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apiratelooksat50 at 23:46 PM on 28 July 2011Rising Oceans - Too Late to Turn the Tide?
Tom Curtis @ 13 If I am reading you correctly, the rate of sea level rise from 16K to 8K is well documented and therefor possible. I agree with you and also agree that we may be on the front end of another acceleration. Time will tell. And, I agree with you that even with rates of change in the upper bounds of prediction we can easily adapt. -
apiratelooksat50 at 23:28 PM on 28 July 2011Earth's Climate History: Implications for Tomorrow
Sally at 12 When you look at the bottom portion of the graph what you see is a classic sawtooth graph. It shows business as usual - periodical and predictable changes in climate over a large scale. Neanderthals may have appeared as long ago as 650K years in Europe and Asia. They survived all those alternating periods of warming and cooling. Homo sapiens most likely left Africa 50K to 100K years ago. That means our direct ancestors survived an Ice Age by technologically adapting. Whether we have more warming, or begin to enter another ice age, humans will technologically adapt again. That doesn't mean times won't necessarily be difficult, but we will adapt and survive. That also does not mean the human race should not currently be developing new and more efficient/environmentally sound forms of energy. We definitely should. -
Ken Lambert at 23:12 PM on 28 July 2011Ocean Cooling Corrected, Again
Rob Painting - Original Post and #6 You say that the latest 2011 result is 0.55W/sq.m and that this "warming trend observed is slightly smaller than that seen in Von Schuckmann (2009), where the authors measure down to ocean depths of 2000 metres, and found a warming trend of 0.77 ±0.11 watts per square metre." Does the 0.55W/sq.m number apply to the surface of the oceans or the whole surface of the globe? -
Rob Painting at 22:56 PM on 28 July 2011Ocean Cooling Corrected, Again
JoeRG - it intrigues me how you gloss over the obvious. The oceans down to 1500 metres are warming. It utterly refutes the claims made by Knox & Douglass (2010). They basically insinuate that global warming has stopped. They're wrong - as the continuing sea level rise also confirms. Furthermore, you missed the section in my post discussing the sensitivity of analyses based on using the uncompleted ARGO data (pre November 2007) versus the completed network. Peruse the previous analyses highlighted in Knox & Douglass (2010) - there's only 1 year of data using the completed network, making the result even less robust. If you read Von Schuckmann and Le Traon (2011) you'll gain an understanding of some of the issues involved. -
CBDunkerson at 22:29 PM on 28 July 2011Ocean Cooling Corrected, Again
JoeRG, this is no different than someone pointing to declining temperatures in Cherrypickersville and using this to 'conclude' that 'global temperatures are declining'. Yes, a study which then takes temperature trends from all over the world is certainly 'comparing sandals with boots'... but it can make an actual VALID analysis of global temperature trends. Ditto looking at only the top 700m vs 1500 or 2000m of the ocean to determine whether they are warming or not. A 'conclusion' that 'the oceans are cooling' based on very limited data can very definitely be 'completely refuted' by a more thorough analyses showing warming. -
JoeRG at 21:31 PM on 28 July 2011Ocean Cooling Corrected, Again
I wonder how you can conclude a 'completely refute' if you compare sandals with boots. Apart from the different time scales, Von Schluckmann uses data down to 1500m (2011), resp. 2000m (2009), while Willis, Loehle, Pielke and Knox&Douglas (used in the 'refuted' paper) only use the upper 700m data. Completely different things. -
CBDunkerson at 21:16 PM on 28 July 2011It's Urban Heat Island effect
As EtR said, this seems like a regional study which yields results similar to those found previously. Basically, rapid urbanization around a temperature monitoring station can bias the results of that station. Which is why global temperature anomaly results have always adjusted for this effect. This is thus further confirmation that the adjustments are correct... though the fact that satellite temperature records (which obviously aren't impacted by UHIs), analyses based only on rural stations, and various other studies ALSO match has long made this a moot point. -
Eric the Red at 21:11 PM on 28 July 2011It's Urban Heat Island effect
Fitz, The results are consistent with other measurements of urbanization effects. -
Fitz1309 at 21:05 PM on 28 July 2011It's Urban Heat Island effect
Could I ask how this paper by Yang et al 2011 relates to this post. It's looking at anomalies but shows different trends for different classes of urbanisation in China. Thanks http://www.agu.org/pubs/crossref/2011/2010JD015452.shtml -
CBDunkerson at 20:44 PM on 28 July 2011Ocean Cooling Corrected, Again
1 joule = 1 watt second 1 zettajoule = 1,000,000,000,000,000,000,000 joules Thus, zettajoules are most often used to describe very large energy transfers. For instance, 'all human energy use amounts to about 0.5 ZJ' or 'the Earth absorbs about 3,850 ZJ of sunlight per year'. Watts per square meter would describe an amount of energy in an area (e.g. how much a section of ocean surface has warmed) while joules per square meter would describe the amount of energy transfer per second in the area (e.g. the rate at which a section of ocean surface is being warmed). -
Arkadiusz Semczyszak at 20:44 PM on 28 July 2011Ocean Cooling Corrected, Again
Here's what they write cited skeptics on this real meaning - importance ”systematic errors”: „It is possible that some unknown systematic error in the Argo float system is causing the flattening. Such an error would not explain the non-Argo NODC OHC result, nor the surface cooling.” ... and who here writes “the kibosh”? Definitely not Knox & Douglas and von Schuckmann & Le Traon: “Before the end of 2007, error bars are too large to deliver robust short-term trends of GOIs and thus an interpretation in terms of long-term climate signals ARE STILL QUESTIONABLE ... -
Tom Curtis at 19:27 PM on 28 July 2011How we know we're causing global warming in a single graphic
While the TOA radiative forcing is maximized in the tropics for both CO2 and solar forcings, the relative strength of polar forcings for CO2 is greater than that for solar forcings. From the gisstemp efficacy page we have the following plots: Adjusted forcing for doubled CO2:
Adjusted forcing for 1.02 times solar radiation:
The adjusted forcing is the initial forcing as adjusted after the stratosphere reaches equilibrium, ie, the radiative forcing as per the IPCC definition.
As you can see, for solar forcing the forcing at the tropics is over four times greater than that at the North Pole, and over six times greater than that at the South Pole. In contrast for CO2 forcing of similar strength, the forcing in the tropics is only 1.6 times greater than that at the North Pole, and only 2.4 times greater than that at the South Pole. So even though the greatest forcing is in the tropics for both forcings, the polar forcing is relatively greater for CO2 than for solar forcings as I had deduced.
It still seems likely to me that this difference will result in some temperature differential between poles and tropic after all feedbacks for two types of forcings. Of course, the feedbacks for both forcings are very similar, so the stronger the feedback (and hence the higher the climate sensitivity) the less difference in temperatures will survive. I see that the GISS model E predicts very similar final temperature outcomes:
As you can see, the model shows the CO2 forcing results in the world being 0.4 degrees warmer at the poles than for solar forcing, but 0.2 degrees cooler in the tropics. That 0.6 degree differential in terms of polar amplification set against an increase in mean global temperature of around 2 degrees C, which would surely be detectable. Of course, with the actual forcing todate, the difference may be two small to use polar amplification for attribution purposes (which I guess is what you would argue). You might also argue that model results are, as yet, insufficiently accurate to place much weight on so small a difference for the two forcings.
Never-the-less, it seems to me that:
1) Polar amplification is currently much stronger than expected, which sits more comfortably with a green house rather than a solar primary forcing;
2) Any "skeptic" who denies that there is a substantial difference to the response to CO2 and solar forcings at different latitudes is thereby committed to a large climate sensitivity, and given the known CO2 forcing from anthropogenic sources, is also logically committed to anthropogenic greenhouse gases being the primary agent in the current global warming.
The second point means that the rapid warming in the Arctic is indeed not just evidence of warming, but evidence of anthropogenic warming.
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scaddenp at 18:38 PM on 28 July 2011It's the sun
Um, it's rather a long stretch from quantifying the uncertainties as of 2007 to "it doesnt know whats happening". As that reference points out, solar forcing is extremely well measured for last 25 years (direct measurement by satellite) but is "B" because of reliance on proxies prior to that. For more up to date look at the solar proxy uncertainties see this . Note that all forcings (indeed all scientific measurements) have uncertainties. What's important is the extent to which these can be quantified. -
MA Rodger at 18:02 PM on 28 July 2011Ocean Cooling Corrected, Again
What is the conversion factor between watt/sq metre or joules/sq metre (used here) & zeta joules (used by Levitus & others)? -
davidh5040 at 17:38 PM on 28 July 2011CO2 is not a pollutant
CBDunkerson@23: Here are the definitions from Macquarie. pollution 1. the act of polluting. 2. environmental pollutants, such as motor vehicle emissions, industrial waste, etc. 3. the results of these pollutants, as city smog, etc. pollutant that which pollutes; a polluting agent. pollute 1. to make foul or unclean; dirty. 2. to make morally unclean; defile. 3. to render ceremonially impure; desecrate. Using the second definition of "pollution", we can get CO2 as industrial waste (in the sense of "anything left over or superfluous, as excess material, by-products, etc."), and therefore as an environmental pollutant. (Interestingly, this particular definition doesn't seem to include damage to the environment as a consideration). And so you are correct. I was largely persuaded by Tom Curtis and muoncounter, but this puts the icing on it by applying a more rigorous application of the authority I have proposed, without having to shift to other definitions. Thanks to you all for your contributions to this. I will now feel a little more relaxed about using the term in future (though I will still use it with care). Finally, one last appeal for patience and empathy: I realise the tremendous frustration at the poor quality of much of the discourse around this issue, but I do believe that there are many out there who genuinely hold different views or who genuinely don't know what to think. We need to make it as easy as possible for them to hear what we are saying... Thanks again all! -
Eclipse at 17:13 PM on 28 July 2011It's the sun
Hi all, Do you have a page dedicated to the Denialist claim that the IPCC itself admits it doesn't know what's happening with solar forcings at the following 2007 report page. IPCC 2.9.1 Uncertainties in Radiative Forcing -
Rob Painting at 16:43 PM on 28 July 2011Michaels Mischief #1: Continued Warming and Aerosols
Dana I didn't choose 1998 as a starting point - Michaels did because Kaufmann did. To be fair, Kaufmann chose it because "skeptics" like Michaels did! -
Chris Colose at 14:46 PM on 28 July 2011How we know we're causing global warming in a single graphic
Actually the TOA radiative forcing for both the sun and CO2 (as well as the potency of the water vapor feedback) are maximized in the tropics...note the spatial structure of the radiative forcing has a complex pattern even for a well-mixed gas. So it's not immediately obvious from simple conceptual thoughts of the forcing that any polar amplification should occur at all The climate sensitivity (for the same forcing) would be higher in the poles for a bare blackbody rock, based on the Stefan-Boltzmann law, where the hotter body must respond more sluggishly to the same input of energy. In reality, the polar amplification (for any forcing) depends on complex dynamical transport processes which "export" sensitivity from low to high latitudes, as well as thermodynamics (radiation, ice-albedo feedback, etc) which tends to produce polar amplification for a wide range of idealized cases and forcing. In the upper atmosphere, the tropics are amplified relative to the poles. See for example, Pierrehumbert RT (2007), The Hydrologic Cycle in Deep Time Climate Problems. Nature 419,191-198 Peter L. Langen & Vladimir A. Alexeev (2007), Polar amplification as a preferred response in an idealized aquaplanet GCM, Climate Dynamics DOI 10.1007/s00382-006-0221-x Ming Cai & Jianhua Lu (2007), Dynamical greenhouse-plus feedback and polar warming amplification. Part II: meridional and vertical asymmetries of the global warming, Climate Dynamics DOI : 10.1007/s00382-007-0238-9 Jianhua Lu & Ming Cai (2010), Quantifying contributions to polar warming amplification in an idealized coupled general circulation model, Climate Dynamics DOI 10.1007/s00382-009-0673-x Also the GISS output shows the patterns I described above as well for solar or CO2 forcing http://data.giss.nasa.gov/efficacy/ -
dana1981 at 14:08 PM on 28 July 2011Michaels Mischief #1: Continued Warming and Aerosols
Albatross @74 clarified nicely. I didn't choose 1998 as a starting point - Michaels did because Kaufmann did. I chose GISTEMP simply to illustrate that not all data sets agree on hemispheric trends - it was a contrasting example with easily accessible data. And as Albatross noted, I also showed the data since 1975, unlike Michaels, to show how the hemispheric trends have changed (I didn't plot the Hadley data for this period, but I did discuss it). I'm forced to conclude Eric's cherrypicking accusation is based on the fact that he didn't read the post very carefully. -
Tom Curtis at 12:57 PM on 28 July 2011How we know we're causing global warming in a single graphic
Chris Colose @26, thank you for your response. I notice that @14 you say:" No, a reduction in the pole-to-equator temperature gradient is one of the most robust responses to any global warming situation."
I have a problem with this in that, if you ignore feed backs than in increase in CO2 will decrease the temperature gradient, while an increase in insolation will increase it. That being the case, even if feedbacks result in a reduction of the gradient regardless, there should still be a difference in the change of the gradient in the two cases. Is that difference really not detectable in the models? -
Paul Magnus at 12:49 PM on 28 July 2011Earth's Climate History: Implications for Tomorrow
@15 i 2nd that. -
Chris Colose at 12:40 PM on 28 July 2011How we know we're causing global warming in a single graphic
Tom, If you take a look at the studies I cited, CO2 itself (directly) plays a very minor role relative to cloud cover development, precipitation, water vapor feedback, aerosol effects, albedo, and other factors like irrigation and soil moisture as you approach the regional level (see Engelhart and Douglas, 2005 for a discussion on Mexico's DTR for example). The shortwave component of the energy flux seems to exert a much stronger control through changes in aerosol burden (Wild et al., 2007; Makowski et al 2008). I think I can buy that large increases in sunlight would tend to enhance the DTR itself, in the opposite direction of the long term trend. One thing I haven't seen in many of these DTR studies is a consideration of the top of the atmospheric energy balance, as opposed to just the surface forcing. This seems, to me, to be a very incomplete view and I'm not convinced the authors in some of these works appreciate this. When the atmosphere is well-mixed vertically, radiative forcing at TOA has a greater influence upon the surface air temperature than forcing at the surface, since the atmosphere itself adjusting its OLR is a primary way that equilibrium is re-established in response to forcing. Much of this re-adjustment occurs in the high atmosphere, since the bulk of the boundary layer is optically thick due to CO2 and water vapor. -
scaddenp at 12:39 PM on 28 July 2011How we know we're causing global warming in a single graphic
I would have thought not quite so simple. Any warming invokes feedbacks, including water vapour though CO2 effect should be more prominent in cold, dry air, but at the poles there are other factors (especially Antarctica) to muddy the waters (eg ozone). -
barry1487 at 12:32 PM on 28 July 2011Michaels Mischief #1: Continued Warming and Aerosols
So Eric, you think the trend of each of the past two decades is statistically significant at the 95% confidence level? How did you work that out? -
Albatross at 12:16 PM on 28 July 2011How we know we're causing global warming in a single graphic
Anybody got some thoughts on Chemware's question posed @13? "Would not another signature of anthropogenic warming by greenhouse gases be that high latitudes are warming faster than areas near the equator?" Chris? -
Albatross at 11:52 AM on 28 July 2011Earth's Climate History: Implications for Tomorrow
Dr. Hansen, Thank you for a very clear, succinct and sobering account of a complex and potentially alarming situation. I very much appreciate (and admire and respect) everything that you have done regarding the science behind both natural and anthropogenic climate change. Not to mention the great progress that your dedicated and hard work has fostered in this field. Your efforts are especially noteworthy considering the relentless attempts to undermine your credibility and interfere with your work by 'skeptics' and those in denial about anthropogenic climate change. History will reflect very favourably on your admirable, professional and principled approach to this issue-- the same will not be true for Lindzen, Spencer, McIntyre, Christy, Singer and Michaels and their ilk. -
Tom Curtis at 11:49 AM on 28 July 2011How we know we're causing global warming in a single graphic
Chris Colose @17, are you saying that increased CO2 will not decrease the DTR, or that the decrease is small compared to other factors, ie, changes in aerosol load, and or changes in specific humidity? Further, do you have any comment on my points 1) and 2) @21. Am I getting the nuances right? -
Chris Colose at 11:48 AM on 28 July 2011How we know we're causing global warming in a single graphic
Tenney-- The sun can melt ice too :-) -
Tom Curtis at 11:45 AM on 28 July 2011How 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. -
Albatross at 11:43 AM on 28 July 2011How 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. -
Tenney Naumer at 11:32 AM on 28 July 2011How we know we're causing global warming in a single graphic
Nothing about retreating glaciers? -
scaddenp at 11:25 AM on 28 July 2011How 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 -
Chris Colose at 11:07 AM on 28 July 2011How 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. -
ptbrown31 at 10:59 AM on 28 July 2011How 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! -
muoncounter at 10:58 AM on 28 July 2011How 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). -
Chris Colose at 10:53 AM on 28 July 2011How 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. -
muoncounter at 10:49 AM on 28 July 2011Earth'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. -
Chemware at 10:46 AM on 28 July 2011How 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. -
Rob Painting at 10:44 AM on 28 July 2011How 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. -
ptbrown31 at 10:40 AM on 28 July 2011How 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. -
Chris Colose at 10:34 AM on 28 July 2011How 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). -
ptbrown31 at 10:27 AM on 28 July 2011How 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. -
Rob Painting at 10:26 AM on 28 July 2011How 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. -
scaddenp at 10:24 AM on 28 July 2011Earth'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. -
Hopeful at 10:12 AM on 28 July 2011Earth'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. -
Bob Lacatena at 09:45 AM on 28 July 2011How 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. -
Paul Magnus at 09:14 AM on 28 July 2011Earth'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.... -
Paul Magnus at 09:12 AM on 28 July 2011Earth'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? -
ptbrown31 at 08:58 AM on 28 July 2011How 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. -
John Hartz at 08:54 AM on 28 July 2011Michaels 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.
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