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gallopingcamel at 16:57 PM on 27 March 2010What CO2 level would cause the Greenland ice sheet to collapse?
Philippe Chantreau, (#67), Thanks. This is really good news. Let's hope they are right! -
How we know global warming is happening, Part 2
GISS shows 0.8C warming since 1880. Not very scary, is it. http://www.woodfortrees.org/plot/gistemp/from:1880/plot/gistemp/from:1880/trend -
How we know global warming is happening, Part 2
Tom, A lot of Cook's links are bogus. For example, the National Post article was just quoting Josh Willis at NASA who said ocean temperatures are declining. Take it up with NASA if you disagree. Once again, none of the mainstream skeptic sites dispute the satellite lower troposphere record. In fact Christy and Spencer are considered trusted sources there.Response: Here are a few links from Watts Up With That, which I believe you would characterise as a mainstream skeptic site, that we're now experiencing global cooling:- UAH Global Temperature Anomaly for June 09 ~ ZERO
- Svensmark: “global warming stopped and a cooling is beginning” – “enjoy global warming while it lasts”
- January 2008 – 4 sources say “globally cooler” in the past 12 months
- The Sun Defines the Climate – an essay from Russia
So regardless of whether mainstream skeptic sites dispute that global warming is happening (and the above links indicate otherwise), the fact remains that many people are being persuaded that global cooling is happening. You haven't been misled by this argument and that's a credit to you. But people less informed than yourself are being misled by these falsehoods. This misconception cannot be left unchallenged. -
Tom Dayton at 16:24 PM on 27 March 2010How we know global warming is happening, Part 2
TH, see this list of links to blogs claiming either that satellites no warming in the past 30 years, or that any satellite evidence for warming has been faked: Links for 'Satellites show no warming in the troposphere'. I found that list the same way I already explained to you how I found the previous list. By the way, it's not nice to move goalposts. Originally you made the sweeping claim that ""No one doubts that the earth has warmed over the last 30 years." When I pointed you to a handy list of such doubts, you drastically narrowed your claim to only the satellite records. -
Tom Dayton at 15:58 PM on 27 March 2010What CO2 level would cause the Greenland ice sheet to collapse?
gallopingcamel wrote "Please tell me where you get the idea that we can look forward to '10s of thousands of years' before the next glaciation." Okay: Berger and Loutre (2002) explained why this interglacial could last 50,000 years past today. I found that article's citation easily, by entering "Milankovitch" in the Skeptical Science "Search" field at the top left of every page, which yielded several pages that explain all this. -
Philippe Chantreau at 15:46 PM on 27 March 2010What CO2 level would cause the Greenland ice sheet to collapse?
Not really. http://www.nature.com/nature/journal/v429/n6992/full/429611a.html -
shawnhet at 15:42 PM on 27 March 2010Is the science settled?
A couple of points here in re: water vapor and its feedback. The primary thing to keep in mind about WV vis a vis CO2 is that WV condenses and precipitates out of the atmosphere. It is this fact that explains the partitioning of WV and lets us know where negative feedbacks associated with WV might come from. For instance, if we assumed that cloudiness increases proportionally with concentration of WV this would be a negative feedback. Likewise, if precipitation increased in proportion to the conc. of WV. Neither of these propositions is at all unlikely IMO. Finally, one should never forget that WV feedback(whatever its magnitude or sign for all but the very recent *atmospheric* temperature changes has *already happened*. There may be some other temperature changes coming along "in the pipeline", but WV adjusts to a temperature change in a period of months or so. Cheers, :) -
gallopingcamel at 15:20 PM on 27 March 2010What CO2 level would cause the Greenland ice sheet to collapse?
Philippe Chantreau (#63), Here is NOAA's view on the last million years: http://www.ncdc.noaa.gov/paleo/ctl/clisci100k.html It looks as if the present warm temperatures are unusual. Much colder temperatures seem to dominate, so please tell me where you get the idea that we can look forward to "10s of thousands of years" before the next glaciation. I really hope you are right but the ice core record from Antarctica suggests that we are still in an Ice Age with short inter glacial periods. -
How we know global warming is happening, Part 2
If you actually read any of the skeptics blogs, WUWT, Climate Audit, etc. you would know that Cook's claims are spurious. None of the writers dispute the 30 year satellite trend of 1.2C/century. http://wattsupwiththat.com/2010/03/05/february-uah-global-temperature-anomaly-little-change/ This argument is a straw man. You are arguing with yourself. -
Tom Dayton at 14:51 PM on 27 March 2010How we know global warming is happening, Part 2
TH wrote "No one doubts that the earth has warmed over the last 30 years." As Ned replied, in fact lots of people doubt it. You can see a partial list of links to public statements of doubt, on the "Links for 'It's Cooling' argument." You can see links to skeptic statements for all the arguments on this Skeptical Science site, in the "Global Warming Arguments, Sorted by Argument" page. An easy way to get there is to click the "Links" link in the blue horizontal bar at the top of every Skeptical Science page. For example, the "It's Cooling" branch of that tree page has a whole bunch of sub-branches that are more specific skeptic arguments, and each of those (if you click on them) has a similar page of links to pro- and con- public statements. -
Ned at 14:49 PM on 27 March 2010Is the science settled?
Ken Lambert writes: Let's have a result boys - the answer is the key to the whole AGW CO2 theory. Personally, I'm pretty comfortable with the range of climate sensitivities given in AR4 (2 to 4.5 C, with an expected value somewhere around 3 C). It seems unlikely to be far off in either direction and it's certainly the best estimate we have now. -
Ned at 14:40 PM on 27 March 2010Is the science settled?
To illustrate the point about positive feedbacks, here are graphs of two cases, one where f > 1 (resulting in a runaway increase) and one, like the real-world positive water vapor feedback, where 0 < f < 1, so that the temperature increase is bounded (2C in this case):
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Ken Lambert at 14:39 PM on 27 March 2010Is the science settled?
Chris #89 Obviously a 3degK rise is "the increase in the Earth's.........'equilibrium temperature'. So it's not obvious (to me anyhow!) what your "key" point actually is.... No Chris, a 3degK rise at the surface if it translates directly to the emitting temperature of the atmosphere will increase the OLR using the (Stefan) S-B equation as follows: Current OLR = 238.5W/sq.m, Pre-industrial OLR = 235.7 Current emitting temperature = 255degK Pre-industrial emitting temperature = 254.25 degK For a 3 degK rise in emitting temperature (above pre-industrial levels) the new OLR will be: (257.25/254.25)^4 x 235.7 = 247.0 W/sq.m. Rise in OLR is 247.0 - 235.7 = 11.3W/sq.m (11.3W/sq.m increase in outgoing longwave radiation) The rise in CO2 radiative forcing from doubling of CO2 to 560 ppmv from pre-industrial levels of 280 ppmv will be (using the IPCC Eqan) : 5.35ln(560/280) = 3.7W/sq.m Therefore to balance the CO2 radiative forcing of 3.7W/sq.m, the emitting temperature of the atmosphere only has to rise by (using inverted S-B) : (239.4/235.7)^0.25 x 255 = 255.995 degK - 255 = 1.0 degK You can do the numbers with slightly different OLR (aroung 240) and temperature (around 255) and get a very similar result. So for a 3 degK rise to be the result of CO2 doubling alone, there must be only a 1 degK rise in the emitting temperature of the atmosphere. The extra 2 degK difference in the rises must be in the increased greenhouse effect (complex feedbacks, back radiation etc etc) which is theroized due to increased CO2 and increased water vapour. While brings us to the critical effects of water vapour and CO2 - where BP #84 and Ned #86 are fighting it out. Let's have a result boys - the answer is the key to the whole AGW CO2 theory. ( -
Paulie200 at 14:25 PM on 27 March 2010How you can support Skeptical Science
Like Zero132132 in the above comment, I also stumbled a bit over the donation process. What sunk my first attempt was that you have to pick an amount (in that funny plastic Ozzie money ;) before the rest of the page will allow you to shift to country specific fields, like U.S. info. (And hey, other then what your bank card might charge for the conversion, it's a deal! An Ozzie $ only costs 0.90 cents U.S.) Thanks for this site, and your hard work, John. -
Ned at 13:47 PM on 27 March 2010There's no empirical evidence
kwoods01 writes: The information I would like to address is that greenhouse gases absorb only certain wavelength bands. Hence, there is a maximum amount of energy that can be absorbed out of the electromagnetic spectrum by the greenhouse gases. [...] with respect to CO2, there is a limit to the amount of radiative forcing that can occur. A couple of points. First, we're nowhere near saturation for CO2. Second, even if the atmosphere as a whole were saturated, CO2 would still be low enough in the upper atmosphere for OLR to escape even within the absorption bands. There are references to a number of papers about this on John's page Is the CO2 effect saturated? and much more discussion at RealClimate. -
Ned at 13:36 PM on 27 March 2010How we know global warming is happening, Part 2
TH writes: No one doubts that the earth has warmed over the last 30 years It would be nice if no one doubted that, but those of us who spend time browsing through the skeptic blogosphere have seen people make exactly that claim plenty of times. Likewise, people also question whether CO2 is actually increasing, whether humans are responsible for that increase, and whether there's any connection between CO2 and warming. Yes, all of those seem like illogical and easily answered questions, but many people do get confused on these points. Ameliorating that confusion is the reason for this site's existence. TH continues: Six years is not a particularly meaningful trend, and the real question is how much? There is no indication of catastrophic warming in this data. The point of this is not to extrapolate from a six-year trend. The point is to show that even during a period when the surface air temperature has been temporarily more or less flat, ocean heat content has continued to rise. I don't think anyone predicted catastrophe by 2010. Unfortunately the climate system and our economic system both have a great deal of inertia, so it's important to start making changes now so as to prevent catastrophe further down the road. Temperatures are rising slower than any IPCC scenario. The IPCC doesn't make six-year or eight-year predictions, because in any such period the trend will be obscured by normal interannual variability. -
kwoods01 at 13:35 PM on 27 March 2010There's no empirical evidence
I'm really glad there is a site like this where we can have civilized discussions about this topic. The information I would like to address is that greenhouse gases absorb only certain wavelength bands. Hence, there is a maximum amount of energy that can be absorbed out of the electromagnetic spectrum by the greenhouse gases. This means that there is a concentration threshold for each gas whereby if the concentration increases, no more radiative forcing is possible for that gas. E.G. If you look at CFC-11 and HNO3 in the figure at the top of the page, their radiances in the bands of 850-900 cm^-1 are near zero. Therefore, increasing the concentration of HNO3 in the atmosphere will not affect radiative forcing anymore because there is no more radiation to absorb. Now don't get me wrong, I'm not saying increasing the concentration of chloroflourocarbons and nitric acid in the atmosphere has no maleffects. Acid rain and ozone depletion are two major problems with those pollutants, that is why they are regulated. But with respect to CO2, there is a limit to the amount of radiative forcing that can occur. Another note is that radiative forcing does not take into account the effects of clouds. If more energy is absorbed, more water will evaporate and convect to the upper atmosphere forming clouds that will reflect radiation. Looking at Ramanathan et al (Science 1989) "Cloud-Radiative Forcing and Climate: Results from the Earth Radiation Budget Experiment," the effect of clouds has a net radiative cooling effect. Hence, the direct correlation between a greenhouse gas increase and an increase in temperature is unfounded due to the radiative cooling of additional cloud cover. About the heat content increase graph, the comparison of 190,000 GW increase should not be compared to nuclear power plant outputs of 1 GW but rather of the amount of insolation hitting the earth from the sun of 160,000,000 GW. That is the correct normalizing parameter. I go into detail about this on the global warming page. -
How we know global warming is happening, Part 2
This is the usual Cook straw man post. No one doubts that the earth has warmed over the last 30 years, and Dr. Roy Spencer has published graphs recently showing that at present the oceans are gaining heat. Six years is not a particularly meaningful trend, and the real question is how much? There is no indication of catastrophic warming in this data. Temperatures are rising slower than any IPCC scenario.Response: If only it were a straw man. I'm sure there are many skeptics that would concede that the earth is warming but only dispute that mankind is the cause. Others concede that humans are causing warming but the warming will not be catastrophic. However, there are also many who deny that global warming is happening at all. Thus "it's cooling" is the 4th most popular skeptic argument.
While I would love to focus my energies on the more reasonable skeptic arguments, practicality dictates I also must pay attention to the most popular ones. -
James Wight at 11:24 AM on 27 March 2010It's not us
What about stratospheric cooling? An increasing greenhouse effect means the surface and the troposphere should be warming, but the stratosphere should be cooling (because the troposphere is trapping more heat and stopping it from reaching the stratosphere). Satellite and weather balloon measurements indeed show a cooling trend in the stratosphere, the opposite of what would be expected if the Sun was causing global warming. And it looks like it isn’t caused by ozone depletion either. -
chris at 09:17 AM on 27 March 2010Is the science settled?
No problem Ned. I suspect Peter knows all this anyway. After all the only alternative is that all those thousands of scientists have inadvertently messed up over the nature of feedbacks...................... ....Doh! -
davidtnw at 09:06 AM on 27 March 2010The 5 characteristics of scientific denialism
I'm surprised that nobody mentioned David Brin's blog about this subject at: http://davidbrin.blogspot.com/2010/02/distinguishing-climate-deniers-from.html Also may I suggest that models of weather patterns and ocean currents are probably quite non-linear, so is it possible that small effects could have very large but, difficult to predict, consequences? -
chris at 09:02 AM on 27 March 2010Is the science settled?
Ken Lambert at 01:04 AM on 27 March, 2010 Ken I think you need to clarify your "key" point, before anyone can consider addressing it: i.e.:The key to this is what portion of the 3degK rise also applies to the troposphere and what will be the increase in the Earth's overall OLR and 'equilibrium temperature'. Humidity and lapse rate are critical parameters around which there is much discussion and uncertainty.
Obviously a 3degK rise is "the increase in the Earth's.........'equilibrium temperature'. So it's not obvious (to me anyhow!) what your "key" point actually is.... -
Zero132132 at 08:49 AM on 27 March 2010How you can support Skeptical Science
It didn't work when I tried to make a donation earlier for some reason. Just got it to go through this time. I don't have a huge amount to donate, but every little bit helps, right? Keep up the good work. It's appreciated by many. -
Ned at 08:43 AM on 27 March 2010It's cooling
kwoods01, you're right that absolute temperatures can vary at fine spatial scales, such that it would be difficult to calculate an accurate average temperature based on a limited number of thermometers. But temperature anomalies are spatially correlated over very broad areas. Thus, it's possible to come up with a very good estimate of changes in the global mean surface temperature based on a relatively small number of stations (i.e., hundreds, not millions) as long as they're reasonably well distributed. Finally, "waiting for more conclusive data" isn't actually possible, since we can't freeze all emissions of greenhouse gases while we wait. The decision to continue with business as usual or to start reducing emissions will have to be made with imperfect information. If we decide to just continue with business as usual while we wait for the scientists to do their thing, that will lock in a lot of warming that can't then be recalled if we later decide that the science is convincing after all. -
hank at 08:24 AM on 27 March 2010Is the science settled?
I looked up 'Gish gallop' and Google found this list of a hundred or so claims often rushed through by people claiming anything they can except the IPCC explains climate, often found on blogs; just in case you'd missed the list, here it is: http://www.dailyexpress.co.uk/posts/view/146139 -
kwoods01 at 07:33 AM on 27 March 2010It's cooling
Very interesting article. About the 6 x 10^21 Joules per year (200,000 GWth), the comparison to nuclear power plants is an unfounded comparison because what is heating the earth is the sun. If we consider that the sun is hitting the earth with 1300 W/m^2, and the radius of the earth is 6.3 x 10^6 meters, the energy input by the sun is: Insolation x Area = 1300 W/m^2 * pi*((6.3*10^6)^2) = approx. 160,000,000 GW. Compared to 200,000 GW of warming. I think this is a better comparison. So approximately 0.12% of the insolation hitting the earth is being absorbed and held. If 200,000 GW is entering an ocean of 100,000,000 mi^2 and 0.25 miles deep, the change in ocean temperature is (200,000x10^6 kJ/s)/((100,000,000 mi^2)(0.25mi)*(4x10^9 m^3/mi^3)*(1000kg/m^3)*(4.184kJ/kgK)) = 5*10^-10 K/s = 0.015 K/year = 1.5 Kelvin/century which is close to the temperature change of the earth. Kudos goes to the person who made the very good estimation in the above article of the change in internal energy of the oceans. However, I am an experimentalist. The second comment I would like to pose is about taking temperature data. The scope of the experiment is that the earth's surface area is 200,000,000 mi^2, and temperature data from 1880 - 1961(Tiros I launched) was taken with < 1,000-10,000 thermometers and averaged to get a full year's average temperature. Making a gross assumption that the thermometers are homogeneously dispursed around the globe, each thermometer must have encompassed a region from >20,000 - 200,000 mi^2. To put that into perspective, Texas is 250,000 mi^2 and West Virginia is approximately 25,000 mi^2. I question whether the data obtained can produce an average annual temperature value within 0.5°C, let alone 0.1°C. If these values are certain, as given by Smith and Reynolds (2004,2005) found on the NOAA website, I question what can be deduced from them. The average surface temperature of the earth is not measured directly just like the temperatures from past climates were not measured directly. However, past climates deviated in degrees over millenia compared to tenths of a degree over decades. The same analysis goes for any water temperature measurement that was done. To derive an average water temperature from measurements of an ocean that is on the order of 100,000,000 mi^2 in surface area and on the order of 0.25 miles deep is unfounded. It is a vast volume to extrapolate precise and accurate temperature data from. This analysis provides me with enough skepticism to wait for more conclusive data. -
cms at 06:54 AM on 27 March 2010Medieval Warm Period was warmer
Since I read this study out of Woods Hole, I have been wondering what responses it has garnered. http://www.sciencedaily.com/releases/2009/08/090827131832.htm -
littlerobbergirl at 06:23 AM on 27 March 2010How you can support Skeptical Science
Go John! So, you are sliding in the good bits of Wiki while keeping overall editorial control. Brilliant! I will contribute where i can (links probably - i love to pull things together). -
A peer-reviewed response to McLean's El Nino paper
Well, chris, I was trying to be nice. I agree - the bandpass operator they use is pretty worthless, as shown by getting equal matches to randomly generated data; I just wanted to point out that big internal consistency flaw between their paper and their (unjustified) conclusions. -
Is CO2 a pollutant?
suibhne, also look at this, which is an excellent explanation of what G&T's attempted equivalence of convective greenhouse heating with radiative greenhouse gas heating really means. -
Is CO2 a pollutant?
suibhne, I read the G&T paper. I've rarely seen a worse article, EVER. I would suggest you look at some of the responses to that which have been linked to from this blog. G&T pose a strawman argument, that the greenhouse effect (radiative heating by greenhouse gasses in the atmosphere 55 pages in their paper) is not the same mechanism as surface greenhouses (blocking convection/conduction heat exchanges, 20 pages). This gets covered in the first two minutes of review in any thermodynamics discussion on the topic - G&T claim this these aren't equivalent, therefore greenhouse gasses don't hold heat, which is bull****. The surface of the earth would be ~33C colder if they didn't. Nobody argues that these two mechanisms hold heat the same way, just that they are similar in effect (warming things up). Side note - they also seem to claim that the IPCC came up with radiative forcing and radiative equilibrium. They're a bit off with that statement; I believe that dates to 1791. Please read that, the references are excellent. G&T misderive path length intercepts for IR and CO2, derive wavelength dependent energy retention for glass but then claim that can't possibly work for CO2, contradicting themselves, etc. There are (by my count) about 2 misstatements per page. The core of their argument, described in regards to a car heating in the sun, is "Conduction, condensation and radiation, which slow down the rise in temperature, work practically the same inside and outside the car. Therefore, the only possible reason for a difference in final temperatures must be convection...". G&T essentially argue that radiation would rapidly equalize temperatures. This means that they haven't done their math! Total energy into the atmosphere (solar plasma emission spectra) warms the surface of the earth, which radiates a different spectra (thermal IR) back up. Increasing CO2 blocks part of this thermal spectra. For the energy output to balance the solar input in a steady state condition, the entire thermal spectra must increase in intensity to counter the CO2 blockage, which means that energy will accumulate (rising temperature) until the sum spectral energies in/out are equivalent. This is pretty basic; G&T either don't understand radiation equilibrium or choose to ignore it. The paper is worthless. Read this, this, and finally this for some useful descriptions of radiative equilibrium. There are some excellent thermodymanics links from those pages as well. -
chris at 04:58 AM on 27 March 2010A peer-reviewed response to McLean's El Nino paper
Ned, McLean et al neglected to reproduce this part of the review:Accept pending major changes (mainly in style not scientific comment) The real mystery here, of course, is how the McLean et al. paper ever made it into JGR. How that happened, I have no idea. I can't see it ever getting published through J Climate. The analyses in McLean et al. are among the worst I have seen in the climate literature. The paper is also a poorly guised attack on the integrity of the climate community, and I guess that is why Foster et al. have taken the energy to contradict its findings. So the current paper (Foster et al.) should certainly be accepted. Someone needs to address the science in the McLean et al paper in the peer-reviewed literature. But the current paper could be - and should be - done better. That's why I am suggesting major changes before the paper is accepted. All of my suggestions have to do more with the tone and framing of the current paper, rather than its content.
An account can be found in RabettRun -
Ned at 04:39 AM on 27 March 2010Is the science settled?
Oh, dear, Chris. Sorry about that. Looks like we were responding simultaneously. Chris writes: Therefore something's wrong with your argument. Can you spot it? I'm afraid I might have given a small hint there. :-) -
Ned at 04:36 AM on 27 March 2010Is the science settled?
Berényi Péter, I don't think you understand the mathematics of feedbacks. You might want to reread the comment by Chris above. A positive feedback does not imply a "runaway" system unless the feedback coefficient f is >= 1. For positive feedbacks 0 < f < 1, the total increase from the feedback will be 1/(1-f), as Chris says. As you yourself said, It is not climate science, not even physics. Just plain old math. However, it's important to have the math correct. This is a common mistake -- many people assume that a positive feedback must increase without bound. -
shopa at 04:36 AM on 27 March 2010How you can support Skeptical Science
John, you are doing a great job. I have started a chain letter to get readers for you in the USA. To readers: I have invented a new way to fight bushfires. www.electric-fluid-pipeline.com Please help me get some attention from the Australian authorities. -
chris at 04:32 AM on 27 March 2010Is the science settled?
Berényi Péter at 03:45 AM on 27 March, 2010 Don't think anyone's going to fall for that BP! Since the water vapour response is positive (after all we can measure the increased water vapour concentration in the atmosphere as a result of warming over the last 30-odd years, pretty much as predicted), and we haven't had your scary runaway scenario, it follows that the latter isn't "inevitable" as you assert. Therefore something's wrong with your argument. Can you spot it? -
Ned at 04:13 AM on 27 March 2010CO2 was higher in the past
Thanks, muoncounter. Also, re: Please note that I accidentally italicized the last sentence ("We don't see...") in #10. That was my statement and not part of the referenced article. Yes ... and I solved that by inserting a "/i" tag (in brackets) at the beginning of my comment. :-) -
Berényi Péter at 03:45 AM on 27 March 2010Is the science settled?
Ned, folks could use some common sense, I guess. If water vapor feedback on CO2 warming is positive, then it is positive on any kind of warming, right? Even on warming caused by some random increase of humidity. At this point one can safely forget about carbon dioxide and start worrying about dihydrogen monoxide pollution. For we have an almost infinite supply of the liquid form of this stuff with an open surface exceeding 3.6 × 1014 m2. As temperature gets higher, the Clausius–Clapeyron relation ensures ever higher rates of evaporation. Or does it? The final state is a H2O atmosphere with trace amounts of nitrogen and oxygen. Surface pressure is 2.6 × 107 Pa, temperature above 600 K. It is called a runaway greenhouse. Can last for some ten million years, molecules split by UV in upper atmosphere, hydogen escapes to space, are left with plenty of oxygen but no water. Limestone releases CO2 slowly, Earth is transformed to hell. Somehow it never happens. Why? Because dihydrogen monoxide feedback is not positive. If it would be positive, the scenario described above is inevitable. It is not climate science, not even physics. Just plain old math. Plus the empirical fact we are still alive. Water feedback should be slightly negative, very close to neutral. Greenhose effect is saturated. So. The one million dollar question to climate scientists is not whether water vapor feedback is positive or negative, but how this negative feedback loop works? -
muoncounter at 03:38 AM on 27 March 2010CO2 was higher in the past
Ned, Those mechanisms are critical to the argument over "high CO2 and glaciation=No". It is certainly clear that widespread carbonate deposition takes up lots of atmospheric CO2, but whether that alone causes an ice age isn't clearly established. It is also clear that the graph of CO2 levels taken from a denialist website, posted above (#6), doesn't take a short-term drop in CO2 due to perfectly valid geological mechanism into account. I have some difficulty with the mechanisms in the "Mountains that froze the world" article John references at the top of this thread. For one thing, the Appalachians weren't all done in the late Ordovician -- it took another 100 MY or so until the Alleghenian Orogeny was complete. The image below is the mid-Ordovician southern ocean:
-- source
All that light blue is shallow sea -- mostly between 10N and 30S latitude -- perfect environment for carbonate deposition from marine organisms.
For another, the idea that Sr86 in Nevada is runoff from the proto-Appalachians just doesn't seem right -- on the map above, Nevada is on the 'north coast' of Laurentia, while the emerging Appalachians are on the 'south coast'.
Other mechanisms abound in the literature, from a mega-volcano to a gamma-ray burst.
From another key paper on this subject, "the waxing and waning of ice sheets during the Late Ordovician were very sensitive to changes in atmospheric pCO2 and orbital forcing at the obliquity time scale (30–40 k.y.)" I've even seen one author who suggests that the concentration of continental land masses at the south pole would perturb the earth's orbit -- but that's a much longer-time scale event.
Please note that I accidentally italicized the last sentence ("We don't see...") in #10. That was my statement and not part of the referenced article.
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Ned at 03:01 AM on 27 March 2010A peer-reviewed response to McLean's El Nino paper
HumanityRules writes: Here is Mclean et als reply to the Foster comment. Warning: this is not peer-reviewed (this becomes obvious very quickly). It also contains reference to the climategate emails which I know some people are a little sensitive about. Hmmm. It looks like McLean et al. went through the CRU emails and found the anonymous reviews of the Foster et al. comment. They quote a couple of sentences allegedly from one of the reviews ("But as it is written, the current paper almost stoops to the level of 'blog diatribe'. The current paper does not read like a peer-reviewed journal article. The tone is sometimes dramatic and sometimes accusatory. It is inconsistent with the language one normally encounters in the objectively-based, peer-reviewed literature.") I'm a bit disturbed by the idea of going through someone's email to find and selectively quote comments from the peer review process, which is supposed to be anonymous and confidential. If McLean et al. are going to do that, I think that they ought to make the reviews of their own (rejected) comment similarly public. And in both cases they ought to show the full text of all the reviews, not selectively chosen snippets from one review. What else did this reviewer have to say about the Foster et al. comment, besides a couple of sentences complaining about the tone? It's hard not to suspect that if there had been any more substantial criticisms, McLean et al. would have quoted those parts, rather than the fairly mild complaint they did quote. -
Ned at 01:38 AM on 27 March 2010Is the science settled?
Berényi Péter, I don't think we're going to throw out Clausius–Clapeyron any time soon. The evidence for a positive water vapor feedback is discussed in some detail on John's page Water vapor is the most powerful greenhouse gas. This can be easily seen over the long term, but it also manifests itself via interannual variability e.g. following the eruption of Mt Pinatubo. I think Solomon et al. 2010 does a nice job of discussing both the long-term role of water vapor as a positive feedback and its shorter-term role in sub-decadal scale variability. -
Ken Lambert at 01:04 AM on 27 March 2010Is the science settled?
Profmandia #7, #25, Ned#66 BP#78 Glad you had a look at the Trenberth paper because I find the overall calculation of the Earth's energy imbalance the most relevant measure of potential warming or cooling. Dr Trenberth's paper estimates that the net overall imbalance is +0.9W/sq.m from net radiative effects which equals 145E20 Joules/year. He can only account for about 0.55W/sq.m (about 80E20 Joules/year)in the energy budget for warming oceans, melting ice, warming land etc. He muses over whether the rest is hidden in the oceans below 2000m (recently found in part by von Schukmann but disputed by BP and at variance with several other ocean heat analyses) Within the 0.9W/sq.m imbalance is embedded the climate reponses from Fig4 of Dr Trenberth's paper. The radiative feedback from increasing Earth's temperature of -2.8W/sq.m is based on Stefan-Boltzman Eqan for 255degK and a surface temperature rise of 0.75 degK which seems to apply faily well to the troposphere for the planet above the 'equilibrium temperature' of pre-industrial times. The critical point is what will be the negative radiative feedback for the postulated 3degK rise in surface temperature (doubling of CO2) when applied to Fig 4 of Dr Trenberth's paper where a doubling of CO2 would by IPCC formula increase CO2 radiative forcing to 3.7W/sq.m and other GHG forcings by unknown amounts. The key to this is what portion of the 3degK rise also applies to the troposphere and what will be the increase in the Earth's overall OLR and 'equilibrium temperature'. Humidity and lapse rate are critical parameters around which there is much discussion and uncertainty. Your thoughts gentlemen? -
Berényi Péter at 01:00 AM on 27 March 2010Is the science settled?
#79 Ned at 21:56 PM on 26 March, 2010 "What is the "it" in that sentence?" The sign of the water vapor feedback loop, of course. There is a rather strong positive feedback if we keep relative humidity constant on all levels (as it is routinely done in computational models of climate). Whether Mother Nature complies with this requirement is not known. -
Christopher Fraser at 00:56 AM on 27 March 2010Better to adapt than mitigate
The Stern Review on the Economics of Climate Change, a 700-page report commissioned by British Government released October 30, 2006, concluded that the benefits of strong, early action on climate change considerably outweigh the costs. -
James Wight at 00:35 AM on 27 March 2010It's a 1500 year cycle
John, I've been reading through Motl's rebuttals to your counterarguments, and I think he does have a point about this one. The title "It's just a natural cycle" implies that the page discusses natural climate cycles in general (including solar cycles, orbital cycles, etc). But your response only deals with the claim that we're experiencing something analogous to a Dansgaard-Oeschger event. Thus the title is a bit of an oversell.Response: I know, this argument started as a focus on the 1500 year cycle but when I started the Global Warming Links directory, I splintered it off into the more general natural cycle and the more specific 1500 year cycle. But I haven't got around to answering the more general argument. Problem is people have already started adding links to the 1500 year cycle argument so I can't go back to the way it was. Long story short, I painted myself into a corner with my argument structure and the only way out is to find the time to write detailed rebuttals to both. Okay, now where is that time, I know I left it around somewhere... -
PatriciaW at 00:06 AM on 27 March 2010How you can support Skeptical Science
I got this message via email and I want to comment that just copying and pasting content from a website to an email message does not work properly. For example the Donate button is not visible, there is no left margin, and lots of characters (Â) are inserted which make it hard to read. -
JMurphy at 00:02 AM on 27 March 2010What CO2 level would cause the Greenland ice sheet to collapse?
Ned wrote : "I do not understand why you [GALLOPINGCAMEL] persist in accusing the honest, hardworking scientists of NOAA and NASA of "throwing away data" that they were never given in the first place ... particularly when many different, independent analyses of the data show there is no effect on the end result." For the very same reason that he/she keeps repeating things like : 'The idea that humans are a significant factor in raising global temperatures rests on a very shaky foundation as "Climategate" has shown.' I.E. A few emails/files (none of which actually relate to the science of AGW, unless you believe in cherry-picking words and quotes) are enough for some to carry on denying. 'Unless better evidence is presented I will continue to believe that natural factors dominate.' I.E. With reference to the previous excuse : 'I don't want to accept AGW and will use any straws to clutch at.' 'The "Copenhagen Diagnosis" mentioned at the top of this thread encapsulates the IPCC's over reaching and exaggeration of mankind's influence.' I.E. 'I don't understand/want to wilfully misinterpret the IPCC and what they do and don't do..because I don't want to accept AGW.' 'This is what I call the "Catastrophe de Jour" approach which has damaged the IPCC's credibility beyond repair.' I.E. 'I must join in with those who want to destroy the credibility of the IPCC and we will use any small errors to try to do so; or, at least, to make sure that we can justify our denial of AGW.' 'The IPCC's Alarmist predictions for 2100 depend on climate models (GCMs) and Michael Mann's adherents who cling to tree ring temperature proxies.' I.E. The conservative projections based on GCM and AOGCM models from 10 different countries are, supposedly, all based on Michael Mann and his friends. Hmm. And, supposedly, they are the only ones using tree-ring temperature proxies. Hmm 'One of the many scientists who doubt mankind's ability to affect climate is Roy Spencer:' I.E. One of the very few, but a trusted expert to those who wish to clutch at straws and deny. And one who is presently struggling to explain the high UAH anomalies without reference to AGW. All the statements are trying to justify denial, and neither facts, figures nor reality will be allowed to get in the way of that. That means constant repetition, ignoring others, repetition, repetition, etc., etc. -
Ned at 23:29 PM on 26 March 2010CO2 was higher in the past
muoncounter: Thanks for the link to that Villas et al. 2002 paper. That's really neat. They claim that marine carbonate deposition sequestered a mass of carbon equivalent to 350 times the current quantity of atmospheric CO2! I like their explanation of the mechanisms for both the onset and termination of glaciation. -
Ned at 23:14 PM on 26 March 2010Water vapor is the most powerful greenhouse gas
Thanks for the comment, Bob Close. First, on the very narrow point of CO2 vs water vapor: As a thought experiment, imagine that you could somehow remove all the water vapor from the atmosphere, and prevent any more water from evaporating into the atmosphere (but you keep CO2 constant). Now, alternatively, imagine that you removed all the CO2 from the atmosphere, but kept water vapor constant. (Yes, both these alternatives are physically impossible on our world, but use your imagination). The world with no water vapor (but normal CO2) would get much colder than the world with no CO2 (but normal water vapor). So in that sense, you could say that "water vapor is more important than CO2 in warming the planet". However, neither of those is a realistic scenario. In the real world, we are doubling CO2 concentration. This has the effect of warming the planet somewhat. Water vapor then acts as a feedback, increasing the warming started by CO2. So we end up with our natural base temperature (t0) plus some new warming from CO2 (dt1) plus some additional new warming from the water vapor feedback (dt2). But in terms of assigning responsibility for that warming ("whodunit?") ... both dt1 and dt2 are a result of the increase in CO2. If we hadn't burned any coal or oil, we would still be at t0. The same would be true if there were some other event that caused warming (or cooling). For example, 65 million years ago a bolide impact on the Yucatan peninsula injected a lot of dust, aerosols, etc. into the stratosphere, which cooled the planet, which in turn reduced the amount of water vapor, which cooled the planet further. None of that cooling would have happened without the bolide impact, so even though some of the cooling involved water vapor, we still would say that all of the cooling was caused by the impact event. That initial cooling was followed by a rapid and extreme warming, caused first by CO and other shorter-lived greenhouse gases, then by CO2 which lasted for many centuries. Much of this new carbon came from the carbonate rocks that were vaporized at the impact site, injecting lots of carbon into the atmosphere. Once again, this warming was amplified by the water vapor feedback, but none of it would have occurred without the presence of CO, CO2, etc. So on both the downswing and the upswing in temperatures, water vapor acts as a feedback amplifying the change in temperature that is created by some other forcing (greenhouse gases, aerosols, solar variations, etc.) -
Peter Hogarth at 22:59 PM on 26 March 2010Visual depictions of Sea Level Rise
Berényi Péter at 21:33 PM on 25 March, 2010 I can only suggest your skepticism about GPS is groundless and would be quite worrying to the surveying/military/geodetics community world wide. Please think about the implications. You should re-read your original reference from Ekman 2000, chapter 4 about the then emerging science of vertical GPS measurements and then update it by 10 years by reading the references I and others have supplied, and continuing with your online course. Your comments about “same story” indicate that you have some belief system against AGW which you are using here to discredit high precision geodesy and GPS. This is not evidence based. You have also seem to have confused differences between Geoid and real Earths surface, (which I agree can be very large), and the absolute measurement error in these differences, which is small. I have first hand experience of modern precision GPS base stations as used for Real Time Kinematic work, such as vessel positioning and real time tidal or even absolute heave corrections of vessel motion. If I place such a system on the Earths surface, turn it on, and then look at the diagnostics, I can see the RMS vertical error gradually reduce and settle over a few minutes to cm level or better. This is reported as a difference to geoid measurement (WGS84 usually) but is ultimately referenced to the ITRF Geocentric frame and GPS orbital parameters as already discussed at length. The Geoid is merely a useful tool (for charting etc). Local chart vertical datums are another story altogether! I appreciate you are learning about Geodesy, but a learner should be cautious about making sweeping generalizations based on casual reading. The following is a practical short introductory guide to real world height measurement, and it is already slightly dated as the technology advances rapidly: Heighting with GPS: Possibilities and limitations. The section on manufacturers quoted accuracy should be noted. These are real systems in everyday use. I can supply more detailed references if you wish, but please take time to absorb first and comment later? I have designed non-GPS cm level long range precision positioning/tracking systems down to component level, and these sometimes rely on GPS for absolute accuracy and repeatability over long periods so I have some hard won knowledge of many of the issues I am trying to explain. I still do not consider myself an expert, though I hope you realise that I answer your points constructively with science modulated by rational thought. If I am allowed an off topic comment your conclusions on GPS are indeed “something completely different!”
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