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Full IPCC AR4 report now available

Filed under: — group @ 29 April 2007

The complete WG1 IPCC 4th Assessment report (AR4) is now available online. It’s missing the index and some supplemental data, but all should be available by May 7.

Over the next few weeks we’ll try and go through the report chapter by chapter, but since this is likely to the key reference for a number of years, we can take a little time to do it properly. Happy reading!


205 Responses to “Full IPCC AR4 report now available”

  1. 101
    Jim says:

    The Second Draft for WG1 from several months ago said the following in Chapter 8 (Climate Models and Their Evaluation), Question 8.1: “As a consequence, models continue to display a substantial range of global temperature change in response to specified greenhouse gas forcing (refer Chapter 10), To date it has not been possible to quantify how errors in a model’s simulation of specific climate observations impact on errors in its future climate projections, but a few studies suggest this may be possible in the future. Despite such uncertainties,…”

    In the final version that was just released this was changed to the following:

    “Consequently, models continue to display a substantial range of global temperature change in response to specified greenhouse gas forcing (see Chapter 10). Despite such uncertainties,…”

    The key phrase eliminated here is “it has not been possible to quantify how errors in a model’s simulation of specific climate observations impact on errors in its future climate projections.” In effect, didn’t the Second Draft said that we can’t quantitatively bound errors in climate forecasts generated by global climate models?

    Why was this eliminated? Did some new research become available or better understood?

    [Response: I’d guess it was because it just didn’t fit. The previous sentence says there are uncertainties, and the next explains what is robust. The missing sentence is related to a distinct issue which is to what extent errors in climatology lead to errors in projections, or even if they do to any significant extent. That is dealt with more comprehensively in Chapter 10. Your rephrasing of the sentence is not the same thing at all. – gavin]

  2. 102
    Ike Solem says:

    RE#42, stephen – current estimates are still for a nuclear plant to take some 5-10 years to construct, and the point is that it’s better to invest in solar cell manufacturing (which produce sources of power, not just power) than in new nuclear facilities. As far as the 70’s versus today, there is nuclear construction going on in India, and individual plant investments are still around 3.5 billion $US. This is still better than using coal for electricity generation, but in the long run nuclear fission is a dead-end technology. The solar resource is far larger and mostly untapped, in contrast to nuclear (~20% of current US electricity generation). Why doesn’t it make sense to boost solar to the same level as nuclear?

    RE#78 – Timothy, I have to admit that that was a quote lifted from the IPCC report. The issue is very complicated what with black carbon and the effects of stratospheric vs. tropospheric aerosols, as you point out.

    RE#100 – CO2 effects on plant growth are well studied and the fact is that there is no evidence that a warming, high CO2 world will result in higher crop yields for a number of reasons: drought, heat waves, nitrogen and phosphorous limitation, etc. It was thought that the increase in CO2 would offset crop losses due to climate change, resulting in a zero-sum effect, but that’s not supported by real-world experiments: Food for Thought: Lower-Than-Expected Crop Yield Stimulation with Rising CO2 Concentrations, Long et al Sci 2006.

    To quote from the science magazine summary: “Although rising CO2 levels may reduce global crop yields through the effects of higher temperatures and decreased soil moisture, arguments have been made that direct fertilization effects will more than offset these losses. Long et al. (p. 1918; see the Perspective by Schimel) present a critical analysis of data on which the Intergovernmental Panel for Climate Change base their projections that elevated CO2 will have a fertilizing effect. The original estimates came from experiments conducted in the 1980s in greenhouses and sheltered enclosures. More sobering figures are derived from open-field studies in which increased CO2 levels enhanced crop yields ~50% less than in enclosure studies.”

    Keep in mind that the IPCC report doesn’t include recent research, and is a valuable reference but not the last word on the topic of climate change.

  3. 103
    Timothy Chase says:

    IPCC AR4 Report. Ok.

    In #71, Ray Landbury states,

    Trevor, CO2 stimulates plant growth only to the extent that there are no other limiting factors. I believe Hank posted on this several posts back. The short answer is that it’s mixed. Some plants do better and some do worse. As I recall, weeds thrive. So, yes, this has been looked at.

    The other misunderstanding reflected by your post is that unless the plant growth involved is dominated by long-lived woody plants, there isn’t much increase in long-term sequestration of carbon. Indeed, as the plants die and decay, a lot of the carbon goes back into the system as CH4, and so actually increases greenhouse efficiency. This straw has been grasped at repeatedly, and hasn’t supplied much bouyancy so far.

    Comment by ray ladbury â?? 1 May 2007 @ 8:25 am

    In #86, B. Buckner states,

    In #71 you discuss stimulated plant growth and the lack of long-term sequestation of carbon that results from the increased growth. There is actually quite a bit of information to the contrary. The article below is a good place to start.

    http://www.co2science.org/scripts/CO2scienceB2C/articles/V10/N18/EDIT.jsp

    Later, in #100, B. Buckner states,

    Well low and behold, section 7.3.2.2.3 of the IPCC AR4 Report “Residual Land Sink” cites the same paper and comes to the same conclusions as the misleading, laughable, PR advocacy, cherry picking, Exxon-Mobil funded, fossil fuel duping CO2Science site.

    Rather than making ad hominem attacks on the authors, perhaps we can deal directly with the science involved.

    Looking at section 7.3.2.2.3, it states:

    Recent studies of the carbon balance of study plots in mature, undisturbed tropical forests (Phillips et al., 1998; Baker et al., 2004) report accumulation of carbon at a mean rate of 0.7 ± 0.2 MgC ha-1 yr-1, implying net carbon uptake into global Neotropical biomass of 0.6 ± 0.3 GtC yr-1. An intriguing possibility is that rising CO2 levels could stimulate this uptake by accelerating photosynthesis, with ecosystem respiration lagging behind. Atmospheric CO2 concentration has increased by about 1.5 ppm (0.4%) yr-1, suggesting incremental stimulation of photosynthesis of about 0.25% (e.g., next yearâ??s photosynthesis should be 1.0025 times this yearâ??s) (Lin et al., 1999; Farquhar et al., 2001). For a mean turnover rate of about 10 years for organic matter in tropical forests, the present imbalance between uptake of CO2 and respiration might be 2.5% (1.002510), consistent with the reported rates of live biomass increase (~3%).

    As such, plants may act as a sink for the sequestration of carbon – just as CO2Science claims.

    However, looking at the following paragraph, section 7.3.2.2.3 also states:

    But the recent pan-tropical warming, about 0.26°C per decade (Malhi and Wright, 2004), could increase water stress and respiration, and stimulation by CO2 might be limited by nutrients (Chambers and Silver, 2004; Koerner, 2004; Lewis et al., 2005; see below), architectural constraints on how much biomass a forest can hold, light competition, or ecological shifts favouring short lived trees or agents of disturbance (insects, lianas) (Koerner, 2004). Indeed, Baker et al. (2004) note higher mortality rates and increased prevalence of lianas, and, since dead organic pools were not measured, effects of increased disturbance may give the opposite sign of the imbalance inferred from live biomass only (see, e.g., Rice et al., 2004). Methodological bias associated with small plots, which under-sample natural disturbance and recovery, might also lead to erroneous inference of net growth (Koerner, 2004). Indeed, studies involving largearea plots (9-50 ha) have indicated either no net long-term change or a long-term net decline in above ground live biomass (Chave et al., 2003; Baker et al., 2004; Clark, 2004; Laurance et al., 2004), and a five-year study of a 20 ha plot in Tapajos, Brazil show increasing live biomass offset by decaying necromass (Fearnside, 2000; Saleska et al., 2003).

    (Emphasis added.)

    This would seem to be precisely the point that Ray Landbury was making in #71.

    Cherry-picking.

  4. 104
    Jim says:

    Re: 101

    Gavin,

    Thanks for your immediate response.

    If the issue being addresses in this point was “a distinct issue which is to what extent errors in climatology lead to errors in projections, or even if they do to any significant extent”, is there some known bound on this error, or is it an undefined potential error?

    Can you point me to the portion of Chapter 10 where it is addressed?

    Thanks in advance.

    Best,
    Jim

  5. 105
    Timothy Chase says:

    Ike Solem wrote (#102 in response to #100):

    Keep in mind that the IPCC report doesn’t include recent research, and is a valuable reference but not the last word on the topic of climate change.

    I completely agree.

    However, judging from what I uncovered in #103, they seem to have done a very good job of anticipating the more recent research.

    Nice.

    Thank you for bringing the article to our attention – it is good to see that sort of confirmation.

  6. 106
    Timothy Chase says:

    Jim wrote (#104):

    If the issue being addresses in this point was “a distinct issue which is to what extent errors in climatology lead to errors in projections, or even if they do to any significant extent”, is there some known bound on this error, or is it an undefined potential error?

    Can you point me to the portion of Chapter 10 where it is addressed?

    I would recommend “10.5 Quantifying the Range of Climate Change Projections.” In essence, what we are dealing with are a hierarchy of models, some wider, yet coarser (due to limitations on computational power), others narrower and more detailed. Then with parametrization it is possible to make probablistic projections, compare these against the evidence by means of Bayesian analysis, fine-tune the narrower, more detailed theories by adjusting their parameters and use these to adjust the wider, less detailed theories. Or so it would appear from my first skimming of the first section.

  7. 107

    Re #80 Where Tamino wrote “Let’s all face the truth: global cooling from the 40s to the 70s is a myth.”

    The dispute is not about whether there was cooling during the 1970s. It is whether there was a scare about an impending ice age. That is not a myth. William Connolley has documented the evidence very well, though his spin on it all is highly questionable. See the comment by the science author Nigel Calder at: http://www.wmconnolley.org.uk/sci/iceage/calder.html

    As far as the cooling in the 1970s goes, the Northern Hemisphere was cooling at the start of the 1970s when the scare started. See http://www.cru.uea.ac.uk/cru/data/temperature/nhshgl.gif

    Of course thhe NH is where the scientists lived. This only makes more clear the point I am trying to make. Scientists do make mistakes. In the early 1970s they could see the world around them cooling and deduced that it would continue and was global, despite the fact that the southern hemisphere was warming.

    But you too are making a mistake. Glacial periods are driven by the positive ice-albedo feedback from advancing NH ice sheets. Thus changes in global temperatures need not necessarily be the best guide to future climate. This was discussed here: Does a Global Temperature Exist? Therefore, in Earth Science, where the systems under discussion are fractal and chaotic, it is wrong to apply simple mathematical techniques such as linear trends and Bayesian logic to make predictions.

    So, using a linear trend to estimate the size of the future Arctic sea ice sheet is a simplification too far. The winter trend is different from the summer trend, and so is the annual trend. Brooks showed that there is a tipping point, where if the size of the summer ice drops below a minimum value then the winter ice can not reform. Without that ice, the Earth’s thermostat is broke. How high will temperatures rise then, and how far from the North Pole will be affected?

    Think about it! Mathematics is not the answer to a world in crisis!

  8. 108
    pete best says:

    IS IT TOO LATE TO PREVENT WHAT IS KNOWN AS “DANGEROUS” CLIMATE CHANGE

    Fact number one aboout climate change is politicians in the UK seem to keep on referring to CO2 levels and not greenhouse gas levels. Greenhouse gases currently reside at 459 ppmv whilst CO2 levels are 380 ppmv. Is this true ? It is according to George Monbiot, a well known UK left wing environmentalist.

    He then goes on to tell us that the IPCC projections for the alleged 2 C of warming “so called dangerous climate change becuase it is then out of our hands” are around 510 ppmv CO2 equivilent so there is way on earth then this is going to be met considering that it is going to take another 50 ppmv before any of this changes in any discernable and another 50 ppmv after that until we have any solution.

    James Hansen tells us that it can be done if we (USA I believe) do not burn anymore coal but that is just not realistic unfortunately and sequestration does not exist in commercial forms as yet and the USA wants to build 159 new coal fired powerstations starting soon that this technology exists.

    Just how long do the people of real climate believe they have to stop the so called 2 degree celcius threshold?

    The aeticle can be found here: http://www.monbiot.com/archives/2007/05/01/1058/. I am presuming that in the main his deliberations on greenhouse gas levels are correct.

  9. 109

    cce — Spencer Weart’s “The Discovery of Global Warming” (2003) is a good one, and if I’m not mistaken you can buy used copies on Amazon for as little as $2.49. It’s also available on-line somewhere for free, but I don’t have the URL offhand.

    John Houghton’s “Global Warming: The Complete Briefing” (2004) is another good one.

  10. 110

    Re #62 — the effect from doubling CO2 by itself is to raise the ground temperature by about 1.2 K. But with feedbacks like water vapor and ice/albedo, this goes to about 3.0 K, just like the IPCC says.

  11. 111

    Re #73 — Ray has a point. I often cite data without telling anyone where I got it from. I’ll try to cite sources from now on. On peer-reviewed journal articles, I’ll try to give the whole citation, if I can remember it or look it up.

  12. 112

    Re #80 and [[Let’s all face the truth: global cooling from the 40s to the 70s is a myth. ]].

    Tamino, I am reluctant to disagree someone who is much better at statistical analysis than I am, but I think that climatologists in general do tend to portray 1940-1970 as an era of cooling. My guess is that it’s not exactly when temperatures were declining that was the issue, but the overall slope for that period compared to the overall slope for earlier and later periods. There is definitely a discontinuity in the graph in this area. Inspecting it visually, it’s hard not to treat 1940-1970 as a distinct period:

    http://data.giss.nasa.gov/gistemp/graphs/

    If you want to rename it as “global temperature stasis” rather than “global cooling” you might have a point.

  13. 113

    [[I was asked to ask you good people whether you think the Hiroshima/Nagasaki/above ground A-bomb tests might have generated enough airborne debris to contribute significantly to the cooling effect ]]

    Almost certainly not.

  14. 114
    Ray Ladbury says:

    Re: Temperature anomalies from 1940-1975. Whether you call it cooling or simply a hiatus in the warming, there certainly was something anomalous about the period. There are a number of things that make it a little difficult to attach a label. First, the 1930s and early 40s saw accelerated warming compared to previous decades–perhaps a product of emerging from the depression and this was followed in the latter part of the 40s by a definite cooling trend lasting a few years. However, how prominent this trend is depends on the dataset you look at–it’s much more evident in the land-ocean index than in meteorological stations.
    Historically, there were some scientists who expressed concern about the cooling, probably with an eye on the end of the interglacial. There were also some who attributed the cooling to aerosols–a viewpoint supported by current models.
    What is certainly true is that there was nothing like the overwhelming consensus we now see. The warming is indisputable, and the only cause that comes close to explaining is anthropogenic ghg emissions.

  15. 115
    Timothy Chase says:

    Alastair McDonald (#107) wrote:

    But you too are making a mistake. Glacial periods are driven by the positive ice-albedo feedback from advancing NH ice sheets. Thus changes in global temperatures need not necessarily be the best guide to future climate. This was discussed here: Does a Global Temperature Exist? Therefore, in Earth Science, where the systems under discussion are fractal and chaotic, it is wrong to apply simple mathematical techniques such as linear trends and Bayesian logic to make predictions.

    So, using a linear trend to estimate the size of the future Arctic sea ice sheet is a simplification too far. The winter trend is different from the summer trend, and so is the annual trend. Brooks showed that there is a tipping point, where if the size of the summer ice drops below a minimum value then the winter ice can not reform. Without that ice, the Earth’s thermostat is broke. How high will temperatures rise then, and how far from the North Pole will be affected?

    But they aren’t using simple linear trends. They are modeling non-linear behavior through each day of each year, and making use of a rapidly expanding wealth of data against which their theories can be tested through both predictions and postdictions. Bayesian methods may then be applied. Then as more data becomes available the process can be repeated reiteratively.

    Think about it! Mathematics is not the answer to a world in crisis!

    Of course not.

    But it is half of the answer. The first half.

  16. 116
    Hank Roberts says:

    > Spencer Weart’s “The Discovery of Global Warming” …available on-line …
    It’s in the sidebar, right side of the page:
    Science Links
    * AIP:Discovery of Glob. Warm.

  17. 117

    Re #115

    Timothy, you obviously have not being studying the poster linked by SCM at http://cires.colorado.edu/events/members/posters/2007/I25M.pdf

    Figure 1 shows attempts to linearise sea ice extent, and Figure 2 shows how the predictions have failed.

    The Summary states “… none or very few individual model simulations show trends comparable to observations.” and “… the IPCC models underestimate the GHG response …”

    The scientists overestimated teh danger in the 1970s but now they are under estimating it :-(

  18. 118
  19. 119
    tamino says:

    Re: linear trends

    It should be emphasized that using linear regression to test for a trend does not assume, or impose, or rely on, the existence of a linear trend. In fact the trends which are so detected are almost never linear.

    The real purpose of linear regression for trend testing, is to test the null hypothesis: that there is no trend (of any kind). If the linear regression gives a statistically significant result, then we haven’t proved a linear trend — all we’ve proved is that there is some trend rather than none. Unfortunately, even many scientists don’t really appreciate this fact.

    One of the reasons for the popularity of linear regression for trend testing, is that it is a very sensitive test. Most trends, no matter what the type, will give a statistically significant response to linear regression, and the regression rate will be indicative of the size of the trend. Another reason for its popularity is that its statistical properties are well understood.

    Actually demonstrating that a given trend is linear, is an enormously more difficult statistical procedure.

  20. 120
    L says:

    Is there any email address for correction if I see typos in the report?

  21. 121
    Steve Bloom says:

    Re #103 and prior: As discussed in the other current thread on CO2 measurement, large urban areas tend to have distinctly higher levels of CO2, on the order of 50-100 ppm more than the global average. If there were a significant CO2 fertilization effect that would dominate other environmental factors, it seems to me that one would expect to see the results in those urban areas. Admittedly this is not a scientific assessment, but I sure haven’t noticed anything in my garden (Oakland, CA), or in the vegetation in the small urban park adjacent to my house, or in the extensive park system running up and down the spine of the East Bay hills. OTOH, the University of California does maintain an experimental agricultural station not far from where I live, so presumably they would have been in a position to notice something. I suppose one could respond that other environmental factors accompanying the CO2 increase might have acted to limit the effect. Indeed.

    Re #107: “Brooks showed that there is a tipping point, where if the size of the summer ice drops below a minimum value then the winter ice can not reform.” Alastair, could you provide a pointer to the source for that? Thanks.

  22. 122
  23. 123
    Jim Crabtree says:

    #121 – Steve Bloom:

    You might want to check the pollen count. (Your local environmental people probably have records going back 10+ years). Pollen count here in the SE US has been increasing for some number of years. Also, think about this – most plants probably don’t know how to respond to increased CO2 since it is higher now than it has been in over 650K years. Posion ivy does – see the following link.

    http://news.nationalgeographic.com/news/2006/05/060530-warming.html

    There are over vines that also respond in a similar way to CO2 fertilization. Haven’t seen anything on how kuzdu responds.

  24. 124

    I hate to change the subject but has anyone heard of anything coming out of the FSU Andrill Workshop?

    Anyone in the know blogging out of there?

    http://www.andrill.org (Check out the Betty Blog!)

    http://www.fsu.edu/news/2007/04/25/global.warming/

  25. 125
    Timothy Chase says:

    Alastair McDonald (#117) wrote:

    Timothy, you obviously have not being studying the poster linked by SCM at http://cires.colorado.edu/events/members/posters/2007/I25M.pdf

    Figure 1 shows attempts to linearise sea ice extent, and Figure 2 shows how the predictions have failed.

    The Summary states “… none or very few individual model simulations show trends comparable to observations.” and “… the IPCC models underestimate the GHG response …”

    The scientists overestimated the danger in the 1970s but now they are under estimating it.

    That doesn’t exactly look like they were attempting linear modeling.

    However, you are right – the ice appears to be melting about 50% faster than our models would predict. This was brought up by either Gavin or Eric a little bit ago. In any case I agree that it would seem there is plenty to worry about, but I honestly don’t think that climatologists are (by-and-large) underestimating the seriousness of the problems we face. Rather, they are having difficulty modeling them – particularly in the case of ice. Complicated stuff. Its a learning process. Moreover, if they could change policy, undoubtedly they would. But it isn’t up to them. They have to convince others – and better modeling will help in this regard.

    In any case, thank you for the link.

    I am quite interested in this area – for a number of reasons. For example, what is the likelihood of a catastrophic collapse of a given ice shelf? How long can we actually expect arctic ice to last? What will rising temperatures in the arctic mean for oxygen circulation in the ocean? The carbon cycle? What about shallow methane hydrates? These are all linked – and each will have important ramifications.

  26. 126
    Rod B. says:

    tamino, I possibly could accept your statistical analysis, but why is the literature rife with graphs that show (all with wobbles) level global temps from 1870 to 1900, an odd drop from 1900-1910, a fairly decent steady rise from 1910 to 1940, a modest but definite drop (about 0.1 degreeC) from 1940 to 1970, and a rise from 1970 or so on. There must be hundreds of ‘em. How can that be?

  27. 127
    Hank Roberts says:

    >Andrill
    I’ve been asking too; last I heard, the last ice cores are on a ship somewhere. There were a few news stories (Google News turns up a couple new since the last time I checked). Big meeting happening right now.

    Digital data should be available here:
    http://www.arf.fsu.edu/digitaldataCP.cfm
    http://www.arf.fsu.edu/Data/CorePhoto.pdf

  28. 128
    James says:

    Re #102: […in the long run nuclear fission is a dead-end technology.]

    In the long run, so is solar. The sun will be too dim in what, only a billion years or so? So strictly speaking, both technologies are dead ends, but only after periods that are far longer than the likely span of human civilization.

    [The solar resource is far larger and mostly untapped, in contrast to nuclear (~20% of current US electricity generation). Why doesn’t it make sense to boost solar to the same level as nuclear?]

    We’ve been through this before, at length. It’s not a case of one versus the other. It does make sense to boost solar, and use it wherever it is practical. The problem is that there are a lot of places and uses for which it is not practical. We need solar and nuclear – and geothermal, wind, biomass, and whatever else people can think of.

  29. 129
    Caz says:

    Re: 81

    Let’s all face the truth: global cooling from the 40s to the 70s is a myth

    Not in the Arctic (or Greenland) it isn’t.

    Incidentally what has happened to the GISS station data – I can’t access it now?

    Also how is the 5.35xln(..) formula for CO2 forcing determined?

    thanks

    Caz

  30. 130
    barry says:

    Hello again,

    I’m trying to reconcile some figures in an argument about solar variability. Unfortunately, I’m a base layman – if anyone troubles to help, I’d very much appreciate it.

    http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Ch02.pdf – p. 191

    From table 2.10 in IPCC AR4WG1, figures for ten studies are given between 0 and 0.68(Wm-2) for the period from the Maunder Minimum. Best estimate IPCC figure of 0.12(m-2) falls roughly in the middle of the last three figures given in that table. Is it that the range of these 3 are solely employed because they excluded “original stellar brightness distribution, or the use of the brightness reduction in the Baliunas and Jastrow”? The argument I’m having is about the validity of “ignoring” or dismissing the higher figures.

    The highest figure in the table, 0.68 (Wm-2), came from Solanki and Fligge
    (1999). Looking at more recent studies by Solanki (and colleagues), I’m trying to figure out how to translate a figure cited by Solanki and Krivova (2004) http://www.mps.mpg.de/projects/sun-climate/papers/solphys-2004.pdf. To whit;

    “On a longer (and for climate studies more important) time scale things are less
    certain. The cyclic component of irradiance variations can be reconstructed back
    up to 1610, although with decreasing reliability and accuracy at earlier times. The
    magnitude of any secular trend remains a matter of intense debate. A recent, careful
    estimate by Foster and Lockwood (2004) gives a value of only 1.7Wmâ��2.”

    Is 1.7Wm�2 measuring solar variance from MM as per the 2.10 chart? (And if so, how come it is 2.5 times higher than the highest figure therein?) The 2004 Solanki/Krivova paper study rejects Baliunas and Jastrow (which was included in the Solanki/Fligge (1999) calculations via Lean et al (1995) as far as I can make out), and acknowledges that solar variance estimates have trended downwards in light of recent studies. I noticed a figure given in a 2007 Balmaceda Krivova Solanki study at 1.3 (http://adsabs.harvard.edu/abs/2007astro.ph..3147B);

    “The model predicts an increase in the total solar irradiance since the Maunder Minimum of about 1.3 rm{Wm$^{-2}$}” [That last equation looks like gobbledygook to me]

    From a Solanki/Fligge ‘high’ of 0.68 (Wm-2) in IPCC AR4WG1, to a more recent figure that is ‘only’ 1.72 Wm-2 (cited in what seems to be a crestfallen tone by Solanki and friends).

    Perhaps the IPCC figure 0.12 is not measuring from MM? But lo, it appears in the section 2.7.1.2 Estimating Past Solar Radiative Forcing.

    How do I relate these figures? Why do Solanki and colleagues lately imply that solar variance is less than ‘most previous estimate’, yet supply what appear to be higher figures? If this is too baby to deal with, I’m very good at following links. :)

    Cheers,

  31. 131

    [[ We need solar and nuclear – and geothermal, wind, biomass, and whatever else people can think of. ]]

    No, we don’t. We need that mix, or another mix that leaves one or more of those components out — like nuclear. I don’t think we have to have any individual component. There are a number of ways to power society without fossil fuels.

  32. 132
    Nereo Preto says:

    Someone linked my name in a previous post (#18) to a “damn spammer” writing. Perhaps because I posted the URL of a wiki? I hardly conceive it could be seen as spamming, and -as far as I know- only God knows whether I’m damned or what.

    However, let me put that argument in a way that does not hurt anyone’s sensibility.

    Pete Best (#21) correctly pointed out that there are places, e.g., USA, where Anthropogenic Global Warming is not yet a fact given for granted.
    Real Climate is doing a TERRIFIC job about that (by the way, thanks!), but it seems to me it usually drifts technical. Most non-educated people probably would find difficult to follow it.

    So I wonder if scientist, pricipally those who know better this IPCC report, should find other ways to reach those people.

    I’m sure many give public conferences, or go to radio stations, and so on. I do so, at a local scale.

    I’d like to suggest another way to reach less-educated people may be considered, which is posting in widely read wikis, in a style understandable by somehow less educated people than Real Climate readers. Some wikis can guarantee that well written articles are not screwed by other contributors, others cannot. However, when yo type a “difficult word” in Google to look for a definition, the most famous wiki very often appears in the first page. This implies many read it. This implies reaching the bulk of people surfing the internet.

    Is someone already doing it? Is this responsability of scientists? Dunno, but I often ask myself when the things I do start to have public relevance, as the IPCC reports surely have.

  33. 133
    Nick Gotts says:

    Re #128 Actually, the sun is getting brighter, not dimmer. I’ve seen it hypothesized that over geological time, the brightening sun speeds up the erosion-driven carbonate-silicate cycle, reducing atmospheric CO2 levels – and that this temperature-stabilising feedback will fail in 600-1000 million years, after which the oceans will boil and we’ll have a true runaway greenhouse effect (time for the orbital mirrors in the unlikely event anyone is there to put them up). As for “We need solar and nuclear – and geothermal, wind, biomass, and whatever else people can think of.”, well there are complementarities between some of these, but there is also competition between them for R&D resources including skilled labour, government subsidies and economies of scale. We need to determine which of them, in what mix, will give the best results, in relation to climate change, and whatever other advantages and drawbacks they have.

  34. 134
    tamino says:

    Re: #126 (Rod B.)

    … why is the literature rife with graphs that show (all with wobbles) level global temps from 1870 to 1900, an odd drop from 1900-1910, a fairly decent steady rise from 1910 to 1940, a modest but definite drop (about 0.1 degreeC) from 1940 to 1970, …

    Let’s look at some of those graphs. When it comes to estimating global average temperature, I think we’d agree that the two “big guns” are NASA GISS and HadCRU. Here are their graphs:

    http://data.giss.nasa.gov/gistemp/graphs/Fig.A2_lrg.gif

    http://www.cru.uea.ac.uk/cru/info/warming/

    Examine the time interval 1950 to 1970. There’s no visible warming in either the GISS or HadCRU graphs. When you run the numbers, there’s no significant trend in the numerical analysis either. In fact, even if you don’t take into account the autocorrelation of the data, there’s still no trend — it’s not even close.

    If you focus on the time interval 1940 to 1970, there’s a distinct drop in the late 40s, followed by reasonably constant temperatures 1950 to 1970. The point I’m trying to make is that “cooling for 7 years followed by flat-as-a-pancake for two decades” does not constitute three decades of cooling.

    I don’t dispute that it was cooler in 1970 than in 1944. But that most assuredly does not mean that we had cooling from 1940 to 1970. I think this is one of those myths that was simply never called into question, so it’s become a scientific “urban legend.”

    How did this come about? Looking at the entire data set (GISS or HadCRU), it’s not unnatural to isolate the time interval 1940 to 1970 (although 1944 to 1975 is a better choice). If you do a linear regression on that data, and you fail to account for the autocorrelation of the data, then you get a significant trend. But first, when autocorrelation is included, the trend is found not to be significant. Second, as I said in an earlier post, a statistically significant result from linear regression does not establish linearity of a trend (it simply contradicts the absence of a trend). “Global cooling from 1940 to 1970″ doesn’t stand up to close scrutiny.

  35. 135
    Ray Ladbury says:

    Re 126, Rod, I sort of address this in a previous post. Basically, I would not trust any trend that doesn’t emergy in the 5 year averages. Moreover, note that the “cooling” depends a lot on which measure you look at–it’s a lot clearer in some than others. Part of the problem is that you had a seeming upsurge in temperature in the late 1930s and early 1940s and then a drop after about 1944. Then things look pretty flat for about 20-30 years. Actually, I would argue (and I emphasize this is purely a SWAG on my part) that this looks like what one might expect if the positive forcer (CO2) and the negative forcer (aerosols, say) had the same time dependence–e.g. if they were both the result of fossil fuel burning. After about 1975, we took the particulates and unburned hydrocarbons out of the equation and warming resumes.
    I’d be very interested to see what solar forcing looked like in the period, say, 1937 to 1944. Finally, note that in contrast to the ambiguity of the trend from 1944-1975, the recent warming is indisputable, independent of which dataset you look at or how you analyze it.

  36. 136
    barry says:

    My post #130 looked fine in preview, but comes out badly formatted, compounding my own lack of clarity. Let me try again. I get the impression that solar forcing is a weary subject for the hosts here – apologies. I have read some of the posts on the subject at realclimate and elsewhere, but could not find the answers to my rather specific questions.

    I get the following from AR4WG1 IPCC (pp 189 – 193)

    http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Ch02.pdf

    1. Table 2.10 (p. 191) gives ten values (various studies) for RF since the Maunder Minimum M to present (roughly), the lowest being 0 Wm-2 (Dziembowski et al. 2001) and the highest being 0.68 Wm-2 (Solanki and Fligge 1999).

    2. IPCC best estimate for RF from solar radiance increase, from Maunder Minimum to present, is 0.12Wm-2. This is less than half the value given in the previous IPCC assessment. It is also much less than the mean/average of the ten studies in the table.

    3. The reason the best estimate value is much lower than the mean is that inputs in most/all of the high range studies have been thrown into doubt.

    (p 190)

    “The motivation for adopting a long-term irradiance component was three-fold. Firstly, the range of variability in Sun-like stars (Baliunas and Jastrow, 1990), secondly, the long-term trend in geomagnetic activity, and thirdly, solar modulation of cosmogenic isotopes, all suggested that the Sun is capable of a broader range of activity than witnessed during recent solar cycles…

    Each of the above three assumptions for the existence of a significant long-term irradiance component is now questionable….” [etc]

    It seems to me that the RF values of the earlier studies, which employed one or all of the above three assumptions, have been excluded. IPCC best estimate 0.12Wm-2 falls between the last three studies.

    Foster (2004) 0.23 Wm-2

    Y. Wang et al. (2005) 0.10 Wm-2

    Dziembowski et al. (2001) 0.00 Wm-2

    Am I correct in assuming these values are the only ones considered valid out of the ten in the table? I had assumed some process of ‘grading’ each study for validity had been undertaken, but then I checked the 2001 IPCC Assessment and found the best estimate at that time was (seemingly) derived by running a line through the middle of the range. Was the 0.12 estimate derived much differently?

    I checked out some later Solanki (and colleagues) studies. Here is where I became really confused.

    Solankia and Kirvova (2004) state that they, like the latest IPCC, have excluded the inference from sun-like stars (Baliunas and Jastrow, 1990) that underpinned later studies (Lean et al. 1995, which Solanki and Fligge 1999 had employed). They implied that a lower RF was the result.

    http://www.mps.mpg.de/projects/sun-climate/papers/solphys-2004.pdf

    Excerpts;

    “The original stellar evidence of Baliunas and Jastrow was not conclusive and it has been called into question by recent studies. The debate on this issue is ongoing, so that at present stellar data are not a reliable guide for the magnitude of the secular variation….”

    “Probably the most sophisticated reconstruction including a secular trend is due to Foster (2004) and to Foster and Lockwood (2004)…. Finally, using the measured distribution function of the magnetic field at recent epochs and assuming that there were no faculae or network features on the Sun during the Maunder minimum they obtained an upper limit of the increase in brightness of the network since the Maunder minimum of 1.7Wmâ��2. [!!] This is lower than most previous estimates of the secular trend (which, however, were based on a possibly flawed interpretation of stellar data)….”

    “On a longer (and for climate studies more important) time scale things are less certain. The cyclic component of irradiance variations can be reconstructed back up to 1610, although with decreasing reliability and accuracy at earlier times. The magnitude of any secular trend remains a matter of intense debate. A recent, careful estimate by Foster and Lockwood (2004) gives a value of only 1.7Wmâ��2.”

    This value 1.7Wm-2 perplexes me. It is 2.5 times larger than the highest estimate given in AR4WG1, yet the impression from the above is that it represents a value “lower than most previous estimates of the secular trend”.

    A more recent study (Balmaceda, Krivova and Solanki 2007), yields a value of 1.3Wm-2 since MM.

    http://adsabs.harvard.edu/abs/2007astro.ph..3147B

    That’s still 1.9 times greater than the highest value (Solanki and Fligge 1999) in the AR4 chart. Are these figures all representing the same thing (solar RF increase since Maunder Minimum?) If so, why the big jump in Solanki’s later studies, which now exclude inputs that previously resulted in higher RFs?

    I hope this is clearer, and am pretty sure the answer will be that I’ve misunderstood terminology or something.

    In advance of someone schooling me, thanks.

  37. 137

    Now it is at least 90% probable that human injection of carbon dioxide into the atmosphere is in process of raising world temperatures to intolerable levels. In the previous IPCC assessment report this was rated as very likely.

    Would someone please point out for dunces like me what new evidence derived since 2001 has led to this change from likely to almost certain? I have followed reports supporting the previous assessment report and searched the AR4 for dates of facts supporting the AR4 statement of near certainty. I have found many studies dated before 2001, some ranging in dates from the nineties up to 2002, but not really revealing new facts.

  38. 138
    David B. Benson says:

    Re #137: Peter Namtvedt — That has been discussed in comments, perhaps in a thread for a earlier topic. As I understand it, considerable new data sets have only become available in the last four years. This seems to have increased the certainty…

  39. 139
    tamino says:

    Re: #137 (Peter Namtvedt)

    One of the important changes since the last IPCC report is that we have now reconciled the discrepancy between computer models, satellite temperature measurements, and balloon-borne measurements. It turns out that the computer models were basically right, while both the satellite and balloon-borne measurements had hitherto unaccounted errors. This strengthens confidence in computer model results, and resolve what was, as far as I know, the single biggest cause for doubt.

  40. 140
    Rod B. says:

    Tamino (et al) says “I don’t dispute that it was cooler in 1970 than in 1944. But that most assuredly does not mean that we had cooling from 1940 to 1970.

    Huh?!!?

    I’m just a simple farm boy (of yesteryear) from Iowa (though with a Math degree). If the temperature is cooler in 1970 than it was in 1940, we kinda think….

    You could argue that it is statistically insignificant and with all of the regression analysis and autocorrelation it might not indicate a general trend. But, and I hate to break it to you, if the temperature drops, IT’S COOLING!

  41. 141
    James says:

    Re #133: [Actually, the sun is getting brighter, not dimmer.]

    OK, I stand corrected on solar physics – the sun will get brighter for a while, then it will get dimmer. I was more interested in making a point that still stands, which is that eventually the sun is going to burn up its supply of hydrogen and become a white dwarf (IIRC it’s not big enough to go nova), rendering those solar power plants ineffective, just as we’d eventually run out of fissionable materials to use for power plants. But in both cases, the time needed would be ridiculously long in comparison to the expected life of the human species.

    […there is also competition between them for R&D resources including skilled labour, government subsidies and economies of scale. We need to determine which of them, in what mix, will give the best results, in relation to climate change, and whatever other advantages and drawbacks they have.]

    So you want to study the problem for another decade or two? I’d think a better, and certainly faster, approach would be to recognize that competition is good. Use taxes to price CO2 emissions according to the potential damage they do, remove the artifical barriers and/or or subsidies for particular technologies, and let the market work.

  42. 142
    James Annan says:

    Tamino (#134) et al:

    If you look at the figures here it is quite clear that there used to be an optically impressive cooling over this interval – I won’t speculate on whether it was “statistically significant” or not – and I think this adequately explains where the “urban legend” came from, even though the data has been subsequently adjusted in such a way as to eliminate this feature.

  43. 143
    Nick Gotts says:

    Re #141 The difference in timescales between the exhaustion of fissionable materials on Earth and of the sun is many orders of magnitude, so your comparison is somewhat absurd, but I agree with you that the former is not a valid objection to nuclear power over the next few decades – and I’ve never said otherwise here. Where did I say I wanted to study the problem for another decade or two? We need swift inter-governmental agreements on emissions targets, and in practice different governments will take different routes to meeting them, but the measures that can be implemented fastest in rich countries are energy efficiency and demand reduction. I agree we need measures to limit emissions, although I’d favour emissions rationing over taxation. So far as low-carbon energy production is concerned, which methods win out in particular countries will be determined largely by institutional frameworks concerning matters such as planning and insurance, and governmental investment in different forms of infrastructure, which are determined politically – at present, that means largely by which coalition of businesspeople and bureaucrats within a country can most effectively exert pressure, with a minor contribution from public opinion in representative democracies. As for “competition is good” and “let the market work” – belief in that sort of tosh is a large part of how we got into this mess. In capitalist economics, what is most profitable within the current institutional and infrastructural context dictates what is produced – and what is most profitable is often extremely destructive both environmentally and socially. Taxing “negative externalities” like GHG emissions is one way of trying to limit this destructiveness by interfering with markets, but not, at least by itself, a very effective one. When a real emergency is recognised (as in WW2 for example) governments of capitalist countries swiftly drop all the “free market” guff and coordinate production by a mixture of negotiation between interest groups and legal imposition. We’ll know these governments are serious about climate change when they start doing something similar – what we’ll need to do then is make sure the process comes under as much democratic control as possible at all levels from local to global, rather than allowing it to be dominated by big business.

  44. 144
    Luke Silburn says:

    Re: #140 (Rob B.)

    Tamino’s point was that it cooled sharply early in the 40-70 period but the temperature trend then went sideways for the last two thirds of the period. That’s quite significantly different from a relatively constant descent that is implied by the (strictly accurate) statement of ‘there was a cooling between 1940 and 1970′. Or the less accurate (according to Tamino’s regression analysis) ‘there was a cooling trend between 1940 and 1970′.

    If you’ve ever done mountain sports you’ll know what I mean – a short red followed by a long flat run off is a very different thing to ski or (especially) snowboard compared to a piste that is blue all the way along, even if they both start and end at the same place.

    Regards
    Luke

  45. 145
    L.R. says:

    #10
    AVERAGE WEATHER (as the statistical description in terms of the mean and variability) and the term CLIMATE does not makes a lot of sense. This can be easily demonstrated when trying to make sense of the term CLIMATE CHANGE (see #2); because any change of statistical description, remain: statistical description, whether one calculates this on months or million years. Which statistics are used and included? So what is CLIMATE?

  46. 146
    Caz says:

    Re: #134

    If you focus on the time interval 1940 to 1970, there’s a distinct drop in the late 40s, followed by reasonably constant temperatures 1950 to 1970. The point I’m trying to make is that “cooling for 7 years followed by flat-as-a-pancake for two decades” does not constitute three decades of cooling.

    Using your criteria we haven’t had 3 decades of warming then. we’ve just had some warming – some cooling – some more warming and according to HadCrut (and RSS and UAH satellite) a more or less flat trend in the last decade.

  47. 147

    [[OK, I stand corrected on solar physics – the sun will get brighter for a while, then it will get dimmer. I was more interested in making a point that still stands, which is that eventually the sun is going to burn up its supply of hydrogen and become a white dwarf (IIRC it’s not big enough to go nova), rendering those solar power plants ineffective, just as we’d eventually run out of fissionable materials to use for power plants.]]

    Before it becomes a white dwarf, the sun will become a red giant, and then puff off its outer layers in a “planetary nebula.” The latter effect will wipe out any surviving life in the solar system, I believe.

  48. 148
    P. Lewis says:

    Re #140 (Rod)

    I’m just a simple farm boy (of yesteryear) from Iowa (though with a Math degree). If the temperature is cooler in 1970 than it was in 1940, we kinda think….

    You could argue that it is statistically insignificant and with all of the regression analysis and autocorrelation it might not indicate a general trend. But, and I hate to break it to you, if the temperature drops, IT’S COOLING!

    I’m just a simple council estate son of a steelworker (of yesteryear) from Wales (with no Maths degree). If the temperature is warmer in 1969 than it was in 1939, we kinda think …

    Yes, step back a year at either end of your chosen time interval: take the years 1939 and 1969 instead. Then, using your definition, state whether “IT’S COOLING!” or it’s warming.

    You could argue it is statistically insignificant (and I’d agree with you, especially as the respective temperature anomalies are -0.001 and -0.01). But, and I hate to break it to you, if the temperature increases, IT’S WARMING!

    Not a lot, I do warrant. But, hey, if cooling is cooling, then warming is warming to my simple way of thinking. ;)

    And what does any of that prove in either case? Why, nothing, except that Tamino is spot on in his assessment.

  49. 149

    Re #121

    C.E.P. Brooks’ idea that “the ice pack was balanced on a knife edge” are described here http://www.pibburns.com/smmia2.htm with a full reference, but Mewhinney implies that Brooks ideas were “not supported by any calculation.” In fact Brooks supplied a table which can easily be converted into a calculation using a spreadsheet, now.

    Spencer Weart also cites Brooks:

    ‘The respected climate expert C.E.P. Brooks offered the worst scenario. He suggested that a slight change of conditions might set off a self-sustaining shift between climate states. Suppose, he said, some random decrease of snow cover in northern latitudes exposed dark ground. Then the ground would absorb more sunlight, which would warm the air, which would melt still more snow: a vicious feedback cycle. An abrupt and catastrophic rise of tens of degrees was conceivable, “perhaps in the course of a single season.”(5) Run the cycle backward, and an ice age might suddenly descend.’

    at http://www.aip.org/history/climate/rapid.htm#M_5_ also with a full reference.

    HTH,

    Cheers, Alastair.

  50. 150
    FurryCatHerder says:

    Re #139:

    One of the important changes since the last IPCC report is that we have now reconciled the discrepancy between computer models, satellite temperature measurements, and balloon-borne measurements. It turns out that the computer models were basically right, while both the satellite and balloon-borne measurements had hitherto unaccounted errors. This strengthens confidence in computer model results, and resolve what was, as far as I know, the single biggest cause for doubt.

    I asked this in another locale, and the person I was trying to make this point to didn’t understand the objective —

    Has anyone validated the current models against an “assumed”, average solar radiance, CO2 increase, volcanic activity, etc. for the 20th century and arrived at the same values as where we are today (or, at least, were in 2000)?

    [Response: See http://www.realclimate.org/index.php/archives/2005/05/planetary-energy-imbalance/ – gavin]

    I have other issues with the IPCC report and projections, although I must admit that the recent find of 100 billion BBLs of oil in Western Iraq, and the US government’s recent declaration that Canada has (I think …) nearly 180 billion BBLs of reserves is slowly eroding my primary objections. I’ve not look at what’s been proven in the Orinoco sands, but if it’s another 180 billion BBL, I think we’re going to be in more trouble, climate wise, than I’ve been willing to accept in the past.


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