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Are we heading into a new Ice Age?

What the science says...

Select a level... Basic Intermediate
Worry about global warming impacts in the next 100 years, not an ice age in over 10,000 years.

Climate Myth...

We're heading into an ice age
"One day you'll wake up - or you won't wake up, rather - buried beneath nine stories of snow. It's all part of a dependable, predictable cycle, a natural cycle that returns like clockwork every 11,500 years.  And since the last ice age ended almost exactly 11,500 years ago…" (Ice Age Now)

According to ice cores from Antarctica, the past 400,000 years have been dominated by glacials, also known as ice ages, that last about 100,000. These glacials have been punctuated by interglacials, short warm periods which typically last 11,500 years. Figure 1 below shows how temperatures in Antarctica changed over this period. Because our current interglacial (the Holocene) has already lasted approximately 12,000 years, it has led some to claim that a new ice age is imminent. Is this a valid claim?

Figure 1: Temperature change at Vostok, Antarctica (Petit 2000). The timing of warmer interglacials is highlighted in green; our current interglacial, the Holocene, is the one on the far right of the graph.

To answer this question, it is necessary to understand what has caused the shifts between ice ages and interglacials during this period. The cycle appears to be a response to changes in the Earth’s orbit and tilt, which affect the amount of summer sunlight reaching the northern hemisphere. When this amount declines, the rate of summer melt declines and the ice sheets begin to grow. In turn, this increases the amount of sunlight reflected back into space, increasing (or amplifying) the cooling trend. Eventually a new ice age emerges and lasts for about 100,000 years.

So what are today’s conditions like? Changes in both the orbit and tilt of the Earth do indeed indicate that the Earth should be cooling. However, two reasons explain why an ice age is unlikely:

  1. These two factors, orbit and tilt, are weak and are not acting within the same timescale – they are out of phase by about 10,000 years. This means that their combined effect would probably be too weak to trigger an ice age. You have to go back 430,000 years to find an interglacial with similar conditions, and this interglacial lasted about 30,000 years.
  2. The warming effect from CO2 and other greenhouse gases is greater than the cooling effect expected from natural factors. Without human interference, the Earth’s orbit and tilt, a slight decline in solar output since the 1950s and volcanic activity would have led to global cooling. Yet global temperatures are definitely on the rise.

It can therefore be concluded that with CO2 concentrations set to continue to rise, a return to ice age conditions seems very unlikely. Instead, temperatures are increasing and this increase may come at a considerable cost with few or no benefits.

Last updated on 1 September 2010 by Anne-Marie Blackburn.

Printable Version  |  Offline PDF Version  |  Link to this page

Further reading

Tamino discusses predictions of future solar activity in Solar Cycle 24.

Acknowledgements

Many thanks to Sami Solanki for his invaluable advice and feedback as well as John Cross for his very helpful comments.

Comments

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Comments 201 to 250 out of 359:

  1. Henry Justice @198 - "Also, I checked the worlds annual mean temperature charts. Not much of a visual upward slant in temperatures everywhere I looked world wide for the last 50 years. The urban site temps were not used as they are unreliable. So upward and downward wiggles appear all but natural variations. Look for yourself and you be the judge!"

    Okay. Comparing all the temperature records



    Henry, the three surface temperature records and both satellite records all show warming. Where have you been looking?.
  2. Henry Justice - " In Greenland, eight WW2 bombers from the "lost squadron" were found in 1986 under 267 feet of ice. How's that for melting glaciers? I didn't take the rest of the article seriously."

    Yeah, heard that one before. And the one about the research station being buried under many feet of snow, and having to be dug out.

    Please note that the center of the Greenland Ice sheet is at high elevation, is very cold and is still accumulating ice. The coastal regions where the glaciers meet the sea, are not, and are rapidly melting. The loss of ice at the coast far exceeds the gain from snowfall at high elevation, this is why the Greenland ice sheet is losing many billion of tonnes of ice every year.
  3. Henry @198,

    I'm afraid you have been hoodwinked by some folks who, on the surface, seem to make a compelling case.

    Research has shown that even if we do enter another Maunder-like minimum, or even a grand minimum, the radiative forcing from elevated GHGs will easily overpower the reduced incoming solar radiation. See this thread for details.
  4. #195 . WRONG !!!
    the satelites together with earth should form one system that it should be moved together in the apply of gravitational forces due to planetary realligment , yet the sun stays steady ....
    Response: [Daniel Bailey] Again, please provide linked references for those claims (published, peer-reviewed sources have the most credibility). Extraordinary claims must of necessity be accompanied by an extraordinary evidenciary chain. Unsupported comments such as yours will be simply deleted in the future. Thanks!
  5. @kfdv #190

    Are you aware this is all written, aren't you? What do you suppose students will think about when they analyze your answer to #188 ?
  6. Have any of those individuals pointing to the “Petit 2000” graph actually bothered to look at it and study what it means?

    According to the graph if you move backward through time to "now" you see a rapid increase in temperature - consistent with other ice ages - but the highest temperature reached, during the present temperature increase period, never reaches the same high it reached in previous ice ages. The high in previous periods is over 3 deg above the baseline whereas it is less than 2 deg above the baseline for the present. How can anybody interpret this as a temperature rise that’s out of control?

    If we’re in the middle of a glacial warming period it stands to reason that each year will be warmer than the next until the warming trend ends.

    BTW: The most efficient way to transfer thermal energy is by convection. If you remember your physics there are three ways to transfer thermal energy – radiation, conduction and convection. Why does the GW model only consider the meager role of radiation heat transfer when convection heat transfer is far more efficient?
  7. Dorianmc,

    Firstly, who said we were undergoing runaway temperature increases? So far warming has been very tightly controlled, doing pretty much what climatologists said it would do in reaction to increasing CO2 levels.

    Secondly, we're in the middle of an interglacial period that should be cooling according to natural forcings, but it isn't. Temperature is spiking rapidly on a geological timescale.

    Thirdly, exactly how do you know that radiative transfer is "meager"? And what gives you the bizarre idea that convection isn't taken into account? Which model states that only radiative effects are taken into consideration? Your previous post is a rambling mess of assertion.
  8. Dorianmc forgets (or is unaware) of the multiple layers of the atmosphere and that at the level of the TOA, convection is largely non-existent and radiative transfer rules.

    And that at no point in the last several interglacials did CO2 concentrations ever approach what they are today, heightening the importance of back radiation. Also remember that the zero baseline of Petit 2000 was 1950. Let's take a look at that whole timeframe, extending it to today's CO2 levels:



    A re-watching of Alley's talk would be instructive here.

    The Yooper
  9. #206: "it stands to reason that each year will be warmer than the next until the warming trend ends."

    That would be nice, if we lived in some kind of cartoon-world, where the requisite laws of cartoon physics apply.

    However, you may be aware we had a 'Little Ice Age' and have fully recovered from that. So your idea that there's any possibility of monotonically increasing temperatures is not even lukewarm.
  10. Perhaps I'm missing something,but several things jump out of this graph:

    1) The data only goes back about 430,000 years, yet the axis goes back 450,000 years. Why? To me it looks as though someone has removed the first part of the line. I'm not saying they did, but such things do happen from time to time. In this instance it's a fairly critical question because the interglacial that occurs at the left of this graph is allegedly the closest fit to the one we have now in terms of the alignment of the planet.

    2) It is apparent that the later data is at a high level of granularity than the more recent data, you can see this by the spikiness (thickness) of the line. This is not surprising because the closer we get to the present the more data we have. However it does somewhat skew one's perception of the graph because when we look at 430,000 years ago compared with now, we are not - in graph terms - comparing apples with apples, due to the granularity difference. I strongly suspect that if the graph was drawn with uniform granularity then the temp change 430,000 years ago would appear more similar to the present temp change.

    3) The temp peak in this current interglacial is presently a very thin one at 2C. Other than that the temp appears to be hovering somewhere between 0-1C, this is actually lower than in pervious interglacials, all of which peak between 2-4C.

    4) There are only really 5 samples of interglacials represented here and that really isn't much of a data set. Now I fully appreciate that this can;t be help given the time periods in question, but it doesn't change the fact that there are only 5 samples for comparison.

    Humans are as yet hopeless at predicting localised weather let alone the climate. This doesn't mean people shouldn't try but perhaps they should hold back predicting catastrophes until we have a better understanding. For all we know the super volcano in Yellowstone National Park could go off in a few decades and that would really throw a spanner into the works. The Earth is a living planet, and nature takes no prisoners. Personally I am glad of all this hoo-har over climate change because if nothing else it is teaching people not to mess around with nature. Unfortunately that doesn't mean that won't mess around with us and everything else on this planet. If nature chooses to make some changes then - take note kids - human beings are powerless to do anything about that. Get used to it.

    In LVX
  11. Here is the full graph. Shows a more similar curve between 430,000 years ago and now:

    http://commons.wikimedia.org/wiki/File:Ice_Age_Temperature.png
    Response: [Daniel Bailey] Not so similar. Remember that ice core temperature reconstructions use 1950 as year zero. Here's what that would look like if CO2 were extended to today's levels (I do seem to be having to show this illustration a lot lately!):
  12. #210: "if the graph was drawn with uniform granularity..."

    If the graph was drawn uniformly, it would be a misrepresentation of the data. The time resolution of an ice core (and many conventional cores) decreases as you move downhole (older). Petit et al 1999 is the classic description of how these data are obtained.

    The mean resolution of the CO2 (CH4) profile is about 1,500 (950) years. It goes up to about 6,000 years for CO2 in the fractured zones and in the bottom part of the record

    "... only really 5 samples of interglacials represented here and that really isn't much of a data set."

    Why is this a concern? This isn't a pattern matching exercise.
  13. Re: Blueflash (210)

    1. Read the study (petit et al 1999)
    2. IBID. Then read this.
    3. You expect all glacial epochs to be Xerox copies?
    4. 450,000 years of data, multiple cores. Say what you want, but it doesn't change the fact that that's an awful lot of years and even more snowflakes.

    Humans do a pretty good job at understanding past and present ongoing climate change and predicting future climate changes. Strawmen distractions about off-topic supervolcano's aside (we are overdue for a Yellowstone blow, tho), human beings are pretty capable of screwing the planet up.

    Get used to it.

    The Yooper
  14. Daniel,

    1) The graph I was referring to was a temperature graph. The one you have responded with is a CO2 graph.

    2) "For 650,000 years, atmospheric CO2 has never been above this line... until now" uses misleading grammar. The word "never" has strong implications. And 650,000 years is not a long time in the grand scheme of earth.

    The correct phrasing would be "CO2 has not been above this line in the past 650,000 years."
    Response: [Daniel Bailey] Sigh. In reverse order (feeling contrarian myself today), 650K years is an immense time in the history of our species; the Earth will abide long after we are gone (unless we get too many handwaving comments). CO2's peak in the Vostok core was 298.3 PPM. The line was to represent 300 PPM. Grammar concerns notwithstanding, the point is unequivocal. And for those who refuse to acknowledge any relationship between CO2 and temps:
  15. Please excuse my ignorance, but are you saying that the increased CO2 levels responsible for global warming have kept us from entering into an Ice Age? Shouldn't we be glad of that? Or is it the case that this global cooling period/Ice Age wouldn't have affected us in our lifetime, or the lifetimes of future generations and as such wouldn't have been of concern anyway?

    I'm just a little confused now.
  16. The current interglacial would have ended in about 10 thousand years based on the natural cycles. Hence, not really a concern for humanity.
  17. Re: Mr_Pants (215)

    Welcome to Skeptical Science!
    "Please excuse my ignorance, but are you saying that the increased CO2 levels responsible for global warming have kept us from entering into an Ice Age?"
    I'm not saying it is or isn't in the definitive sense, but the emerging evidence would seem to indicate that.
    "Shouldn't we be glad of that?"
    Dunno. Personally, I'm glad to have a job and a family that loves me.
    "Or is it the case that this global cooling period/Ice Age wouldn't have affected us in our lifetime, or the lifetimes of future generations and as such wouldn't have been of concern anyway?"
    Absent the warming effects of the CO2 bolus we've injected into the air, then the understanding is that the Earth would've continued its gradual cooling trend from the Holocene Optimum for at least the next several thousand years before any onset of an ice age would've become worrysome. But that's neither here nor there.

    Of bigger and more immediate concern is what damage the warming still in the pipeline will do to our climate and crop production:

    "I'm just a little confused now."
    Been there, done that.

    The Search function in the upper left corner of every page is your friend here. If you have questions, type in a few keywords & search away. Odds are there's a thread or three here covering that topic.

    For some good background on Skeptical Science and climate science in general, go here and here.

    Enjoy!

    The Yooper
  18. Even if there was eminent danger of mile-high sheets of ice sitting on Minnesota, such as in 'Fallen Angels' by Larry Niven, we have already drastically overshot the mark.
  19. #218: Biblio,
    Maybe we could build a Ringworld. It would be cooler (from a scifi point of view).
  20. @ 219

    I hear General Products was founded by Koch Industries...

    The "Louis Wu" Yooper
  21. #220: Ha! Even the Puppeteers were done in by what could only be called PGW

    The Puppeteers had to make some drastic alterations to their home system, during their history, as waste heat due to overindustrialisation was rapidly making their planet uninhabitable. They moved their planet further from their sun, to lessen the effects of global warming ...
  22. @ 221

    You mean...they had their own waste heat thread?

    One is enough to do in any civilization, apparently.
  23. There seems to have been several comments in this thread regarding the shifting of the axis of the planet. I don't know whether those who propose such things simply do not understand how the planet moves in space and interacts with it's environment, or are simply misunderstanding some real events and relationships.

    For the record. The axial tilt of the planet moves. Over a period of about 41,000 years it gradually "wobbles" from 21.2° to 24.1°. On it's own the effect on climate will not be that great as it accounts for something in the region of a variance of about 0.021 W/m² of solar radiance, hardly enough to have a drastic input on it's own. This wobble has a wobble imposed upon, that also has a wobble..you could say that the wobble has a wobbling wobble!! However, joking aside, these are minor and do not have any real effect. There is no evidence that I am aware of showing the axis of the planet has ever exceeded the extremes of the wobble I mention in the last 4Gy, thus I think it unlikely too now.

    Where I feel many laymen get confused is between the axial pole and the magnetic pole, which are wholly separate. The Magnetic pole wanders about like a drunk, all over the place and up to 40km per year, currently it holds a Canadian Passport! Further, it is a proven fact that the magnetic pole does "flip" and also disappears for short periods, perhaps up to 10,000 years, and this process is not understood really, although theories abound as to the cause.

    Whether there is an interaction between these magnetic reversals and the climate I do not know, I don't think any research has been done in this respect, but I stand to be corrected on this.

    Any sceptic who claims that the axis of the planet changes drastically and this causes Ice Ages, Warm periods, sea level changes or even the death of species is talking out of their hat and they do not do the debate any favours at all as they simply make those who question the climate research conclusions seem like crack pots.

    Now perhaps we can avoid discussion of the planets axis moving and stay on track?
    Response: I'm unsure whether you are arguing against the existence of Milankovitch cycles, but if you are, you are wrong. You can see Richard Alley explain it in 30 seconds. Doing an internet search for "Milankovitch cycles" will get you a bunch of diagrams, animations, and explanations. That will help you understand when you reread the original post at the top of this page.
  24. @ Response...surely you have a name :)

    I am unsure why you feel I was arguing about Milankovic cycles, and I wonder if you read my post correctly?

    I am not arguing against Milankovic cycles in the slightest, on the contrary, I am a firm believer that these cycles can and have played a part in the varying climate here on Earth, but I think this is only when they coincide with other effects that are "home grown" on Earth and simply add to it. My comments are self explanatory, the axis of the planet does not shift beyond the natural variance I noted and firmly believe that many get this mixed up with magnetic pole displacement, which is a proven scientific event in Earth history.

    Many seem to misunderstand the motion of the planet in space, and seem to think these changes have a greater impact on Earth than they do. Combined they may well have a big effect, but as far as I am aware, no-one has created a model of the solar system accurate enough to models our planet's motion in space over the last 4 billion years to see whether, at any time, the disparate cycles have ever coincided enough to have anything more than an arbitrary effect. That is why the last paragraph of my post was worded the way it was.

    I am not convinced by AGW, but if one is to argue against something, then one must do it with credible arguments that at least are worth research time, and polar shift of the planet is not one of them
    Response: You just now did argue against the dominant role of Milankovich cycles in triggering ice ages. Make up your mind.
  25. #224: "models our planet's motion in space over the last 4 billion years ... "

    A complete and utter red herring strawman. There is more than enough understanding of the current orbital dynamic to fully describe the orbit's control over solar insolation. There is more than enough measurement of insolation to fully describe its input to earth climate.

    "... to see whether, at any time, the disparate cycles have ever coincided enough to have anything more than an arbitrary effect."
    What does that even mean? What is an 'arbitrary effect'?

    "I am not convinced by AGW"

    Let's try to establish credibility rather than make declarations. Have you read each of the SkS threads relevant to whatever aspects of AGW you disagree with? Have you weighed the arguments of actual scientific research against 'I am not convinced'? What specifically do you disagree with? Can you mount credible cases against the points made in the relevant SkS threads to qualify as scientific arguments?

    Those who arrive at SkS already in a confirmed state of denial usually wind up with little more to do than pose red herrings and make blanket 'no its not' statements. Nobody said understanding AGW was easy; being a competent skeptic certainly isn't easy either.
  26. @ Response:

    Yes I did, your correct. The Milankovic cycle is a real phenomena, however I do not accept the assertions of many that it is a dominant factor is our planet's climate. I do not need to make my mind up as I know exactly what I mean. I actually agree with many climate scientists on this important point, but feel that they have failed to publicly really kill this point, that's why some people keep bringing it up.

    @Muoncounter. I am not impressed with your personal attack, you are a moderator here and I would have expected better from you.

    My comments are clear and in obvious English. For your information, my comment about an "arbitrary effect" is one that on it's own has little overall impact...

    Regarding reading all the threads on here, do you think I have lived in a cocoon for 44 years? Your making an assessment of me based on something that, forgive this comment..rather arbitrary :)

    I subscribe to several Science Journals, and stay up to date, at least with Astronomy/Space related research, but I have interests in Nuclear and particle physics too. I am slowly working through SkS.I think you will agree it's not a 5 minute job to read all the posts in every thread...and I do have to go to work to!

    You see your assuming that I am in a state of denial, your making this a religious discussion in effect. I used the words "Not Convinced", that means I have an open mind and am open to being convinced, but having a science background means I require more evidence as I personally feel that the argument is not there, there is compelling evidence, I am not against reducing CO² or any other gas or poison being put into the environment, but the arguments have not proved their case for me personally, but I accept that the arguments posed against it are generally lacking in detail and quality...so I am on the fence. The anti AGW camp actually drive me as mad as the ardent Pro camp does.

    That is not the same as Denial.

    However clearly you have an issue with my ability to think for myself...so you might like to know I own and Drive Land Rovers...:)

    Now please, lets not allow this to get personal, we are all above that and mature adults, if the arguments are weighted correctly, match up with the science, then they will carry the day...whichever side ultimately proves to be correct...
    Response: [Daniel Bailey] Please stay on the topic of the post. Thanks!
  27. @LandyJim: muoncounters didn't make any personal attacks towards you. Please have the courage to defend your opinions without whining when someone challenges them!

    As the effect of Milankovitch cycles on cliamte are well-understood, you're going to need to provide some evidence to support your extraordinary claims that the varying insolation caused by the various wobbles doesn't in fact significantly affect the climate.

    In other words, if you're going to challenge current science, you better not all hat and no horse.
  28. #226: You stated you were 'not convinced' by AGW; I recommended, as I often do, that one needs to establish the credibility of one's doubts in a systematic way. That could neither be construed as a personal attack nor a religious discussion in any way whatsoever.

    But this thread is about whether a new ice age is on the horizon. My comment #225 rejected your suggestion that a 4 BY solar system model has merit in this particular discussion. And the question 'what is an arbitrary effect?' in this context was warranted, as I do not find that particular phrase to have definite meaning in 'obvious English'.

    The solution to the problem of being misunderstood by others who may read your comments in a different light than you intended is simply to stay on topic, stick to facts and avoid gratuitous opportunities to drop off-the-cuff declarations into your comments whenever possible.
  29. LandyJim,

    "Dominance" isn't a relevant term in regards to Milankovitch Cycles. MC's are forcings, meaning they initiate a change. CO2 and other greenhouse gases begin to accumulate in the atmosphere in response, which is why we call them feedbacks. Once those gases reach a certain concentration, they exert a greater influence on climate than the relatively small change initiated by the change in Earth's tilt toward the sun.

    Let me say this again: Milankovitch Cycles do not "dominate", they initiate.
  30. #4 WASP
    You claim we recently came out of a glacial period, yet we never reached the normal high temperatures of a normal interglacial period. The relatively flat temperatures that one would have assumed would have reversed into a glacial cycle, began several thousand years ago, this lack of reversal has been in no way related to anything man caused. Studies have also shown that over the short term, temperature changes are much more closely correlated to sun activity than to CO2 levels. It has been shown else where on this site, that over time the CO2 released by the oceans during the warming trend, eventually slow and the rate of absorption of CO2 by the oceans reverse the trend of increasing CO2 levels in the atmosphere. In fact "WHAT IS GLOBAL WARMING DOING TO THE OCEANS? It's raising the oceans' temperatures ever so slowly, but also, it's making it easier for the ocean to absorb carbon dioxide (CO2).
    click here Thus the absorption of CO2 is not static and in fact increases as ocean CO2 emissions decrease and temperatures rise. I have seen no explanation of this several thousand year flattening of temperatures. I have seen no accounting for the decreasing emissions and increasing absorption by the ocean which would appear . Where are these statistics taken into account?
    Response: [Daniel Bailey] Let me first thank you for being on-topic. However, one of the things to keep in mind from the Comments Policy is no all-caps. Lastly, user WASP has "gone silent", with their last post occurring on 30 July 2008. It might be a while before getting any reply.
  31. stephenwv (#230)
    You make a number of assertions about Solar Activity and CO2 but do not provide any citations for them. Please include some links to back up your claims so that we can discuss their merits. Without data all we have is opinions.
  32. #230: "... we never reached the normal high temperatures of a normal interglacial period.... no explanation of this several thousand year flattening of temperatures."

    What are you referring to? I can't make any sense out of your comments; it would be helpful if you made specific reference to events on the temperature graph labeled Figure 1 on this post.

    As to the repeat of your CO2/oceans comments, you've already been directed to the appropriate threads.

    Solar comments should likewise go to the It's the sun thread, available as #1 on the Most Used Arguments.
  33. Stephen,

    There is no "normal" high temperature for an interglacial. They typically represent an increase in temperature of roughly 2-4 degrees C. What you have to keep in mind is that the change in temperature depends largely on how the planet's orbit and tilt coincide; they don't always act in synchronicity.

    Secondly, what studies are you referencing in regards to solar activity? As that activity has been roughly flat since the 1950's there is goof reason to conclude the current warming is not primarily due to the sun.

    As for a flattening of temperatures, I assume you are referring to the graph at the top of the post which outlines temperature fluctuations over the last five interglacials. I'm sure someone more knowledgeable will correct me if I am mistaken, but I would posit the "flattened" appearance of the current interglacial is due to greater paleoclimate resolution. In other words, it looks flattened because we have a more detail the closer we get to the present.
    Response: Any more conversation by and in response to Stephen about the Sun belongs on the thread It’s the sun.
  34. stephenwv, I responded to your claim that rising temperatures increase CO2 absorption, on the ocean acidification thread.
  35. stephenwv - a couple of other points for you to ponder when you compare what is going on now, to what happened in ice ages.
    Rate of temperature change is around 10 degrees in 20,000 years or 0.05C/century. Rate of warming now is around 0.8C/century (more than 10 times faster). And from an earlier post. "The milankovitch forcing that drives ice age is due to change in forcing that is about 0.25W/m2 per hundred years at 65N. Globally, its maybe a tenth of that. By comparison, anthropogenic GHG is about 2.5-3W/m2 over last 100 years globally, not just at 65N." Do you think natural factors are going to trump that?
  36. Please take a look at the 100,000 year glacial cycle again

    http://upload.wikimedia.org/wikipedia/commons/7/77/Vostok_420ky_4curves_insolation.jpg
    http://en.wikipedia.org/wiki/File:Ice_Age_Temperature.png

    You can see the 100,000 year cycles. You will note that warming occurs very rapidly at the start of each interglacial. Subsequent cooling occurs very gradually. You can also see the temperature delta over those 100,000 years is only 10 to 11 C. You also see how repetitive the saw tooth wave form is.

    We are still 4.5 C below the peak temperature normally achieved during an interglacial. Ie - we are only just above half the temperature delta normally experienced during an interglacial. This source provides that number

    http://news.nationalgeographic.com/news/2007/07/070705-antarctica-ice.html

    Why is our climate still so cold during this interglacial? We are only about 6.5 C above the lowest temperature we normally experience during the 100,000 year glacial cycle.

    Chris Shaker
  37. Chris Shaker @236 - You're just repeating what you claimed earlier in this thread. Have you forgotten all the information that was provided to you by other commenters?. If so, please re-read this thread from the beginning.
  38. cjshaker... "We are still 4.5 C below the peak temperature normally achieved during an interglacial."

    That's an interesting bit of information given that we're in the process of adding a significant additional radiative forcing to the climate system. You are essentially arguing for climate sensitivity in the high estimated range of ~9C.
  39. I'm looking at the graphs again, to see what is really there, instead of what I assume is there.

    Chris Shaker
  40. I am also curious as to whether other people seeing the same things in the graph that I am seeing, ie - is the temperature delta over the 100,000 year glaical cycle 10 to 11 C, as it seems to me?

    Does someone have a better number for the current temperature than the one provided in that National Geographic article?

    Chris Shaker
  41. I see the same thing in the graph at the top of this page, we appear to be cooler than the peak during all of the previous interglacials on the graph. Also, it looks as those the temperature has previously been higher during this interglacial, and is slowly cooling overall? The line is quite thick, but it seems to trend down over the past 15,000 years or so.

    Chris Shaker
  42. "it looks as though", not "it look as those"

    Chris Shaker
  43. Here is another way of finding the temperature delta over the 100,000 year glacial cycle, from measuring the concentrations of atmospheric noble gases dissolved in groundwater. He came up with a delta T of 8.8 C, which is fairly close to what we see on the graph of proxy temperatures derived from the ice cores
    http://www.ldeo.columbia.edu/~etg/werner/maryland/MD.Abstract.html
  44. Regarding whether or not we are heading into another ice age, my buddy's son, Jed Kaplan, is a climate scientist who believes that mankind has been changing the environment for at least 8,000 years, reversing the declining temperatures we experienced during this interglacial. He and palaeoclimatologist William Ruddiman believe that the agriculture of early mankind changed the CO2 level and helped stabilize our climate against the start of the ice age

    http://www.nature.com/news/2011/110325/full/news.2011.184.html

    "Proposed by palaeoclimatologist William Ruddiman in 2003, the theory says that human influences offset the imminent plunge into another ice age and helped create the relatively stable climate that we are familiar with today"

    If that is true, we need to learn to better control our environment by better controlling our CO2 emissions, ie - not just by cutting it. We would need to manage it, figuring out what level of emissions is needed to stabilize temperatures, and be able to mange our CO2 emissions to match. Climate control...

    Chris Shaker
  45. I was directed from another thread to this topic. From what I have been able to gather, the addition of man in the climate equation, has created a new hypothesis:

    That man contributing CO2 levels in the atmosphere have altered the climate in such a way as to prevent future ice ages from happening.

    The reason behind this being that CO2 is a forcing that far exceeds any counter negative feedback.

    If true this is a whole new direction of thought.
    Response: Click the Intermediate tab. Then read.
  46. Dana,
    The question is: did man change the climate 5,000 years ago to prevent the change to an ice age or was the climate not changed until the last 100 years? ASFIK that question is still under debate. With the current carbon in the atmosphere the next several ice ages have been prevented. As we emit more carbon the time until it will be removed by natural causes keeps getting longer and longer.
  47. Created this post to explain Milankovitch cycles. It uses links to NOAA and NASA sites instead of SkS as deniers are complaining about the bias and religiosity of SkS.

    Milutin Milankovitch calculated the effect of eccentricity cycles in the 1920's. This effect was validated by ice core samples in 1976.
    http://earthobservatory.nasa.gov/Features/Milankovitch/milankovitch.php
    - follow links under "on the shoulders of giants"

    Astronomical calculation indicate insolation should increase _gradually_ over the next 25,000 years. We aren't due for a decrease in insolation from orbital eccentricity for 50-100,000 years.
    http://www.ncdc.noaa.gov/paleo/milankovitch.html

    While Milankovitch cycles can explain centuries long changes, they do not explain the rapid greenhouse gas caused changes in the past decades.
    http://www.ncdc.noaa.gov/oa/climate/globalwarming....

    I hope the fact that the Milankovitch theory you appear to be just learning has been well known and accounted for in climatology for over 30 years gives you the ability to better discriminate between scientific websites and dodgy ones. Hint: the dodgy ones wonder if the current warming is due to natural variation.
    Response: [John Hartz} It would be helpful if you could provide us with specific examples of what deniers are saying about SkS. Thank you in advance for your assistance.
  48. Is seems to me that there is a good chance that the arctic melting will stop the Atlantic conveyer by dumpling lots of fresh (therefore lighter) water into the North Atlantic. While studies I have seen indicate that this will be swamped by global warming and thus not have a huge short term effect, it seems to me that if we adopt a policy of minimizing coal use(for which there are certainly lots of good arguments from a pollution standpoint as well as C02 emissions) that by the time we hit 50K years from now we will be set up for a very nasty ice age as the Milankovitch cycle kicks in. This would mean the people at that time (assuming we do not destroy civilization first) will have to do some serious efforts to prevent it or live through it.

    Or am I missing something somewhere?

    This is not an argument for the current C02 emissions since the current threat is warming, but might be one for large amounts 50K years from now.
  49. Randy Subers#248: "by the time we hit 50K years from now we will be set up for a very nasty ice age"

    Don't you think there are more immediate problems on the table than what may or may not happen in 50000 years? Like what will most likely be happening in 50 years?

    That shutdown idea has kicked around for several years; there doesn't seem to be any evidence of it yet (that was in March 2010).
  50. Randy,
    You do not need to worry. The entire next glaciation cycle has already been averted so we are good for 100,000 years. If they needed to keep off the glaciers a single, small flourocarbon plant can manufacture enough greenhouse gas to prevent an ice age. We need to worry about problems for the next 50 years, not 500,000 years in the future.

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