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Global Warming and Predictions of an Impending Ice Age – Predicting Future Climate


by Bill Chameides | October 30th, 2008
posted by Erica Rowell (Editor)

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This is the fourth and final post in a series on the connection between the sun, sunspots, and climate.

Where is the climate headed? The Intergovernmental Panel on Climate Change (IPCC) predicts continued warming [pdf]. But others proclaim that an ice age is just around the corner (like this editorial from the online paper the Australian). Who’s right?

Predicting the future is a bear. Predicting climate change is especially uncertain. But given global warming’s potential consequences, we ignore an educated look ahead at our own peril. And let’s face it, models serve us well in all sorts of areas in the modern world.

Predictions of Warming

Other Posts in This Series
Part 1: Total Solar Irradiance
Part 2: Sunspots
Part 3: Global Warming Since 1998
Part 4: Predicting Future Climate

The IPCC’s warming predictions are based on climate simulations with an important underlying assumption — what I call the “all things being equal” assumption: the models assume that external factors, such as the solar output, continue to behave pretty much the way they have in the recent past. These models also use a reasonable range of projections for greenhouse gas emissions and values for uncertain model parameterization. All the models predict continued and significant warming.

Of course, these predictions could all be wrong. The models themselves could have a serious flaw (which causes them to over-predict rather than under-predict greenhouse warming), and/or some important external parameter like the Sun could suddenly, unexpectedly change in a way to cancel out greenhouse warming. But while it’s important to recognize these possibilities, it is essential that we weigh their probability versus the risks we face if the models are correct. (And remember the models could also be under-predicting.)

In that vein, let’s look at two of the more popular arguments that global warming is not a problem.

Ice Ages

Our current climate regime -– a regime we’ve had for the past ~2 million years –- is characterized by long periods of ice ages and shorter warm periods. The last ice age ended about 12,000 years ago, and since then we’ve been in a warm period. Some argue that global warming is no concern, since the Earth will naturally switch back to an ice age.

This is very likely to be true: an ice age is almost certainly in our planet’s future. But it’s a question of when.

Our current concerns about climate change focus on the coming decades to the next century –- the time period relevant to our children’s and grandchildren’s experience. But the ice age/warm period cycle operates on a time scale of tens of thousands of years.

Scientists have figured out that ice ages are triggered by subtle changes in the Earth’s orbit about the Sun. The next such triggering is not expected to occur any time soon – tens of thousands of years from now. Not quite soon enough to be relevant to our children’s well-being.

The Sun as the Deux Ex Machina Saving Us from Global Warming

Others argue that the Sun’s output will suddenly shut down and stop global warming. Indeed, some now predict that a brutally cold period much like the Little Ice Age that began in the 1200s and ended in the mid-1800s has already begun. There are two intriguing aspects to this claim:

  1. The Little Ice Age was likely caused, at least in part, by a relatively quiescent Sun. Characteristic of this quiescence was the Maunder Minimum (~1645-1715) when there was an anomalous absence of observed sunspots (see my earlier post).
  2. We are currently in an unusually long and strong solar minimum. In fact, 2008 has been a year of unusually low solar activity, with more days sans sunspots (called “spotless days”) than any year in the past five decades and on a pace to challenge 1913 as the century’s most quiescent year (see graphic).
Top: A histogram showing the last half-century’s blankest years. The vertical axis is a count of spotless days in each year. The bar for 2008, which was updated on Sept. 27, 2008, is still growing. Bottom: A histogram showing the last century’s blankest years. As in the above histogram, the bar for 2008 is still growing. (Credit: NASA)

Some now argue that the current quiescent period is heralding a new Maunder-like minimum in the Sun and, as a result, a new ice age. Don’t worry about global warming, they advise — worry about global cooling.

Think (and Grok) Before You Leap to Conclusions

Of course, proving such a prediction wrong is impossible, but please keep a number of things in mind before you run out to buy that snow parka:

  1. Using one year’s worth of sunspot data to infer a long-term climatic trend is a highly questionable practice.
  2. While the Sun’s current quiescent period is unusual, it is not unprecedented. The year 1913 had more than 300 spotless days, and an ice age did not follow. Indeed, the long-term trend in global warming continued apace.
  3. Sunspots affect climate, but they are not the only factor. Don’t forget that 2007, the third most spotless year of the past 50 (see graphic), was also the third warmest year on record. And while the winter of 2008 was unusually cold (possibly because of La Nina), the rest of the year has been quite warm. According to the National Oceanic and Atmospheric Administration, March 2008 was the second warmest March on record; the spring was the eighth warmest on record; and the summer was the ninth warmest. And bear in mind that these relatively high temperatures occurred while the Sun was at its minimum and a strong La Nina persisted in the South Pacific.

Predicting future climate is an “imperfect science.” Uncertainties and unknowns are unavoidable. Still, our models represent our best understanding of how the climate works. Does that mean that the Sun couldn’t shut down and “save us” from global warming? Of course not. Would I be willing to bet my children’s and grandchildren’s future on that possibility? No.

Other Posts in Global Warming and Predictions of an Impending Ice Age

Part 1: Total Solar Irradiance

Part 2: Sunspots

Part 3: G
lobal Warming Since 1998

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22 Comments

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  1. DON COLLICOTT
    Dec 18, 2008

    in your own words The IPCC’s warming predictions are based on climate simulations with an important underlying assumption — what I call the “all things being equal” assumption: the models assume that external factors, such as the solar output, continue to behave pretty much the way they have in the recent past. These models also use a reasonable range of projections for greenhouse gas emissions and values for uncertain model parameterization. All the models predict continued and significant warming. Of course, these predictions could all be wrong. well sounds like the debate is over isn’t (lets make massive changes in our lives over these models that do not work) your 2007 temp ref is i beleive wrong they had some 2006 temp’s that did not get changed to true 2007 figures when the total was figured. was refigured and i was not close to being that warm please understand i can not buy into this man made global warming this is an agenda that hurts the poor and will do nothing to slow global warming. they want to make changes in our society and the rich and powerfull will not make any changes by the way what is the tempature change per co2 reduction and how would you know when everything that is treated neutral is not neutral i play great computer games that someone programed they look real but there not, neither are these computer programed models that could not predict this cold weather we are having sorry not convinced” title=”global warming

    • erica
      Jan 5, 2009

      DR. CHAMEIDES replies – Don – Predictions are just that predictions and thus subject to a good deal of uncertainty. But uncertainty cuts both ways — the predicted warming could be too large, but it could also be too small. Why are you so willing to bet the future on the coin falling on the “too large” side? Is it perhaps because you “can not buy into this man made global warming?” What is the reason for your inability? Is it based on scientific understanding or a gut feeling?” title=”Science or gut?

      • DON COLLICOTT
        Jan 6, 2009

        my feelings about not believing man made global warming is a problem or such an tiny problem is through looking at facts on past warming and ice ages. man has only been on this earth for a very short time and producing co2 in a even shorter time frame. green house gas did not stop past ice ages. the modeling would never show another ice age coming. the factors that produce climate change are very complicated and the temperature change they produce makes co2 a very very small factor in climate change. we as people can not solve more important problems facing us. do you really believe the people of this world can change climate because i do not think man can in fact i believe that we are right now going in to a long period of cooling looking at some of the things going on (lack of solar sunspots, la ninia shift, and the earths tilt.) and i think you might want to read farmers almanac they have done a good job prodicting future climate and they do care what the co2 level is sorry i can not see wasting money on this” title=”global warming

        • erica
          Jan 6, 2009

          DR. CHAMEIDES responds: Don – Perhaps you have heard of the expression ignoratio elenchi (more commonly a red herring). Your comment is full of such logical fallacies. Climate has changed in the past and man has been on Earth for a short time – both of these are true but in no way prove that global warming is not human-caused. And your point about the Farmer’s Almanac is not relevant. Without getting into the accuracy of its predictions, the almanac makes medium-term weather predictions (i.e., what temperatures and precipitation will be like next summer). It does not make long-term climate predictions. And so of course it does not worry about CO2, whose increases from year to year are too small to cause significant year-to-year weather changes. But if you are concerned about climate change on decadal timescales, you’d better consider CO2. ” title=” ignoratio elenchi

          • DON COLLICOTT
            Jan 6, 2009

            you expressed my very point “And so of course it does not worry about CO2, whose increases from year to year are too small to cause significant year-to-year weather changes” and i think to small to change true climate cycles yearly or longer to many things in co2 modeling has been set to neutral i guess we need to explain why we have had past ice ages and warm periods man did not cause them? i know you think i should care about this co2 problem and global warming and we can not take the chance to not stop it. what i feel is the things people want to do to stop it will do more damage to our society economically then what it would save in the future even if cutting co2 would do anything the cost to benifit is not worth it there is nothing wrong with a warm earth we should spend our money on figuring out how better to survive in it. buy a coat i think its gonna get cold!! solar minimum ” title=”global warming

          • DON COLLICOTT
            Jan 6, 2009

            here is something of intrest about co2 Carbon Dioxide Solubility in Water as temperature go’s up the solubility go’s down earth has alot of water when temperature go’s up less co2 in the water which matchs past climate changes recorded in ice samples in antartica so i have a hard time believing co2 is a cause of global warming and not a effect of global warming. when increased co2 levels follow temperature increases in these records yes their may be a very very small increase in greenhouse effect but because co2 does not control global climate it is a waste of money to worry about when Dihydrogen Monoxide is a much larger greenhouse gas ” title=”global warming

            • erica
              Jan 7, 2009

              Dr. CHAMEIDES replies: Don – Nice try but no cigar. 1. The solubility of CO2 follows a specific law – Henry’s Law. You cannot explain the more than 30% increase in atmospheric CO2 by the rise in ocean temperatures. 2. Scientists have been able to use changes in the carbon isotopic composition of atmospheric CO2 as a virtual fingerprint to conclusively show that the extra CO2 in the atmosphere comes from fossil fuels. 3. By “dihyrogen monoxide” I guess you mean water vapor. This is another red herring since the amount of water vapor in the atmosphere is controlled by temperature and therefore (among other things) CO2. 4. Essentially all the points you are raising here have been raised and responded to in earlier posts. Please limit your comments to new issues.” title=”NIce try but …

              • DON COLLICOTT
                Jan 7, 2009

                well we agree to disagree but much colder this winter than last ice pack on north pole back to 1979 levels i guess we will see thanks” title=”global warming

              • Gary
                Apr 26, 2009

                You all need to refresh your K-12 science. Atmospheric gas does not heat the earth. The sun heats the ground, which heats the lower atmosphere. THINK SUN. CO2 has absolutely no ability to raise the temperature of a closed system. Fill ten green houses with ten different gasses, the resulting day heating is not affected by the gas enclosed, but by the amount of radiant heat supplied by the sun. End of argument. ” title=”Global Temperature

                • Nolan Perreira
                  Nov 25, 2009

                  I expect that a good climate model could predict the past at least as well as it does the future. Do your models, when run backward, predict the start of the interglacial, the mini Ice Age of the 18th century, and the start of the previous glaciation. If not. why not? and if so, how well? Since Carbon dioxide is soluble in water, and the solubility decreases with an increase in temperature, how much of the CO2 increase is attributed to human causes an how much is attributable to warming of the oceans? Since warming of the land can also result in increases in CO2 in the atmosphere, how much of the increase in CO2 attributable to warming of the land? Since warming of land and sea result in increasing Carbon dioxide and increasing Carbon Dioxide results in increasing temperatures, there is some positive feedback operating. IS this parametrized? ” title=”Global Climate Modeling

      • Peter Brodek
        Dec 16, 2009

        Predictions must have several factors in order to be even vaguely demonstrably valid. First of all, a model of climate/global temperature must accurately predict future temperatures within a DEFINED range of uncertainty, and WE MUST KNOW the magnitude of the uncertainty (error bars must be able to be clearly drawn, and actual measured phenomena must fall within the error bars 95% of the time). None of the current models accurately predicted the 2000-2009 trends in actual temperatures. Also, if you plug actual PAST data into a model, the model should come up with a reasonably accurate reconstruction of the past. If you plug actual data from the past into the models, none of the models accurately predict what actual temperatures in the past were either. When the models are so badly flawed that there is less than a 50% probability of them being correct, your coin-flip analogy fails.” title=”predictions

  2. alan falk
    Nov 15, 2008

    arguments, data, arguments, data… i’ve been playing this game for months and collected some of my favorite arguments at http://www.plusaf.com/lessons/globalwarming.htm . scroll down to the 04.17.2008 dated entry. unless the data are all bogus, it’s a nice example of why a snapshot can mislead you very nicely, thank you! http://www.ncdc.noaa.gov/paleo/milankovitch.html, also linked from that page, provides a laundry list of drivers which might just overwhelm the effects of anthropogenic CO2. …. care to look at 10Mb of pdf? http://www.plusaf.com/lessons/christy-jr-rcgeospatial-10-17-07.pdf will show you some graphs that you’ll have to completely throw out… such as “water vapor’s effects compared to CO2…” and, finally, for now, can you really look at this graph… http://www.plusaf.com/pix/figure5-global-temp-history.gif linked from near the bottom of my http://www.plusaf.com/lessons/globalwarming.htm page and say, “well, we’re near the top of the graph, as it shows, so obviously what we’re doing now is going to make that curve go further up and to the right”???? cheers!” title=”other data… more views…

    • erica
      Nov 17, 2008

      Dr. Bill Chameides replies – Alan, As I explained in the response to your previous comment, my argument is not based on a “snapshot” so these comments are not really relevant. And as far as your graphs of the coming and going of ice ages are concerned – take a look at the time scale – 10s of thousands of years. How is that relevant to the issue of global warming in THIS century? In fact the next ice age is not predicted to arrive for at least another 10,000 years (this is addressed in today’s post – http://www.nicholas.duke.edu/nicholas/insider/thegreengrok/iceage-nature).” title=”Next ice age at least 10,000 years away ….

      • alan falk
        Nov 17, 2008

        and that’s what happened when i looked at the http://www.plusaf.com/lessons/globalwarming.htm#vostoktemps graphs. the first one might imply that anthropogenic global warming might just be holding off the Next major Ice Age, too… again, you’re getting a feeling for how this engineer deals with data and graphs… :) i’ve been trying to track down the source for some other info, too, unsuccessfully so far… a few years back, i began to run across a laundry list of driving forces which could or do impact average global temperatures. things like axial precession, orbital shape change, orbital axial shift and a few more. one that caught my mind particularly had to do with the “zodiacal light”, caused by dust particles in the plane of the ecliptic that earth passes through. apparently, there is also a cycle, i believe related to orbital axis precession, which moves the earth into and out of denser concentrations of those particles. the density changes were believed to be enough to change the mean solar insolation by a factor of _several percent_! i agree, it’s a wise thing to look at the short-term future more than events which might be tens of thousands of years away, but again, if things like water vapor concentrations and methane concentrations have many times more impact than CO2, AND coal mine fires in India and China are on the same order of magnitude as CO2 emissions from just about all sources in the United States, it still looks like our priorities are misplaced. thank you for your replies and comments. i need my conclusions and observations to be challenged, too.” title=”extrapolating backward….

      • dmos
        Apr 24, 2009

        How are the previous 10′s of thousands of years not relevant? You are talking about building a model of climate change according to history, am I correct? If that’s the case, 100 years would be considered small scale, short-term, cherry picking. Would it not be wise to include the previous 400,000 years into the research? For you maybe, because you will see a natural cycle that for some reason humans are just unable to break. To quote you, “In fact the next ice age is not predicted to arrive for at least another 10,000 years.” This would mean that you are assuming the earth goes through an ice age every 75-100,000 years. If that’s the case, then you already know that our current cycle is caused by something other than humans. Consider Astronomer Milutin Milankovitch’s studies on Earth’s orbit, tilt, and precession. Why are these factors not added into any research? The people advocating for this position that humans cause climate change all look at the small scale. Take a look at the big picture, our position in reference to the sun, relative distance, relative growth in the sun(it does not stay the same shape constantly), etc. When the scientists trying to prove man made global warming take these factors into consideration and come up with solid, scientific proof that we the people are causing our climate to change, then I may listen. Until that day, it’s nothing but heresay. Good day sir.” title=”Relevant?

        • erica
          Apr 24, 2009

          dmos: depending on the question you are trying to answer, climate variations on all time scales are relevant. That’s why scientists have been studying the area of paleoclimate for as long as they have been studying climate. Our conclusion that humans are causing the current warming is not based on long-time or short-time scale considerations. It is based on the most fundamental law of physics — the First Law of Thermodynamics, that energy is conserved. For the atmosphere to have warmed there must have been an extra source of heat. The only extra source we can find is greenhouse gas warming.” title=”Dr. Chameides responds -

          • Peter Brodek
            Dec 16, 2009

            Your assertion makes no sense. You state, “For the atmosphere to have warmed there must have been an extra source of heat. The only extra source we can find is greenhouse gas warming.” However, you also state that you are fully aware that the Earth has undergone perfectly natural and cyclical warming and cooling throughout the geological history of the earth. So, which is it? Is the current warming (which appears to have stopped around 1998) part of a perfectly natural cycle, or has there been “extra warming” compared to what there “should have been”. If your assertion is that there has indeed been extra warming compared to what there should have been, please demonstrate too me what the 100% natural trend would have been absent human interference, and then prove to me that the current trend is actually different from your demonstrated 100% natural trend.” title=”Warming

  3. Travis
    Nov 6, 2008

    But you would be willing to turn your children’s and grandchildren’s futures over to the vagaries of government central planners. The itensity of climate change may be unknown, but the repeated failures of government central planning are well known. To believe that Obama’s central planners will do any better than the disastrous central planners under bush is ill-informed in the extreme. Travis Cork MF ’89″ title=”ice age

    • erica
      Nov 6, 2008

      Dr. Chameides replies – I’m not sure what my post had to do with central planning or the Obama administration. Did I say anything about these things? No. Please try to keep your comments on topic, folks.” title=”Let’s Stay on Topic Please

  4. DocNavy
    Nov 5, 2008

    Bill, Been reading these articles and especially enjoy the “Hey Skeptics, take me on” challenge that you tossed out in your first article. As have already been put out by others I think that your statement that Global Warming is still continuing has pretty much been refuted in the short term. (Meaning, since 1998) Of course Alarmists always point out that using 1998 as a starting point is “Cherry picking”, so to that end I can reasonably say that averaging out the ENSO effects, both positive and negative, leaves us with zero net warming since oh…1994 or so. Further, if you average in the global cooling that happened from 1940-1979 then you get NO NET WARMING SINCE 1940! This despite the fact that CO2 has steadily risen something like 800% (Which of course SOUNDS like a huge number but we are really talking about one miniscule amount in ppm rising to a slightly higher miniscule amount in ppm) Anyway, I include here a link to a graph of the entire UAH satellite record up to sept08 and its averaged trends. http://icecap.us/images/uploads/uah7908.JPG On top of that, you and I both know that the NDO and PDO have flipped, AND that there is strong correlation (Albeit ~I~ would never say “causation”) between global temps and the warm/cold phases of these oceanic cycles. Add to that a quiet sun and the possibility (if not probability) of a VERY weak solar cycle 24 and we are looking at least 15-25 of further “Non-Warming”. I’d be willing to bet my next paycheck that even with India and China RAPIDLY catching up and surpassing the US in Anthropogenic CO2 output within the next 5-10 years, Global temps will continue to fall, or at the very least… not Warm. Over the last 10,000 years HAS the Earth gotten warmer… sure, it’s even gotten warmer since the Little Ice Age, but that’s what happens when you come OUT of an Ice Age. Things get warmer. Humans don’t play any part of that, never have, and until some Mad Genius figures out Weather Control… Never will. DocNavy ” title=”Warming vs Cooling

    • erica
      Nov 5, 2008

      Dr. Chameides responds: Docnavy – Take the annually averaged global temperatures over the past 5 years (2003-2007) and average them. Then do the same for the previous 5-year periods (1998-2002, 1993-1997, 1988-1992). In each successive 5-year period, including the last one, the temperature has increased. That is a continuing warming trend, not a cooling one. With regard to the “UAH trend” you refer to: a temperature dip over a 2-3 year period — which the graph shows (with, by the way, a very significant peak interposed in 2007) — is not a climate trend. It is a 2-3 year temperature dip. Again, look at the temperature record over the past 100 years. It is littered with short term dips and peaks — the key feature is the trend not the dips and peaks. And by the way, maybe it’s just me, but did you ever wonder why NOAA shows such a different temperature trend from the same satellite? Check it out: compare http://www.ncdc.noaa.gov/img/climate/research/2007/ann/msu2007-pg.gif with the graph you cite from UAH. Don’t see that big dip you are so excited about. Thanks for the comment.” title=”Trends vs. Dips and Peaks

  5. crf
    Nov 4, 2008

    If we think on long time scales, presently, the earth is not within a spiral arm of our galaxy, but will eventually move into one. It is very speculative on what effect this might have upon climate, but it is another unknown. Climate change from carbon dioxide emissions is a very present problem. We have to deal with it, and not count on us, or the near-future generations observing an astronomical event seriously affect climate in a fashion that overwhelms the carbon dioxide effect. ” title=”other astronomical events

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