Arguments
Recent Comments
Prev 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 Next
Comments 60551 to 60600:
-
John Russell at 04:45 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@danielc As someone who spends a considerable amount of time fighting fake scepticism/denial -- call it what you will -- I very much agree with what you say. At my age (semi-retired) I accept I'll never get my head round everything to do with climate but I can clearly see how the jigsaw pieces fit together and the more I understand, the more I can do my bit to correct misinformation wherever it occurs. Like Hansen, I'm driven by concern for my grandchildren's future. -
r.pauli at 04:37 AM on 10 April 20122012 SkS Weekly Digest #14
Everything is a lesson. Lessons not learned will be repeated. -
Sapient Fridge at 04:31 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
danielc, I'm a bit confused. Near the top of your post you said "(High Tilt Angle = HTA) the polar regions receive a lot more sunlight in summer" and "(Low Tilt Angle = LTA) the summers are cooler" but further down you seem to have it the other way round:"High tilt = Cooler polar summers coupled with warmer polar winters = ice growth (assuming there are continents around to support glaciers). Low tilt = Warmer polar summers and cooler polar winters = ice shrinkage."
Lack of understanding on my part, or mistake in your post? -
mdenison at 04:14 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
#18 Nature link supplementary pdf -
mdenison at 04:10 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
... In the same post, Willis Eschenbach criticized the paper saying "My rule of thumb about these kinds of things is, no error bars … no science." ... Not only do such comments ring hollow on reading the paper but a look at the supplementary material shows page after page after page (37 pages) of reasoned discussion, analysis and quantification of the uncertainties in the paper. For those who want a look the supplementary pdf is not behind a paywall. It's hard work reading through it and you may not come away much the wiser but I think you certainly come away with a clear idea of the care climate scientists put into their work. -
danielc at 04:04 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@John, being skeptical is not a problem... it's a requirement to do good science. It's when one hides one's complete unwillingness to admit the reality of solid facts, data, and basic math and physics behind a rhetorical mask of supposed skepticism that problems begin to arise and civility begins to decay. Honest questions deserve honest answers. False skepticism that masks accusations of fraud, dishonesty, lies, and alarmism for political advantage (e.g. Lindzen, Monckton, and the rest) deserves nothing but contempt. -
boba10960 at 04:03 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@9 and @13 I wrote the following before seeing the post @14 by danielc, but I will post it anyway. Three features of Earth’s orbit change in regular patterns: 1) The shape of the ellipse (more elliptical vs. more circular) varies on a 100,000 year cycle, 2) The tilt of Earth’s axis varies on a 41,000 year time scale (the greater the tilt the more sunshine reaches polar regions to melt ice sheets), and 3) Earth’s axis wobbles on time scales of 19,000 and 23,000 years. All three cycles combine to regulate the amount of sunshine reaching high latitude regions in summer, the primary variable regulating the growth and melting of ice sheets according to the Milankovitch hypothesis. Of particular importance is the combination of (1) and (3), whereby maximum melting of northern hemisphere ice sheets occurs when the phase of the wobble causes the northern hemisphere summer to coincide with Earth’s closest approach to the sun during a particularly elliptical orbit. As far as I know, each of the last several ice age termination occurred under these conditions. -
John Russell at 03:57 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@danielc #14 Thanks very much for the very clear explanation. I got it. Apologies if I took it back to basic levels! I really don't understand why so many 'sceptics' claim they've been 'abused' when asking questions on SkS. Ask a straightforward question and you get a straightforward answer. Thanks. -
John Russell at 03:46 AM on 10 April 2012More Carbon Dioxide is not necessarily good for plants.
@Eric #232 You say, "My argument is not that this is good (likely not), but that the net biosphere response will not be 'overwhelmed' as R. Gates puts it, rather the opposite. " It's worth pointing out that R.Gates actually said, "Not only can short-term feedbacks be overwhelmed, long-term biosphere feedbacks might as well" (my bold). It's clear that R.Gates was not suggesting -- nor did I assume -- that a rapid increase in CO2 would lead, necessarily, to a die-back of the biosphere. In the worse case though I'm sure you would agree that it could certainly lead to a die-back of life as we know it. To my mind that's bad enough. We're playing with fire. -
danielc at 03:32 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@John Russell: The tilt and the change of tilt with time actually has a huge impact in several ways. 1) with the rotation axis tilted strongly toward the sun (High Tilt Angle = HTA) the polar regions receive a lot more sunlight in summer, and that sunlight in summer is more direct (more watts/m2). The result of HTA is extreme temp. differences between short hot polar summer and long cold polar winter. The result is ... no ice age - the hotter summer makes more of a difference than a winter that is just a bit cooler. 2) With the rotation axis weakly tilted toward the sun (Low Tilt Angle = LTA) the summers are cooler and the winters relatively warmer, however the short, cool polar summer encourages retention of winter ice and snow, and season upon season, the snowpack grows, compresses and forms glacier ice... LTA appears to correspond well with glacier/ice cap growth. 3) Couple Tilt changes from HTA to LTA with longer and shorter term periodicities in the orbital shape (eccentricity) and precession of the seasons (where in the eccentric orbit the tilted earth faces the sun) and you can map out high-latitude insolation reasonably well. 4) Couple that with the position of continents (Low heat capacity rock at high latitude vs high heat capacity water... as well as a stable platform needed to grow ice caps in the first place) and you start to see strong correspondences between orbital forcing and ice growth or shrinkage. So it is NOT that there is a global heat increase triggered by orbital mechanics!! Given the minor and short term cycling of solar output, the fact is that over long time scales, the total global heat budget is approximately constant. It is that the distribution of heat - the timing of when certain areas get hot, and how hot they get - changes. High tilt = Cooler polar summers coupled with warmer polar winters = ice growth (assuming there are continents around to support glaciers). Low tilt = Warmer polar summers and cooler polar winters = ice shrinkage. Juice that system a bit with eccentricity and precession to magnify or dampen the tilt signal... Now, here's the funny thing: currently the earth is head from a high-ish tilt scenario into a lower-tilt scenario... and the polar summers are getting warmer. Either the theory is wrong... or something else is happening! What else could be happening? Well, perhaps the total heat budget being relative stable is no longer operative!!! Adding more heat-retentive materials to the atmosphere, losing heat reflective materials from the polar regions = keep more heat. The heat budget is now in a state of IMBALANCE. Homeostasis (invoked by Lindzen and Monckton) has been disrupted. The current trend of observed year on year and decade on decade temperature and heat changes in particular regions runs counter to what the geological record and orbital mechanics tell us should be happening. -
John Russell at 02:58 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@MA Rodger #9 Apologies for my 'woolliness' -- the result of trying to use simple language! Yes, I was meaning that the sun's output remains constant but, as a result of the orbital cycles, the distance between the sun and Earth (and thus the energy arriving) varies. However there seems to be more to these orbital cycles than you mention. As I understand it our position relative to the sun varies in at least three ways. 1) The shape of the ellipse varies -- sometimes being closer to circular and sometimes being flattened. 2) The position of the sun within the ellipse varies (or more accurately it's the position of the Earth's orbit that's varying), sometimes being nearer the centre and sometimes slightly off to one side. And 3) the Earth wobbles on its axis as you describe, favouring one pole or the other in terms of arriving warmth. I'll stand corrected but I don't think this last variation, 3), is going to be a trigger for a global heat rise, as it's just redistributing the sun's energy from one one half of the globe to the other. So the main cause of an ice age is both 1) and 2) conspiring against us. Is this correct? Sorry if this is a bit simple for some, and perhaps veering a little off-topic. But certainly for me, and probably many other non-scientists, it's useful for basic understanding. -
danielc at 02:50 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
http://www.pnas.org/content/105/44/16855.full.pdf+html?with-ds=yes is a good reference for talking about the weathering aspect... Basically, weathering of glacially derived sediments (in moraines) takes ~12 to 25 kyears to run to completion... so weathering and CO2 stripping lags well behind CO2 and T increases... but it does catch up in the end ... as long as no extra CO2 is released. Ooops. -
Eric (skeptic) at 02:30 AM on 10 April 2012More Carbon Dioxide is not necessarily good for plants.
michael sweet, I realize now that thrive is not the right word. The vegetative biosphere will grow net and fill in with plants that can grow in more varying and/or stressed conditions. A lot of those plants will be weeds. OTOH will a little part time effort I can make 5 acres thrive. Full time with equipment I could do 4-5 times that. That will be repeated worldwide on various scales. I also realize there are millions of acres that won't come back to a productive and diverse state, not just because of climate change as you mention but because of CO2 selectivitity. All the papers I referenced back up the reduction in diversity. They also mostly back up the net growth. -
dana1981 at 02:18 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
CBD @6 - what I mean is that ~7% of the net warming occurs between the orbital 'trigger' and the CO2 rise. The remaining ~93% of the warming lags behind the CO2 rise (as illustrated in Figure 1). -
michael sweet at 01:56 AM on 10 April 2012More Carbon Dioxide is not necessarily good for plants.
Eric, It is good that you are referencing peer reviewed papers. Your first reference shows that some ecosystems have evolved to survive very hot temperatures. How does this limited example show "clearly that the biosphere will thrive"? Your second reference states "demonstrating the reality of multiple-factor influences, and reminding us that surprises can be expected. I read more "surprises can be expected" not the biosphere will thrive. There is also the strong posibility that what thrives will be jellyfish and the tuna will die out. While lots of jellyfish means the biosphere is "thriving" it is not very useful to those who are looking for something to eat. When you cut down rainforest, jungle grows back. It takes decades, or more, for the rainforest to repair itself. If climate continues to change, the rainforest will never come back. If farmers cannot count on an orchard yielding fruit for 30 years they will not plant the trees in the first place. Few people expect all life on the planet to die off. It is possible that much of the useful life will die off and all that is left is weeds. Can 8 billion people be fed and housed on weeds? -
danielc at 00:58 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@ #4: Silicate weathering. Increased CO2 and temperature cause (among many other things) 1) a decrease of ice cover, exposing fresh rock that was once covered, and 2) enhanced production of carbonic acid (acid rain) in the atmosphere (higher partial pressure of CO2 and warmer temperatures to help drive the reaction H2O + CO2 --> H2CO3 (l). The net result of acid rain falling on fresh rock with small grain sizes is enhanced silicate weathering and net reduction of CO2(atm). This cycle is one of the stronger negative feedbacks that drives the system back toward equilibrium, but it works on a much slower time scale than the initial dumping of CO2, so it takes a while to kick in... -
Eric (skeptic) at 00:15 AM on 10 April 2012More Carbon Dioxide is not necessarily good for plants.
John Russell, thanks for the reply. Other than my work, I spend the largest amount of my time combatting weeds: mulching, pulling, cutting, planting non-weeds, spraying, and burning (in order of preference). The bottom line is clearly that the biosphere will thrive, see http://tbi.montana.edu/topics/inthenews/pdfsdocs/Science_Stout.pdf for one example and figure 1 here http://research.eeescience.utoledo.edu/lees/papers_PDF/Norby_2004b_NewPhyt.pdf for another. But it won't be pretty. Evolution is slow like you say, but infilling with invasives will happen in a few years in an area where native plants are wiped out by climate change effects. My argument is not that this is good (likely not), but that the net biosphere response will not be "overwhelmed" as R. Gates puts it, rather the opposite. -
John Hartz at 00:08 AM on 10 April 2012More Carbon Dioxide is not necessarily good for plants.
Suggested reading: “Which plants will survive droughts, climate change?,” UCLA Newsroom, April 5, 2012 To access this news release, click here -
John Hartz at 00:06 AM on 10 April 20122012 SkS Weekly Digest #14
Speaking of plants… “Which plants will survive droughts, climate change?,” UCLA Newsroom, April 5, 2012 To access this news release, click here -
MA Rodger at 00:05 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
John Russell @7 To be precise (that is you make the point but using rather woolly terminology at times), it is the Earth's wobbly orbit (Milankovitch cycles) that is the "trigger." The sun shines normally but the orbit provides increasing sunshine in Northern latitudes (& less in the South). The sun is thus not a "main driver." Indeed, the concept "driver" may be unhelpful here. The orbit "triggers" a shift of heating from South to North. This destablises the global climate with the relative influence of the agents causing that destabilising change (be they "feedbacks" or "drivers?") presented above in fig 5 of this post. This graph shows in order of importance - CO2 behind (presumably reduced albedo from) ice fields & vegitation. To consider them as "actual drivers" only makes sense if you want to calculate Climate Sensitivity resulting from other "actual drivers" (eg anthopogenic ones) & (I assume) within the constraint that the process addressed (eg AGW) will not result in significant "feedbacks" from the "drivers?" that are used in the calculation. (This last point likely does not hold if Climate Sensitivity is high or if Anthopogenic Forcing is high.) -
John Russell at 23:55 PM on 9 April 2012More Carbon Dioxide is not necessarily good for plants.
@Eric #229 I think if you read back through the comments on this thread, everything you say has already been discussed at length. But to summarise... Plants have evolved to suit the conditions in which they thrive. This is self-evident when you consider that a plant that thrives in a certain place will often not thrive 10 miles up the road, at a higher altitude, or in a different soil type. So every plant has its niche. Given long enough, plants can adapt and/or evolve to suit different conditions. But if everything changes too rapidly then, as R. Gates says, the biosphere could be overwhelmed; for plants are generally at the bottom of the food chain. Clearly you can find examples of specific plants in specific circumstances apparently being 'improved' by a change in growing conditions. That's because we're looking at things from a human perspective. When a farmer increases the CO2 in a glasshouse to boost growth, he also monitors all the other things that the plant needs to be healthy: moisture; pests; nutrients; temperature, and so on. And remember he's probably not interested in the plant's ability to reproduce -- it's served its purpose and is in a plastic bag on the supermarket shelves long before that happens. So what matters, away from human intervention in the biosphere, is that a plant receives what it's historically received in the location it's growing, and anything that changes -- moisture, temperatures, sunlight, nutrients, CO2 -- is likely to compromise its health. I mean, even water is good for plants -- but too little or too much of it will certainly kill off a lot of them. And a few hundred years is not long enough for most of them to evolve to cope with a changed atmosphere and climate. And as plants fare, ultimately, so do animals. -
Alexandre at 23:51 PM on 9 April 20122012 SkS Weekly Digest #14
About the Issue of the Week: Not optimistic at all. Actually, I would be really surprised if there were any effective international mitigation agreement in the next few years. Anthropogenic PETM, here we come! -
mdenison at 23:34 PM on 9 April 2012Shakun et al. Clarify the CO2-Temperature Lag
R Gates #2 Could you provide some references for these points. I think what you write needs clarification. -
KR at 23:34 PM on 9 April 20122012 SkS Weekly Digest #14
Sapient Fridge - Plants as CO2 absorbers? Unfortunately, plants tend to grow then decay, releasing CO2 back into the atmosphere. This is seen in the annual CO2 cycle. If we had plants that created coal as an output, or in some other fashion sequestered the CO2 for the long term, that would be great. But barring some serious genetic work, I cannot see that happening... -
KR at 23:29 PM on 9 April 20122012 SkS Weekly Digest #14
caerbannog - Very clear work. As Tom Curtis said, not surprising if you understand the data, but very clear for those who don't. Regarding high latitude stations appearing closer, you might want to look at the very simple boxing procedure used by Hansen and Lebedeff 1987 (Fig. 2), where they used larger longitude ranges at higher latitudes to keep the enclosed areas similar - 16 longitude boxes at the equator, 4 near the poles, for 80 different regions. -
John Russell at 22:27 PM on 9 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@CBD #6 In my head (which I hasten to clarify is not that of a scientist) I imagine that the shift in orbital variation between the point where the trajectories are all acting together to push us to the greatest extremity from the sun and the point when the variations tend to cancel one another out, is a gradual process taking many thousands of years. Consequently the increase in energy arriving from the sun which triggers the warming then kicks off the CO2 rise. After that it's a process of the main drivers -- increasing amounts of energy arriving from sun and increasing atmospheric CO2 levels -- each contributing to the rise in the planet's temperature. And at the same time, of course, the rising retained energy inputs also push along rising atmospheric CO2 concentrations. Then only when the energy input from the sun stops rising can the carbon cycle achieve a new, globally warmer, equilibrium. So it's a complex interaction (and I'm sure there are several other contributors) which cannot really be separated out, I would think (or can they?). I don't know whether this perception is right but it's always the way I've imagined it in my, very visual, rather unscientific, imagination. Am I correct? One other question. With regards to the apparent difference between lag in the Antarctic and globally; could this be due to the Earth's axis wobble? -
Eric (skeptic) at 22:23 PM on 9 April 2012More Carbon Dioxide is not necessarily good for plants.
R. Gates suggested on the Shakun thread that our current fast rise in CO2 (doubling in about 300 years) could overwhelm the biosphere and therefore cause an overshoot in temperature. That will require several things to be true: first that extra CO2 is a net negative for the biosphere; and/or second that rapid climate changes are also net negative for the biosphere; and third that the biosphere changes will exacerbate the temperature rise causing the overshoot. I would like to discuss some issues with all three of those. Some studies http://www.biosphere.ibimet.cnr.it/File_Publications/thirty%20years%20in%20situ%20forest%20responses.pdf show that elevated CO2 leads to more rapid juvenile tree growth. Other studies http://www.up.ethz.ch/education/biogeochem_cycles/reading_list/koerner_sci_05.pdf show no net change in mature tree growth. The first study also showed that increased CO2 allowed more drought tolerance and the second has neutral results for the 2003 Western Europe drought. For the third item, the biosphere has been modeled for many years to benefit climate models. In this paper http://www.fas.harvard.edu/~eps5/writing_assignment/T_GHG_RECON/bonan_2008_forests.pdf they summarize some basic results: reduced albedo (causing net warming) versus increased transpiration (causing net cooling). I don't see any resolution yet to the question of net climate result. The bottom line is that R. Gates concern is somewhat speculative. The climate may overshoot due, essentially, to desertification. It may undershoot due to enhanced net biosphere growth if the desertification is essentially localized (which I believe it is) and the "warmer = wetter" is the net result for the world (that discussion belongs on a different thread). -
CBDunkerson at 22:07 PM on 9 April 20122012 SkS Weekly Digest #14
"How optimistic are you that the human race will get its act together in time to stave off catastrophic climate change?" Depends on how we are defining "catastrophic". That could range anywhere from an increased incidence of natural disasters (which we have already seen and thus cannot possibly stave off) to a mass extinction or sudden sharp decline in human population. Many other activities of humans are also contributing to mass extinction and it thus isn't clear whether we'll be able to avoid that even if we get climate change under control. Ditto human population. It now seems clear that solar power technology will drop well below fossil fuel costs (even ignoring the imbalance in externalities and subsidies) over the next few decades. However, a switchover to solar power would also require improvements to power distribution (which will require political will) or storage (which will require technological breakthroughs). I see very little evidence of political will. Thus, to me it all comes down to 'batteries'. If we develop ways to store energy roughly four times as quickly and compactly in the next decade or so then there will be a 'sea change' away from fossil fuel power to solar. If not we'll continue on as we have been for another thirty years or more and things will eventually get very bad indeed. Obviously Bern's 'global CO2 scrubbers' or some other technological breakthrough could also change the game, but solar and batteries are the current front-runners in my mind. -
CBDunkerson at 21:38 PM on 9 April 2012Shakun et al. Clarify the CO2-Temperature Lag
"According to the Shakun et al. data, approximately 7% of the overall glacial-interglacial global temperature increase occurred before the CO2 rise, whereas 93% of the global warming followed the CO2 increase." How exactly is this derived, given that neither the temperature increase nor the CO2 increase was a singular event? In previous examinations of this question an important point has been that the (then supposed) initial increase in temperatures caused an increase in CO2 levels... which caused a further increase in temperatures... more CO2... et cetera. The changes were going on concurrently, with only the initial triggers being offset. That argument made sense and still does... but then how do you compute '93% after' from two concurrent processes? My best guess is that they are looking at the time period between the start of the orbital forcing and the start of the CO2 increases and finding that it accounted for 7% of the total temperature rise. However, that might then create a perception that the 93% 'after the CO2 increase' was entirely due to the CO2, when in reality the continued orbital forcing was also likely involved. That said, a lot of the reporting on this has described it as a change from 'CO2 lagged temperature' to 'temperature lagged CO2'. However, the actual study still finds that the warming from the orbital forcing came first... so the increase in atmospheric CO2 levels still started after the increase in temperatures. That temperature increase was just concentrated first in the Northern hemisphere (as expected due to the forcing) and then in the Southern (the real 'new' finding of the study) apparently due to AMOC. Using the 'accelerated' Southern hemisphere temperature as a global value made the CO2 lag look longer than it was, but even with the 'global' values used by this paper they found 7% of the warming prior to the CO2 increase. The 'skeptics' who aren't thus appear to be freaking out over how the paper has been reported without stopping (or possibly being able) to understand what it actually says. -
Lionel A at 21:35 PM on 9 April 2012Climate Scientists take on Richard Lindzen
keith @13 & dana1981 @15 On the origins of CAGW Wiki gives a brief resume of one potential trigger for this term here, John T. Houghton, see under Falsely attributed . Tim Lambert had a post on this at Deltoid, Akermangate: Piers Akerman fabricates some more . -
Sapient Fridge at 21:04 PM on 9 April 20122012 SkS Weekly Digest #14
Bern wrote: "someone might invent a solar-powered gizmo that sucks CO2 from the atmosphere, converts it into solid carbon + O2, and just keeps powering on." Aren't such machines called "plants"? -
Bern at 20:26 PM on 9 April 20122012 SkS Weekly Digest #14
How optimistic are you that the human race will get its act together in time to stave off catastrophic climate change? Not at all. I think there will be catastrophic impacts, and that it will be these catastrophic impacts that finally trigger global action to stop CO2 emissions. I also think some of these might occur much sooner than later. But, as always, it's a question of degree. With sufficient resources thrown at the problem, atmospheric CO2 could be sequestered technologically at a similar rate to emissions, so we might get 'back to normal' within only a century or so after tackling the problem. On the other hand, so many resources are going to be taken up with mitigation and adaptation to the early impacts, that, combined with the economic impacts of those climate impacts, there might not be enough spare to work on techno-sequestration. On the gripping hand - someone might invent a solar-powered gizmo that sucks CO2 from the atmosphere, converts it into solid carbon + O2, and just keeps powering on. In which case, we've at least got a running chance... -
John Russell at 18:43 PM on 9 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@question #4 Here's the simple explanation. The ultimate driver of temperatures on our planet is energy from the sun, which is affected by the variations in the shape and offset of the Earth's orbit and wobbles of our axis. Changes in these, immediately preceding the end of the ice ages, triggered the rise in temperature which led to a release in CO2 and the warming that took place (as described in the post). So to answer the question: Earth's energy balance always seeks equilibrium which, once the variations in orbit and wobble had then stabilised (or more correctly 'neutralised' each other), our planet eventually achieved. Further warming then stopped and we settled down to a new, warmer, state which -- this time round -- happened to coincide with a level of human development conducive to the beginnings of civilisation. As I started by saying this is a very simplistic explanation. I'm sure the scientists here will be happy to provide more detail (or, for that matter, correct me if I've oversimplified anything). -
question at 17:44 PM on 9 April 2012Shakun et al. Clarify the CO2-Temperature Lag
Can anyone clarify the reasons for the levelling off of both CO2 and temperature at the end of the transition? Thanks. -
Sapient Fridge at 17:16 PM on 9 April 2012Shakun et al. Clarify the CO2-Temperature Lag
Good article, but some typos: "feebacks", "mananges", "equilibirum", "unerstanding" and "depocted" (Delete after fixing if you want) -
R. Gates at 15:23 PM on 9 April 2012Shakun et al. Clarify the CO2-Temperature Lag
Excellent summary of the Shakun et. al. paper and the predictable skeptic response by Easterbrook et. al. In terms of sensitivity, I personally think the 3C estimate is pretty solid, as the rate of CO2 growth, not just the actual raw number must be considered. The response of the climate to a doubling of CO2 that takes 10,000 years versus 350 years is a different dynamic. Specifically, natural negative feedback pathways become overwhelmed when the doubling occurs in the shorter time frame. Not only can short-term feedbacks be overwhelmed, long-term biosphere feebacks might as well. Additionally, in the case of the current Anthropocene, it is not just CO2 that is increasing from human activity, but N2O and methane as well. Thus, even if the sensitivity of the climate to a doubling of CO2 from 280 ppm to 560 ppm that took 10,000 years is around 2.5C, it may not be the case that this is the same sensitivity for a doubling that takes 350 years. What might happen, for example, is a classic overshoot situation where, even if we manage to keep CO2 at 560 ppm, because of the rapid rise of CO2, and the overwhelming of the feedback processes. the system overshoots what would have been an equilibrium temperature of 2.5C, and spikes higher. In spiking higher, some new biosphere, hydrosphere, or cryosphere threshold is crossed, that mananges to send the system to a higher equilibirum temperature because the character of the system has been changed by the rapidity of the CO2 spike. -
geologic at 15:15 PM on 9 April 2012Shakun et al. Clarify the CO2-Temperature Lag
good summary...can anyone add detail to how the see-saw works? All I've been able to find is somewhat vague descriptions that heat accumulates in the tropics when the AMOC shuts off, this heat then somehow gets transferred to the southern ocean....how? what turns on the S. Atlantic circulation system that re-distributes the heat southward out of the tropics? -
Tom Curtis at 15:08 PM on 9 April 2012New Understanding of Past Global Warming Events
danielc @1, currently the rock weathering process is approximately in balance with global CO2 emissions from volcanoes. We know this because of the very nearly stable CO2 concentrations over the holocene. That means that the rock weathering process removes approximately 0.224 to 1.1% of annual anthropogenic CO2 emissions every year. Put differently, for each year of emissions at current rates it will take between 90 and 450 years to remove the emitted CO2 from the atmosphere. At least it would if there were no ongoing CO2 emissions from volcanoes. Put another way, if the rate of CO2 removal by rock weathering where doubled while the rate of CO2 emissions from volcanoes remained the same and humans stopped all CO2 emissions, it would take on average 5500 year to remove the emissions of the last 20 years from the surface reservoirs of CO2 (ocean, soil, biosphere and atmosphere). Fortunately increased warmth does increase the rate of rock weathering by increasing chemical reaction rates directly, and by increasing the strength of the water cycle, thus increasing the rate of erosion. But it may still be from tens to hundreds of thousands of years before CO2 levels are restored to pre-industrial levels. -
Tom Curtis at 14:45 PM on 9 April 20122012 SkS Weekly Digest #14
Caerbannog @1, I, for one, find your results very interesting if not entirely unexpected. Indeed, I think the work that you and other amateur climate scientists have done of the surface record should be given much more prominence. To that end I suggest that you contact John Cook so that your results can be published as a blog post here on SkS, rather than simply being lost in the comments. With regard to the actual results, I noticed that some stations in the sparse network are very close together. There appear to be two from Alaska, for example. There are also two from northern Scandinavia, and one each from east Texas and Louisiana (I think). These stations might be seized on as distorting the result, although I strongly suspect they do not. Perhaps you could modify your program to select boundary locations to maximize the average distance between stations (or perhaps to maximize the cube root of the distances between proximal stations to give greater weight to avoiding close pairings) so as to avoid this criticism. Alternatively you could just drop out the shortest of any two records from the analysis where they are closer than some minimal distance. (I am sure you can think of other ways to avoid the issue as well.) Further, as an antipodean, I would appreciate maps of station sites that show the entire globe, and not just the North Atlantic and surrounding lands. -
Daniel Livingston at 14:39 PM on 9 April 20122012 SkS Weekly Digest #14
How optimistic are you that the human race will get its act together in time to stave off catastrophic climate change? This is quite a subjective question, so forgive me for an answer that may appear quite subjective on a scientific site such as SkS. I am actually optimistic about the future, but not about humanity fixing this climate issue. Extraordinary problems require extraordinary solutions, so I am not looking to science, technology, markets, policies or regulations to fix this. According to my belief in the Bible, outside intervention will arrive before humanity succeeds in destroying the planet and ourselves. My optimism, however, is not placed in some inherent capacity of nature to always come up trumps against the onslaught of human activities, or in human ingenuity to always result in progress and improvement. The Bible paints a different picture. According to the Bible humanity can succeed and achieve improved life, but only a minority of humanity will find such success. -
Chris G at 14:11 PM on 9 April 2012Climate Scientists take on Richard Lindzen
In 2005, Lindzen wrote: "... Let me summarize the main points thus far: 1. It is NOT the level of CO2 that is important, but rather the impact of man made greenhouse gases on climate. 2. Although we are far from the benchmark of doubled CO2, climate forcing is already about 3/4 of what we expect from such a doubling. 3. Even if we attribute all warming over the past century to man made greenhouse gases (which we have no basis for doing), the observed warming is only about 1/3-1/6 of what models project. We are logically led to two possibilities: 1. Our models are greatly overestimating the sensitivity of climate to man made greenhouse gases, or 2. The models are correct, but there is some unknown process that has cancelled most of the warming. ..." I'm thinking he egregiously overlooked a 3rd possibility, that the system has not yet reached an equilibrium. -
caerbannog at 13:29 PM on 9 April 20122012 SkS Weekly Digest #14
(This is a modified version of a post I put up in the realclimate.org "unforced variations" thread). Off and on, I had been experimenting with some "simple minded" processing methods applied to the GHCN raw temperature station data. I have found it surprisingly easy to replicate the published NASA/GISS "meteorological stations" index with some pretty simple data-crunching procedures applied to *raw* station data. The global temperature record is really amazingly robust -- the global-warming signal just "jumps out of the data" even with the crudest processing approaches. I’ve been trying to put together a simple, easy to understand visual demonstration of the reliability/robustness of the global temperature record, in an easy-to-digest “eye candy” format -- i.e. something that won’t make non-technical folks’ eyes glaze over. The goal is to have an easy to comprehend "visual refutation" of the most popular "skeptical" claims about the global temperature record. With that in mind, I put together 3 images. 1) A plot of what I call the “Sparse Rural Stations Index", which is just a set of global-average temperatures computed from a very small number of scattered rural stations, displayed along with the official NASA/GISS “Meteorological Stations” temperature index.
The procedure used to generate the "Sparse Stations Index" is really quite simple:
Divide up the globe into 20 degrees x 20 degrees grid-elements (at the Equator; longitude dimensions adjusted as you go N/S to keep grid-element areas approximately constant). Search each grid-element for the rural station with the longest temperature record. Use one and only one station for each grid element.
About 85 stations were selected via this procedure. Because of varying station record lengths, data-gaps, etc., significantly fewer stations reported data for any given month/year. Over the 1880-2011 time-period, an average of about 50 of the selected stations reported data for any given month/year.
Compute the year/month temperature anomalies (relative to the standard NASA 1951-1980 baseline) for the selected stations, and just straight average the anomalies all together for each year.
2) A Google-Earth visualization of stations used to compute the NASA/GISS “Meteorological Stations” index. (If you have a bit of programming experience, getting the station lat/long metadata into Google-Earth readable format is pretty easy.)
3) A Google Earth visualization of stations used to compute the “Sparse Rural Stations Index”.
The results pretty convincingly demonstrate the following:
1) UHI is a non-issue (I used only rural stations).
2) Data "homogenization" is a complete non-issue (I used only raw temperature data).
3) The global temperature record is incredibly redundant and robust -- you can really throw away ~98 percent of the temperature stations and *still* confirm the NASA/GISS global temperature estimates.
-
Chris G at 13:04 PM on 9 April 2012Climate Scientists take on Richard Lindzen
Eric, Also, Lindzen's conclusion from the empirical results assumes that the oceans, ice sheets, permafrost, methane clathrates, and ecologic zones are already in an equilibrium state with the current radiative imbalance. That seems pretty absurd to me. I'm not saying that the current measurements are wrong; I am saying his conclusion based on them can only be correct if the all the above conditions are met, and I think it is pretty clear that they are not. -
Chris G at 12:42 PM on 9 April 2012Climate Scientists take on Richard Lindzen
Note: On a long average, energy in is equal to energy out; when I said balance point, I meant the equilibrium temperature at which SW absorbed and LW emitted are equal. -
Chris G at 12:37 PM on 9 April 2012Climate Scientists take on Richard Lindzen
Eric (#17), I may have made an inference that Lindzen has not explicitly stated, but for instance, here is an explanation of his for how heat fluxes between equator and pole can make it so that summers are to warm for snow and winters are too cold (loosely paraphrased). The article talks a lot about snow and ice, and Hadley cell circulation. A note on orbital control of equator-pole heat fluxes Since the phase of water on the surface does not add or subtract energy from the earth system, and neither do convective currents, I infer that he is talking about albedo changes. As I understand it, the vast majority of the energy coming and going from the earth does so through radiative processes. He does state that changes in flux can change the global temperature (which is a function of energy content), and for that to be the case to the extent that was observed in the glacial-interglacial cycles, there has to be a change in the balance point between radiative energy in, and radiative energy out. Changing albedo is the only way that is apparent to me for the presence or absence of ice and snow to have that effect. I did not see any mention of water vapor feedback in that paper; so, I do not think he was thinking of that being a GHG forcing or feedback. That paper is 20 years old; so, he may have changed his mind (or modified his hypothesis), but I was not able to quickly find anything more recent where he described a mechanism by which glacial cycles should coincide with Milankovitch cycles, and not have GHGs play a significant role. There as another aspect. Energy lost is proportional to the fourth power of the absolute temperature (Stefan-Boltzmann). I suspect that means that a body that has a more equal distribution of temperature looses less energy than a body where the energy is concentrated more in some region. (Imagine a plate with one half several degrees higher than the other half versus a plate with the same heat content uniformly distributed.) So, how the energy is distributed would affect the overall balance point (global temperature). However, he talks about how the winter heat flux between pole and equator is increased during periods of high asymmetry, and I think that means that there is more energy distribution taking place. More energy distribution should lead to less total energy loss. This aspect does not agree with his conclusion; so, I do not think this is what he had in mind for how changes in tilt account for the glacial cycles. Still thinking that he was implying albedo changes. -
dana1981 at 12:17 PM on 9 April 2012Climate Scientists take on Richard Lindzen
I agree that for the most part Lindzen has been pretty consistent - and consistently wrong, of course. Personally I prefer it when people are able to admit they're wrong, as opposed to steadfastly repeating the same arguments after they've been proven wrong. -
danielc at 11:47 AM on 9 April 2012New Understanding of Past Global Warming Events
I think those land bridges were tectonic in origin, rather than sea-level related... 1) continental collision, subduction and plate motion brought new territories into reasonable proximity, and in some cases my have opened sub-aerial connections.. 2) Loss of ice in the Arctic, coupled with still connected Norway/Spitzbergen/Greenland/Canada (in short, North Atlantic rifting was nowhere near complete, and Labrador Sea was no nearly open...) gave rise to passable pathways from Asia, through N. Europe, to N. America.... that's the basic idea here (http://www.pnas.org/content/103/30/11223.full ). One aspect of the PETM that is not discussed here is the impact of North Atlantic Volcanic Province activity - massive shallow submarine flood basalt eruption.... there are those who point to that as the trigger for a lot of the early Eocene craziness. -
actually thoughtful at 11:20 AM on 9 April 2012New Understanding of Past Global Warming Events
Curious why a land bridge appeared during warming - wouldn't that indicate higher sea level, and therefor fewer land bridges? -
danielc at 10:51 AM on 9 April 2012New Understanding of Past Global Warming Events
Feedbacks, feedbacks everywhere you look. I'm still struggling with some of the rates, however: the temperature/CO2 feedback works pretty fast, and the cloud/H2O vapor feedback works in concert and at similar rates. One question about this I have is this: Where is the silicate weathering (carbon sequestration) signal in all this? Is it: warming reduces ice and increases available rock for weathering, but that is a much slower process? Or is it: warming reduces ice, increases available rock, but only until sea level rise covers more rock than is exposed by ice loss? Or is it: absent mountain building on a globally significant scale, warming/CO2 release/water vapor increase effects will swamp the silicate weathering signal over long periods of geological time? -
Eric (skeptic) at 10:43 AM on 9 April 2012Climate Scientists take on Richard Lindzen
The claim of shifting goal posts is correct in some cases, but it is better to argue against the argument than an alleged change in argument. Lindzen has made a consistent argument against high sensitivity for at least a dozen years: http://www.pnas.org/content/94/16/8335.full. I have always made the argument that models will not calculate water vapor feedback without properly modeling weather: http://www.realclimate.org/index.php/archives/2006/08/the-missing-repertoire/comment-page-1/#comment-17399 and here
Prev 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 Next
