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dvaytw at 18:41 PM on 28 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
Got it guys, thanks!
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Andy Skuce at 15:39 PM on 28 August 2013Toward Improved Discussions of Methane & Climate
Michael Tobis rebuts Nafeez Ahmed:
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There's no empirical evidence
dvaytw - Point them to the RealClimate page The CO2 problem in 6 easy steps, which is perhaps the most succinct and numerically supported explanation I have come across.
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Tom Curtis at 14:24 PM on 28 August 2013How much will sea levels rise in the 21st Century?
jja @44 & 45:
1) You have forgotten to allow for the fact that ice is not as dense as water. You need to calculate the volume of water needed to raise sea level, convert that to mass as water, and then determine the volume of ice needed generate that mass of water. Doing so increases the energy needed per meter of sea level gained from ice melt to 120 Zettajoules.
2) You also neglect the fact that the ice, once melted, warms further till it matches the temperature of the surrounding water. That requires additional energy. Further, as the melting of ice results in greater gains of sea level in the tropics than at the poles, the temperature gain is substantial. Using a conservative estimate of 10 C temperature gain increases the energy required to 135 Zettajoules per meter of sea level gain.
3) You are not entitled to assume thermal expansion is a constant 1/3 of the sea level rise due to melting ice. The sea level gain is constant for a given level of OHC gain (assuming similar distributions of the heat). Ergo the sea level gain from thermal expansion for the B2 scenario is 0.12 - 0.28 meters. Allowing the upper limit, you need to find 4.72 meters of sea level gain from ice melt for a 5 meter sea level rise, not 3.33.
4) Currently, OHC accounts for about 95% of energy gains at the Earth's surface, leaving 5% for temperature gains in atmosphere and soil, and the melting of ice. For any 5 meter sea level gain, you need the amount of excess energy absorbed by the melting of ice to increase by a factor of 10 or more. That, however, will reduce the energy gained by OHC, reducing significantly the sea level rise by thermal expansion.
5) Using my estimate of TOA energy balance for RCP 8.5 at 43 above, you have approximately 1.45 W/m^2 TOA energy imbalance averaged over 87 years with which to melt your ice. That estimate assumes that the TOA energy imbalance increases linearly from its current value, which is a generous assumption for you. That gives you 2000 Zettajoules to play with to melt your ice. That means you require over 30% of energy from the TOA energy imbalance to go into melting ice to get your 5 meter sea level rise.
That is not impossible. Ice rafting of sufficient magnitude could channel much of the oceans gain in heat content into melting ice. However, nearly all your ice melt must come from such rafting, and there is no plausible mechanism to launch that much ice (approximatly equivalent to 2/3rds of all the ice in Greenland) onto the ocean in just 100 years.
Energy considerations cannot by themselve disprove the possibility of a 5 meter sea level rise, but they do show that you require a number of very implausible conditions to obtain it.
Regardless of these considerations, however, I remain convinced that the past is the guide to the future. Such massive rates of sea level rise greatly outstrip anything seen in transitions from glacial to interglacial states. That is despite the fact that those transitions involved far more ice available to melt, and at far lower latitudes. Absent detailed mechanisms explaining how a more rapid melt could occur, and specific evidence suggesting those mechanisms will come into play (neither of which exist for rates of increase of sea level greater than 2 meters per century), suggestions of such rapid melts must be considered as implausible, unscientific and needlessly alarmist.
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Levitus et al. Find Global Warming Continues to Heat the Oceans
dvaytw - The ocean skin layer, constrained by surface tension, is thicker than IR can penetrate and again with surface tension not convecting. Only thermal conduction can remove energy from deeper penetrating visible sunlight.
Downward IR warms the top of the skin layer, which decreases the thermal gradient across it, and less energy moves to the atmosphere.
Analogy: Take a metal rod, heat one end relative to the other. If the difference in temperature is, say, 10C, a certain amount of energy (heat) will flow from one end to another, at a rate determined by the thermal conductivity of the rod. If the difference between ends is only 5C (say with IR warming of the cool end), then less energy will be conducted through the rod, as the gradient is lower. That is equivalent to the thermal conduction of the ocean skin layer - a warmer surface means less energy flowing through the skin layer.
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DSL at 13:46 PM on 28 August 2013Andrew Dessler on Why It's Stupid not to Act on Climate Change
Yah, KR, I was hoping that pointing out Kampen's lack off engagement with the actual science would deter further garbage, but then the guy threw Chris Essex at me. My ensuing sigh nearly collapsed my lungs.
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jja at 12:14 PM on 28 August 2013How much will sea levels rise in the 21st Century?
correction to 105 cubic KM above - should be 360,000 cubic KM
with corrected math error the final energy deposition value per meter of sea level rise due to ice melt is ~110 ZJ per meter sea level rise (using above calc) or very close to MA Roger's 5 ZJ per 50mm rise @19.
so total energy deposition in ice to raise sea level by 3.333 is then calculated to be 367.4 ZJ, not the 107.13 quoted @43. -
jja at 11:12 AM on 28 August 2013How much will sea levels rise in the 21st Century?
if 105 cubic kilometers of ice melt has the capability to raise sea levels 1 meter (Lakes Agassiz and Ojibway melts 8,400 y.b.p.) and the enthalpy of fusion of 1 km cubed of ice is derived from the following:
105 km^3 = 1.05 X 10^17 cm^3
.9167 g/cm^3 of ice = 9.63 X 10^16 g of ice = 9.63 X 10^13 Kg of ice
enthalpy of fusion of ice = 334 KJ/Kg
9.63 X 10^13 Kg of ice * 334 Kj/Kg = 32.14 Zj per meter of sea level rise due to ice melt.Assume 1/3 of sea level rise is due to thermal expansion
3.3333 meters of sea level rise due to ice melt = 5 meters of total sea levle riseenergy deposition in landed ice = 32.14 ZJ * 3.3333 = 107.13 ZJ
so how does MA Roger get 100ZJ for only a 1M worth of sea level rise in @19?
and if the 107.13 X 10^21 Joules is all that is needed in total landed icemelt to raise sea levels by 5M (with 1.67M of rise due to thermal expansion) and the proportion of energy deposion is proportional to forcing and the final 2100 energy imbalance is 3.5 W/m^2.(I am sorry but your calculation does not include increased ice melt due to convective forces in a warmed world as well as albedo-induced localized warming in an ice free summer arctic-dicrectly increasing arctic amplification above current proportional rates -affecting greenland- your calculation also doesn't appreciate the effect of a slowing Thermohaline circulation on the western antactic shelf (localized warming-shelf undercut and the potential for a shelf collapse similar to the late E-Tr rise- but we will neglect that)
Then the average TOA between now and 2100 is about 2.125 W/m^2 which is equal to 1.08375 x 10^15 W (surface of earth = 5.1 X 10^14 m^2)
multiply by seconds
=3600 seconds/hour *8760 hours/year *86 years = 2.71 x 10^9 seconds
1.08375 X 10 ^ 15 W * 2.71 X 10^9 seconds = 2.93923 X 10^24 Joules = 2,939 ZJ total cumulative energy imbalance between now and 2100 assuming current TOA is .75 and 2100 TOA is 3.5 W/m^2any way you look at it, we cannot reasonably assume that sea levels will not rise by 5 meters under the scenarios that I presented in @ 16
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Andy Skuce at 11:10 AM on 28 August 2013Toward Improved Discussions of Methane & Climate
There is a rebuttal of the Whiteman et al paper by Nisbet et al here:
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davidnewell at 09:54 AM on 28 August 2013Andrew Dessler on Why It's Stupid not to Act on Climate Change
And if this URL reference doesn't scare the H--- out of you, then flash back to the early '60's, take two hits of the then legal Sandoz Labs LSD, and go see "A Clockwork Orange", or other thriller.
(No illegal action is hereby advocated.)
We are absolutely living in a horror story.
http://climatestate.com/2013/08/26/methane-release-from-the-east-siberian-arctic-shelf-and-the-potential-for-abrupt-climate-change/
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Rob Honeycutt at 06:38 AM on 28 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
Dvawtw... You might also want to challenge your skeptic friends on their eyeball rolls related to models. (Sorry, I know it's off topic here. We can move elsewhere if there is more to discuss.) Your friends use models every day, even though they may not realize it. Models are not wrong. They're "boundary condition" experiments, like the model you use in your head (or planner) for planning your own activities through the day or week. They are not exact depictions of weather, which are "initial condition" experiments. Nor is your mental or planner model expected to exactly depict your activities.
More on that issue here.
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gws at 06:33 AM on 28 August 2013There's no empirical evidence
dvaytv @192
There is a logical argument that you can make:
Since all the physico-chemical properties of CO2 are well-established, and we can measure CO2's greenhouse (i.e. IR absorption) activity in the laboratory, and we have worked out both the math of its action in the atmosphere, and done the actual outgoing IR radiation reduction measurements -- spectrally resolved -- from space, we are very sure that CO2 is he most relevant greenhouse gas at this point in time. As we have, at the same time, overwhelming evidence that the increase in atmospheric CO2 since preindustrial times is entirely man-made, it follows logically (from these two lines of evidence) that man must be -- directly and indirectly -- 100% (with respect to CO2) responsible for the climate crisis that awaits us.
Ask them what contrary evidence they have.
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michael sweet at 05:34 AM on 28 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
Dvawtw:
"There is a clear dependence of the skin temperature difference on the net infrared forcing." The Ocean surface emits IR radiation upward and absorbs IR from the atmosphere (backradiation). The temperature of the ocean surface depends on the difference between how much it emits and how much it absorbs (the net forcing).
"The net forcing is negative as the effective temperature of the clear and cloudy sky is less than the ocean skin temperature, and it approaches values closer to zero when the sky is cloudy. " The ocean is usually warmer than the atmosphere so the ocean loses energy to the atmosphere. On clear days the atmosphere is cooler and the ocean radiates energy into the atmosphere. On cloudy days the net forcing is small and the ocean loses little energy.
" This corresponds to increased greenhouse gas emission reaching the sea surface." On cloudy days more IR radiation from the atmosphere hits the ocean surface so the net forcing is small.
Is that any better?
The ocean is warmer than the atmosphere so the ocean emits IR to cool off. They measure a change in the ocean surface temperature that depends on the difference between how much the ocean emits upward and how much it abosrbs from Greenhouse gases emitting downward. When GHG increases, the downward emissions increase and that warms the ocean.
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dvaytw at 03:48 AM on 28 August 2013There's no empirical evidence
Hi fellas sorry for my usual blockhead question in this mostly quite technical discussion, but I'm wondering whether any/all of the empirical evidence outlined tells us about the amount of the warming for which we are responsible as well as simply identifying C02 as one of the culprits.
The reason I'm asking is because I've been arguing quite a bit with some guys who claim that they accept C02 is responsible for some warming, but the extent to which it is responsible can't be or at least hasn't been proven. I had a look at the "human vs. natural contribution" page, but it seems the studies there are mainly using models, which of course gets the inevitable eye-rolls from skeptics. Thanks in advance for any help with this blockhead question!
Moderator Response:[DB] In addition to the fine advice already rendered to you, this post is a treasure-trove of information:
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Tristan at 03:41 AM on 28 August 20132013 SkS Weekly Digest #33
There may be no debate under some definitions of the term, but Qld's Premier and its Minister for Environment seem to be getting their information from some source, and I wouldn't be surprised to learn that said source had some connection with Ms Codling and hubby. Not that I'm in any way insinuating that Campbell Newman would take scientific advice from billionaire mining magnates. Oh wait, yes I am!
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dvaytw at 03:15 AM on 28 August 2013Levitus et al. Find Global Warming Continues to Heat the Oceans
Hey guys I'm sorry to keep pushing here, but I'm trying to communicate these issues to people who don't understand the science well - which is difficult, when I don't either! I read the "Real Climate" article on GHG ocean heating, but this paragraph in particular I found hard (and obviously it is key):
"The figure below shows just the signal we are seeking. There is a clear dependence of the skin temperature difference on the net infrared forcing. The net forcing is negative as the effective temperature of the clear and cloudy sky is less than the ocean skin temperature, and it approaches values closer to zero when the sky is cloudy. This corresponds to increased greenhouse gas emission reaching the sea surface."
Can someone translate this into plainer English?
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hank at 02:41 AM on 28 August 2013A Looming Climate Shift: Will Ocean Heat Come Back to Haunt us?
Rob, I'm puzzled to find you've published exactly the same article in two places; this site and at
http://climatestate.com/2013/06/24/a-looming-climate-shift-will-ocean-heat-come-back-to-haunt-us/
Doesn't that divide the comments and keep people from seeing updates and related information? Or is there a reason for doing it this way?
Moderator Response:[JH] Rob Painting's article was posted on the website Climate State by Because all materials posted on Skeptical Science are published under a Creative Commons license, they may be reposted by others. Reposting allows more people to access an article than otherwise would be the case.
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MA Rodger at 22:43 PM on 27 August 2013Andrew Dessler on Why It's Stupid not to Act on Climate Change
Mark Bahner. You insist that your questioning requires answering on terms that you yourself set, yet your questioning revolves around a single statement made in the first 30 seconds of the Dessler video clip. If you find the answers provided in this thread less than what you wish for (I note you even list your own comments in this regard), do bear in mind that this questioning of yours is entirely off topic.
So here is a question for you to answer. Why don't you watch the video clip to the end? I ask that because I cannot see how somebody could have done so and then go on to assert that the statement "97% of scientists agree that global warming may be severe." is "unactionable;" Or indeed be so intent on demanding that a possibility ("may be severe" ) be converted into a quantified probability for a specific prediction of global climate, economy and society in the year 2100.
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Glenn Tamblyn at 22:26 PM on 27 August 2013Andrew Dessler on Why It's Stupid not to Act on Climate Change
Mark Bahner #23
You said 'the statement that AGW could cause "devastation on a similar scale to the impact of an asteroid (1-2 km in size) in the next 100 years" is patently ridiculous. ....
....And the effects are much more devastating for a 2-km asteroid. Estimates for that size asteroid are that more than 1 billion people would be killed.'
Estimates of yeild declines with temperature for a range of major grain crops report drops of 10% or so per degree C of temperature rise. Rice in many parts of the world is currently grown near the upper limits of its temperature range. Extreme weather events have a similar effect. 50% of the worlds food supply comes directly or indirectly from cereal crops.
Warmer water can hold less oxygen and reduces the carrying capacity of a patch of ocean, so warming of the ocean might reduce available fish stocks in the ocean. Ocean Acidification is already starting to impact the shell formation abilities of some small marine creatures at the base of the ocean food chain. The ocean supplies the primary source of protein for 1 Billion people.
As temperatures rise, growing season times are changing. This potentially changes the relationship between plants and their pollinators and predators.
For every 1 DegC of temperature rise it is estimated that wet bulb temperature, which governs how much an animal can cool itself through evaporation, rises by 66-75% of that. That animal might be a human being, who might be able to retreat into an air-conditioned space if they live in the western world. But it could also be a sheep, goat, cow, chicken etc that can't. With excessive heating heat stress sets in. Even if the animal doesn't die (some will) yields of essential food products (meat, milk, eggs, even blood) drop off.
If temperatures warm by several deg C latter this century, yield declines of all food production of 20% aren't unreasonable. Might be higher, might be lower. 20% seems rather middle of the road.
The world's population is currently around 7 Billion, trending towards 9-10 billion by mid century. And roughly speaking, current food supply is just managing to feed 7 billion. Yes, there are inefficiencies etc, but the food system we have now just manages to feed 7 billion. A 20% decline in food production, retaining current efficiencies would mean that we would only feed 5.6 billion.
And if our population has risen to 10 billion, that is a shortfall of 4.4 billion.
A middle-of-the-road estimate of how much all the effects of AGW might impact says tnat 4.4 billion people would starve. Not guaranteed. Might be less than that. Might be more.
But it doesn't look so patently ridiculous to me. Just because devastation happens in decades not days doesn't make it any less devastating.
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Chris8616 at 22:21 PM on 27 August 20132013 SkS Weekly Digest #34
Well, i was wondering since you write weakend considerably in light of the 1998 El Nino, but guessing otherwise it would have been even more pronounced is kind of dramatic thought. Thanks for your fast reply.
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grindupBaker at 19:27 PM on 27 August 2013Andrew Dessler on Why It's Stupid not to Act on Climate Change
@StealthAircraftSoftwareModeler #26 I was going to suggest you read SKS post 18 October 2011 by Rob Painting "How Increasing Carbon Dioxide Heats The Ocean" which includes "This heat cannot penetrate into the ocean itself, but it does warm the cool skin layer..." and refute it with science to make your point that LWR cannot heat the ocean and get some creds, but your comment is gone or I imagined it.
Moderator Response:[DB] Hot-linked referenced post.
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Rob Painting at 18:52 PM on 27 August 20132013 SkS Weekly Digest #34
Chris - Not sure what you mean, but I'll have a stab at it.
The 1997/1998 monster El Nino happened at a time when the wind-driven ocean circulation was spinning up - having spun down to a low point at around 1993. This spin up - a strengthening of the transport of warm surface water out of the tropics, and enhanced downward (Ekman) pumping in the subtropical ocean gyres - may have prevented the El Nino from being even more severe.
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grindupBaker at 18:41 PM on 27 August 20132013 SkS Weekly News Roundup #34B
@Shizel #1 chriskoz #6 My suggested recent opinion piece on the methane (above) was SkS Weekly News Roundup #32B 10 August 2013 by John Hartz "How Much Should You Worry About an Arctic Methane Bomb?" at "mother jones" site Thu Aug. 8, 2013.
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Chris8616 at 16:42 PM on 27 August 20132013 SkS Weekly Digest #34
Methane release from the East Siberian Arctic Shelf and the Potential for Abrupt Climate Change
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Chris8616 at 16:37 PM on 27 August 20132013 SkS Weekly Digest #34
Rob Painting, please clarify, explain: 1997-1998 El Niño the most recent event (exceptional warm year on record) when you write "the positive IPO phase weakened considerably and has been in the negative phase since the year 2000. In other words, La Niña been the dominant pattern of late."
Thanks.
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Tom Curtis at 16:27 PM on 27 August 2013Human CO2 is a tiny % of CO2 emissions
YubeDude @250, there is not one isotope, but two.
First, C14 is a radioactive isotope with a short half life (5730 years) as a result of which C14 is effectively undetectable in carbon sources more than 50 thousand years old (at which stage it has fallen to 0.2% of its original value. Because of that, fossil fuels are almost completely devoid of C14, as are volcanic emissions. The very rapid decline in C14 in the atmosphere since the onset of large scale combustion of fossil fuels shows that the source of the rapid rise in atmospheric CO2 is devoid of C14, and therefore does not come from recent vegetation, or the ocean.
Second is C13. C13 is a stable isotope of carbon, that does not increase or decrease in quantity with age. It is heavier than C12, however, as a result of which many plants will take up proportionally more CO2 with a C12 isotope than with a C13 isotope. The result is that carbon from organic matter, including fossilized organic matter in the form of fossil fuels, is deficient in C13. The decline in the C13/C12 ratio in the atmosphere since the large scale combustion of fossil fuels shows the resulting increase in atmospheric CO2 to come primarilly from an (originally) organic source, ie, from vegetation or from fossil fuels.
Taking the information from both isotopes, we see that the increased CO2 cannot come from modern vegetation because of the decreasing C14 concentration, and that it also cannot have come from volcanoes because the decreasing C13/C12 ratio. The only possible source that explains both trends is fossil fuels. Ergo, the increased CO2 concentration is a result of the combustion of fossil fuels.
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barry1487 at 16:10 PM on 27 August 2013The Beginners Guide to Representative Concentration Pathways - Part 2
Perhaps it will be covered in part 3 ("we will describe key metrics of the RCPs"), but is it possible to use the publicly available RCP model tools to model the tropical troposphere projections? I ask because Roy Spencer in his "Epic Fail" blogs posts is comparing tropical tropospheric temp observations to 73 RCP 8.5 models, and despite a few requests for him to spell out the parameters for the model runs he presents, he has not specified whether or not they are displaying surface temps or the hot spot zone.
Is it even possible for him to compare apples with apples in this case?
(I realize there are other issues with his posts, but that's the specific question I'm interested in)
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Andrew Dessler on Why It's Stupid not to Act on Climate Change
DSL - A fascinating article, if only because the 2011 publication has zero citations to date according to Google Scholar.
Background - Kampen claims all of the IPCC work, all of AGW, is based on correlational studies. That claim completely ignores satellite observations, spectroscopy in general, downwelling IR, isotope ratios, stratospheric cooling, faster nighttime warming, etc.. It is therefore utter nonsense.
This does raise an issue that I've seen from time to time on 'skeptic' discussions - that without control cases there is no way to tell what the single 'experiment' we are conducting on climate might be caused by. Absurd - we face the same issues in evolution, yet that is well accepted, and in gravity, in that there is no situation without gravitational influence.
Every day is another experiment, another relationship of forcings, temperatures, ice mass, etc. Time provides multiple replicates, with a huge amount of data available to discern between solar, GHG, aerosol, natural cycle, and even leprechaun influences on the climate.
Kampen also makes the unsupported claim that AGW is not falsifiable - again, untrue, as even just simple fingerprint tests such as the vertical atmospheric profile of warming or carbon isotope ratios could, if they gave certain results, falsify anthropogenic causes. But they don't - and in fact they reject other hypotheses such as solar variation.
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Kampen's paper is in essence a strawman argument - incorrectly describing anthropogenic global warming as correlative, as unfalsifiable, untestable, and arguing against that false depiction; when none of that is even remotely the case.
Promoting this kind of argument is (IMO) one of the identifying hallmarks of denial - when faced with an inability to raise solid disagreements with the science, create a strawman to argue against. It's simply a sign that the skeptic shouldn't be taken at all seriously.
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DSL at 13:58 PM on 27 August 2013Andrew Dessler on Why It's Stupid not to Act on Climate Change
Along these lines, someone just threw Jarl Kampen at me in a news comment stream.
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YubeDude at 13:48 PM on 27 August 2013Human CO2 is a tiny % of CO2 emissions
I am in search of an answer that I have not found in the comments tread or searching other references...relating to the isotope ratio signature that identifies ACO2 emissions. Is there also the signature of O18? The isotope signature that identifies Oxygen combustion either from natural events such as wild-fires or or anthropogenic events such as fuel combustion.
What I want to know is if there is any signature that has O18 along with a C13-C12 ratio that would show combustion of older Carbon sources. It would appear to this layman that a signature directly related to the combustion of older Carbon would surely be the smoking gun of anthropogenic activity; not that any logical suspision really exist but another brick in the wall surely would be welcome.
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Tom Curtis at 13:40 PM on 27 August 2013Andrew Dessler on Why It's Stupid not to Act on Climate Change
Mark Bahner @46, at the very start of the video, Andrew Dessler says:
"Should we listen to the 97% of scientists representing the mainstream view of climate science ..."
The view of the 97% is, therefore, clearly indicated as being the "mainstream view", which is the position represented by the IPCC. This has previously been indicated to you, and ignored by you. You may have formed the opinion that the IPCC AR4 is neither "incisive" nor "complete" enough to answer your questions, but that view must be considered ideosyncratic, and IMO is purely tactical. You may be prepared to say it, but it is for effect rather than to represent your beliefs.
What the IPCC AR4 doesn't to is suit your rhetorical ploy. It is not so stupid as to reduce "may" to a simple probability, because the probability of a particular severity of climate change depends essentially on the ongoing actions of humans as a result of explicit or implicit policies. It does indicate probabilities given an approximate implicit policy (ie, emissions following particular scenarios). That is, apparently, not incisive enough for you - which only shows that by incisive you mean "simplistic to the point of absurdity". Nor, obviously, does the AR4 quantify likely deaths because these again depend on actions taken, nor not taken to avoid those deaths. Again, to answer your questions in the framework you have chosen is to be simplistic to the point of stupidity.
You have not wanted a complex, and nuanced response to your questions because such a response does not give you a rhetorical hostage. That does not, however, mean that such a response has not been given. It has! You have simply chosen to ignore it.
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Mark Bahner at 13:05 PM on 27 August 2013Andrew Dessler on Why It's Stupid not to Act on Climate Change
Please demonstrate where "on this forum" (not just in the video) you have not been given your "incisive and complete answers".
My questions were:
1) What percentage probability did Andrew Dessler mean by the word "may" (e.g., <50%, <10%, <1%)?, and
2) What measurable parameters did he mean by the word "severe" (e.g., “global surface temperature change greater than ‘x’,” “sea level rise greater than ‘y’, ”reduction in life expectancy greater than ‘z’, etc.)?
Since not one comment has been from Andrew Dessler, or has quoted Andrew Dessler in responding to my questions, or has referred to any document from which Andrew Dessler was obviously getting his information, it's obvious that nowhere on this forum have I been given "incisive and complete answers" to my questions, since my questions were about what *Andrew Dessler meant* by the statement that 97% of scientists think that "climate change may be severe." If you'd like me to list each comment wherein I did *not* get "incisive and complete answers" to my questions, they are: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, and now 46.
P.S. Just FYI, it's much more common in science for people who make a claim like "you have received incisive and complete answers to your questions" to point to the specific place where those alleged "incisive and complete answers" exist, rather than to ask the questioner to point to all of the places where the alleged “incisive and complete answers” do *not* exist.
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michael sweet at 10:44 AM on 27 August 2013Climate sensitivity is low
Paul and MA,
This discussion seems to me to come down to how useful the IPCC terms are in a scientific paper. These terms have been discussed a lot beore and some people do not like them. On the other hand, people also did not like using numbers before the IPCC adopted the current terms. It seems to me extremely likely that the scientists reading the review paper are familiar with these terms, the paper is not intended for a lay audience. Most of the users here at SkS are also familiar with these terms. They are not perfect, but they are what we currently have. I imagine that if we switched to new terms someone else would complain. It is difficult to please everyone.
Perhaps you could write a new post that explains things better? Good explainations are always welcome.
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Tom Curtis at 07:56 AM on 27 August 2013How much will sea levels rise in the 21st Century?
jja @42, MA Rodgers @40 did not claim that the TOA energy imbalance will stay constant (or near constant) as temperature rises. Rather, he claimed it would be approximately proportional to the rate of change of Forcing. The 2011 radiative forcing according to the GISS was 1.635 W/m^2. An increase to 6.5 W/m^2 by 2100 (RCP 6.5) requires a mean increase in radiative forcing of 0.055 W/m^2 per annum, or 30% greater than the current mean. For RCP 8.5 (ie, BAU), the mean annual increase is 0.077 W/m^2, or 80% greater than current levels. Thus MA Rodgers should be understood as claiming that the TOA energy imbalance forcing could almost double over the coming century with BAU, but is unlikely to do more than that.
An alternative approach to that used by MA Rodgers is to predict the TOA energy imbalance at time t, as equalling the Radiative Forcing at time t, minus the climate sensitivity factor times the change in GMST since the preindustrial era at time t. For a climate sensitivity to the doubling of CO2 of 3 C, the climate sensitivity factor is 0.8. Using the simplifying assumption that during periods of significant changes in forcing, temperatures approximate to the transient climate response, which is approximately 2/3rds of the equilibrium climate response, we have that the TOA energy imbalance equals 0.27 x the Radiative Forcing. That formula predicts a current TOA energy imbalance of 0.44 W/m^2, and a 2100 imbalance of 1.76 and 2.3 W/m^2 for RCP 6.5 and 8.5 respectively. The formula will become inaccurate when forcings cease to increase overtime.
It will be noted that both MA Rodgers and my formulas underpredict the current TOA energy imbalance. That is what we would expect at the end of a period in which RF has continued to rise, but temperatures have risen more slowly than predicted, a situation that will create a larger than expected TOA energy imbalance - which in turn will lead to faster near future temperature rises.
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jja at 04:09 AM on 27 August 2013How much will sea levels rise in the 21st Century?
davidnewell @ 41
Thank you for your comment. I am in complete agreement. it appears at even 350 is too high of a CO2 concentration for the long term. MA Roger's response to 7C was not intended to be a summary response to the circumstances of reality associated with a world-ending 7C of warming at 2100 (because we would then overshoot an additional 7C over the next 300 years after that).
His response was basically helping me with my math.
MA Rogers @ 40
Yes, cumulative delta RF is not a proxy for the integral of the TOA curve between t=0 to t=2100a That value is different due to longwave emissions, I understand that now.
you are therefore asserting that the current radiative imbalance will stay the same as temperature rises. I get it. I find this highly implausible as feedbacks (and anthro emission rates!) are non-linear, indicating a growing energy imbalance, even as temperatures increase.
I find it interesting that you can assert the outgoing radiative transfer value in 2100 with 7C of warming and assuming the CO2 forcing using an ECS of 4.3 Are you also including albedo and methane as well as NOx and SOx values in your computation? you came to a very precise value. Where did you develop the equation?The potential for a 7C of warming in 2100 is remote. based on positive, non-linear feedbacks and a worst-case emissions and ECS scenario. In my estimation of 58-81.2ZJ p.a. I used a total 2100 RF imbalance calculated as 3.75 - 5.25 W/m^2 . This value was stated as RF but was estimated lower to provide conservatism in the calculation.
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John Brookes at 23:58 PM on 26 August 20132013 SkS Weekly Digest #33
Like the cartoon. I used to be a regular thorn in the side at Jo Nova, but it just seems to me now that they are irrelevant. There is no debate that we are causing global warming, its just about the size of the effect and the problem of getting action from governments.
Moderator Response:[JH] Thank you for the positive feedback about the Toon of the Week and welcome to SkS.
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chriskoz at 20:48 PM on 26 August 20132013 SkS Weekly News Roundup #34B
grindupBaker@5,
You're likely taking about this Nature article co-authored by Peter Wadhams and based largely on Shakhova's research, looked by Chris Colose here with interesting comment thread. Intetresting it was, indeed.
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MA Rodger at 19:52 PM on 26 August 2013Climate sensitivity is low
Paul from VA @310.
You are right that it is confusing, but because it is actually more confusing than you say, as it also refers to "the most likely value."
The caption for Figure 4 (in the Advanced version of this post) says "The circle indicates the most likely value. The thin colored bars indicate very likely value (more than 90% probability). The thicker colored bars indicate likely values (more than 66% probability)." The original Knutti & Hegerl paper sort of copes with this by talking of "most like values" and "likely ... and very likely value ... ranges" (my emphasis) but I would consider this poor description for a Review Article where the audience is very likely less attuned to the underlying science and so more reliant on the actual descriptions presented. And at SkS the audience is even less steeped in the science (although it is an advanced level SkS post).
The problem is also encountered in the other Knutti & Hegerl figure used in the advanced level post (SkS figure 6) where the terms "most likely warming" and "likely range" cope reasonably well. Yet if this is an advanced level post I would have thought the concept of a confidence interval would be preferable as suggested @ 310.
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grindupBaker at 15:12 PM on 26 August 20132013 SkS Weekly News Roundup #34B
@Shizel #1 There's a recent SKS post stating (or maybe quoting) that a 50 gigaton methane release would not be a disaster. Seem to recall it was basically due to methane's short life. I recall a commenter disagreed. I can't remember the post date, within the last 5 weeks anyway.If you have time and interest you might want to find it and study, see what you think.
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barry1487 at 14:31 PM on 26 August 2013Greenhouse gases are responsible for warming, not the sun
Tom (and DSL), thanks for going to the trouble. I'll have to read this and the linked comments section carefully and more than once to get a grip on it.
Cheers,
B.
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Paul from VA at 13:06 PM on 26 August 2013Climate sensitivity is low
Michael, I'm well aware of that. My point is that if one didn't go digging through to the original article AND understand IPCC terminology AND frequentist statistics, the graph would seem to be confusing.
If it were labelled for example "66% confidence interval" and "90 % confidence interval" one wouldn't have to go chasing footnotes to understand it....
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michael sweet at 12:28 PM on 26 August 2013Climate sensitivity is low
Paul,
The 90% interval is from 5% to 95% so it includes the 66% confidence interval. Therefore it is more likely to occur since if the 66% occurs the 90% must also occur.
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Riduna at 10:25 AM on 26 August 20132013 SkS News Bulletin #16: Leaked IPCC Report
Ho-de-hum. SLR <1m. by 2100. Nothing new.... No worries.... I wish!
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Tom Curtis at 10:04 AM on 26 August 2013Greenhouse gases are responsible for warming, not the sun
barry @9, you may be being misled by the explanation of stratospheric cooling in the main article here, which is IMO incorrect. Essentially, the stratosphere is warmed by UV radiation absorbed by O3. It is cooled by IR radiation from CO2, O3, and to a lesser extent, H2O and CH4. If you double the quantity of CO2 and hold all else equal, you will effectively double the IR radiation from CO2. That is because nearly all of the IR radiation emitted in the stratosphere either escapes to space or to the troposphere due to the thin atmosphere in the stratosphere. Doubling the IR radiation results in more energy being radiated than is absorbed, thereby cooling the stratosphere until the IR radiation emitted matches that prior to the doubling of CO2.
In the explanation given in the main post, it is assumed that increasing CO2 in the tropophere will reduce IR emissions from the troposphere to the stratosphere (which is true). What is ignored is that the CO2 in the stratosphere also doubles, meaning it will absorb (approximately) twice as much radiation for a given amount of incoming radiation. This effect approximately compensates for (and may more than compensate for) the reduced IR emission from the stratosphere.
The question arises, could the mechanism described in the main post actually result in a decreased temperature in the stratosphere from reduced emission by H2O in the troposphere. The answer is no. H2O is restricted to too low an altitude by condensation due to falling temperatures.
Below is a graph showing the cooling trends induced by various gases at various levels of the atmosphere. Note, positive numbers represent a cooling trend. Also note, this is produced by a Line By Line model, and as such presents straightforward physics that is very well understood; but it does not show any compensating adjustments to restore radiative equilibrium.
You will notice the very strong cooling effect (deep blues and reds) caused by H20 in the upper troposphere, with altitude depending on the strength of absorption. That cooling is likely caused by the reduced IR radiation from lower levels due to increased H2O which is not fully compensated at upper levels by increased absorption because the condensation of H2O limits the increase in watervapour at those levels. In sharp contrast, the cooling in the troposphere from increased CO2 is limited because the CO2 concentration increases approximately equally at all levels. There is even a slight warming at the tropopause where radiation that previously escaped to space is now traped in the atmosphere.
In the stratosphere itself, the cooling effect of CO2 rises to the mesopause (the highest temperature region of the stratosphere), then falls to the thermopause, before rising again. That is, it follows the temperature curve of the local gas - something predicted by the explanation I give above, but not predicted by the explanation given in the main post.
Although much weaker, a similar pattern can be seen in the stratospheric cooling from H2O. That would be expected if the stratospheric cooling effect of H2O were due to increase H2O in the stratosphere from the combustion of fuels by jets in the stratosphere rather than from a shading effect from increased H2O in the troposphere. (As noted in my post @8, increased tropospheric H2O cannot cause increased stratospheric H2O.)
Finally, and crucially, we see a different pattern from O3. Reduced O3 will cause a warming of the stratosphere by the same mechanism that increased CO2 causes a warming (and with the same temperature dependent pattern). However, the far stronger effect is a decreased absorption of UV radiation in the upper stratosphere, which cools by reducing the energy input. That is accompanied by an increased absorption in the lower stratosphere as more UV reaches those levels (due to not being absorbed at a higher level). The net result is a pattern of strong cooling in the mesophere and upper stratosphere, and a warming in the lower stratosphere and upper troposphere. Due to the thinness of the atmosphere, and hence very low initial absorption of UV radiation (I presume), it appears that in the thermosphere the warming effect of reduced O3 due to reduced IR emissions dominates over the cooling effect due to reduced UV emissions.
The distinctive cooling and warming patterns of CO2 and O3 with altituded allow us to see that there is a strong CO2 cooling in the stratosphere. We can see that because cooling is weak in the lower stratosphere where CO2 and O3 have opposite effects, but very strong in the upper stratosphere where both cause a cooling trend. Absent the effect of CO2, the stratosphere would cool in the upper stratosphere and warm in the lower stratosphere.
Interestingly, a third possible cause of a cooling stratosphere is reduced reflection of visible sunlight due to reduced aerosols or clouds. That, however, would have its strongest effect in the lower stratosphere, and scale of rapidly with decreasing atmospheric density. Thus the distinctive pattern of CO2 cooling in the stratosphere allows us to be certain that it is a major factor in the cooling of the stratosphere.
Finaly, you will note in the stratospheric temperatures above any sign of the 1997 El Nino, while volcanic erruptions are clearly visible as a positive (warming) temperature spike in the lower stratosphere. That spike is weakest where the negative trend is strongest showing clearly that the dominant influences on stratospheric cooling are reduced O3 and increased CO2.
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Paul from VA at 09:37 AM on 26 August 2013Climate sensitivity is low
Hey, so I was linking your excellent version of Knutti and Hegerl graphic used in this post and noticed that it uses a potentially confusing notation both here and in the original paper. The 90% confidence interval is labelled "very likely" and the 66% confidence interval is labelled as "likely." That's sensible from a science perspective, but a bit confusing in that values from the 66% region are more likely to be the drawn values than those in the 66-90% interval. Not sure there's any way to better label the figure, but I thougt I'd just put that out there to see if there's a less confusing way of doing so....
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DSL at 06:15 AM on 26 August 2013Greenhouse gases are responsible for warming, not the sun
Barry, some of what you may be looking for might be found here in the comment stream.
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barry1487 at 04:09 AM on 26 August 2013Greenhouse gases are responsible for warming, not the sun
Tsk, spelling errors. I really need to keep more sensible hours.
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barry1487 at 04:04 AM on 26 August 2013Greenhouse gases are responsible for warming, not the sun
Tom, thanks for the reply.
I might be a bit dim here, but you appear to be answering the question "why do we not see enhanced warming in the stratosphere from water vapour?"
I'm interested in the effect of stratospheric cooling as a well-known signature of surface/tropospheric warming from enhanced CO2 in the troposphere.
Water vapour, like CO2, is a greenhouse gas. Why would not enhanced water vapour in the troposphere - which amplifies surface warming from any source (WV feedback) - also cause the lower stratosphere to cool? On short time scales, wouldn't we see this effect with a strong persistent el Nino providing warming at the surface with attendant water vapour increase? I guess solar forcing would both heat the stratosphere and enhance the greenhouse cooling effect on the lower strat through increased water vapour, acting as a kind of negative feedback on stratospheric temps. I assume the solar heating of the stratosphere would outweigh the cooling effect on it from increased water vapour in the troposphere. But I've never seen that particular point addressed, so I'm curious. Makes me wonder about the this particular effect when the surface is warmed from different forcings.
Slightly orthoganolly perhaps, the modeled impact of ozone depletion over the last century or so shows warming of the surface and cooling of the stratosphere.
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-2-2.html [ panel d) ]
Which might make attribution of stratospheric cooling a bit complicated?
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davidnewell at 01:51 AM on 26 August 2013Carbon Economics and the Cost of Inaction
One Planet Only Forever @5 and all the others.
I believe I've met another realist. All arguments based on past projected scenarios are highly suspect, if not totally obsolete.
We can rationalize any thing we want to do, but using "future value scenarios" predicated on the artifice of monetary gain is an exercise in .. futility.
What we have, here, is the "going away" of ALL value, as measured by the rate of species extinction: which is OUR EXTINCTION... If our ankles were rotting away, perhaps the seriousness of the scenario would be apparent.
We'd best be about managing a radical change to a more sustainable future immediately, or society will disintegrate, social unrest will be rampant, and we will not be able to mount a response other than dying.
One Planet Only Forever, amen.
—used to express solemn ratification or hearty approval (as of an assertion)
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Tom Curtis at 20:33 PM on 25 August 2013Greenhouse gases are responsible for warming, not the sun
Barry @7, the difference between the stratosphere and the troposphere is convection. Because of the thinness of the atmosphere in the stratosphere, convection transfers energy far slower than does radiation, with the result that very little convection occurs. The point in the atmosphere where this breakdown in convection occurs is the tropopause, a region of the atmosphere lying between the troposphere and the stratosphere. Crucially, the temperature at the tropopause is well below freezing. That means any water carried to the tropopause in its liquid form (as for example, in a thunderstorm) quickly freezes, and is unable to be carried to a greater altitude by diffusion. It is also, of course, unable to be carried to a greater altitude by convection, which goes no higher. This prevents the increased absolute humidity in the troposphere from resulting in an increased humidity in the stratosphere, preserving the unique greenhouse temperature signature.
It should be noted that there has been a slight increase in humidity in the stratosphere, not from increased humidity in the troposphere, but as a waste product from the combustion of jet fuel. As it is a direct anthropogenic effect, and is not temperature dependent for its strength, it is a forcing rather than a feedback and is included in IPCC modelling.
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