with that string but does find a lot with a slightly revised string:

  17. 217
    Ray Ladbury says:

    Julius St. Swithin spins ice loss figures: “An alternative spin on the ice figures is that the average area of earth’s ice caps is reducing at 0.07% per annum.”

    That might provide some comfort if ice loss trends were linear. They ain’t. What’s more the physics says that the more ice melts, the faster the rest will go.

  18. 218


    I discussed a possible wager with someone earlier in this year that 2009 was not going to be warmer than, I think you’d said either 2005 or 1997. Care for a gentle-peoples wager at this point?

    [Response: No. – gavin]

  19. 219
    Hank Roberts says:

    Remember, if you’re in the USA, Internet gambling is illegal these days. Else

  20. 220
    Ike Solem says:

    For a very good general overview of El Nino:

    If you read that and then go to the Australian BOM page, , you can see the current conditions, a cold tounge extending west at the equator. The SOI index is explained here:

    Australia is very interested because of the El Nino effect on drought, which will be increased by a warming atmosphere:

    According to Beard, the widespread decline in Australia’s water reserves over the past five to seven years has involved numerous factors, including the two El Niño events, natural variability and climate change. “It’s impossible to disentangle these down to specific numbers, but the climate change signal will not reverse,” said Beard.

    Neville Nicholls from Monash University, in Melbourne, who is an author on recent U.N. Intergovernmental Panel on Climate Change (IPCC) reports, and a former group leader at BOM’s Climate Forecasting Group, said that predicting the impact of climate on the ENSO is complex and beyond the capabilities of current models.

    “However, all the models and physical reasoning and empirical studies all indicate that future droughts will be warmer even if they are no drier – we have already started to see this happening,” says Nicholls. “The warmer conditions will presumably lead to a greater demand for water.”

    So Australia will have to get used to living with worsening droughts and the unpredictable cycles of wet and dry are here to stay. As the BOM explains: “El Niño is not a freak of climate, it’s not a rogue weather phenomenon, and it isn’t in any way abnormal”.

    Note to William:
    Uncertainty and lack of uncertainty is the issue in the settling of science… which settles like what? It’s an open-ended approach. When cold fusion was refuted by the APS, all they said was that they were 99% sure that cold fusion was just experimental error. Would you go tell someone to invest a few billion in cold fusion, because that 1% chance justified it?

    Another example is the risk involved in living next to a nuclear power plant vs. the risk involved in living downwind to a coal-fired power plant. You will certainly be breathing in a lot of pollutants downwind from a coal plant – mercury, arsenic, sulfur and nitrogen oxides, and particulate matter of widely varying composition. For example, see this 2004 study on the air in Beijing (pdf)

    A nuclear power plant carries a risk of catastrophic failure and/or limited radioactive releases. The limited releases are the greater actual threat to anyone living nearby, and the global safety record is not too bad – it’s just that any catastrophic failure is one too many. However, faced with the certainty of inhaling coal particulates, vs. the uncertainty about radioactive releases, I’d far rather live next to a nuclear power plant.

    Perhaps one could avoid the certainty of inhaling coal emissions if you had your own personal filtered air supply… and they do build such systems, I believe. You’ll want to get one of these:

    Those aren’t the only two choices, though. I’d rather live next to solar or wind-powered generators linked to electricity storage systems. That would be the lowest-risk solution.

  21. 221
    Andrew says:

    Internet gambling is illegal in many areas, but there is no reason why a person can not take a stand and make a prediction of future average global temperatures. For example, I’m confident enough to predict that the average global temperature for 2009 will be among the top decile of the instrumented record using the NCDC database as the measure. In fact, we will all probably witness every year of the foreseeable future being in the top decile. This is based on several factors:

    First, CO2 levels are consistently rising and driving global temperatures higher. There is enough momentum in the system that even a leveling of CO2 level will not result in significant cooling for at least a decade.
    Second, the extent of spring and summer NH snow cover has shown a consistent long term trend downward, thus increasing solar absorption and may have crossed a tipping point threshold.
    Third, Methane levels, stable for the last decade have started to rise and may represent another feedback.
    Third, ENSO is predicted to be neutral for next year. Even if La Nina conditions were to develop, temperatures would likely be no cooler than 2008, which was also a top decile year. That is La Nina conditions are no longer sufficient to drive global temperature out of the top decile.
    Fourth, Solar Irradiance being at a 50 year low, is more likely to rise than to fall any further. That 2008 was a top decile year with irradiance at a 50 year low is proof enough that the sun is not driving the current rise in temperature.
    Sixth, Aerosols are not likely to increase meaningfully. Of course, this could change with a significant eruption and could eventually result in a single year not being among the top decile.

    Curious to see if anybody else is willing to make a prediction for next year before 12/31/2008.

  22. 222
    David B. Benson says:

    Andrew (221) — The committed warming from additional CO2 continues upward for many, many centruies. It takes a long time to warm the oceans.

  23. 223
    Rod B says:

    Andrew, interesting analysis. But, how do you account for the level or decreasing 5-10+year periods in the past while CO2 was continuing to rise dramatically? What’s the basis for your solar irradiance prediction? And is 2008 really a top decile? What is “a” or “among the top? Are you looking at the most recent decade?

  24. 224
    Ray Ladbury says:

    Rod, You already know the answer to your question: weather. All increased CO2 means is that it is warmer than it would be otherwise. And yes, if you look at the data, 2008 is the 9th warmest year. Would you like me to tell you anything else you already know?

  25. 225
    David B. Benson says:

    Rod B (223) — Link1:

    links back to thread with same name here. Link2

    points out the climatological year 2008 was warmer than any year last century other than 1998.

  26. 226
    dhogaza says:

    But, how do you account for the level or decreasing 5-10+year periods in the past while CO2 was continuing to rise dramatically?

    If you can’t answer this one yourself, Rod, then the lengthy period of time you’ve spent here have been totally wasted.

  27. 227
    tamino says:

    Re: #223 (Rod B)

    … the level or decreasing 5-10+year periods in the past while CO2 was continuing to rise dramatically …

    Rod, go read this. Thoroughly. Then please stop bothering us with this ludicrous argument.

  28. 228
    davidgmills says:

    So Ray and Gavin:

    I want a guarantee. I want to know for certain that if the sun goes spotless for the next thirty, forty or fifty years, we will not have another mini-ice age.

    All this data about GCR and UV may be suspect as far as you are concerned.

    But the public will want to know: Can you guarantee there will not be another mini-ice age if the sun goes spotless for decades?

    How can you make this guarantee? What do you know about the mini-ice age that makes you so certain a weak magnetic sun was not responsible for it?

  29. 229
    dhogaza says:

    But the public will want to know: Can you guarantee there will not be another mini-ice age if the sun goes spotless for decades?

    Science can’t even guarantee the sun will *exist* tomorrow. You might wake up to find that poof! It’s gone!

    But the public will want to know: Can you guarantee there will not be another mini-ice age if the sun goes spotless for decades?

    I don’t hear the public clamoring for this particular guarantee. I’m sniffing a thought train on your part that’s analogous to arguing that you won’t stop smoking unless your doctor can GUARANTEE that a truck won’t fall on your head.

  30. 230
    Ray Ladbury says:

    Davidgmills, Oh, that’s what that was. I wondered what that noise I heard earlier was. It must have been the public clambering for a guarantee that we weren’t going to have another mini-ice age!

    David, first, the mini-ice age seems to have had several causes, including increased volcanic activity and decreased solar irradiance. Second, even if we were to have a mini-ice age, it would last at most a few decades, after which CO2 would kick right back in where it left off. This is because the effects of CO2 persist for centuries, while Grand Solar Minima last at most a few decades.
    Second, if you want a guarantee, might I suggest religion rather than science.
    Third, Added forcing from CO2 probably makes a mini-ice age pretty unlikely at this point.
    Fourth, why not learn the real science before going off on some wild goose chase for a mechanism that may or may not be extant.

  31. 231
    Andrew says:

    Rob B:

    In the past, decreasing global temperature over 5 to 10 year periods were the result of natural variations. Those natural variation of course continue to exist. However, what has changed is that rising CO2 (and CH4) levels are now driving global temperatures higher to such a degree that natural variations (with the exception of large volcanic erruptions) are no longer sufficient to drive any particular year out of being a top decile year.

    The fact that 2008 was a top decile year with both solar forcing and ENSO aligning to lower temperatures is another sign that we are in a new era. Of course, the recent La Nina was not the strongest La Nina there has ever been and it was not lined up to drive all of 2008 towards lower temperature, but then again 2008 was a warm enough year that it was clearly within the top decile.

    Anyhow, I also realize that eventually, we won’t be witnessing every year falling within the top decile, but it is clear enough that that will take a long time.

    So, anybody willing to make an educated guess as to which decile 2009’s global average temperature will fall in?

  32. 232
    Hank Roberts says:

    > What do you know about the mini-ice age that makes you so
    > certain a weak magnetic sun was not responsible for it?

    I know how to look things up. You can too.

    David Mills, try this kind of search in Google:

    You’ll find discussions, for example this one cautioning about how to approach what we know:

    Solar Forcing of Past-Climate Proxies….
    NASA GISS and Columbia University Feb 2008

    Solar signals in paleo-data
    Best efforts use multiple proxies/spatial patterns
    Problems abound:
    –Non-climatic noise in data archives
    –Ubiquity of decadal variability in climate:
    –10-12 year cyclicity does not imply solar response
    –Unclear interpretation of proxies
    Wishful thinking in the literature:
    –too much correlation, not enough causation
    –phase drift often ignored (or described as ‘non-linear’)
    –explained variance often very low (or suspiciously high!)


    And you’ll find original data contributions at this page:

    Where you can download much, including just for example this paper:

    Radionuclide-based Solar Magnetic Activity, 1,000 Years, Muscheler et al. 2007, Text or Excel

    Tell us what you read.
    Remember the cautions — don’t just go browsing until you find the one paper that fits your preconceptions about The Truth. Think.

    Don’t rely on me, I’m just some guy on a blog, why believe anything I tell you?

    Do for yourself.

  33. 233
    Geoff Beacon says:

    Are there any month to month estimates of the Earth’s radiation balance similar to GISS Surface Temperature Analysis?

  34. 234
    Ray Ladbury says:

    Geoff Beacon, Well, there might be some good measurements had the current administration launched Triana instead of mothballing it. Now they’re trying desperately to launch it–after removing ALL the Earth-observing instruments.

  35. 235
    William says:

    Journal of the Atmospheric Sciences October 1973 in article titled “A parameterization for the Absorption of Solar Radiation in the Earth’s atmosphere” has an illustrative graph that shows that CO2 at most has an effect of 1 watt per square meter per 100A at wavelengths that are also duplicated by H2O. The study states “The principal absorbers in the earth’s atmosphere are water vapor in the troposphere and ozone in the stratosphere.” One of the authors was Mr. Hansen.

    [Response: why do you think this is interesting here? None of the models would work at all if they didn’t take into account the absorption of solar by water vapour. I do hope you are not confusing absorption of short-wave solar radiation with the absorption of long wave radiation from the surface, which as I’m sure you know is the famed ‘greenhouse effect’. – gavin]

  36. 236
    Rod B says:

    Ray, David, dhogaza, tamino, Your paranoid defensiveness is showing. I wasn’t asking anything for my understanding. I was asking Andrew for his explanation following his assertion that 2009 will be hotter because of increased CO2, not because of random weather changes. Odd how Andrew’s assertion did not seem to bother anyone. Especially since David, et al are wrong or misleading in reading the GISS references. 2008 is the coolest year since 2001, the 3rd coolest in the past decade, and “between the 7th and 12th warmest” year since 1880(?). I’m not sure what Andrew meant by decile — why I asked — and that of course might change things here. (not that anyone cares about little details of fact, though…)

  37. 237
    Rod B says:

    Andrew (231), just read your post. If decile means “in the top ten” then your statements make sense. You implied that there was something extraordinary about the CO2 effect in 2008 (which I contended would be incorrect), while I suspect you meant that the factors mitigating temperature rises will be less than in some previous periods. Yes?

  38. 238
    Ike Solem says:

    Mini Ice Age? Anyone see this:

    The paper in the press release is on the role of pandemics in causing a spike in reforestation across the Americas from the period ~1500-1750, based on sediment studies of carbon isotopes:

    “We looked at ice cores and tropical sponge records, which give us reliable proxies for the carbon isotope composition of atmospheric carbon dioxide. And it jumped out at us right away,” Nevle said. “We saw a conspicuous increase in the isotope ratio of heavy carbon to light carbon. That gave us a sense that maybe we were looking at the right thing, because that is exactly what you would expect from reforestation.”

    During photosynthesis, plants prefer carbon dioxide containing the lighter isotope of carbon. Thus a massive reforestation event would not only decrease the amount of carbon dioxide in the atmosphere, but would also leave carbon dioxide in the atmosphere that was enriched in the heavy carbon isotope.

    The reforestation scheme (photosynthesis drawing down CO2 over a long period) fits the cooling trend better than either solar variability or volcanic eruptions. There can be multiple events involved besides just altering atmospheric CO2 levels – for example, as marshes turn into forests natural methane emissions are reduced, and less agriculture means a reduction in methane emissions as well.

    That was a slow change over many years… and if that can induce a little Ice Age, the much larger changes of today should have a larger effect, and probably for a longer period of time than 250 years.

  39. 239
    dhogaza says:

    If decile means “in the top ten” then your statements make sense.

    Top tenth, actually …

    And, Andrew’s wording is very clear …

    The fact that 2008 was a top decile year with both solar forcing and ENSO aligning to lower temperatures…

    He didn’t imply there was anything “extraordinary” about the CO2 effect in 2008.

    Nor did he say this:

    I was asking Andrew for his explanation following his assertion that 2009 will be hotter because of increased CO2

    He quite clearly stated that 2009 is predicted to be ENSO-neutral, rather than La Niña/cooling. He quite clearly stated that since 2008 has seen a 50-year solar minimum, his guess is that solar output is more likely to increase or remain constant in 2009, rather than go down further.

    So, all things being equal, one might expect 2009 temps to be higher than 2008. Increasing CO2 makes it more likely, but nowhere does he sat what you claim he says.

    Go read what he said again. I’m sure you can figure it out.

  40. 240
    Ray Ladbury says:

    Rod, You said, “But, how do you account for the level or decreasing 5-10+year periods in the past while CO2 was continuing to rise dramatically?”

    I answered weather, and that you already knew the answer. How is it paranoid to respond to what you wrote? Precision matters in science.

  41. 241
    Pat Neuman says:

    Something weird is happening to Arctic sea ice lately. The rate of change in extent has flattened to near zero. The implications are astounding.

  42. 242
    Hank Roberts says:

    Pat, check the ocean temperature outside the Arctic basin. Sea ice about filled up the basin early in December, per the same NSIDC page.

    Pure speculation follows; perhaps this warm water
    is delaying formation of sea ice outside the Arctic?

  43. 243
    davidgmills says:

    Oh, I haven’t been guaranteed that there will be global warming? I must have missed something.

    You guys apparently don’t know a guarantee when you give one:

    “CO2 would kick right back in where it left off.”

    Is this an implied guarantee or an outright express guarantee, because I’m confused.

    But it is just as I suspected, no one here really seems to have a clue about what decades and decades of low solar magnetism would do to climate models.

    And yet we have scientists who are predicting by 2014 or 2015 the magnetism of the sun will be so low as to produce no sunspots.

    Fess up guys. You don’t know jack about the sun.

    [Response: Neither do the people you are quoting. If instead of warbling on about guarantees (which don’t exist), you’d asked simply what is the relationship between the radiative forcing expected from a prolonged solar minimum and the expected forcing from increasing CO2, you would have got a much more productive answer (assuming of course that is what you actually wanted). The forcing from a solar minimum (compared to the mean) is about 0.12 W/m2, the extra forcing from 10 years of CO2 increasing at ~2ppm a year is 0.27 W/m2, 20 years +0.78 W/m2 etc. Therefore, after approximately 5 years, the CO2 change would dominate, even assuming we were in radiative equilibrium to start with (which seems unlikely). Thus there is no evidence that the solar change would dominate even over a decadal period. – gavin]

  44. 244
    Hank Roberts says:

    PS, Pat, I’d also wonder if that’s not a data glitch, comparing it to the Cryosphere Today image. Has anyone asked NSIDC about it directly?
    “downfall plant being” says ReCaptcha
    Trouble with plankton?

    [Response: Yes. – gavin]

  45. 245
    Jim Cross says:

    Gavin and Hank

    Nice weather report! :)

  46. 246

    241-242, Pat, Hank… Read the report, is nice, but misses the cloud bit, last year had more open water hence more latent heat from freezing sea water, yet it was a bit colder last year vicinity of the Pole, DWT temperatures quite warm in November. Sea water was warmer last year during the summer super melt, so I doubt that sea water has something to do with this. Tropical Thunder clouds begets more Arctic low clouds, so it seems, fall of 2008 being a busy year for hurricanes, ie tropical cloud activity, it stands to reason that there was more aerosol seeded clouds here, hence more heat, thinner ice, warmer surface air. For the GCR “gives more clouds” gang, explain why I see 5.2 mag stars now, in finally super cold weather (starting from the South), it appears to me that aerosol activity is abating and clear skies are finally starting to expand.

  47. 247
    Hank Roberts says:

    > 241, 242, 244

    Not a data glitch:

    “The NSIDC’s Mark Serreze responded to my question about the recent data on Arctic sea ice extent, using their own data:

    ‘We are quite certain that the almost complete lack of increase in ice extent since about December 10 is real. ….Past 10 days has also seen a very unusual atmospheric pattern. It has been very warm over the Arctic Ocean, and wind patterns have favored a compact ice cover. … appears to be weather related versus climate related. It will be interesting to see what happens over the next week.’

  48. 248
    Ray Ladbury says:

    Davidgmills asks: “Is this an implied guarantee or an outright express guarantee, because I’m confused.”

    Actually, it’s called science. Maybe you want to try it some time. And I will certainly admit I don’t have any idea how you take a flux of 6 particles per square cm per second and amplify it into significant warming event. But then, from what I’ve heard, nobody else can do much with that problem but wave their hands so hard the levitate.
    Now, CO2, that I understand. It’s documented, verified and well understood. But, again, David, that’s science–you know where you explain things in terms of the understood and not in terms of totally speculative mechanisms that seem to be contra-indicated by the evidence.

  49. 249
    Rod B says:

    Ray, ’cause your answer had no bearing on my question, which was what Andrew knew, not what I knew (or didn’t know).

  50. 250
    Andrew says:

    When it comes to average global temperature, there are no guarantees since a climatically significant volcanic eruptions randomly occur. However, the physics of CO2 warming is strong enough that the odds are very good for next year to be among the warmest of the instrumental record. This prediction is not limited to 2009 and will likely be true for every year of the foreseeable future until a climatically significant volcanic eruption actually occurs.

    With regards to the sun and its impact on climate, consider that solar cycle was at a minimum in 1986.
    Any guess as to where the years 1987 and 1988 were ranked for average global temperatures?

    Likewise, consider that sunspots in 1996 were at a minimum and solar irradiance was at a lower value than in 1986.
    Any idea as to where the years 1997 and 1998 were ranked for average global temperatures?

    This is not to suggest that 2009 and 2010 will each establish new maximum average global temperatures, but going forward such records can be expected to be broken every few years.