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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.

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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)

At a glance

In something like a Day after Tomorrow scenario, the idea that a new ice-age was just around the corner was the subject of a book, a DVD and a website created in 2002. The author was a retired architect, by the way. Fortunately for us, both the movie and the quote above are figments of someone's fertile imagination. But let's have a quick look at ice-ages and what makes them tick, after which we hope you will agree that the notion that another ice-age is just around the corner is nonsensical.

Ice-ages, also known as glacials, are cold periods that occur in a cyclic fashion within an Icehouse climate state. Earth's climate has been mostly of the Hothouse type (no Polar ice-sheets). However, on occasion it has cooled down into Icehouse, as has been the case in the last few million years. There are regular variations in Earth's orbit around the Sun, taking place over tens of thousands of years. These affect the amount of Solar radiation reaching our planet. During the Icehouse state, such variations can lower and raise planetary temperature sufficiently to trigger swings between cold glacials – when ice-sheets expand towards the Equator – and mild interglacials – when the ice retreats back polewards.

To give an idea of the time-scales involved, Europe and North America have seen glacials and interglacials come and go repeatedly over the last 2.5 million years, this being known as the Quaternary Period of geological time. The last glacial period started 115,000 years ago and the Last Glacial Maximum (LGM), when the greatest ice extent was reached, was around 22,000 years ago. The current interglacial – also known as the Holocene, commenced 11,700 years ago.

A general pattern may be seen here with a long cooling down towards Glacial Maximum but a relatively quick warming into an interglacial. The speed of the warming-up part of the cycle is due to climate feedbacks. Removal of pale, reflective snow and ice cover revealing the darker ground beneath allows more solar heat energy to be soaked up. Melting of permafrost releases carbon dioxide and methane. These and other feedbacks serve to amplify the warming effect, speeding it up.

However, our burning of fossil fuels has happened on such a vast scale that we have blown such factors apart. The atmospheric concentration of CO2 has risen well above the 180-280 ppm range typical of recent glacial-interglacial cycles. The current level, getting on for 420 ppm, is more typical of the mid-Pliocene. That was a geological epoch that happened around a million years before the start of the Quaternary. Mid-Pliocene ice-sheets were much smaller than those of the present day. Rather than being due another glaciation, we can expect a continued transition towards mid-Pliocene conditions.

Please use this form to provide feedback about this new "At a glance" section, which was updated on May 27, 2023 to improve its readability. Read a more technical version below or dig deeper via the tabs above!


Further details

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? No.

To explore this topic further, it is necessary to understand what has caused the cyclic shifts between ice ages and interglacials during the Quaternary period (fig. 1). Such shifts are in part a response to regular changes in the Earth’s orbit and tilt, which affect the amount of summer sunlight reaching high northern latitudes and were described by the Milankovitch Cycles, first proposed in the early 20th Century by Serbian mathematician Milutin Milankovi? (1879-1958). For more about Milankovitch cycles this NASA page offers lots of graphics and explanations.

Figure 1: Temperature change through the late Quaternary from the Vostok ice-core, Antarctica (Petit et al. 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.

When incoming sunlight declines in the high north, the rate of summer snow and ice-melt declines and the ice sheets begin to grow. When incoming sunlight increases, the opposite happens. So where are we in these cycles today? Changes in both the orbit and tilt of the Earth do indeed indicate that – were they singularly responsible for climate shifts - the Earth should be slowly cooling. However, recent research shows that is too simple. That's because we now have analyses of ice-cores going back 800,000 years or more. We have devised ways to use stable isotope ratios of various elements in things like fossils and we have developed many other proxy methods for telling us more about conditions in the relatively recent past that the Quaternary represents.

A number of irregularities in glacial-interglacial cycles have been determined, for example times when interglacials were skipped when orbital patterns suggest they should have happened. (Koehler and Van de Wal 2021). Such research has also been aimed at resolving the question of why Earth's 41,000 year obliquity cycle was a strong driver of glacial-interglacial transitions up until around one million years ago. Since then, glacials have instead typically lasted for much longer - around 100,000 years.

The importance of feedbacks within Earth's climate system has been increasingly recognised as the decades have gone by. A good example is the speed of transition from glacial to interglacial, which is relatively rapid because certain very effective climate feedbacks are involved. One such feedback involves albedo, defined as the ability of different bodies to absorb or reflect sunlight (e,g, Thackeray and Fletcher 2016).

Albedo is expressed on a scale of 0 (black body, absorbs everything) to 1 (white body, reflects everything. Fresh snow has a high albedo of as much as 0.9, whereas the muck revealed when old snow and ice cover melts has a much lower one in the range 0.2 to 0.4 – it can absorb lots more solar energy. So melting snow and ice leads to more heat energy retention, amplifying the warming (Fig. 2). 

Albedo Explainer (John Mason)

Fig. 2: Albedo feedback explained. Freshly-fallen snow is highly reflective of incoming sunshine, so that most of the solar energy is simply bounced back towards space. Bare sea ice can potentially absorb about half of the incoming energy, so if conditions become warmer, causing the snow to melt, there’s more energy retained on Earth. If the sea ice melts too, then almost all of the incoming solar energy is absorbed by the much darker surface of the sea. So an initial warming directly results in further warming. Graphic: John Mason.

Another feedback happens when permafrost gets thawed out, since the ground is then able to release previously trapped CO2 and methane. During a glacial, the extent of permafrost is vast, so as it thaws, the release of such gases occurs on an enormous scale – again, amplifying the warming.

Researchers have also modelled ice-sheet dynamics, investigating how the sheets behaved as they melted, for example. It has been found that the shorter-lived, lower latitude Northern Hemisphere ice-sheets that existed prior to one million years ago were much thinner and therefore easier to melt. So ice-sheet dynamics looks to have a role in the much longer freeze-ups of the past million years. This all goes to show that glacial periods arise through a whole lot of factors interacting with one another, of which orbital cycles are but one, albeit important, cog in the gearbox and are not necessarily able to drive the climate system from one state (glacial) to another (interglacial) in total isolation (e.g. Bintanja and Van de Wal 2008; Berends et al. 2021).

Talking of cogs in the gearbox, we are another – and a big one. Our intentional disturbance of carbon reservoir rocks – what we do when we seek, extract and burn the fossil fuels – is unique in the geological record. It's a one-off in the planet's 4.56 billion year long history and while the consequent overloading of atmospheric CO2 levels is still insufficient to take Earth back into a Hothouse state yet, it is perfectly adequate to prevent another glaciation any time soon.

Last updated on 27 May 2023 by John Mason. View Archives

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Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

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.

Further viewing

potholer54 published a video tackling this myth on June 27, 2020

 

Dave Borlace explains why we are not headed towards an ice age in this "Just have a think" video published in December 2019:

 

Denial101x video

Comments

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Comments 226 to 250 out of 411:

  1. @ 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!
  2. @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.
  3. #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.
  4. 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.
  5. #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.
  6. 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.
  7. #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.
  8. 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.
  9. stephenwv, I responded to your claim that rising temperatures increase CO2 absorption, on the ocean acidification thread.
  10. 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?
  11. 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
  12. 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.
  13. 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.
  14. I'm looking at the graphs again, to see what is really there, instead of what I assume is there. Chris Shaker
  15. 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
  16. 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
  17. "it looks as though", not "it look as those" Chris Shaker
  18. 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
  19. 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
  20. 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.
  21. 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.
  22. 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.
  23. 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.
  24. 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).
  25. 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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