Arguments
Are we heading into a new Ice Age?
What the science says...
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Worry about global warming impacts in the next 100 years, not an ice age in over 10,000 years. |
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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 Milankovitch (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).
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
As a followup to my previous comment, real scientists doing real studies have already looked into whether the Earth will warm or cool, long-term. As opposed to empty assertions, let's examine the facts, shall we:
Per Tzedakis et al 2012,
For reference, we are at about 394 right now…and climbing, so we can be relatively sure the next glacial epoch won't be happening in our lifetimes.
But what about further down the road? What happens then? Per Dr Toby Tyrrell (Tyrrell 2007) of the University of Southampton's School of Ocean and Earth Science at the National Oceanography Centre, Southampton:
and
So no ice ages and no Arctic sea ice recovery the next million years...
Facts, like Tiggers, are wonderful things, for those who have them.
Also covered by Stoat, here.
Given the radiative imbalance at the TOA is still present and that CO2 levels are still increasing (and that human emissions are not ending anytime soon), it is reasonable to presume that the impacts of a warming planet will increasingly impact the most vulnerable aspects of our remaining cryosphere: the Arctic sea ice (a goner), the Greenland Ice Sheet and the West Antarctic Ice Sheet.
We are, through our own actions, effectively locking-in a world of another 8-12 meters SLR above present. Unless we can magically arrest our emissions and also initiate methods to draw-down atmospheric concentrations of CO2.
Kevin You might find this paper interesting, the question of the regularity of glacials is apparently not quite as straightforward.
As to the question "Who decided that the temp after the industrial revolution was the "accurate" temperature the earth should be at, and that we are exceeding that perfect temp?", that really is a canard that has been answered here repeatedly.
A reasonable answer to that would be "the perfect temperature of the Earth is that to which our civilisation (and especially agricultural practices) has become highly adapted". It is the change in climate that is the principal problem, as adapting to change has costs. It seems likely that mitigation will reduce the cost of adaptation, so that would appear to be the rational strategy. It isn't rocket science.
Do you accept that answer?
OK. But then, the LIA was quite cold, and people adapted, agriculture adapted, but at cost (which is part of your point - in other direction but applicable). During the Roman optimal, wine grapes were grown in Great Britain. During the Medieval Warm period, grains were reported to be much more bountiful.
On another note, how is it that you were able to respond to my post, yet my post does not appear?
the appearance issue was regarding my second post, sorry about that.
Prove it. We await the links to the reputable sources.
Kevin There are plenty of historical precedents for civilisations not surviving climate change (e.g. Egyptian Old Kingdom). At the time of the LIA, global population was much lower, and agricultiral land less over-exploited, which made adaption very much easier than it is now. There are large parts of the world that are relatively poor, where large populations exist with marginal subsistence agriculture. Adapting for us will be much easier than it will for them. There is also the point that the rate of change is also relevant to adaption. Even then the LIA caused great hardship for many, the natural climate change we can do little about, but that doesn't make it O.K. to cause some more for ourselves.
The point is that questioning whether there is a perfect temperature for the Earth is a straw man - nobody is claiming that there is one, and it isn't really relevant anyway, it is the change that is important.
Now if you have evidence to show that we will have no problem adapting to the projected climate change, then I am sure there is a relevant post at SkS on which to discuss it, but this isn't it.
The post to which I responded is still there (at least I can still see it).
Kevin:
Wine production appears to have been more-or-less continuous in the UK since the Roman invasion, albeit patchily implemented at commercial scales and vulnerable to sociopolitical changes.
As far as I am aware (courtesy of a survey of the Met Office and Environment Canada sites), the UK, and in particular southern England, has had, for some centuries, a climate that is comparable to current wine-growing regions in southern Ontario and British Columbia, despite being at a comparatively higher latitude.
IMO the significance of Roman viticulture in the UK is overstated in the context of climate change discussions.
While England had 42 vineyards at the time of the Domesday Book, as is well known, there are now over 300 commercial English vineyards today. So the climate today in England is much more conducive to wine-making than during the Roman occupation of England, consistent with the proxy reconstructions of temperatures covering those times.
http://www.english-wine.com/vineyards.html
http://www.englishwineproducers.com/history.htm
[Source]
Without a link to a source for that claim I must conclude that Kevin just made that claim up. Especially given that it took me all of 3 minutes to look up the material for this comment...and that Kevin has had more than 4 hours to do likewise...
Also apparent from DB's graph, is that rate of temperature change (which strongly influences our ability to adapt) is much faster now than going into the LIA. Accounts of the time suggests adapting to LIA wasnt all beer and skittles either. I'd rather avoid that kind of pain and paying more for my energy is certainly acceptable. We adapted pretty well to change in oil price to $15 to $80 and projected energy change costs not in that league.
Kevin:
1) Figure 4 of the intermediate version of the above article shows expected future temperatures based on milankovithch cycles and CO2 concentration. Even by eyeball it is evident that at preindustrial CO2 levels, no new glacial is imminent for thousands of years.
2) I will see you your "wine in England", which as Daniel points out, is a very current phenomenon, and raise you three vinyards in Scotland (one indoors), and four commercial vinyards in Sweden! I will note that traditionally grapes were grown in England not because they produced good wine, but because wine was needed for sacramental reasons, and until recently, wines turned to vinigar if transported any distance.
DB @ 280:
(Source)
Release No.: 03-10
For Release: March 31, 2003 20th Century Climate Not So Hot
Cambridge, MA - A review of more than 200 climate studies led by researchers at the Harvard-Smithsonian Center for Astrophysics has determined that the 20th century is neither the warmest century nor the century with the most extreme weather of the past 1000 years. The review also confirmed that the Medieval Warm Period of 800 to 1300 A.D. and the Little Ice Age of 1300 to 1900 A.D. were worldwide phenomena not limited to the European and North American continents. While 20th century temperatures are much higher than in the Little Ice Age period, many parts of the world show the medieval warmth to be greater than that of the 20th century.
Smithsonian astronomers Willie Soon and Sallie Baliunas, with co-authors Craig Idso and Sherwood Idso (Center for the Study of Carbon Dioxide and Global Change) and David Legates (Center for Climatic Research, University of Delaware), compiled and examined results from more than 240 research papers published by thousands of researchers over the past four decades. Their report, covering a multitude of geophysical and biological climate indicators, provides a detailed look at climate changes that occurred in different regions around the world over the last 1000 years.
"Many true research advances in reconstructing ancient climates have occurred over the past two decades," Soon says, "so we felt it was time to pull together a large sample of recent studies from the last 5-10 years and look for patterns of variability and change. In fact, clear patterns did emerge showing that regions worldwide experienced the highs of the Medieval Warm Period and lows of the Little Ice Age, and that 20th century temperatures are generally cooler than during the medieval warmth."
Soon and his colleagues concluded that the 20th century is neither the warmest century over the last 1000 years, nor is it the most extreme. Their findings about the pattern of historical climate variations will help make computer climate models simulate both natural and man-made changes more accurately, and lead to better climate forecasts especially on local and regional levels. This is especially true in simulations on timescales ranging from several decades to a century.
For more information, contact:
David Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7462 Fax: 617-495-7468
daguilar@cfa.harvard.edu
Christine Lafon
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016
clafon@cfa.harvard.edu
[Sph] Original comment edited to correct formatting issues.
Kevin, that is not proof, Bauliunas says that vinyards flourished in England, but that doesn't make it true. Is there evidence in the paper on which the press article was based?
BTW you do know that Energy and Environment is not a science journal, but a social sciences journal, don't you?
DM, you're being generous. Kevin might want to take a look at some of the other studies that E&E has published.
Kevin, you might also look at the Soon & Baliunas (2003) affair, and also what Willie Soon is capable of trying to pull over on his target audience. What a world it would be if fake skeptics gave the same level of scrutiny to those they pedestalize as they do to the studies that do not support their worldviews.
source for grain abundance is
faculty.history.wisc.edu/sommerville/123/123%2013%20Society.htmAs far as I can see, that source provides no real evidence (references to primary sources?) and provides only rather equivocal support for your assertion, e.g.:
"More people meant smaller acreage of land per person and this led to "harvest sensitivity." In years of poor harvests (such as the wet summers of 1315-1316) insufficient grain was grown and the poor starved."
"English agricultural methods and productivity remained stagnant throughout the Middle Ages. The "strip" system of farming was equitable and extremely inefficient. Yields of grain per acre remained stagnant."
"Food production was only increased by bringing more land under the plow - a process that stopped once all available waste land had been improved."
Also the graph of population (reproduced below) suggests that a fair proportion of the population didn't adapt to the LIA (except perhaps by dying).
Regarding grain abundance, your source emphasises a point I was making: "More people meant smaller acreage of land per person and this led to "harvest sensitivity." In years of poor harvests (such as the wet summers of 1315-1316) insufficient grain was grown and the poor starved." That sitation is far worse now in a world with 9 billion mouths to feed. As far as I can see you have provided very little evidence to suggest that the past suggests we can adapt to future climate change without substantial hardship.
Here is one for the Roman Optimal
www.english-wine.com/history.html
The last source was for the Medieval Period, for grain.
[DB] It is noted that your referenced source does not support your earlier contention. Therefore, the conclusions reached in this comment apply and you tacitly agree to its conclusion:
By agreeing, you concede you earlier comment was in error and therefore invalid. If you disagree, you will need to then further support it here before being allowed to comment elsewhere on this site.
If I can end the game between Kevin and the Moderators, this is evidence of viticulture in Roman Britain:
So also does this article about the same site, but note that while "...the apparent lack of viticultural tools and wine presses in the archaeological record in Britain is not reliable evidence for the absence of viticulture at that time", it must be considered evidence that viticulture was not widespread.
Regardless, as I have noted on other occassions, the presence or absence of vinyards is a poor proxy of climate as human and economic factors play too large a role. Is the decline (but not absence) of viticulture in Anglo-saxon Britain and indication of cooler climates, or just an indication that the Anglo-saxons has a taste for ale in preference to wine? Does the post norman decline in viticulture in England reprsent a decline in climate or the fact that improvements in wine manufacture and transport made French wine cheaper in Britain?
More importantly, if you are going to use viticulture as a proxy for climate in the past, then you must be consistent and do so in the present. So, if viticulture in England in Roman and Norman times is evidence of warm climates at that time, then viticulture in Scotland and Sweden now must be considered evidence that it is warmer now than in Roman or Norman times. The extent to which deniers cherry pick data rather than following evidence is shown by their refusal to follow the clear logic of this argument.
Dikran Marsupial @291, the very sharp decline in population in the 14th century has almost nothing to do with climate, and everything to do with the Bubonic Plague. Much of the increase before that had little to do with climate, and much to do with the adoption of the horse collar in Europe.
Kevin pretty much scored an own goal here.
Tom, yes you are absolutely right about the cause of the decline in European populations, doh! The info on English wine growing was also very interesting, ISTR there is something about it in the book on the British Climate compiled a few years ago, I think in honour of Hubert Lamb, but it is back in the library now, so I can't check. I hope Kevin learns from this exercise that perhaps his information on the topic of climate isn't perhaps all it could be, and will moderate the attitude in his posts somewhat. We are all happy to discuss science here, but generally those who arrive with a bit of an attitude tend to provoke a correspondingly confrontational response.
http://antiquity.ac.uk/ant/075/Ant0750745.htm
Try this source for Roman Optimal Wine production n UK.
Kevin, thanks for the link, it is a shame that the article is paywalled - it looks interesting (see also Toms comment). Please do take on board my comments in the previous post. We are happy to discuss science here, but you will get a much better reception if you make your points in a measured scientific, rather than a confrontational hubristic manner, especially as your previous comments suggest a lack of understanding of some important issues.
There is a free-access, text-only version of that paper available here.
Cheers Andy, very interesting, the differing standards of acceptable evidence in archaeology and climatology is very evident (of course this is inevitable and not an indication of a problem with archaeology)!