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Comments 78451 to 78500:

78451. Tom Curtis at 11:45 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       ptbrown @31, I think there is a crucial logical point that is often missed in popular discussion of the fingreprint of the greenhouse effect. That point is that no individual "fingerprint" is unique to the enhanced greenhouse effect. What is unique is the combined pattern of effects. It is also important to realise that the water vapour feedback, being itself an enhanced greenhouse effect will contribute some of the finger print of an enhanced greenhouse effect to any warming. It will, however, do so by counteracting the primary effect of many warmings, so while it means we cannot be simplistic in our analysis, it does not prevent fingerprinting analysis. With that in mind: 1) An increase in albedo due to increased aerosol optical depth will decrease the Diurnal Temperature Range, as will a decrease in Total Solar Irradiance. However, both of these phenomena will also cool the lower troposphere overall. Cooling the lower troposphere will also reduce average specific humidity, which will tend to increase the diurnal temperature range. So, to the extent that increased aerosol optical depth (or reduction in TSI) is responsible for the reduction in DTR, it is only because some other factor is increasing tropospheric temperatures more than they are tending to decrease them. 2) As it happens, global sulfur dioxide emissions have reduced since 1975. Therefore, to the extent that they do influence the Diurnal Temperature range (which is substantial) we would expect the DTR to have increased over that period. The fact that it has not suggests some other factor is causing the DTR to decrease. Thus we could divide the later part of the 20th century into to intervals. During the period 1950 and 1975 the two factors influencing DTR acted in concert to decrease it, while after 1975 one factor continued to decrease it, while the influence of aerosols was to increase it, with no net effect. This is in effect the reverse of the temperature trend. Between 1950 and 1975, increasing aerosols tended to cool the planet, counter acting some other factor that was warming it with a resulting very small change in global temperatures; while after 1975 both the reduction in aerosols and the other factor have tended to warm the troposphere, resulting in a sharp rise in temperatures. This other factor, which both reduces the DTR and warms is therefore an enhanced greenhouse effect. 3) If your argument at this point were valid, then it would also apply to the effect of aerosols. Hence in that you apparently accept the influence of aerosols on DTR, you are contradicting yourself.
78452. Albatross at 11:43 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       My two cents worth on the DTR. In my humble opinion (and understanding) the reduction of DTR is theoretically a (subtle) symptom of an enhanced "greenhouse" effect. The problem with the DTR is finding a suitable dataset (and long enough) that has not been affected by other factors that might influence trends in DTR. I think that Braganza is one record saying that because of the myriad of factors that can affect DTR in the real world, it is not the most robust fingerprint of AGW-- note that does not equate to saying that it is not a fingerprint, or that the enhanced "greenhouse" effect has been overturned. If I recall correctly, Braganza considers the seasonal change in warming to be a far better and unambiguous fingerprint of an enhanced "greenhouse" effect. I suggest reading this informative post by Dr. John Nielsen-Gammon, as well as the recent paper by Zhou et al. (2010). At the end of the day, when we consider the body of evidence, a coherent and robust picture of an enhanced "greenhouse" effect on account of an increase of CO2 levels from humans burning fossil fuels emerges. As to which of the many indicators is the best or more robust, well that is open for discussion.
78453. Tenney Naumer at 11:32 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       Nothing about retreating glaciers?
78454. scaddenp at 11:25 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       I'm not that fond of any single phenomena being called a "fingerprint of anthropogenic warming". I think it would be better to think of the fingerprint as being a set of phenomena observed together. This is much more discriminatory power for comparing anthropogenic warming to natural forcing. Ideally you run the model with anthropogenic forcings, and then same model but with different natural forcings, all of the same strength and compare outputs. There is some data for that here and perhaps in the Hansen et al 2005 paper
78455. Chris Colose at 11:07 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       muon-- Hopefully we'll gear future posts away from that meme, or at least clarify the many nuances. ptbrown-- Thanks! I got my B.S. there too, but am doing graduate work elsewhere. Room 1411 will be missed.
78456. ptbrown31 at 10:59 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       10, Chris Colose Thanks for the support. By the way, I have seen your posts around the climate blogosphere before and I noticed you are at Wisconsin. I got my undergrad from the AOS dept in '08. Go Badgers!
78457. muoncounter at 10:58 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       DTR looked better than a weak fingerprint on this prior thread. We are currently experiencing global warming. If an increased greenhouse effect is a significant part of this warming, we would expect to see nights warming faster than days. There have been a number of studies into this effect, which confirm that this is indeed the case. One study looked at extreme temperatures in night and day. They observed the number of cold nights was decreasing faster than the number of cold days. Similarly, the number of warm nights was increasing faster than the increase in warm days (Alexander 2006).
78458. Chris Colose at 10:53 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       ptbrown-- There's a lot of examples of erroneous but popularly held notions that many people have :-) Don't blame the site too much, hopefully that will correct itself. Keep in mind that something not being a 'fingerprint' doesn't necessarily imply it is consistent with everything either. There's no indication that the trends in DTR are consistent with a pure natural forcing. Chemware-- No, a reduction in the pole-to-equator temperature gradient is one of the most robust responses to any global warming situation.
78459. muoncounter at 10:49 AM on 28 July 2011
       Earth's Climate History: Implications for Tomorrow
       Sally #12: "Are we able to scientifically link the rise in extreme/severe weather events in terms of being attributable to climate change ?" That's a hot button issue. Most people will respond with a cautious 'maybe'; statements like the probability of extreme events has increased due to global warming. See the prior extreme weather thread for cautious discussion of 2010's events. The frequency of extreme warm anomalies increases disproportionately as global temperature rises. "Were global temperature not increasing, the chance of an extreme heat wave such as the one Moscow experienced, though not impossible, would be small" See this recent Scientific American series for this year's version: Increasingly, the answer is yes. Scientists used to say, cautiously, that extreme weather events were "consistent" with the predictions of climate change. No more. "Now we can make the statement that particular events would not have happened the same way without global warming," says Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research (NCAR) in Boulder, Colo. Is it a good sign that the language used by the experts is changing? Sorry, didn't mean to give you another reason to lose sleep.
78460. Chemware at 10:46 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       Would not another signature of anthropogenic warming by greenhouse gases be that high latitudes are warming faster than areas near the equator ? This is the opposite of what one would expect from increased insolation, and is only explicable by a mechanism that increases the insulating properties of the atmosphere.
78461. Rob Painting at 10:44 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       ptbrown31 - let me refine my comment. The DTR is weak evidence for the increased Greenhouse Effect, but insofar as a human 'fingerprint' on climate, that seems to be on far safer ground. This is evident in the 'weekend effect' in heavily industrialized areas for instance. The DTR undergoes change over the weekend when industrial sources of pollution abruptly drop.
78462. ptbrown31 at 10:40 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       Rob - Yes, that is exactly how I understand it as well. It is also what the literature indicates. This is why it bothers me that SKS continues to imply that the DTR changes are a fingerprint of an enhanced greenhouse effect. It undermines the credibility of the site and I am a big fan of the site in general.
78463. Chris Colose at 10:34 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       Sphaerica, Actually, there's nothing in ptbrowns post that indicates he doesn't know what he is talking about. Indeed, I believe he is mostly right in describing the complexity of the variations in the diurnal temperature range, and how it depends on cloud cover, vegetation, and in some studies, aerosol effects-- many of these forcings (or feedbacks) are of anthropogenic origin, but it's not obvious that increasing CO2 alone is a primary factor here, or that it is a significant attribution tool (see e.g.,Dai et al., 1999, J. Climate; Stone and Weaver, 2003, Climate Dynamics; Makowski et al., 2008, Atmos Chem Phys; Zhou et al., 2009, Climate Dynamics).
78464. ptbrown31 at 10:27 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       7, Sphaerica - Please enlighten me of the errors that I have made rather than simply being dismissive and condescending.
78465. Rob Painting at 10:26 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       ptbrown31 - actually there's far better case to be made that human-caused aerosol pollution explains the DTR trend, moreso than the increased Greenhouse Effect. It would also explain the patchy distribution of DTR trends. As aerosol pollution is short-lived in the atmosphere, local effects depend upon where the pollution came from and the seasonal atmospheric circulations (weather patterns). The massive increase in industrialization and growth after the 2nd World War pumped huge amounts of aerosols into the air. This would have served to decrease solar radiation reaching the Earth's surface - ergo daytime cooling. At the same time, the increased Greenhouse Effect would have kept nights warmer. After the clean air acts of the 70's were introduced, and sulfates particularly were dramatically reduced, days would have warmed up because of the increase in solar radiation now heating the Earth's surface. What we'd expect to see is an increase in the DTR range, and indeed that is what happened. The timing matches well. I'm covering all this in some posts on aerosols and 'Global Dimming/Global Brightening'. The DTR range as a GHG 'fingerprint' is not compelling IMO.
78466. scaddenp at 10:24 AM on 28 July 2011
       Earth's Climate History: Implications for Tomorrow
       "Anyone know a ball park figure for the carbon footprint in switching our fossil fuel infrastructure to a sustainable one? " Lets look at two things that would make most difference. 1/ Stop building FF power stations. No immediate effect but once an aging power station has to be replaced, then the replacement generation needs to be non-FF type. Since you are only replacing stations that would be have to be built anyway, the carbon footprint of changing to sustainable is zero unless the carbon-footprint of renewable generation is significantly higher than than of construction FF power. Also, once you have around 50% of energy from non-FF, then carbon cost of construction would also start to drop off significantly. You do know that say windmills and solar very rapidly produce more energy than the cost of creating them? 2/Electrification of transport. If vehicles are replaced with electric ones at end of life only, then again, the carbon footprint of change neutral, then decreasing if energy of construction is from non-FF.
78467. Hopeful at 10:12 AM on 28 July 2011
       Earth's Climate History: Implications for Tomorrow
       My background is health science not climate science. Thankyou to all the contributors to Skeptical Science for dedicated and heroic efforts in reporting and explaining the science. This nightmare is almost too difficult to comprehend, wakes me up at night in fear for my children's future and the future of millions of people in terms of food supply and wars - it is probably waking some of you up at night also. Up until now I had been telling people that 2 degree C was the guardrail - not so. Are we able to scientifically link the rise in extreme/severe weather events in terms of being attributable to climate change ? To me it seems like having a cohort of smokers and finding increased rates of cancer, stroke, heart attacks, peripheral vascular disease and emphysema as predicted by science.
78468. Bob Lacatena at 09:45 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       6, ptbrown31,

       ...I do not think...

       Your post is riddled with errors. You seem to have a very, very weak grasp of how the greenhouse effect works, and as a result you draw many invalid conclusions from invalid premises and illogical arguments. I started to detail them for you, but really, it just became too much. I would strongly suggest that you put your cynicism aside and spend a lot of time studying and learning what is involved, and then make a judgment on this issue when you are actually qualified to do so.
78469. Paul Magnus at 09:14 AM on 28 July 2011
       Earth's Climate History: Implications for Tomorrow
       "To me, food supply is the most serious risk. If a poor man runs out of food, he starves, if a man with a gun runs out of food, bad things happen." Bad things.... survival of the fittest....
78470. Paul Magnus at 09:12 AM on 28 July 2011
       Earth's Climate History: Implications for Tomorrow
       Anyone know a ball park figure for the carbon footprint in switching our fossil fuel infrastructure to a sustainable one?
78471. ptbrown31 at 08:58 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       I have made the comment quite a few times at SKS that I do not think there is adequate evidence that DTR changes are due to an enhanced greenhouse effect. Here are my main points: 1) I have looked quite a bit and I have never found a peer reviewed article that attributes the observed change in DTR to an enhanced greenhouse effect alone. All of the references above either do not attempt to attribute the change in DTR to anything or they attribute it to cloud/aerosol suppression of daytime warming (while both tmin and tmax are presumed to be warming do to an enhanced greenhouse effect). This makes a change in DTR an anthropogenic fingerprint but that is very different than an enhanced greenhouse effect fingerprint. 2) the IPCC AR4 Summary for Policy Makers says the following: " A decrease in diurnal temperature range (DTR) was reported in the TAR, but the data available then extended only from 1950 to 1993. Updated observations reveal that DTR has not changed from 1979 to 2004 as both day- and night-time temperature have risen at about the same rate. The trends are highly variable from one region to another. {3.2}" They are saying that DTR has not changed during the time period when greenhouse warming is thought to have been largest. This certainly does not seem to support DTR changes as a signature of an enhanced greenhouse effect. Not to mention, if it really was a signature of an enhanced greenhouse effect wouldn't that have made it into the report? 3) The following conceptual model seems over simplified: " This is because at night, the Earth's surface cools by radiating heat out to space. Greenhouse gases trap some of this heat, slowing the night-time cooling." For one thing the earth is always radiating heat to space and it actually should radiate more heat to space during the day when its warmer. Therefore it does not seem obvious why an enhanced greenhouse effect should cause more warming at night than during the day. I believe the argument goes something like this: "relatively speaking, nighttime temperatures are effected more by the greenhouse effect because daytime temperatures are a product of solar radiation + back radiation whereas nighttime temperatures are dominated by back radiation." My main issue with this is that it seems to imply that Tmin and Tmax are independent. They are not. The greenhouse effect suppresses cooling at night but then when the sun comes up it will cause the temperature to begin rising from wherever nighttime cooling left off. Therefore any suppressed cooling at night should feed back into daytime warming and thus effect the tmax as much as tmin.
78472. John Hartz at 08:54 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       If Eric the Red is just regurtitating stuff that he has previously posted on other threads, why indulge him on this thread? SkS is not obliged to provide a forum for repeat performances.
78473. spencerd at 08:41 AM on 28 July 2011
       CO2 limits will harm the economy
       In a recent press release, Lord Monckton claimed:- "Forestalling all of the 0.24 C° global warming predicted by 2020 would demand almost $60,000 from every man, woman and child on the planet. That cost is equivalent to almost 60% of global GDP to 2020. He repeated these figures at his National Press Club debate. Treasury modelling states that the carbon tax will reduce Australian GDP by 0.3% in 2020 ($171 per head per annum)and reduce our CO2 equivalent emissions by 25% over business as usual. Why should a global solution cost 60% of GDP? Not surprisingly, Monckton employs a number of "tricks" to exaggerate the cost of a climate change solution. Firstly he calculates the cost of implementing a solution with NO manmade CO2 emissions. This raises the cost to 0.3%*4 =1.2% of GDP. Next he uses the reduction from 2000 levels (5%) instead of the reduction from business as usual 2020 levels(25%). That multiplies the result by another factor of 5 to get to 6% of GDP. This is still not large enough, so Monckton calculates the gross value of the tax rather than the impact on GDP. Even when calculating the gross value of the scheme, he adds both the tax received and the expenditures from the tax (such as administration, renewable energy support and coal and steel support). By this means, Monckton estimates the net cost of the current scheme as $13 billion per annum or 1% of GDP instead of Treasury's figure of 0.3% This calculation brings Monckton's calculation of the global abatement cost up to 20% of GDP but Monckton has a few more "tricks" up his sleeve. Monckton assumes that the carbon pollution measures only the impact of CO2 - 51% of manmade forcings. He therefore doubles the cost again to allow for eliminating all the other manmade forcings such as methane - bringing us up to 40% of GDP. Of course the Australian carbon tax does tax methane emissions ( as the coal industry will attest to ). Monckton understands that Australia has 2% of global GDP but contributes only 1.2% of global CO2 because we have high energy efficiency. He therefore implicitly assumes that the cost of abatement in countries with low energy efficiency would be the same as Australia's. Multiplying 40% by 2%/1.2% brings Monckton up to his 60% of GDP. Just in case all the tricks haven't been enough to scare the public, Monckton has one last card to play. He calculates the cost per head over a 10 yesr period rather than a cost per year. The cost per head becomes $59,000 instead of $5,900 per head per annum. The bottom line is that Australia will reduce its emissions by 25% over business as usual levels at a cost of 0.3% of GDP per annum or $172 per head per annum. I could only conclude that Lord Monckton deliberately set out to deceive his audiences with a patently ridiculous cost for tackling climate change.
78474. Tom Curtis at 08:25 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Badgersouth @70, no!
78475. Albatross at 07:43 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       EtR @72, "You criticized Michaels for cherrypicking his datasets (CRU) and time frames (1996-), then you did the same thing (GISS and 1998-)." You are very confused, and wrong. Dana showed the GISTEMP data for the same period as the HadCRUT data 1998-2010. Had you read Pat's piece, is seems that you have not (or at least not properly) you will have noticed that Pat refers two different time frames in order to fabricate his deception: monthly HadCRUT data from November 1996 through 2010; and annual HadCRUT data from 1998-2010. Dana made it very clear that the GISTEMP data show a different story to the HadCRUT data with reference to Pat's cherry-picked 1998-2010 window. Unlike Pat, Dana showed data going back to 1975, not just for the cherry-picked 1998-2010 window. To achieve his deception Pat had to 1) Cherry-pick the data set, 2) Cherry pick the time frame. Disingenuous and deceptive at best. I could say more but doing that would violate the comments policy. Pat can play this game of cherry picking ad infinitum all the while the long-term and statistically significant temperature trend is UP. KR is correct, most "skeptical" scientists (e.g., Lindzen, Spencer and Michaels), are interested in advocacy, not the advancement of science.
78476. KR at 07:28 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Eric the Red - Dana simply used available data to look at Michaels' claims in the context with which they were made. In my opinion (your mileage may vary) it's a decent article. "More work is needed to ascertain the temperature effect." (aerosols) Correct, although statements like this are often presented when someone wishes to use uncertainties to claim that we don't know well enough (or, alternatively, anything) to act upon. Michaels' statements about aerosols and their effects are really quite distorted - I would classify them as advocacy statements (from a PR person) driven by the desire to present a particular point of view on policy, not objective statements about the science. And hence Dana is quite right to show that even when Michaels cherrypicks recent data, he's still wrong - even with that small of a data set.
78477. Eric the Red at 07:12 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Dana, You criticized Michaels for cherrypicking his datasets (CRU) and time frames (1996-), then you did the same thing (GISS and 1998-). There is enough scientific data to not argue on a similar level. Aerosols are a much bigger question, which needs to be answered. Michaels was referring to sulfate uncertainty, not sulfate effect. This was probably intentional on his part, and meant to confuse. The geographic dispersion of aerosols may very well be as Michaels claims. The atmospheric interaction between the hemispheres is limited. More work is needed to ascertain the temperature effect.
78478. dana1981 at 06:44 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       I'm a bit confused as to how I'm supposed to have cherrypicked anything. I showed the hemispheric trends in GISTEMP to illustrate that they're different from HadCRUT, and because they had the most easily-available hemispheric temperature data. Since when is it cherrypicking to criticize cherrypicking? I should also note that probably half of the post was about aerosols, which I don't think anybody has mentioned in the comments yet! Fortunately Rob P is working on a post devoted exclusively to aerosols, so hopefully we can get an interesting discussion the subject there without being bogged down in statistically insignificant cherrypicking silliness.
78479. John Hartz at 05:58 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Out of curiosity, is Eric the Red arguing anything on this comment thread that he hasn't previously argued on the threads to other SkS articles?
       Response:

       [DB] Not AFAIK.

78480. muoncounter at 05:20 AM on 28 July 2011
       Did Global Warming stop in 1998, 1995, 2002, 2007, 2010?
       EtR#176: "These oscillations occurred about the linear trend, which has remained unchanged." That same linear trend, which you said was man made, is unchanged since the 1880s, 1910s, 1940s? Despite significant differences in man made and other environmental (forcing) factors? How strange. How unphysical. But your comment explains quite a bit; you are another 'line and sine' man. No physical mechanism exists to support this purely observational exercise, but then again, no mechanism is needed as you can rely on the mythic 'natural cycles'. What next, the harmony of the spheres?
78481. Eric the Red at 04:56 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Barry, Statistical significance is understood to be the 95% confidence level. This commonly applies to standard deviations, t-tests, etc.
78482. Eric the Red at 04:48 AM on 28 July 2011
       Did Global Warming stop in 1998, 1995, 2002, 2007, 2010?
       Muoncounter, The two datasets show similar trends. The slope is the same for both sets (I use monthly data, but annual should produce similar results). The changes in slope that occurred in 1880, 1910, 1940, and 1970 are real; it is too soon to ascertain if a change har occurred in 2000. These oscillations occurred about the linear trend, which has remained unchanged. Tom, The oscillation could be fitted about an exponential trend. In this case the R2 for the linear would be 0.81, while an exponential would be 0.80, essentially no difference. Sphaerica, ( -Snip- ). We were comparing the periods of steep slopes, not the last decade which you pointed out were not part of the slope.
       Response:

       [DB] Inflammatory snipped.  I suggest taking a deep breath to cool off prior to composing your messages.

78483. barry1487 at 04:06 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Eric, could you describe what you understand statistical significance to be? It might clear the confusion.
78484. Eric the Red at 03:59 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Albatross, I thought I answered all three of your questions. About what else were you inquiring? ( -Snip- ).
       Response:

       [DB] Argumentative & inflammatory snipped.

78485. John Hartz at 03:33 AM on 28 July 2011
       How we know we're causing global warming in a single graphic
       I’m not particularly enamored with the following two sentences of John’s essay: “If the sun was causing global warming, it would cause summers to warm faster than winter, days to warm faster than nights and the upper atmosphere to warm. Observations rule out the sun.” Although the statements are correct in science-speak shorthand, they may not make sense to the average person reading the article. After all, the ultimate source of the infra-red radiation that is reflected back to Earth via the greenhouse effect is the sun. Perhaps John should tweak these two sentences.
78486. Albatross at 02:29 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       EtR @58, Really, that is the substance of your case and to obfuscate? You have still not replied to the three questions posed to you, so please don't continue to try and take me and others on a wild goose chase by making more unsupported assertions. The one thing that we both agree on is that Pat Michaels is guilty of cherry picking. Addressing those very cherry picks of his does not constitute a cherry pick. You have the logic all wrong. Now can we move on please (unless you are interested in actually answering those three specific questions). As for: "Read the original Forbes article and the Kaufmann paper" A rather peculiar strawman Eric. In fact I have read both, and in fact it was I who (to my knowledge) brought Pat's diatribe to the SkS community's attention on 19 July 2011 after reading Dr. Gleick's refutation. Now instead of engaging in debating tricks, please try and focus on and stick to and learn about the science.
78487. muoncounter at 01:56 AM on 28 July 2011
       Did Global Warming stop in 1998, 1995, 2002, 2007, 2010?
       EtR#172: ""acceleration" is severely lacking in this plot." Surely there is more to this disagreement than just CRU vs. GISS. So let's plot both together using WFT (note there is a -0.1 shift applied to GISS to bring the two curves into visual alignment). -- link to original I've applied a 5 year (60 month) average to both to be consistent with the GISSTemp graph refd above. Your '0.6C/century' is the blue line. The other line is a trend from 1970 on; it is a much larger slope than your 'long-term trend.' Is this larger slope 'what we are currently experiencing' or do you persist in saying we are still on 0.6C/century? "The linear portion is largely driven by man," Agreed! We have driven the slope up to nearly 2C/century. You're a genuine AGWarmist now.
78488. Hyperactive Hydrologist at 01:53 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       In my opinion when talking about climate you should be looking at periods of a minimum of 30years.
78489. Tom Curtis at 01:47 AM on 28 July 2011
       Did Global Warming stop in 1998, 1995, 2002, 2007, 2010?
       Eric the Red @172, by my calculation the linear trend on gisstemp from 1880 to 2010 is 0.00586 per annum, with an R^2 of 0.756 In contrast the accelerating curve shown below has an R^2 of 0.8142. Leaving aside the virtues of curve fitting, why should we use a linear trend for the effect of GHG concentrations when an exponential curve gives a better fit? And if you insist on curve fitting with an oscillation thrown in, why not add the oscillation to the exponential trend rather than to a linear trend? It seems to me that as you do not have a physical theory to fall back on to guide your choice, excluding an exponential curve as the underlying trend is at best ad hoc.
78490. Bob Lacatena at 01:45 AM on 28 July 2011
       Did Global Warming stop in 1998, 1995, 2002, 2007, 2010?
       172, Eric the Red,

       The "acceleration" is severely lacking in this plot.

       No, it's not. Your eye is deceived, because you are paying attention to those final 10 years which are not part of the trend (i.e. averaged over a full 15 year time frame). Such incomplete "tails" often show anomalous behavior, because their true shape depends very much on the years that have not yet come to pass. In this case, by looking at that tail, it levels everything out. If you instead focus on the statistically significant portion of the graph, from 1970 to a about 2003 (which has 7 full years before and after it to account for 15 years worth of data) then it is clearly accelerating. You can't opt to give weight to a shorter trend at the end just because it shows what you'd like to see.
78491. Eric the Red at 01:11 AM on 28 July 2011
       Did Global Warming stop in 1998, 1995, 2002, 2007, 2010?
       The "acceleration" is severely lacking in this plot. http://www.cru.uea.ac.uk/cru/info/warming/ The increase for the three decades 1911-1940 was 0.154C / decade, while the 1971-2000 increase was 0.171C / decade. While the rate is slightly higher, I would hardly call this an acceleration. The 1990s were influenced by the two events you mentioned. That is one reason why I prefer not to use these decadal trends, and have been cautioning others who claim that the increase is accelerating based on this change. I am not "ignoring" these transients, but trying to focus people on the long term. Since 1880, both the CRU and GISS datasets show a long-term trend of 0.6C / century. For the first five months of 2011, the CRU data falls right on the trendline, GISS is 0.05 above. This is short term fall due to the recent strong La Nina, and I expect that temperatures will climb later in the year. The long term trend is not linear, but rather oscillating with a long period. The linear portion is largely driven by man, while the oscillations are natural, most likely driven by ENSO changes. Other drivers, like volcanoes and solar, are apparent on shorter intervals. Aerosols are a wildcard in the entire scenario, possibly being a very large influence.
78492. muoncounter at 00:35 AM on 28 July 2011
       Did Global Warming stop in 1998, 1995, 2002, 2007, 2010?
       Continuing from here. EtR#57: "rather that we are not deviating from the long term trend. What we have currently experienced (and may continue) is a return to that trend after the large increase in the 1990s. " This statement begs two questions: a. What, in your interpretation, is 'the long term trend'? b. What, in your interpretation, are we currently experiencing - and what is driving it? If you look at the GISSTemp graph and focus solely on the 1990s, you will see a large decrease (well-known to be the cooling effect of the Pinatubo eruption), followed by what you label the 'large increase,' which is equally well-known as the 1998 el Nino anomaly. The net effect is an excursion of more than 0.5C within the decade. You seem to ignore the fact that these are transients -- not due to the 'long-term trend.' Further, 1910-1940 was approx 0.3 degC in 3 decades; 1975-2005 was 0.7C in 3 decades; what part of 'acceleration' do you not recognize?
78493. muoncounter at 00:27 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       EtR#61: "you are repeating the mistake of others. " Debatable, but I'll try again. However, I take my response to Did global warming stop in ___?, where it belongs.
78494. Eric the Red at 00:12 AM on 28 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Barry, No, I am saying it is statistically significant. Previous posts claimed that the temperature increase was accelerating because the average temperature in the 2000s increased from the average temperature in the 1990s by more than the increase in the previous decade. I was pointing out the fallacy in this analysis in that the greatest increase occurred during the 1990s. I made no mention of statistical significance, nor implication thereof. The last paragraph is a reference to Tamino's analysis. You should probably check his work to understand the issues of statisically significant. The recent trends do not differ significantly from the long term.
       Moderator Response: [Dikran Marsupial] The point is Eric, that if you are going to base an argument on a trend, then it must be at least statistically significant for your argument to have any scientific basis. The fact that recent trends do not differ significantly from the long term does not mean that they have not changed from the long term, just that there is insufficient evidence to rule out the possibility that they are the same as the long term.

       If by "I am saying it is statistically significant" you mean decadal trends, then you need to provide the details of the analysis (as Tamino and others have already demonstrated they are not statistically significant).
78495. DSL at 23:54 PM on 27 July 2011
       Guest post: scrutinising the 31,000 scientists in the OISM Petition Project
       Ken, answer the following: 1. Can science ever predict anything with 100% certainty? 2. If so, show me. If not, what level of certainty is acceptable to you? This is the problem. Scientists are certain enough to say, "we're in danger." Yet there are people who ignore the science but have the means, motivation, and morality to spread the idea that "No, there are too many uncertainties." The question you, as a non-scientist, should ask yourself is not "who should I believe?" but instead "why do I believe who and what I do believe?" Do you believe that there is significant uncertainty? Why? Who led you to believe this, and what were the arguments? There is no doubt about the basic mechanism, but it's my word against some doubter's word unless you're willing to engage the science. I've had this debate with others. It all comes down to giving up control over your beliefs. If you're not willing to spend the time to understand the issue, then you must give up some control over your beliefs and the resulting actions. Most people do that willingly in many areas of their lives. I've yet to meet the person who is totally in control of their beliefs (and probably won't; he/she's living in a cave somewhere, alone forever). The social production of scientific knowledge gives us the most objective understanding of 'reality' we can get. It's not perfect, nor are we. One of the persons with whom I was arguing claimed to be an Objectivist--someone who believes rational self-interest and the economic mode of capitalism are the keys to individual freedom. Yet this person parroted others who, in turn, had parroted others. The claims made by this person were easily dismissed with a few simple observations and the application of physical laws (that the person clearly accepted). Yet this advocate for rationality and objective thought still refused to admit error and, in fact, repeated the same errors in another, subsequent post. Whenever someone mentions individual liberty in an argument, I begin to suspect that the only things the person is interested in are defending the profit motive and excusing themselves from responsibilities. I'm not saying that you, Ken, generate this response; rather, experiences such as the one I describe above do.
78496. barry1487 at 23:53 PM on 27 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Eric, You state, "I am not treating 10-year trends as statistically significant, others are." I wondered if I had misinterpreted you, so I checked. To quote:

       I am not sure exactly what you mean by steeper than linear, but assume that you are implying that the linear trend is increasing. That is simply not occurring, as the greatest increase in the past 40 years was observed in the 1990s, with the smallest occurring in the past decade.

       You are saying the trend of the past decade is less than the previous. In order to say such a thing, these trends must be statistically significant. Yet you have just stated that ten-year trends are not statistically significant.

       Best is to use a long term trend (with good statistics), and then compare the most recent data to that trend.

       In every one of these plots, the increase is significantly less in the past decade, and approaching zero

       Do you see a pattern? You are referring to the last decade's trend as if it's statistically significant. I don't see anyone else making that mistake.
78497. Ken Lambert at 23:50 PM on 27 July 2011
       How we know we're causing global warming in a single graphic
       Moderator #1 "Radiation is decreased by GHGs, which causes temperature increase, which causes increase in attempted radiation, offsetting at least some of the greenhouse gas blocking. It's tricky to estimate how much total successful radiating will be increased or decreased at each of the times in that time course of events. Also tricky to adequately measure total radiation" What is 'attempted' radiation. Are we now assuming that radiation makes attempts and succeeds or fails? Sounds more like Mallory 'attempting' Everest. A better description of the analagous process might be a heat transfer one. The 'R' or insulation value of the atmosphere is increased, the average temperature differential (T1 - T2) to drive the same heat flux upward to space is increased. Heat flux is not 'trapped' - it requires a greater temperature differential to drive it across a better insulator.
78498. Eric the Red at 23:25 PM on 27 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       Muon, It appears my post was lost completely on you, as you are repeating the mistake of others.
       Moderator Response: [Dikran Marsupial] This post is unhelpful; if muoncounter has misunderstood you, then explain the misunderstanding (as you see it). Note also that if many appear to be misunderstanding your posts, perhaps the problem lies with the composition of your posts, rather than their comprehension.
78499. MA Rodger at 22:56 PM on 27 July 2011
       Earth's Climate History: Implications for Tomorrow
       CO2 has risen at 3ppm pa momentarily but the average is still about the 2ppm level. (I will attempt to support this assertion with some graphical support. This will involve a web link which I have a bad history with.) See graph here.
78500. muoncounter at 22:54 PM on 27 July 2011
       Michaels Mischief #1: Continued Warming and Aerosols
       ETR#57: "some people are restricting themselves to these time frames of 15+ years, and assuming that is what is occurring today." That's a bizarro-world statement with no apparent basis in this reality. Using a 15+ year time frame to establish an averaging period for a trend is not a 'restriction,' it's a necessary step. For example, look at the familiar graph below: -- accessed July 26, 2011 The red curve is a 5 year running mean; it stops in 2008 (because it needs 2 1/2 years of data on either side). The curve rose above 0 in the mid 1970s and has touched +0.7C; that's a 4 decade slope on the order of 0.17-0.2 degC/decade; if you are saying that 'what is happening today' is the slight 'wiggle' at the end of the red curve -- and if you think the existence of that wiggle proves something about what is happening now -- then you are deeply confused. Look at the rest of the red curve; it wiggles a lot -- because it is based on 5 year averaging! Of course, this has veered off-topic - see the thread Did global warming stop in ____? and you can fill in your choice of year.

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