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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.

Basic rebuttal written by Anne-Marie Blackburn


Update August 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

 

Last updated on 7 August 2015 by MichaelK. View Archives

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.

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:

 

Comments

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Comments 401 to 409 out of 409:

  1. To my mind, this is denial of physics. You cannot change CO2 concentration without affecting the radiation at surface. Furthermore you have the problem of synchronous glaciation in Southern hemisphere which is easy enough to explain with change in CO2 being driver. Methane and isotope populations in ice bubbles also point to importance of eurasian wetland in the CO2 budget. This is not deny that dust is also important part of the feedback mechanism. I havent read paper, but is it implying that lowering CO2 is responsible for reduced vegetation? Any evidence of this in tropical regions? To me, it sounds handwavy and selective in the evidence that the hypothesis is using.


  2. MA Rodger & Scaddenp,
    Thank you so much for your quick responses.

    MA Rodger, very interesting. So dust-albedo blunting has always been a proposed mechanism for glaciation escape, but perhaps at MPT, the source for the dust “dried up” so it stayed cold longer? Ellis says MPT is beyond this paper’s scope, but he has a line suggesting that elevation of the Himalayas may have influenced MPT. Ellis suggests the earth beneath dying forests as a source for dust. His theory is: forests die from combination of low temp and low CO2 (both of which lower at higher elevations). I was just curious of what you thought of the correlation he found with dust in his graphs at the end. The paper’s first page or so lays out his premise. The charts and graphs are interesting, especially the one at the end where it shows temperature & CO2 drop, followed dust formation, followed by temperature rise. I thought it looked convincing. But I lacking the knowledge most of you have, am not qualified to critique it. If you have a moment, would you mind?

    Scaddenp, your response draws on knowledge that I don’t have (synchronous southern glaciation showing CO2 being driver), and thus I cannot follow. Forgive me. I'm not sure what you mean about the denial of phyiscs.  I know CO2 air concentration can affect temp (greenhouse) and temp can affect CO2 air concentration (water solubility). (Is that what you were referring to?). Ellis says that going into glaciation, temp drop caused CO2 drop. He says CO2 was 190 ppm, but it got low enough to affect trees at certain elevations (where partial pressure is low enough to reach a critical level of 150-160). He has a chart showing temp and CO2 concentration at various elevations in tropical and alpine regions. So far, I’m impressed with his data, but hesitant with his conclusions (in light of other overwhelming data)… but my level of knowledge makes my critique of limited value.

    My goal is to read this entire website… this happens to be just one nugget I’m trying to digest at the moment.

  3. "Ellis then concludes that CO2 is too weak to threaten overheating us or runaway greenhouse effect, "

    This statement. But I guess could be more nuanced. He is right that burning every piece of fossil fuel will not cause a runaway greenhouse, but "overheating" is a subjective judgement. It is certainly capable of raising average global temperatures beyond 4C.

  4. Lawrence Tenkman @402,

    I do hope to get round to giving Ellis & Palmer (2016) a read through but it isn't the shortest of papers & gives the impression of not being so well set out for a quick skim-through.

    On the subject of dust and Ice Ages, as much of the data which folk play with is derived from ice cores and dust is one of the things found in ice cores, it isn't too much of a leap to understand where all the dusty theorising comes from. Some other examples of dusty theorising include the likes of Alfredo Martínez-Garcia et al (2011) [described here] which proposes that iron-rich dust has a significant role in the ice age cycle and Simonsen et al (2019) [described here] who examine the local-origin dust as evidence of ice build-up in an Ice Age.

  5. Lawrence Tenkman @402,

    I did manage a read-through of Ellis & Palmer (2016). I note it isn't published properly which is likely why it fails to get mentioned within the literature. (It is published here but only as an “unedited manuscript” which was to “undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form.” I see no “final form.”)

    There is within Ellis & Palmer mention of “another story for another day” with the suggestion that this would add to the grand theorising with explanations of Dansgaard-Oeschger events and the mid-Pleistocene transition. A paper co-authored by Ellis has appeared on the web explaining the pre-MPT 41ky Ice Age cycle as resulting from there being an extra southern-driven version of the Ice Age cycle which post-MPT ran out of land in the post-MPT permanently-iced-over Antarctica and leaving only the northern-driven post-MPT 100ky Ice Age cycle.

    I'm not sure how the pre-MPT cycles would fit in with the Ellis & Palmer theory of dusty interglacial-triggering. (The appearance of interglacials in beat with the orbital eccentricity wobble is described in this follow-on thesis as purely coincidental. The frequency is defined by the 70ky it takes to prime the system with ice.)

    The absence of proper follow-on work, of publication or of citations is a kiss of death to theories such as set out by Ellis & Palmer. But that does not explain what it says or why it is wrong to say it.

    Ellis & Palmer (2016) is a poor piece of work. It occasionally says some very silly things but I shall ignore those. It also gallops past the science rather than addressing it, indeed describing it as “scientific lacuna.” But I shall here ignore such hubris.

    The grand theory presented explains that the precession/obliquity within the Milankivitch cycles does not always lead to an interglacial and that this is not immediately explained by CO2/albedo alone. To cause an interglacial Ellis & Palmer invoke a dusty atmosphere which reduced ice albedo and, as warming takes hold, adds to this albedo reduction when warming brings greater levels of dust to the melting ice surface.

    They say the dust results from reduced CO2 which causes lower tree-lines globally and this increasing dust as plant-less dusty mountain tops grow into dusty mountains and then dusty hills with the lowered tree-line. A correlation of dust and CO2 is presented. This dust-correlation could be made with many other different factors so is effectively an exercise in curve fitting with the low-CO2>>high-dust relationship remaining speculative.

    What is also not explained in all this is the mechanism driving the CO2 reduction and why this cooling doesn't keep on going. The peak-dust levels do not appear to have a threshold level and if there is a CO2/ice-volume/Milancovitch/dust mechanism at work it has yet to be convincingly demonstrated.

    So without further work beyond those referenced here, work to fill in the gaps and thus enable this allegedly important theory to be properly published, it is fair to say that not a great deal has been done since the initial appearance of this work in 2015 which was then, with its parting comment “So the only evil in this world is not in the atmosphere, it lies in the hearts of those who wish to starve plants and animals of their most essential food supply — CO2. “, certainly more work concrened with denialsim than with scientific analysis.

  6. MA Rodger , geoengineering climate by distributing iron (as fertilizer) to pelagic ocean, has been discussed in previous years.

    Tim Conway & Seth John (2014, Nature ) indicated that a large proportion of North Atlantic ocean-water iron was deriving from Saharan dust.

    There has been some more casual  discussion of the idea of dust from dry land similarly producing algal bloom and thus a reduction of atmospheric CO2.   This climate-cooling mechanism (which I have not seen quantified) would act in opposition to the dust-albedo mechanism suggested by Ellis & Palmer (2016) .

  7. Scaddenp & MA Rodger,

    Thank you so much for your responses.

    MA Rodger, thank you for reading that article an phelping me with it. Please clarify a few things for me if you don’t mind. You mentioned that "Ellis & Palmer fail to explain the mechanism driving the CO2 reduction and why this cooling doesn't keep on going… and that the peak-dust levels do not appear to have a threshold level." My impression from reading was they propose Earth gets cold enough at the nadir of orbital Milankovitch cycle to start forming ice, and if enough ice forms, albedo is sufficient resist subsqeuent Milakovitch warming cycles, and Earth plunges into into a glacial period via increasing of both ice formation & ice albedo feedback. Ellis & Palmer suggest CO2 falls because the cold makes the ocean draw CO2 in (increased solubility of the cold water) and this CO2 drop is what stops further cooling, b/c plant death from low CO2 & low temp causes the dust.

    It all sounded interesting to me… but even if their theory about dust were true about glaciation exit mechanisms, I don’t think it would be right to conclude that infinitely high man made CO2 & greenhouse doesn’t matter in today's world. This website has so much data suggesting we need to care.

    I’m not sure what you mean by: "the peak-dust levels do not appear to have a threshold level." What does that mean? Threshhold referring to a temp or CO2 level at which dust forms? Threshhold referring to a level of dust at which it is can melt ice? I thought the dust elevations seemed to occur during temperature & CO2 nadirsand seemed to precede warming consistently.

    Ellis & Palmer’s parting comment wasn’t in the website link I had (http://science.uwaterloo.ca/~mpalmer/stuff/ellis.pdf) (“So the only evil in this world is not in the atmosphere, it lies in the hearts of those who wish to starve plants and animals of their most essential food supply — CO2.”). But on YouTube, I did hear Ellis suggest we may be put here by “intelligent design” to burn fossil fuels to save us from an ice age. Sounded a bit off to me…. and made them seem quite biased. Hence, I wanted to hear from someone more educated that me on these concepts. Thank you so much for discussing this with me.

  8. Lawrence Tenkman @407,

    To clear up the "parting comment", it appears in a 2015 blog-post linked at the last paragraph of #405 above. The denialist flavour of this "parting comment" does explain some of the very odd comment in Ellis & Palmer (2016).

     

    The 'CO2 mechanism' I say is not explained is specific to the glacial maxima. Ellis & Palmer (2016) demonstrate temperature, dust and CO2 are correlated (in their figs 1, 4, 8 & 9). We could also include sea level/ice volume and methane into such correlations. So the question arises - What is driving what?
    During the drop into an ice age we can be reasonably confident that reduced northern insolation allows a build-up of northern ice sheets reducing regional albedo which has a global impact on temperature and kicks-off positive feedbacks in albedo, CO2 & methane.

    But the glacial maxima appear to have a particular pattern to them, perhaps clearest when sea level is considered. The Ice Ages step up a gear as they dive into the maxima.Ice Age Sea Level

    Ellis & Palmer point the finger at the CO2 feedbacks. They would have difficulty using albedo as the dust-levels are building at these points in the Ice Age cycle and Ellis & Palmer dismiss the idea of atmospheric dust-levels being a significant cooling factor.

    Given the constraints placed on the workings of Ice Age maxima by Ellis & Palmer, their hypothesis seems to rely on some strong CO2 feedback that comes into play at this point in the Ice Age cycle. So my question - Are the measurements of CO2 showing a big enough reduction?  What is causing these large reductions in CO2? And what causes these reductions to quickly reverse when the maxima is over?

     

    And not greatly removed from any discussion of 'CO2 mechanism'....

    Regarding the lack of 'threshold' for dust levels to bring Ice Ages out of their maxima, Ellis & Palmer Fig 4 (below) shows great variation in the peak level of dust as well as variation in the duration of high-dust prior to the glacial maxima. This I term a lack of 'threshold'. The general impression is that a generally high level of dust reducing albedo of global ice sheets awaits the increase in nothern insolation caused by the Milankovitch cycle.

    But surely this variability means the power of the dust-reduced albedo forcing is not strong enough of itself to be the trigger. It is possible that analysis would show the Milankovitch cycle and the dust-albedo in combination provides a consistent threshold level, or perhaps CO2 levels are also a factor in the mix. But such necessary analysis would require an approach somewhat less simplistic than Ellis & Palmer. (For instance, compare the Ellis & Palmer approach with that of, say, Willeit & Ganopolski (2018).)

    Ellis & Palmer fig 4

    I think that covers the issues from #407, hopefully in an understandable form.


  9. MA Rodger,


    Thank you so much for your kind resopnse. I much appreciate you. Very interesting. So complex.


    It seems that the article by Willeit & Ganopolski (2018) suggest that much dust comes from the equatorial advancing edge of the glacier (erosion from the advancing ice edge as I understand?)… not necessarily plant death as Ellis & Palmer suggest. Also, albedo blunting for glaciation escape is not accomplished by dust alone… albedo is increasingly blunted by the increase of both snow age & of dust accumulation, combined together. Perhaps this explains the lack of a critical level for the dust as a single factor blunting albedo… as multiple factors that combine to do it.

    Those equations made my head hurt. I feel like a patient sitting in a doctor’s office asking questions and expecting them to make me understand concepts it took years of medical school to understand. For sure, that’s not possible, as I’d have to go through all the training you did… year by year ... more answers leading to more questions.

    But I do appreciate you very much. Thank you for taking the time.  Thank you for doing what you do.

    LT

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