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Climate Hustle

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.

Comments

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Comments 351 to 366 out of 366:

  1. @jhnplmr:

    Please note that posting comments here at SkS is a privilege, not a right. This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it. Thanks for your understanding and compliance in this matter.

  2. JH: Fair enough.

    jhnplmr: I have replied on a more appropriate thread.

    Response:

    [JH] Thank you.

  3. "Response:[RH] Fixed image width.

    What should I do next time I use an image?

    Response:[JH] Keep your graphic width to 500 pixels or less."

     

    Wouldn't it have been easier to say this in the first place?

    Response:

    [JH] Lose the snark or lose your posting privileges. No more warnings.

  4. #349 HK

    If you want to duplicate the graph I displayed on #339 you will find the temperature data on edc3deuttemp2007.xls.  This gives EPICA Dome C ice core temperature differences from the 1000 year mean temperature (col 5).  The age of the sample is given in col 3.

    The Jul 65N Milankovitch data was drawn from orbit91 for the years BP and the data for the 10,000 years into the future was derived from the mean values of Jul 60N and Jul 70N in bein11.dat.  A correction factor had to be used for the future years to give the same zero year point.  I used 0.479775 instead of 0.4843 to convert langleys/day into W/m2.  This gives an error of less than 1% in the absolute data but does not effect the date of the minimum point.  I used the formula "=PRODUCT(AVERAGE(DV15:DV16),0.479775)" on my spreadsheet where DV15 and DV16 are the cells holding the relevant data.  The location of these cells will obviously alter as you go down the spreadsheet but *intelligent copying" will make this easier.

  5. #349 HK

    "That’s why much of the last glaciation endured through higher insolation than today without ending"

    The sun reflecting off the widespread ice sheets offset the effects of the higher insolation.  This positive feedback from the ice acts both ways, it slows the rise out of the glacial period but accelerates the rise once the ice sheets start to melt and less of the sun's power is reflected.

  6. jhnplmr...  It actually is stated in the comments policy how to post images. But don't worry about it. Lots of people make the same mistake and we just fix it.

  7. jhnplr:

    I didn’t bother to duplicate your graph, just inverted it (better with time running from left to right, don’t you think?) and adjusted it a bit.

    First of all, let me emphasize that I’m not a sceptic of the Milankovitch theory in general as it fits the temperature data quite well. And the reason why the summer insolation in the north seems to control the climate in the south is clearly related to the fact that the albedo feedback from ice sheets and vegetation is much larger in the north.

    As explained earlier, the main reason why I don’t believe in a new glaciation within the next few millennia is that the summer insolation in the north won’t drop much further before starting to rise again in 2-3000 years. Let’s look at the graph and study the end of the last interglacial, the warm Eemian.

    Insolation changes at the end of the Eemian

    When the temperature had dropped to present level about 118,000 years ago (1) the 65N July insolation (2) was already lower than during the Last Glacial Maximum about 20,000 years ago! It was in fact lower than at any time during the last 110,000 years, except for a short period about 70,000 years ago. When the insolation reached it minimum 3-4000 years later (3) after a drop of nearly 100 watt/m2 from the peak, the temperature (4) was still comparable to the level 14,000 years ago – when the insolation was almost 60 watt/m2 higher!

    It clearly takes a large increase of insolation to pull us out of a glaciation once it has started and a large decrease to initiate a new glaciation from an interglacial. The next few millennia will not give us that large decrease, but some of the CO2 we’ve already emitted will stay in the atmosphere long enough to keep the concentration above 300 ppm – highest for 800,000 years – until the insolation start to rise again.

    The claim that early agriculture and deforestation may have prevented or delayed the next glaciation is an interesting theory. We shouldn’t dismiss that early humans may have had a significant impact on the environment despite their primitive technology if given some tens of millennia considering what we have done in only a few decades. But some of these impacts, deforestation and desertification from overgrazing, have increased the Earths albedo and therefore acted as a negative forcing. I don’t know if the positive forcing from a few more ppm of CO2 was enough to counteract this. Maybe no one knows for sure, but it’s an interesting topic.

  8. Its worth pointing out that the other thing you need to turn a local NH glacial event into a global event, is to pull down the GHG levels. See Hansen and Sato 2012 (esp Fig2). NH Albedo change only really affects NH climate.

  9. How is Figure 4 determined?

    (-snip-).

    Response:

    [DB] Figure 4 is based directly on Figure 3 from Archer 2005.

    Sloganeering and arguments from personal incredulity snipped.

  10. The link to Archer 2005 is stale.  Here is a new location of that paper:  http://geosci.uchicago.edu/~archer/reprints/archer.2005.trigger.pdf

  11. Climate Dialogue has a good and recent overview of the potential effect of a new Maunder Minimum, in its "Introduction" to that topic.

  12. Will somebody please add to the Further Reading section of this post, a link to Ari's bibliography of readings on future glaciation?

  13. The fact is that through out recorded history a significant increase in Volcanic activity along with a weak solar maximum has always been a precursor to an Ice Age. Anything that has skeptical in its name is bullshit. They are skeptical about the truth and the evidence that goes with it.

    Response:

    [PS] Welcome to Skeptical Science. Please take your time to familiarize yourself with the Comments Policy. Conformance in not optional. Please in particular note the prohibition on sloganeering. If you wish to challenge the science, then do so with evidence, preferably from peer-reviewed sources. Thank you.

  14. Echo_Alpha @363, evidence please.  Or are you only interested in sloganeering?

  15. Echo_Alpha...  Then if it's a fact you should be able to show us the research that supports that position.

  16. I don't see how the author of this thread can say the next ice age is 10,000 years away. I see from the graph at the top of this thread that the previous interglacials were all very short, and it appears from the green bars on the graph that the Holocene is already longer than any of the past 4 interglacials. What evidence is there that we can expect 10,000 years of Holocene?

    Response:

    [TD] Read the text. Then click the Intermediate tab and read that text.

     

  17. As you can see the data provided by SS proves that this is not the first time temperatures have reached this point. Just like the upcoming ICE age will not be the first time Tempertures dropped significantly after a decrease in solar activity and increase in volcanic activity. Yes we are in deed headed for another Ice age. 

    Response:

    [JH] Sloganeering snipped.

  18. CO2 levels are now above 400 ppmv, 33% higher than at anytime in the last 800,000 years:

    Of course HydrogenOne concludes from this that temperature in the Eemian was similar to that today, and in the face of strong orbital forcing, it fell back into an interglacial, the much stronger CO2 forcing, and much weaker orbital forcing today will also drive us back into an interglacial.  No doubt it is the massive loss of NH albedo due to the loss of sea ice that convinces him of this:

    (2012 Aug arctic sea ice (purple) overlaid on 1938 Aug arctic sea ice.)

  19. From the time-stamp history of the past 368 comments I see a drastic slow-down in discussion of this topic in the last 4 years.  Is there a better "Arguement" topic in which to post regarding this topic?

    Response:

    [JH] Enter "Ice Age" in the search engine and take your picks among the articles that are listed.

    [PS] All threads remain open. Regulars use the "Comments" item to view comments so anything added to any thread is visible. If this article has the content you wish comment on then go ahead here, but be sure to read and abide by the comments policy.

  20. Thanks JH and PS.  This topic appears to be the most relevant to my question, and my apologies as a newbie if it has already been debunked somewhere in the past 360-odd comments.  

    I am familiar with the arguments against a new ice age coming any time soon submitted by Anne-Marie Blackburn (the discussion of the <href="https://www.skepticalscience.com/Milankovitch.html">Milankovitch Cycles and the CO2 emissions override to which Daniel Bailey added the effects of solar insolation contained in the header's Intermediate tab.  

    My idea comes as old memories from research I made in preparation for my 7th grade geography class term paper on the ocean floor in 1962.  At that time I had read a 1958 article published in Harpers written by Betty Friedan called "The Coming Ice Age" that proposed that an open water Arctic Ocean could essentially jump-start a new ice age by saturating the usually very dry Arctic air with moisture that would in turn increase winter snowfalls to the point that increased albedo from snowpack in the northern hemisphere would create a feedback loop that would continue the snowfall throughout the year in these latitudes.

    Of course, if you read that entire article you can poke holes in all manner of the supportive evidence since the science at that time was just in its formative years.  But, I wonder about the central premise because the catalytic state of an ice-free Arctic Ocean is soon to be achieved.  And, just as one releases the choke on one's snowblower after getting it started, I wonder if the world's now-underway switch from fossil fuels to renewables (turning off the choke) will remove the CO2 threat over the next century just at the time when it would be helpful to mitigate against the snow cycle about to come.  I would appreciate your views on this idea. 

  21. The first hyperlink above was mistyped and should be Milankovitch Cycles.  The second link to "The Coming Ice Age" is not directed properly and I don't know how to fix it.  The Harpers URL works only sporadically, so to those interested in this bit of ancient history I can only suggest Googling a term such as "The Coming Ice Age Harpers" and look for the link in the search results.  My apologies for this inadequacy.  Another good book for detailed descriptions of Blackburn's original response submission is the book The Ice Chronicles by Paul Mayewski et. al., 2002.

  22. Dave, I have a couple of objections to idea that ice-free arctic would trigger an ice age.

    Firstly, an historical look (something not known in 50s). Last time we had 400ppm of CO2 and open water was Pliocene and we didnt have an ice age cycle then (but still have milankovich cycles).

    But why?

    A warming world will certainly have more precipitation and for cold, wet parts of the globe it will certainly mean heavier snow falls. However, an open arctic ocean is still freaking cold so the contribution to water in the atmosphere from arctic basin is small compared to the warmer oceans elsewhere. An open arctic isnt going to be trigger point.

    But could thick snows more than offset the albedo loss from having dark water instead of ice in the summer arctic ocean? The forcing of the ice ages from Milankovich cycles implies that critical factor is persistance of snows around 65N through summer. In cold part of the cycle, there is not enough radiative heat to surface to melt the snow. The summer extent is more important for global albedo than winter. Summer extent continues to decrease implying there is more than enough heat to melt the winter snows even as they get heavily.

  23. DaveMartsolf @372, adding to scaddenp's comment, I would note that Flanner et al (2011) measured the albedo feedback from snow and ice between 1979 and 2008  (see here for discussion).  As can be seen from the second panel of the figure below, the only month in which the albedo feedback had increased over that period was October, and that by a very small amount.  It in no way compensates large increases from March through to July:

     

    A more recent review finds a global Snow Albedo Feedback of 0.1 W/m^2 per degree K, but that is significantly increased over spring, amounting to a 1% decrease in surface albedo per degree K over spring.

    In either case the effect of a more open Arctic sea has been to decrease the snow albedo effect, resulting in further warming.  That has been despite some indications of a thicker snowpack in the depths of winter, particularly January.  The increased snow depth in winter has minimal impact because winter days are much shorter in the relevant latitudes, and the sunshine weaker durring those days.  Despite the thicker snow pack, however, it continues to melt earlier, just as the sunshine strengthens and the days lengthen.  The result is an overall increase in albedo.  There is minimal effect in the late summer because by that time nearly all the snow pack, except at high altitudes, has already melted. 

    Overall, Anne-Marie Blackburn's idea, as described by you, is an interesting one, but appears to be failing the empirical test.  It also contradicts the current understanding of the causes of glacials and the end of interglacials.  In relation to the later, and as shown by the Vostock and Epica C ice cores, declines from interglacials to glacials tend to be long drawn out affairs (unlike the very rapid transitions from glacial to inter glacials).  That is the opposite of what would be expected if Blackburn's idea had merit:

  24. Tom, I think you are confusing Betty Friedan (author idea that open arctic might trigger ice age), with Anne-Marie Blackburn (Sks author of Milankovich article).

  25. scaddenp @374, I was, and apologies to both ladies.

  26. I remember as an undergrad in the 1970s that an open Artic Ocean was thought to be one possible way of creating enough precipitation to initiate the growth of continental ice sheets - i.e. initiate a glacial period.

    I also remember that the 1970s was a period where much of the knowledge of glacial geology in Canada's Arctic was being re-written. Flynn's (?) massive single Laurentide Ice Sheet idea was losing to the idea of several ice domes and much more complex movements. (I was a lowly field assistant working in Canada's Keewatin District, on the west side of Hudson's Bay, on research that helped definitively establish the Keewatin Ice Divide as a long-standing feature, not the late glacial feature that it had been claimed to be.)

    So, the idea that moisture from the Arctic Ocean could lead to glacial periods was a serious idea at the time. Knowledge of the systems and causes are much greater now.

  27. Wow!  Thanks for all the feedback everyone.  You are so kind.  I will review all this new data and if I have any further questions I'll jump back in.  This is a real learning experience for me.  Thanks again.  

    Looks like we're in for warmer weather.  We live at about 300' altitude in New Hampshire.  I've told our daugher to hold onto the property as it will likely become beachfront generations down the road.

  28. Wouldnt get your hopes up. You can get 70m (230') by melting all the ice, but melting all of EAIS and GIS would take 1000s of years.

    However even 1m of sea level rise would displace a couple hundred million people who are not so fortunate in their location.

  29. Yes, I was joking on that point and understood on the 1000s of years time required to melt all the ice.  

    But, don't all these forecasts assume some type of elevated CO2 presence for years to come?  I understand that even the most hopeful time scale for full conversion from fossil fuels to renewables with or without the nuclear option is still estimated to be many years away, but I do believe this will happen, and sooner than many people predict today.  As that happens, and as we figure in the relatively rapid natural sequestration of our currently elevated atmospheric CO2 levels (half life in the order of only 20-30 years), I still wonder what the models will show when ocean temperatures have been elevated through all the current (and perhaps for another 50-100 years into the future) CO2 emissions to rather suddenly find their warmed surfaces evaporating into crystal clear skies that can quickly radiate all that heat (but not the moisture) into space.  It will be a unique set of conditions not often seen on the planet.

  30. As a second comment I was intrigued by scaddenp's first link in the discussion above, a link to John Mason's 2013 post regarding past geologic records of 400ppm CO2 found in Russia's Lake E, referred to as a super-interglacial, and ending with the query, is this what we are headed for?  Likely, the answer is yes, but as I mentioned above there should be a caveat that those Pliocene-Pleistocene Series precursors to our current situation had to have had both non-anthropormorphic entrances to and exits from their warm periods.  If the earlier entrance to the 400ppm plus CO2 atmosphere happened as relatively quickly as ours has, then that past cycle might mimic ours.  Does anyone reading this know if the record shows that the CO2 level changed that rapidly, perhaps as the result of some extraterrestrial fireball such as created Lake E and may have burned up all flora on the planet within several years or less?  My apologies for being so uninformed in these things.  But, I am so curious.

  31. DaveMartsolf, concerning CO2 residence time, warming potential can last centuries.

     

    It is true that an individual molecule of CO2 has a short residence time in the atmosphere. However, in most cases when a molecule of CO2 leaves the atmosphere it is simply swapping places with one in the ocean. Thus, the warming potential of CO2 has very little to do with the residence time of CO2.

     

    CO2 emissions change our atmosphere for centuries

  32. Dave Martsolf @379, carbon cycle models have shown that a significant portion of the excess CO2 in the atmosphere will be retained for many thousands of years.  This has been illustrated, along with the relevent processes for drawing down CO2, by David Archer:

    The important thing here, however, is not so much the retained fraction as the rate at which CO2 is drawn down, which approximately matches the rate at which temperatures approach equilibrium with a constant CO2 concentration.  The approximate match of the rates means that with zero emissions, temperatures remain approximately constant:

    That means that if we were to eliminate all CO2 (and other greenhouse) emissions over night, we could expect an equilibrium temperature of 1 C above the preindustrial.  If we allow cumulative emissions 1000 GtC before ceasing all emissions, we could expect an equilibrium temperature of 2 C.  On current policy settings, the stable temperature will be at least 3 C, if achieved at all (it only requires 5-10% of current emissions to result in a constant, or even slightly rising concentration, and no policy pursued by any government currently pursues zero emissions).

    Those estimates hide a host of details.  For instance, while GMST will be approximately constant with zero emissions, ocean temperatures will continue to rise for a short period, while land temperatures fall slightly.  Sea level will continue to rise, both because of the rising ocean temperatures and because the ice sheets will melt back in the face of the constant elevated temperatures. 

  33. "should be a caveat that those Pliocene-Pleistocene Series precursors to our current situation had to have had both non-anthropormorphic entrances to and exits from their warm periods."

    I am not quite sure I follow you, especially with regard to entrance/exit of warm periods. In very broad terms, CO2 has been falling right through the Cenozoic, with exception of PETM. In transition from Pliocene to Pleistocene, CO2 (and surface irradiation) had fallen to level where Milankovich cycles could drive an ice-age cycle. Prior to then, climate was too warm (and CO2 too high). Noone is disputing that orbital forcings drive the Pleistocene ice ages, though turning variations in albedo at 65N into a global event involves several feedbacks of which CO2/CH4 feedbacks are very important. These are hardly analogues of current situation. The pace of change for a start is orders of magnitude faster. If we keep warming, we will also get carbon cycle feedback enhancing the warming but not for 100s of years.

    Perhaps time to look at "Climate has changed before" article as well? Or have I completely misunderstood you?

  34. Deep thank yous to Yail Bloor, Tom Curtis, and scaddenp.  Together you have cleared up all my questions regarding the interrelated processes that are bringing out an unfortunate future to our planet.  I totally understand now why current and near future increased levels of CO2 will be around for centuries.  And, scaddenp's link to Howard Lee's article describing an outcome of rapid CO2 increase that I did not think possible.  I can understand why these facts have not been made into a movie, although they should be.  I want to thank all of you for opening my eyes and for filling in all the blanks in my understanding.  May our future generations find a way to survive The Once and Future Planet.

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