The Independent today has a full page article analysing the scientific arguments -- and in particular the striking and very persuasive graphs -- presented in the GGWS film.
Obviously, the more determined skeptics in this forum will find some way to dismiss this catalog of errors - and convince themselves that the GGWS graphs are correct and all the more recent, up-to-date figures are wrong.
I present it here for the consideration of those of you - and I'm sure there are plenty - who prefer to keep an open mind.
I agree they didn't do a very good job on that graph.
I would be interested to know if a valid graph like the one they presented in the programme exisist. Clearly, without such a graph, the direct evidence for sun-induced warming is weak.
I'm pleased that the Independent's report agrees with the list of errors noted in the "A list of errors in the GW Swindle documentary." thread of this forum.
Originally posted by antidogma: I agree they didn't do a very good job on that graph.
I would be interested to know if a valid graph like the one they presented in the programme exisist. Clearly, without such a graph, the direct evidence for sun-induced warming is weak.
The print edition of the Independent had a graph showing the more accurate, up-to-date data - unfortunately, the online version doesn't show them! I left my copy in the office, but I'll look up the source tomorrow morning and post the details. I think it may have been NASA.
The article doesn't mention the graph in "Swindle" which shows the long-term ice-core and temperature data. As far as I know, this graph is accurate. The misleading claim in the program is that it shows that CO2 doesnt cause warming. What it does show is that CO2 can't be the only factor!
This long-term graph showed the cylic pattern of ice-ages and warm, interglacial periods - and it's well known that this is caused by the Milankovich cycle. The major factor in this long-term climate graph is well understood. Variatons in the earth's angle of tilt etc. cause changes in the amount of solar energy absorbed by the atmosphere; hence the ebb and flow of ice ages. The shift to an inter-glacial warm period has various effect on the natural carbon cycle (mostly through increased biomass)... gradually releasing more CO2 into the air.
Of course, this doesn't mean that increases in CO2 have no warming effect. The evidence for this is very clearly seen in the shorter time-scale graph, used by Gore in "an inconvenient truth". At this time-scale, variations caused by the Milankovich cycle are too small to be seen. However, as Martin Durkin said in Swindle, this graph "CORRECTLY" shows a very close relationship between CO2 variation and temperature.
(as was the much Shorter term graph which Al Gore used in "
Dear Heretic, could you tell me when the film claimed that most global warming occurred during the early part of the 20th Century because I must have missed it!. With regard to the the graph of temperatures over the past 1000 years and your claim that there "is a more recent, and widely available, composite graph (which) would have shown average temperatures far exceed the past 1,000 years" that isn't the infamous Mann hockey stick graph as used by the IPCC is it ?. The point about pollution causing cooling is one that is covered well in the Skeptical Environmentalist, which also covers the dodgy Mann graph. Does anybody know what has happened to Global Temperatures since 2002, with all the pollution from India and China, could they have fallen?.
Thanks for an excellent post Heretic. There will of course be those who dismiss it, it's in their nature. And Jud K, have you been off planet? Quote: 'Does anybody know what has happened to Global Temperatures since 2002...?' I think you'll find they've increased as have extreme weather events.
Originally posted by Jud K: Dear Heretic, could you tell me when the film claimed that most global warming occurred during the early part of the 20th Century because I must have missed it!. With regard to the the graph of temperatures over the past 1000 years and your claim that there "is a more recent, and widely available, composite graph (which) would have shown average temperatures far exceed the past 1,000 years" that isn't the infamous Mann hockey stick graph as used by the IPCC is it ?. The point about pollution causing cooling is one that is covered well in the Skeptical Environmentalist, which also covers the dodgy Mann graph. Does anybody know what has happened to Global Temperatures since 2002, with all the pollution from India and China, could they have fallen?.
Originally posted by Jud K: Dear Heretic, could you tell me when the film claimed that most global warming occurred during the early part of the 20th Century because I must have missed it!. With regard to the the graph of temperatures over the past 1000 years and your claim that there "is a more recent, and widely available, composite graph (which) would have shown average temperatures far exceed the past 1,000 years" that isn't the infamous Mann hockey stick graph as used by the IPCC is it ?. The point about pollution causing cooling is one that is covered well in the Skeptical Environmentalist, which also covers the dodgy Mann graph. Does anybody know what has happened to Global Temperatures since 2002, with all the pollution from India and China, could they have fallen?.
Hi, Jud K. Approximately 10 minutes into the program, the narration is as follows:
"Since the mid 19th century the Earth's temperature has risen by just over half a degree celsius, but this warming began long before cars and planes were even invented. What's more, most of the rise in temperature occurred before 1940, during a period when industrial production was relatively insignificant."
The Mann-Bradley-Hughes graph was one of the first published reports covering this data set. As you probably know, a paper was published which suggested that this result was the product of a statistical error. However, this paper has itself been comprehensively debunked in the literature. In any case, its argument applies only to the MBH analysis; several other research teams have analysed the data using different statistical methods and come up with the same results. That's why the "hockey stick is a lie" argument doesn't convince me.
Second, the temperature trend since 2002 has been rapidly upward. I don't have figures for India's & China's particulate pollution emissions in this period. No doubt they are rising -- but apparently, not enough to mitigate global warming all that much.
Dear Heretic, thanks for your reply and yes I did miss that part. However the debunking of the critcism of Mann does not really hold water, given that it was primarily by Mann and, reportedly by groups closely associated with him. The primary criticism was not the statistical methods used but the interpretation of the raw data. If you use flawed analysis you will get flawed results. Can you tell me why Mann and co miss out the Medieval warm period? Oh by the way have a look at temperature data since 2002, shows what you can do with careful selection of data. Pete Password have you got that evidence yet?
The original graph showing the Medieval warming period (MWP) and Little Ice Age was a schematic, drawn in the 1980s, based on European historical understanding rather than studies of data. Constructions such as Mann et al provide a global perspective by bringing together large numbers of studies by diverse scientists.
I have backed up my own implicit trust in Mann et al by reviewing a few of the archive of papers about the MWP on the co2science.org website. My small sample of checks demonstrates that co2science lie about contents of papers they point to, so I kind of think, if they are lying there musn't be any real evidence - just a feeling.
eg. one of the papers they cite in support of the MWP, on New Zealand tree rings, finds a couple of warm spells lasting 50 years or so each within the MWP domain of 950-1300. However, there are also more cold spells, and in particular, the period when the Vikings were colonising Greenland, NZ would appear to have been colder than it ever was.
Another paper they cite was on a study of 6 glaciers in the Andes and Tibet, one of which indicated that some periods in the MWP were a bit warmer than the 20th Century. But co2science only mention this one, whereas the other 5 match the "hockey stick" graph very well.
For some papers, co2science are arguing that dry periods are hot periods (not necessarily true).
So in short, if a denier organisation such as co2science can't find compelling evidence for an MWP, then I'll stick with Mann.
So far 1998 is the warmest year, but this was a big El Nino year - which releases a lot of warmth from the ocean. Global near surface temperatures have been pretty constant for 5 years, but since predictions are for .1-.2C rises per decade that's within the norm. The Met Office are saying there is a 2 in 3 year chance that this year will be warmer than 1998 (because of another El Nino event - albeit much smaller than 1998).
I am not convinced we can so easily dismiss the Medieval Warm Period on the basis that it is a local phenomenon, whereas today's phenomenon is global. After all, the antarctic does not seem to be getting any warmer. So today's "global" warming is in fact not as global as some make out.
Can someone tell me why since 2000 the southern hemisphrere appears to have a stable temp and yet the northern hemisphere has increased quite dramatically. Over the past 20 years or so i thought that antaritca was leading the global race for temp rises. Whats changed?
What worries me about all these graphs of temperature are the fact that they use "temperature anomolies" rather than the actual temperature. The anomolies range from -1 deg C to +1 deg C. Plot these on a graph with a vertical scale of -1 to +1 and, of course, the changes look dramatic.
It took me a lot of digging around but it turns out that the base for most of these graphs is the average temperature between 1951 - 1980 (NASA). This average was 14 deg C. According to NASA in 2006 there was a temperature anomoly of 0.54 deg. This compares with an anomoly of -0.25 deg C in 1886.
Now if you plot temperatures ranging from 13.75 up to 14.54 degrees on a chart with a range from, say, 0 - 15, then the whole thing looks a lot less alarming.
It also should be noted that temperatures rose from 13.75 in 1886 to 14 in 1936, a 50 year period of relatively little CO2 emissions compared with today. So it is obviously quite possible for temperatures to rise at a rate of 0.25% every 50 years by natural means unconnected with CO2 emissions.
The post-war rise in CO2 emissions has occurred at the same time as a rise in temperatures from 14 deg C to 14.54 deg C (70 years).
If it is possible that temperatures could have risen at a rate of 0.25 deg per 50 years naturally during that period anyway, then it is clear that the rate of change over and above that which could be explained by natural causes is about 0.54 - (0.25 x 70/50) = 0.19 degrees. Now, of course, it may be true that temperatures might have fallen during this period, however even before the rise in CO2 emissions we were in a period of gently rising global temperatures anyway so that is unlikely.
As we are in a period of high solar activity as well I think it is most likely that tempertures are high partly because of that. As it has been stated that there is a 92% chance that solar activity will be a lot lower in 50 years time it is quite possible that temperatures may not rise at all in that period, or may even fall.
I wonder what odds William Hill are offering on global average temperatures being lower in 2050 than they are today? Bearing in mind the current level of panic probably very high!
Maybe it is worth a punt? Mind you, I would have to leave my winnings to the kids!
From 1910 to 1940 the 5 year mean anonalie in the Nasa figures goes from -0.33 to 0.08 a rise of just over 0.4. Post war the rise slows and in fact temp fell for a period because of the output of soot and pollutants into the atmosphere (so the theory goes). It doesnt start to rise again until 1980 when it goes from 0.11 to 0.56 by 2006. From 2000 to 2004 it has risen 0.1.
On this basis the temp increase by 2050 should be 1.5 degrees. However i dont think it is this simple and if anything the rise is increasing at present.
if you have some figures for co2 output 1886 to 1936 i would be interested. The assumption that it was low seems too vague.
I am not convinced we can so easily dismiss the Medieval Warm Period on the basis that it is a local phenomenon, whereas today's phenomenon is global. After all, the antarctic does not seem to be getting any warmer. So today's "global" warming is in fact not as global as some make out.
There was never any real evidence for the MWP.
The evidence for a global, or semiglobal period of warming for any period within 950-1300 does not exist.
The evidence for sustained warming in six continents and the oceans at the same time now exists. There is evidence that central antarctica has warmed, but by nowhere near as much. The antarctic peninsula is the fastest warming part of the planet apparently (I've seen this stated in a couple of places), not sure this is relevant since I understand it concurs with movements of wind patterns.
Attacks on the "hockey stick" are a diversionary tactic since we have warming caused by CO2 now.
if you have some figures for co2 output 1886 to 1936 i would be interested. The assumption that it was low seems too vague
I would love to post figures, but unfortunately no direct measurements were being made during this time. The following Wikipedia link gives an idea of the change in the magnitude of fossil fuel combustion in that time period. Wiki link
It is well established from ice-core samples that pre-industrial CO2 levels were 270ppm. According to the Manua Loa observatory they are currently 380 and were 315 in 1960. Assuming a linear extrapolation (dangerous, but what else can I do?) then the 1936 becomes 280. Add a bit for a non-linear curve and it was, say, 285. Therefore in the whole of the industrial revolution from 1750 to 1936 the CO2 level rose from 270 to approximately 285. If we assume there was some rise in CO2 levels prior to 1886 to, say, 275, then tempertures rose 0.25 degrees in a time period (1886 - 1936) when CO2 levels rose from (approx) 275 to 285 (+3.6%). Yet in a period when we have seen CO2 rise from 285 to 380 (33%) we have only seen temperatures rise half a degree. It is quite possible that some of this would have occurred anyway, in which case the greenhouse effect from CO2 rises in the last 40 years does seem a bit small.
Obviously this can be explained in terms of a time lag between a rise in the CO2 concentration and the effect on global temperatures but any idea what that lag should be?
Steve_M its a bit ironic that you chose to validate Mann by using evidence from a "denier organisation" however three questions 1) did the MWP and the mini ice age every feature in IPCC Temperature graphs 2)Do the Hadley Centre graphs show a rise in temperature of about 0.5 c from 1910 to 1940 and a rise of 0.45 c from 1980 to 2006 3) Which parts of the Skeptical Environmentalist do you take issue with (and you are not allowed to say all of it) Regards
Originally posted by Jud K: Dear Heretic, thanks for your reply and yes I did miss that part. However the debunking of the critcism of Mann does not really hold water, given that it was primarily by Mann and, reportedly by groups closely associated with him. The primary criticism was not the statistical methods used but the interpretation of the raw data. If you use flawed analysis you will get flawed results.
There's been a lot of misinformation circulated about the "Mann Hockey Stick graph." There are lots of Hockey stick graphs. The Realclimate website has a useful guide: "Myth vs. Fact Regarding the "Hockey Stick". Here's an excerpt:
"MYTH #1: The "Hockey Stick" Reconstruction is based solely on two publications by climate scientist Michael Mann and colleagues (Mann et al, 1998;1999).
"This is patently false. Nearly a dozen model-based and proxy-based reconstructions of Northern Hemisphere mean temperature by different groups all suggest that late 20th century warmth is anomalous in a long-term (multi-century to millennial) context".
"Some proxy-based reconstructions suggest greater variability than others. This greater variability may be attributable to different emphases in seasonal and spatial emphasis (see Jones and Mann, 2004; Rutherford et al, 2004; Cook et al, 2004). However, even for those reconstructions which suggest a colder "Little Ice Age" and greater variability in general in past centuries, such as that of Esper et al (2002), late 20th century hemispheric warmth is still found to be anomalous in the context of the reconstruction (see Cook et al, 2004)."
Since it was alleged that the 1999 Mann, Bradley & Hughes paper contained errors, several papers have been published by other experts in the field, debunking these claims and vindicating Mann's team. But ultimately, this is unimportant; the case doesnt rest on one researcher, one paper or one research group. Other researchers, using a variety of statistical methods, have independently published long term temperature reconstructions of this kind -- and their results are simmilar. (for instance, Moberg et al. 2005, Rutherford et al. 2005, D’Arrigo et al. 2006, Osborn and Briffa 2006, Wahl and Ammann 2006).
Could ALL these studies be flawed, in such a way that they all spuriously produce a "hockey-stick" graph? No one has seriously suggested this. It would mean that each research team made elementary statistical mistakes -- quite DIFFERENT mistakes, since they were using a variety of different methodologies -- which nonetheless, all just happen to give rise to similar outcomes! It's not really credible, is it?
quote:
Can you tell me why Mann and co miss out the Medieval warm period?
They don't. To quote from Mann, Bradley and Hughes' 1999 paper:
"The late 11th, late 12th, and late 14th centuries rival mean 20th century temperature levels (see Figure 3a). Our reconstruction thus supports the notion of relatively warm hemispheric conditions earlier in the millennium, while cooling following the 14th century could be viewed as the initial onset of the Little Ice Age... Considerable spatial variability is evident however [see Hughes and Diaz, 1994] and, as in in Lamb's [1965] original concept of a Medieval Warm Epoch, there are episodes of cooler as well as warmer conditions punctuating this period. Even the warmer intervals in our reconstruction pale, however, in comparison with modern (mid-to-late 20th century) temperatures."
In more recent reconstructions, the MWP doesn't show up as dramatically as it did in research published a decade or so ago. The reason for this seems to be that the more recent studies use a broader, more international data-set. It's now become evident that was a climate variation, not a global one. Yes, Northern Europe got warmer -- but other regions cooled. For example, at the time of the MWP, South America was experiencing a period of relative cooling.
What's more, the warmth of the MWP is often exaggerated. For instance, although the graph shown on "Swindle" which has no quantified temperature scale -- it looks like the MWP must have been very much hotter that in was. You've probably heard skeptics like Fred Singer and Tim Ball talking about English mediaeval vinyards, Viking farmers in Greenland etc.
However, estimates of the number of vinyards in England during Mediaeval times, based on contemporary records, vary between 46 and 60. Yet way back in 1977 (when some people still thought we were experiencing a *cooling* trend!) there were over 124 vinyards in Wales alone!
It's reasonable to ask what causes regional climate changes, like the MWP. It has now become clear that this warming was largely confined to regions surrounding the North Atlantic -- strongly suggesting that it had to do with the behaviour of ocean currents.
There is evidence to suggest that the little Ice Age is associated with an increase in volcanic activity and a period of reduced solar activity. These seem to be the strongest candidates and it seems likely that they both played a part. (A much more speculative idea is that Little Ice Age was prolonged as a result of massively reduced human agricultural activity following the depopulation of Europe during the Black Death -- since the the resulting growth of forests would have taking up more carbon from the atmosphere.)
