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JoeTheScientist at 11:37 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
Data seems to indicate more of a variation between roughly 80,000 and 120,000 year cycle length rather than the nominal "100,000" years, but it's rather irregular. Unfortunately there is no "cut and dry" level of insolation that is the exact trigger, no single simple trigger. On thing that seems to be a prerequisite for a full-blown interglacial/ termination is a very large accumulation of ice (probably both in terms of extent and thickness). Only a massive runaway ice melt seems to be able to dump enough fresh water fast enough into the arctic ocean to alter thermohaline circulation sufficiently to prod the deep southern ocean into disgorging its accumulated hoard of CO2, thus locking in the warming and the new interglacial. Melting the Greenland ice cap wouldn't be enough. It has to be HUGE! At one point in the last termination, the melting rate was fast enough to raise sea level 5 meters in a single century!!! Ice amok stops AMOC! A termination starts when NH summer insolation becomes intense enough to start net melting of the NH ice sheet. There are two runaway feedback effects involved. One occurs at the ice edges where the ice albedo begins decreasing as bare, newly exposed land absorbs more and more solar energy, shifting the energy balance even more than just the insolation change alone, leading to runaway melting at the edges. However there is also a less well known ice elevation feedback. As the ice sheet begins to melt at its elevated surface, it slowly decreases in elevation, but the more it does, the warmer the temperature at the ice surface and the faster it melts, leading to an almost irreversible runaway that rips through the ice not just at the edges but ultimately over much its surface. The thicker the NH ice sheet is and the greater its southern extent, the more dramatic its melting will be when the insolation balance shifts, and the more commandeering its effect on the thermohaline circulation which, if great enough, triggers the CO2 release from the deep southern ocean. Without this CO2 release, there isn't a full-blown termination, but just a pause in the ice age. -
Eric (skeptic) at 11:26 AM on 10 April 2012More Carbon Dioxide is not necessarily good for plants.
Thanks Tom. As usual you understand my question and the issues. I agree with most of what you say, but I am not sure if the forest loss will be significant enough to cause a temperature overshoot as postulated by R. Gates. My understanding from figure 1 in my second link in 232 is that the rapid rise in CO2 makes some trees more immune to subsequent temperature increases. The ultimate outcome will be dependent on the uniformity of the tree species and whether they are CO2-selected. In lands managed by the US Forest Service 2.5 million acres are replanted annually out of about 200 million and that can probably be increased significantly to meet new needs. -
mdenison at 10:21 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
Readers may also find the recently published paper Carbon Isotope Constraints on the Deglacial CO2 Rise from Ice Cores J Schmitt et al interesting. I was particularly intrigued by the timing they place on CO2 up-welling from the southern ocean. "Our new, high-resolution δ13Catm data constrain the period of this release of isotopically depleted carbon from the deep ocean to the atmosphere to between 17.4 kyr BP and 15 kyr BP" which appears to tie in very neatly with the Shakun et al period of low AMOC strength. -
Sceptical Wombat at 09:47 AM on 10 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?" At some stage China is going to understand the importance of doing something serious about carbon emissions. When that happens it will use its economic and diplomatic clout to push its trading partners and neighbors to shoulder their fair share of the burden (or China's perception of their fair share). How far down the track we will be before that happens I don't know. -
mdenison at 09:26 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
There are some interesting questions raised near the end of an article by climate central regarding some of the uncertainties regarding details presented in this paper. They also report that Shakun and his collaborators are confident the main picture will not change significantly.The climate central article has been reposted at climate progress. -
Tom Curtis at 09:12 AM on 10 April 2012More Carbon Dioxide is not necessarily good for plants.
Eric (skeptic) @234, one aspect you are not taking into account is the succession of regrowth. If you clear an area of forest, the cleared area is quickly colonized by small rapidly growing plants. As years go by they are replaced, first by small woody shrubs and then rapidly growing soft wood trees, and then finally by slow growing hard wood trees. In a situation of rapid climate change, large sections of woodland will find themselves left behind by their climate zone and die back. With a pace of change of several degrees C per century, the rapidity of die back will be such that the successor plants will be the small rapidly growing plants, ie, grasses and weeds. These then may be supplanted by woody shrubs, but with sufficiently rapid climate change the climate will change to fast for the full succession (which takes centuries) to follow. The result will be the wide spread replacement of forests by open woodland or grassland. Such a replacement will result in a large loss in biomass, both because trees have more mass for a given deployment of leaf area than do shrubs and grasses, and because forests have a layered ecology with a canopy, potentially midlayers, and floor which enhances capture of available sunlight and (hence the lower albedo) and opens up more ecological niches which increases the efficiency of exploitation of available energy. This mechanism is medium term only. After a few centuries temperatures will stabilize if only because we will run out of fossil fuels. Once temperatures are stabilized, within a century the normal succession will reassert itself so that biomass will again increase. But the significant loss of forest land for grassland can certainly act as a short term positive feedback on CO2 warming. As an addendum I will note two further points. The first is that large scale species loss will result in a loss of specialization in ecologies, ie, a loss of efficiency in exploiting available energy. That will result in a long term loss of biomass, although much smaller than the effect described above. It is probably also a smaller effect than the gain in plant mass due to high CO2. However, (my second point) that gain in plant mass will also result in a loss of albedo in grasslands. -
funglestrumpet at 09:01 AM on 10 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?" It is difficult to argue that the scientific case, apart from crossing a few ‘t’s and dotting a few ‘i’s, is as good as settled. That means that we as a species know that climate change is going to be a major issue for coming generations with the high probability that a great many are going to die from its effects. Yet even intelligent people with children and grandchildren who will likely suffer badly prefer the 'business as usual' scenario to facing the facts staring them in the face. The less intelligent will just agree what these opinion formers say and support such action or inaction they recommend. With the above in mind, I have absolutely no confidence whatsoever that we stand any chance of combating climate change, other than what will result from the efforts that will be made when it becomes impossible to ignore. Unfortunately by then positive feedbacks will have kicked in - if they have not done so already - and so it will be far too late. "Told you so!" will be very small compensation. I am also only too aware that if Nassim Nicholas Taleb’s Black Swan makes an appearance, it very likely will screw up things completely anyway. In truth, the only reason I keep on fighting is that I want to see all the people that have used (abused?) their positions of influence to put the human species, and with it my children and grandchildren, in this perilous circumstance face a court of law, preferably in The Hague, and be given long custodial sentences ('throwing away the key' length). While I probably may not live to see it, I sincerely hope that they do. -
Charlie A at 08:24 AM on 10 April 20122012 SkS Weekly Digest #14
SkS should be looking at the science, rather than doing science by cartoon. Re: the cartoon with the caption "Evidence is that increased extreme weather is due to climate change" --- it's a cute cartoon, but the message is incorrect. It's not clear who is supposed to be inside the "anti-science bunker". Perhaps it is Joe Romm or the IPCC since the latest IPCC SREX report says in section 4.5.3.3. Attribution of Impacts to Climate Change:Observations and Limitations, "There is medium evidence and high agreement that long-term trends in normalized losses have not been attributed to natural or nthropogenic climate change" And then goes on to say "The statement about the absence of trends in impacts attributable to natural or anthropogenic climate change holds for tropical and extratropical storms and tornados" and "The absence of an attributable climate change signal in losses also holds for flood losses" ------ There is a difference between peer reviewed studies of extreme weather and sensational newspaper reports. IPCC SREX looked at the actual scientific literature.Moderator Response: [JH] My God man, lighten up! -
dr2chase at 07:15 AM on 10 April 2012Eocene Park: our experiment to recreate the atmosphere of an ancient hothouse climate
@BernardJ, #16. I remain grumpy, and your points do little to make me ungrumpy. The people who live in the hottest (hottest+humidest) places on earth now often do not have air conditioning, and often engage in manual labor. They have heat waves, too. Disease vectors need more than just favorable climate. There was a malaria epidemic in Philadelphia in 1780. The town where I went to elementary school used to be called "Yellow Bluff", but yellow fever epidemics (in Florida) made "yellow" a bad word for attracting new residents. It's not just climate; public health is a big part of it, too. We also adapt in more ways than just deploying air conditioning. I grew up, and attended college and gradual school, in some pretty hot and humid places (Florida, Houston). Growing up, I often engaged in actual, outdoor, physical activity. Your body learns to sweat, you learn to drink more, you develop shade-seeking habits, etc. When I return to the ancestral home, it takes a few days for my body to figure out WTF to do, and then it copes. These places are nonetheless well cooler than true tropics. In addition, everything I read suggests that the greatest warming will occur away from the tropics, and recently I've read that jet stream changes around the poles may be the cause of our more extreme hot/cold/wet/dry weather in recent years. Looking at current maps of maximum wet-bulb temperatures, my guess is that if anywhere becomes uninhabitable, it will be places like Iraq (already hot and humid). Brazil's future weather might be like Iraq's weather now, and perhaps Houston will become more like Brazil today, and Washington DC more like Houston. There will be much whining, but Houston is already hot, already urban, already a heat island, and people live there now. An aggressive program of painting roofs and roads white would counter the heat island effect handily at little inconvenience to residents, in Houston and in every other city. I don't think the effort to slow climate change is helped by hyperbolic "we're all gonna die!!!!" pronouncements. There are some low-probability events that really would kill us all (oceans going anoxic). If sea level rise hits the high-end estimates (5cm/year for a century or so), millions of people will need to move to higher ground. But within the predicted range and distribution of future warming (at least in this century, maybe the next), no, the heat will not be a killer. (I'm aware of the killer-wet-bulb predictions. Those are for the case of a 12C rise in global mean temperature. IPCC BAU to 2100 is +4C, right?) -
MA Rodger at 06:50 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
John Russell @14 & boba10960 @16 Deary me! There's me calling for precision in terminology & then I call all aspects of the Milankovitch cycles "wobbles." However I think we're pretty much on the same hymn sheet. One thing mentioned but not explicitly is that the 100,000 year wobble (the variation in eccentricity) is by far the weakest yet is the one apparently triggering the recent ice age cycles. The same effect also has a 400,000 beat that is far stronger but I hear say that its effects aren't evident over the last 1 million years. And prior to that time, the more obvious 41,000 year wobble (angle of tilt) appears to have been triggering the ice age cycles back to when the 'modern' ice ages started 30 (?) million years ago. I will be a smart git & say that radial speed of orbit changes more with more elliptical orbit (in the extreme, think of comets) thus winter/summer for a particular hemisphere can vary in length. And there are two components to the precession 'wobble' (orientation of tilt & of eliptical direction) which combine to give a 21,000 year effect. My point here is that it all gets rather complex. That the 'trigger' occurs at the termination of an ice age is something I assume given the saw-tooth temperature profile of recent ice ages but I've yet to encounter authoritative discussion of it. (Perhaps I should emphasis use of the word "authoritative.") -
william5331 at 06:24 AM on 10 April 2012New Understanding of Past Global Warming Events
I'm a tad suspicious of the sudden appearance of land bridges without some sort of proof. However, in a fairly recent copy of New Scientist it was reported that under the sediment in an area between Iceland and Great Britain, sonar studies have discovered a reticulation of river beds. Apparently the hot spot that keeps Iceland above the surface of the earth sent a blob in this direction and there was for a time, land above the sea. Rivers developed and then as the magma cooled, this land sunk. They also point out other areas in the world where they think this is likely. Still not land bridges, though. -
Bob Loblaw at 05:40 AM on 10 April 2012Climate Scientists take on Richard Lindzen
Chris G @23: Are you sure that his 3/4 forcing and 1/3-1/6 observed warming numbers are actually correct?. Does he "show his work"? I wouldn't trust him to have provided accurate information... ...but I agree with your comment about reaching equilibrium. It's sort of like arguing that the bill of sale says the house cost $500k, but that can't be right because you've only paid $30k on the mortgage since you bought it last year. -
boba10960 at 05:08 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@1 geologic “can anyone add detail to how the see-saw works?” Cooling of surface water in the high-latitude North Atlantic Ocean causes the density of water to increase so that it sinks toward the bottom (deepwater formation). The cold water that sinks flows southward, and it is replaced by northward flowing warm surface water. This large-scale process transports heat from the southern hemisphere to the northern hemisphere, making the southern hemisphere cooler than it would be in the absence of North Atlantic deepwater formation. When melting ice sheets add freshwater to the North Atlantic Ocean, the surface water is no longer dense enough to sink (freshwater is less dense than salty water), which stops the northward heat transport, leaving more heat in the southern hemisphere. Thus, according to the Shakun et al. paper, it is the initial melting of northern ice sheets that stopped the formation of deepwater in the North Atlantic, leaving more heat in the southern hemisphere, and causing the early signs of warming to appear in Antarctica. Related to this, one problem with the Shakun scenario is that they invoke an initial reduction in North Atlantic deepwater formation (AMOC - in the penultimate paragraph of their paper) about 19,000 years ago. They cite Pa/Th ratios in North Atlantic sediments as evidence to support this view (their reference 24). However, the actual data in reference 24, as well as sediment Pa/Th records presented in subsequent papers (e.g., J.-M. Gherardi et al., Earth and Planetary Science Letters 240 (2005) 710–723; Gherardi et al., PALEOCEANOGRAPHY, VOL. 24, PA2204, doi:10.1029/2008PA001696, 2009) all show the Pa/Th changing after 18,000 years, or nearly synchronous with the onset of rising CO2. This raises questions about the lags and ocean thermal inertia invoked by Shakun, and it suggests that other mechanisms with faster response times may have been involved. -
danielc at 05:03 AM on 10 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@ Sapient Fridge... wow... sorry about that. Just a typo/brainfart of epic proportions. High Tilt = Warmer polar summer Low Tilt = Cooler polar summer My apologies for the confusion, and thanks for picking that up. -
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.
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