Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings

All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Bluesky Facebook LinkedIn Mastodon MeWe

Twitter YouTube RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
New? Register here
Forgot your password?

Latest Posts

Archives

Recent Comments

Prev  2507  2508  2509  2510  2511  2512  2513  2514  2515  2516  2517  2518  2519  2520  2521  2522  Next

Comments 125701 to 125750:

  1. Increasing CO2 has little to no effect
    Re #2 (Hugh) Considering the study is the first of its kind, its finding of reduced radiation precisely in the wavelengths associated with increased GHG concentrations remains remains highly suggestive, no? Suggestive that there is a slight increase heat absorbance of CO2 and MH4 - but only if you cherry pick the data. Any atmospheric gas that absorbs infrared is considered a GHG. If you look at the full data you will see that although there is some increase in the heat absorbance of CO2 and MH4, you are seeing more heat escape at wavelengths different from CO2 and MH4. When talking about the causation of global warming, what does that suggest about the "greenhouse effect"?
  2. Antarctica is gaining ice
    As a physicist and as a windsurfer who relies on shoreline thermals for sail power, I wonder if any one has considered that rising ocean temperatures in the Southern Seas has increased the offshore flow of ice-cold air from the continental land mass. Might this not also contribute to the increased cooling of the ocean surface and to more sea ice?
  3. Predicting future sea level rise
    Definitely. Were governments able to easily take rational choices and had people and countries enough money, why there should be meetings and discussions in Copenhagen and the like? ;) Back in topic, whatever the world will do, sea level won't stop rising any soon and adaptation is going to be essential in many places. And money, a lot indeed, is required.
  4. Philippe Chantreau at 10:31 AM on 23 December 2009
    Predicting future sea level rise
    Some don't have that money Riccardo (Bengladesh). Some could but it gets lost in corruption and all that (Nigeria). If only the use of money by governments was based on rational choices...
  5. Predicting future sea level rise
    batsvensson, oh, ok, now I see your point. I'd like people living in the big river deltas of our planet could have similar attention, money and technology from their governments to plan their future.
  6. Hockey sticks, 'unprecedented warming' and past climate change
    re #26 HR, I’m curious about your statement re Mann: “Mann's desire for certainty in his work is his shortcoming.” Especially in relation to this comment you made earlier in the thread: “…we shouldn't forget this particular bit of science has been seriously affected by it's collision with politics.” Well I wouldn’t say that the science has been affected, although there’s been a rather persistent effort to create a false perception of the science. Let’s have a look: Mann’s original millennial paleoproxy reconstruction was published in a paper entitled: Mann ME et al. (1999) Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations Geophys. Res. Lett. 26, 759-762 which doesn’t sound to me like “a desire for certainty”, and Mann’s analyses have consistently addressed the uncertainties in the data and its interpretations. On the other hand, Mann might have every right to have confidence in his analyses. He’s made a series of strong contributions to paleoanalysis of climate-related indices (the paper above has more than 600 citations), and has seen his analyses supported and validated by subsequent studies, despite a pretty dismal and rather pathetic effort to undermine his work. Considering the MWP, one can examine the set of paleoproxy reconstructions that extend back to that period and see that essentially all of these find an MWP that is close to the temperature of the original Mann et al reconstruction (Moberg's "highly variable” temperature reconstruction, puts the NH MWP perhaps 0.2 oC warmer than Mann's; that's a fairly trivial difference, and of course we don't know whether this is any more or less correct than Mann's analysis). Your comment on “politicisation” of this issue is highlighted by contrast with another scientist, this one a darling of the scientific misprepresenters. His presentation of his methodology was launched with a robust assertion of certainty: Spencer RW and Christy JR (1990) Precise monitoring of global temperature trends from satellites Science 247, 1558-1562 And despite the fact that the methodology was early shown to be anything but “precise”, and that the practitioners made ae extended series of errors indicating (at best) a less then competent relationship with their data, resulting eventually (15 years later) in an embarrassing climb down [see Christy JR, Spencer RW (2005) "Correcting temperature data sets", Science 310, 972-3; and comments by Mears, Wentz and Sherwood, Lanzante], the scientist (Spencer) is considered to be one of the luminaries of the anti-science movement. The difference between the way that these two scientists are treated in some quarters is really where the politicisation of this subject lies
  7. Predicting future sea level rise
    @Riccardo in #51, my intention was to support what you said earlier, but also to underline that the Dutch government spends a lot of tax money on this issue, not just because of some academic research interest in the sea and/or weather but because of pure self preservation. Therefore, one can suspect that the Royal Dutch Metrological Institute, KMNI, will taking any climate change issue based on sound scientific research very very very seriously - after all they are responsible for the well being of about 16 million humans lives.
  8. Predicting future sea level rise
    @SNRatio in #50, "Sea level rise is not constant over the globe" I did not claim that either, and I am fully aware of the variability of sea levels, my claim was that the Dutch keep track on sea level changes simply because it is of great concern for them.
  9. Climategate CRU emails suggest conspiracy
    Michael949, please stick to the facts. None of them ever said they were going to delete the email.
  10. Predicting future sea level rise
    SNRatio, fast and slow are relative to the ocean response time. Using only the first linear term in temperature you cannot follow the trend even over several decades. You also need to smooth the temperatre data up to when dT/dt is also smooth (i.e. a "nice" regular trend), otherwise you would force the second term to follow temperature interannual variability which would in turn produce highly amplified and unphysical fluctuations.
  11. Predicting future sea level rise
    batsvensson, I apologize if I misunderstood you comment. But from the first paragraph it looked to me that you were pointing to reaction to weather events more than climate changes: "The reason the Dutch taking this very seriously is because they already had a break in the sea walls a fee decades ago due to an Atlantic storm [...]"
  12. Predicting future sea level rise
    @Riccardo "the data are strongly smoothed. The degree of smoothing is not quoted for fig. 2 here but in fig. 4 in the paper it is quoted to be 15 years. Whatever it is, it's strong and i would not expect much sensitivity on short term fluctuation." ...Yes, but, then what about the "rapid" term in the expanded model presented, proportional to dT/dt? That's exactly what gives this new model the improved performance. It may all be explained there, but, skimming through, I could not find it. @Bern, 34: Sure we agree on the factual description, but the context here is the paper with its model. And the model looks very simple, with no apparent thresholding, catering for differential rates of rise corresponding to ice cap conditions. In the model, there can be no accelerating ice cap loss at constant temperature without a concomitant deep ocean cooling. So, if the model is right, the recent acceleration of ice loss at near constant temperature is just a transient phenomenon. Wish it were right. @batsvensson, 47. Sea level rise is not constant over the globe, and some places it may even be mostly canceled out by land rise. The Dutch themselves make the distinction between local trends - they have been approximately constant for a long time - and the global, which, on the same time scale, has accelerated. They have already been adapting to sea level rise for a long time, so if people elsewhere are to look to them, it can only be to set up a similar apparatus for managing the changes.
  13. Predicting future sea level rise
    "I sggest you also read it before claiming that their concern is just weather." Did I claim that? No I did not.
  14. Models are unreliable
    hotair, Human-produced direct heat is trivial compared to human-produced greenhouse gas forcing. For details see (in the post The Albedo Effect) the comment 56 by Steve L, and the subsequent comments 57 and 58 by me.
  15. Climategate CRU emails suggest conspiracy
    "While some of the private correspondance is not commendable"... It is more than that. The authors said they were going to erase emails subject to a Freedom of the Information Act request. That is a felony.
  16. Models are unreliable
    The actual physics of CO2 cannot be questioned. There is a secondary player with the CO2 emissions that I do not see discussed. What I would like to be pointed to is reference information on the actual heat generated by the oxidation of hydrocarbon fuels. Where can I find discussion about the retention, transmission, and conversion behaviors of the ~4 exajoules of infrared radiation released annually by burning fossil fuels?
  17. Climategate CRU emails suggest conspiracy
    RE:#6 batsvensson. From your attack on science articles it sounds like you have absolutely no experience with academic scientific research so I suggest you start doing the homework yourself and tell us all why it only takes excerpts from two leaked emails over 13 years to prove that the whole of climate science is far from settled.
  18. Predicting future sea level rise
    batsvensson, yes, I asked. Or better, I read the Summury Report of the Delta Committee. They found two climate related effects that exacerbate the risk of flooding, increasing rate of sea level rise and increasing river discharge. I sggest you also read it before claiming that their concern is just weather.
  19. Predicting future sea level rise
    @Roccardo in #22. "Indeed, as far as i know the Dutch have taken really seriously the threat posed to their country by sea level rise." The reason the Dutch taking this very seriously is because they already had a break in the sea walls a fee decades ago due to an Atlantic storm with devastating consequences for the whole western country, and after that they decided "never again" and built a wall construction that now are able to with stand any storms the Atlantic can hurl at it. The western provinces, which are among the most densely populated regions in the world, is sunken like 5 meters below sea level and if the country would be flooded again it would lead to an economical impact of enormously scale not only because it is a densely populated region with important international trade exchange but it has also a highly efficient farming and agricultural landscape that would be destroyed. There is simply to much on stake for the Dutch to not be considered. But the concerns lies more with weather or not they need to reinforce the sea walls or not as the protection was built with a certain specification in mind, and if the specifications still holds true then there is no need to ask for extra tax money to reinforcing the present sea wall construction. So if anyone knows what is happening with the sea levels right now, ask the Ducth - they will know.
  20. Predicting future sea level rise
    neilperth @42: I don't dispute that humans have been around for tens of thousands of years, and that humans as a species will (probably) survive any climatic upheavals we might trigger. My comment was in reference to human *civilisation* - prior to about 10000 years ago, humans were hunter/gatherers, as I understand it. Indeed, if I remember correctly, the substantially lower sea levels during the last ice age allowed humans to spread to many areas of the globe they previously didn't inhabit. But I stand by my point: if we see dramatic climate shifts, do you really think modern civilisation will come through unscathed? Even ignoring the issue of hundreds of millions of refugees from sea level rise, you've got issues with trade interruptions from drowned seaports, potential crop failures & famines, severe water shortages, and many other problems. I think human civilisation *could* adapt to the sorts of climate change being posited by the experts, but it would take a mighty effort, and it would probably be as disruptive as the 20th century was. And that's assuming no wars break out over land or resources...
  21. Predicting future sea level rise
    @RSVP in #8: "would'nt that volume of extra water dampen global warming?" "does more ocean mean more water vapor and more global warming?" I find these question interesting: If I follow your reasoning correct here; we know that melting ice absorbs heat, thus would not this dampen the warming. However, the whole point with global warming is that the heat is accumulated locally at earth and not beamed away again into space, so in that respect the answer would be ‘no’ to your first question. The second question on the other hand is a bit more tricky to analyze. Amount of evaporations is a function of surface area and temperature. With more ice melting the sea surface will increase, but the change in water evaporation due to a surface change will be insignificant compared to any change in water temperature. Melting ice will not increase the temperature of any local sea water but rather decrease the temperature (liquid water will transfer heat to the ice causing it to melt and as melted ice adds mass/volume to the water it will lose temperature), therefore melting ice will tend to decrease local water evaporation and since water vapor is a green house gas it will thus work as negative feedback on temperature change. However if ice melts at the cost of ice sheets areas then more darker areas - sea water - will be exposed which in turn will contribute to an increase of solar radiation absorption and thus contribute to heating the local water and therefore increase evaporation. What the net effect of these both effects would be is thou unknown to me,and I think your question deserves a proper answer.
  22. Predicting future sea level rise
    @Ned in #10, "raising sea level by one meter adds 3.6 x 10^17 kg to the ocean. That presumably would increase the ocean's thermal mass by 0.0026%." Interesting calculation, but is it relevant? I dont think so unless one like to treat all the oceans of the world as one(1) single thermal transparent medium.
  23. There's no empirical evidence
    It is wonderful to find such a detailed debate on this important topic. Can you confirm that my understand, as outlined below, is correct, or at least not nonsense. As life on Earth evolved, the Earth’s atmosphere was slowly changed. The atmosphere changed quite profoundly once the process called photosynthesis evolved. Much of the carbon dioxide in the atmosphere was sucked up by photosynthesis and transformed into oxygen and carbon. Carbon became the building material upon which life was based, and oxygen, as we all know, became essential for sustaining life. When a living thing died, the carbon that formed the building blocks of life was often reabsorbed by the soil. This fertilised the soil, making life even richer. Some of the carbon left when plant and animals died was subjected to enormous pressures, and over the aeons was turned to oil and coal. Life itself acted as means of storing carbon. In particular forests are like massive carbon storage facilities. Over millions of years, as life had the effect of reducing the amount of carbon dioxide in the atmosphere, the Earth cooled down. This was not a smooth process, and was subject to other variables. The question is this: by burning up carbon deposits that have stayed in the ground for aeons, and also through deforestation, is man reversing a process which took place over millions of years in a blink of the evolutionary eye.
  24. Hockey sticks, 'unprecedented warming' and past climate change
    @SNRatio #31, Says who? And would you mind be more specific on what you mean with "other factors" and what numerical data is the solution of the probability density function you refer to based on? - - - @Ned #32, Thanks for an informative answer. It is really a mind boggling thought that raised CO2 level today could have an effects 50 thousand year ahead in time. But according to this hypothesis, woudl you know how much extra CO2 would then be needed in the atmosphere today to prevent the next glacial cycle to be triggered? One thing I note with the cure is that the noise in the plotted line increase with growing time. The first part shows a very smooth line while the last is very smeared or "noisy". If the curve was taken to be factual measurement, a signal analyst would directly observer that the signal to noise ration is increasing by time. The signal would then be regarded as the low frequencies component of the plot. If we interpret the "signal" as "climate variations" and the "noise" as "weather variation", then the curves makes perfect sense: it follows that the curve should be more noisy with increased time as this shows our ability to track weather as well. In order to get a better understanding of variations in the past error bars may be very useful tools in the analysis because they would not only show the uncertainty in signal level but also indicate the possible variability of the noise. However we are not talking weather but climate, so the interesting question with this graph is: is there anything in this particular graph, taken out of any context of other research, that suggest the signal has changed? - - - @Bern #28, you are not addressing the question but asking another one, a "what-if" question and proposing we do something based on that. Another what-if question with an action is, "What if Al Gores ears causes global warming? Perhaps we should cut them off just to be sure..." Clearly, this is a potential very dangerous method of answering questions and proposing solutions. Using fear to aid decision and action will maybe not do harm, but it is also equal reasonable to assume that one may do harm as often when no harm would had been done else.
  25. CO2 measurements are suspect
    Isn't strange that similar data are reported, whereas NASA reported recently: "Chahine said previous AIRS research data have led to some key findings about mid-tropospheric carbon dioxide. For example, the data have shown that, contrary to prior assumptions, carbon dioxide is not well mixed in the troposphere, but is rather "lumpy." Until now, models of carbon dioxide transport have assumed its distribution was uniform." http://www.jpl.nasa.gov/news/news.cfm?release=2009-196
    Response: Note that AIRS measures mid-tropospheric CO2 levels, some 5 to 12 kilometres above the Earth's surface, as opposed to direct measurements of CO2 which are made on the surface.
  26. Predicting future sea level rise
    Ned writes: quoting me (RSVP) "But for the short run of 100 years, as oceans grow, would'nt that volume of extra water dampen global warming? (since the heat capacity of water is twice that of ice)" Don't take this personally, but are you seriously suggesting that the change in the thermal mass of the ocean as a result of melting ice would have a significant effect on the rate of increase in global surface temperature? A few seconds with Google suggests that the mass of the oceans is 1.4 x 10^21 kg. (e.g., http://hypertextbook.com/facts/1998/AvijeetDut.shtml). The area of the ocean is 3.6 x 10^14 square meters. One cubic meter of water masses 1000 kg, so raising sea level by one meter adds 3.6 x 10^17 kg to the ocean. That presumably would increase the ocean's thermal mass by 0.0026%. ------------------------ Maybe my suggestion was not worth while, but I dont think that is the correct comparison. One could do a similar calculation comparing the contribution of the incremental radiative energy of man-made CO2 to the total radiative power of the Sun on the Earth and come up with an even smaller number. The correct comparison is the difference between the net energy required to raise the temperature of all that ice, vs the energy to raise the temperature of all the water that comes out of that ice.
  27. Predicting future sea level rise
    Bern @35 I am a bit stumped at your statement that: "On human time-scales, sea levels (and climate) have been more-or-less constant since before those pyramids you mentioned were built. Human civilisation hasn't seen the sort of climate variation you're talking about, and whether it would survive the encounter is debatable." In the last 20,000 years sea levels have risen around 120 metres. This time is well within the span of humans. Aboriginals have been in Australia for about 40,000 years for example. Over the last 20,000 years humans have done well even without our modern technology. Thus I am perplexed as to why you would argue that humans in the near future may not survive the relatively minor changes forecast for temperature, sea levels etc.
  28. Predicting future sea level rise
    RSVP, land subsidence and uplift as well as glacial isostatic adjustment (also called post-glacial rebound) are well known and measured. They are taken into account in slr data.
  29. Predicting future sea level rise
    RSVP There are many phenomena which can affect relative sea levels. These include : 1. Ground movements in the general area of Benioff Zones ( eg West coast of North and South America). 2. General rising or falling of land due to the addition\removal of ice-sheets ( eg, Scandinava. UK, Canada.... ) 3. General subsidence/ rising of large areas of the Earth's crust ( eg Pacific ocean ) For example, coral atolls in the Pacific ocean have been drilled to depths of 400 to 1000 metres and the drill has remained in coral. Yet massive coral formations can only grow within about 50 metres of the sea surface. So how is this drilling result explained ? The answer is not that the sea-level rose, although this may have played some part. The main factor was general subsidence of the ocean floor. Another interesting aspect of this discovery is that even though the sea-floor subsided by hundreds of metres, the corals did not die, they just kept on growing as the relative sea level rose.
  30. Predicting future sea level rise
    Couldnt continental plate tectonics also complicate sea level measurements over time? Land is continually moving up and down, which could affect reference elevations, but also to some extend perturb volume through displacement.
  31. Predicting future sea level rise
    John: re the number affected - I think I pulled that number out of Ned's post #9, referring the number of people living within 10m of sea level. Sorry, I should have said where that came from. The 254 million affected by a 5m SLR in Dasgupta 2007 is still a pretty scary number! Thanks for that paper, I'm going to read through it tonight.
  32. Climategate CRU emails suggest conspiracy
    "What do the 'Climategate' hacked CRU emails tell us?" It tells us what we already known since long; the science behind climate changes is far from well understood - if it was then it would not be any interesting Nature/Science articles left to write and the whole area would "degrade" into an engineering discipline taught as an academic subject at universities where one could graduate as a climate engineer. However we dont have any graduated climate engineers - only climate researches.
  33. Predicting future sea level rise
    RE:#36 Neilperth I inferred from your nickname you were from Perth (as opposed to Illinois USA) as you don't often find 4WDs referred to as SUVs in Australia. What you wrote (RE:post#6) clearly is a copy paste job from that site but since you claim you are Randall Hoven and did write it on the original site then I guess i'll just have to take your word for it, but i remain skeptical... (but as a skeptic yourself wouldn't you think that is good thing?)
  34. Predicting future sea level rise
    Yocta re #33 Yes. I am Randall Hoven, but you can call me Randy. Apologies accepted :)
  35. Predicting future sea level rise
    Neilperth: I (and pretty much every climate scientist out there) would agree with your point that both temperature and sea level have fluctuated in the past. But, as John pointed out in his response to your post at #27, this was on geologic time-scales. On human time-scales, sea levels (and climate) have been more-or-less constant since before those pyramids you mentioned were built. Human civilisation hasn't seen the sort of climate variation you're talking about, and whether it would survive the encounter is debatable. Tony O'Brien's list of references at #25 looks like interesting reading in that respect. But consider this: if sea levels rise by 5-6 metres, whether by natural or anthropogenic means, how are you going to deal with 600 million refugees? That's a nasty problem, and the science is indicating that it's one that we're bringing on ourselves.
    Response: Just wondering where you get your 600 million refugees figure? I've been looking at Dasgupta 2007 for data on the impact of sea level rise - was wondering if there would be something more recent.
  36. Predicting future sea level rise
    SNRatio @30: ice cap melting with little surface temperature change is not that unexpected - after all, ice melting to water absorbs very large amounts of energy (334kJ/kg) with negligible temperature changes, compared to about 4.18kJ/kg for every degree you heat liquid water. In other words, to absorb the same amount of energy as it took to melt at a constant temperature, you'd have to heat liquid water from 0ºC to 80ºC. That's actually quite a substantial buffer effect on temperatures, when you think about it. Temps increase to the point where icecaps start to melt, then stay there while they do, after which you'd expect a substantial acceleration of temperature rise (unless changes to weather patterns decreased coupling between regional temperatures).
  37. Predicting future sea level rise
    RE#6 Neilperth Sorry to sound rude but the way you rose concerns made me believe that these were your questions and your findings (but it looked too neat and I myself are skeptical of everything in lift) I just did some quick googling on the phrases you used. On this site here: http://www.americanthinker.com/2009/08/my_global_warming_epiphany.html "How can you blame man for sea levels rising when about 99% of that rise since the last ice age occurred before man built the pyramids, much less SUVs? A rise in sea level over the last century should not be surprising; it's been rising for the last 20,000 years." - Randall Hoven. August 26, 2009 You said: "How can you blame man for sea levels rising when about 99% of that rise since the last ice age occurred before man built the pyramids, much less SUVs? A rise in sea level over the last century should not be surprising; it's been rising for the last 20,000 years." Either you are Randall Hoven which I apologize for, or you copied the statement from him, or, both you and him copied this statement from someone else. I'm not so fussy about using other peoples arguments but since people spend a lot of time replying, I think it is good manners to at least inform where you got the information from so at the very least they can more directly reply to your arguments/concerns.
  38. Svensmark and Friis-Christensen rebut Lockwood's solar paper
    From http://www.independent.co.uk/environment/climate-change/sun-sets-on-sceptics-case-against-climate-change-1839875.html "Friis-Christensen now accepts that any correlation between sunspots and global warming that he may have identified in the 1991 study has since broken down. There is, he said, a clear "divergence" between the sunspots and global temperatures after 1986, which shows that the present warming period cannot be explained by solar activity alone."
    Response: There's more details on how Friis-Christensen came to this conclusion on the Solar Cycle Length page.
  39. Hockey sticks, 'unprecedented warming' and past climate change
    Ian Love, "NAS reckoned more data was needed, which the paper provides." acutually it is a never-ending story, scientists always need more data :)
  40. Predicting future sea level rise
    SNRatio, the data are strongly smoothed. The degree of smoothing is not quoted for fig. 2 here but in fig. 4 in the paper it is quoted to be 15 years. Whatever it is, it's strong and i would not expect much sensitivity on short term fluctuation. The same is true for ice melting itself, its slow response time "smooth" away temperature fluctuations.
  41. Predicting future sea level rise
    FrankT, thank you for the link. On the long run and if really huge Greenland melting occurs there may well be the gravitational pull effect. Unfortunately (especially for the Dutch), the same applies to the melting in Antarctica. This branch of oceanography is in its infancy, though. I bit more clear, instead, are the effects of the prevailing winds, atmospheric pressure gradients, redistribution of water due to large currents and temperature changes. These better apply to the short term trends, at least untill massive ice sheet melting will take the lead.
  42. Hockey sticks, 'unprecedented warming' and past climate change
    SNRatio, I still can't see your points but the last sentence. I agree the the 3°C for doubling CO2 have a large uncertainties, we can take it for granted. I also agree that the zero feedback sensitivity is much lower than the "true" sensitivity, roughly 0.3 °C/Wm^-2 against 0.8 °C/Wm^-2. But then comes the last sentence that appers to be uncorrelated with the reasoning above. The "degree of overlap" does not change with H2O concentration, it is due to the basic properties of the individual molecules. For example, the well know 600 cm-1 CO2 band will never overlap with H2O bands in any plausible atmosphere; and where there's already overlap it won't change if we increase CO2 and H2O concentrations. Consider also that the radiative transfer codes takes into account all of these, concentration of all the consituents, absorption band frequency, band width, dependence on temperature and pressure and, finally, superimposition of the absorption bands. I think that the only point scientifically valid is the "true" value of the sensitivity, trying to constrain it as much as possible; i.e. lower the uncertainty.
  43. Hockey sticks, 'unprecedented warming' and past climate change
    In addition to the papers Chris cites in #17 and #34, there is Mann et al.s most recent (Sept 2008) PNAS paper on the proxy reconstructions over the past 2000 years: www.pnas.org/cgi/doi/10.1073/pnas.0805721105, which brings together the work on S hemisphere as well as N. And concludes that the MWP was a variable phenomenum and was at a lower temperature than current. This was indicated as likely by the National Academy of Sciences review in 2006, as well as by the IPPC AR4. NAS reckoned more data was needed, which the paper provides. McKitrick et al. still try to show otherwise (of course) but Mann rebuts their criticism in PNAS 2009.
  44. Predicting future sea level rise
    At first glance, I must say that I don't like fig 3a in the paper, your fig 2, because they dont follow the development up to 2009. (It seems to have been last revised in October). The last years, we have had a trend closer to 2.5 cm/decade, the longer term trend still being ca 3.4 cm/decade. Furthermore, I feel a bit unsure about the modeling in the light of observations from the last 10 years. We may in fact have an accelerating ice cap melting going on with little surface temperature changes.
  45. Predicting future sea level rise
    Riccardo@26 Quite correct. The open question for research is why there is no correspondence between the local and global trend. This is peculiar, since the obvious causes(in particular sinking/rising land) are all carefully measured, and do not explain the difference. A related issue which is important for the long term implications for Holland is the recently re-discovered effect of 'self-gravitaion'. This is not yet included in the KNMI 2006 scenario's, but will be in the 2013 version. Self-gravitation refers to the effect that large ice-sheets on land attract the sea through the force of gravity, leading to a substantial local increase of the sea-level. The surprising implication is that a complete melting of the Greenland ice-sheet would hardly lead to any sea-level increase on the shores of Greenland. The gravitational effect of the Greenland ice sheets is still very noticable in Holland. Model calculations from different researchers are not in agreement yet, but as a rough indication it would probably diminuish the impact on sea levels at the Dutch shore by a factor three. So instead of a rise by 6-7 meters after a complete melt of the Greenland ice-sheet, the increase of the sea level at the Dutch shores would only be 2 meters. On page 15 of the popular publication of the Delft Technical University 'Delft Outlook' 2009-02 (url below) you can find a bit more context about this, in an article primarily about the new GOCE sattelite. http://tinyurl.com/yht6tdj
  46. Hockey sticks, 'unprecedented warming' and past climate change
    "Here you are linking sensitivity and temperature. It's correct, they are by DT=lambda*DF. So the issue is wether the forcing is logarithmic or not. If it is, whenever CO2 concentration happens to double, you'll get 3 °C." I don't see the situation that way. While we can be pretty sure that the forcing is approximately logarithmic at the current levels of CO2, our 3 °C estimate for sensitivity is the estimated mean of an unknown pdf with quite big variance. Furthermore, there is a very long adaptation time, so it can't be safely estimated even 20 years after forcings have changed. Several 'proofs' of low sensitivity are based on such short time observations. The basic, zero-feedback forcing of ca 1.0 °C/doubling of CO2 is usually derived under the assumption of independence from other GHGs - as far as I can see. If we use Chris Colose's http://chriscolose.wordpress.com/2009/10/08/re-visiting-cff/ presentation, we have dT0 = k * ln(2) * lambda_Planck. lambda_Planck is the reciprocal of the partial derivative of Stefan-Boltzmann wrt temperature, with approx numerical value of 0.27, an often used approximation of k is 5.35, and it all multiplies to approximately 1. Different degees of overlap with H2O could influence the sensitivity.
  47. Was there a Medieval Warm Period?
    Given normal climate cycles, how valid is it to compare an estimted (proxie) global average for a three hundred year period to a recent ten year period. There must have been a good number of 10 year periods during the 300 years that varied well outside the average.
  48. Predicting future sea level rise
    neilperth @27: I don't know if we're getting anywhere; you aren't saying very much and you repeat a high proportion of what you have said. Regarding your last question, my answer is "Not necessarily -- it depends on future forcings." Read this: http://www.skepticalscience.com/High-CO2-in-the-past-Part-2.html
  49. Predicting future sea level rise
    Steve @23..... Hey we are getting somewhere in our discussion! So you agree that sea level and temperature changed over time in the absence of anthropogenic forcing and that they will continue to change while humans are here and after humans are extinct. Do you also agree that it is likely that the cyclical ice-ages which have occurred on earth over the last 600 million years will continue to occur in the future ?
    Response: These are fundamental and well established issues. Every climate scientist will agree that:

    1. Temperature has changed naturally in the past (before humans).
    2. As sea level is directly affected by sea level (as established in Vermeer 2009) then sea level has changed naturally in the past

    Do not fall into the logical fallacy that past natural climate change means humans can't influence climate now. On the contrary, past climate change shows us that climate is sensitive to radiative forcing - to energy imbalance. As we are currently imposing an energy imbalance through an enhanced greenhouse effect, past climate change is actually evidence for our climate's sensitivity to CO2.

    Is it likely that cyclical ice ages will occur in the future? In the short term (geologically speaking), the peer reviewed science says no. The radiative forcing from CO2 far outstrips the radiative forcing from orbital changes that initiate cyclical ice-ages. I touch on this tangentially on We're heading into a new Little Ice Age although that page is talking more about the forcing from falling solar levels, not orbital forcing. However, orbital forcing is even less than solar forcing so the argument stands (one of these days I'll do a post specifically focusing on Milankovitch cycles).
  50. It hasn't warmed since 1998
    Tim228, i guess you refer to fig.1. The paper from which it is taken is an observational study, they measured the actual heat content of the oceans. Consequently the latent heat of evaporation of sea water as well as all the other energy related effects are automatically included.

Prev  2507  2508  2509  2510  2511  2512  2513  2514  2515  2516  2517  2518  2519  2520  2521  2522  Next


The Consensus Project Website

THE ESCALATOR

(free to republish)


© Copyright 2024 John Cook
Home | Translations | About Us | Privacy | Contact Us