In light of news that the sun may be heading into a quiet period like the Maunder Minimum from 1645-1715, it is time to revisit a blog entry from last year.
Here’s a slightly revised version of what I wrote.
Something unusual has been going on in the Sun’s magnetic activity. For the last three centuries or so that we have been observing sunspots, we have seen a regular eleven-year cycle in their behavior. At solar minimum, sunspots are few and far between (sometimes totally absent). This has usually been followed by a sharp upsurge after about 16 months, but the last two cycles have been different.
According to the opening paragraph of an article posted at the Science Now website of the American Association for the Advancement of Science, “Scientists studying sunspots for the past 2 decades have concluded that the magnetic field that triggers their formation has been steadily declining. If the current trend continues, by 2016 the sun’s face may become spotless and remain that way for decades—a phenomenon that in the 17th century coincided with a prolonged period of cooling on Earth.”
Later, the article notes, “Sunspots disappeared almost entirely between 1645 and 1715 during a period called the Maunder Minimum, which coincided with decades of lower-than-normal temperatures in Europe nicknamed the Little Ice Age. But [William Livingston of the National Solar Observatory in Tucson, Arizona] cautions that the zero-sunspot prediction could be premature.”It may not happen,” he says. “Only the passage of time will tell whether the solar cycle will pick up.” Still, he adds, there’s no doubt that sunspots “are not very healthy right now.”
As expected, global warming skeptics are making a big deal about this report, arguing that this proves that solar effects are far more important to global climate change than human activity. If they are correct, does that mean we can continue to burn fossil fuels with abandon while atmospheric CO2 levels soar?
My answer is a resounding “No,” and here’s why:
(1) Correlation does not mean causality. The Maunder minimum may have been responsible for seven cool decades in the 17th-18th century, but there is no consensus on the physics of how changes in solar activity (and consequent changes in Earth’s ionosphere) could have resulted in global cooling. It may well have been coincidence. But even granting that it was causal does not change my position, as the subsequent points explain.
(2) We are not certain that we are on the verge of another Maunder minimum. Even if we are, it will likely only cool the Earth for a few decades while the effects of increased greenhouse gases in the atmosphere will continue beyond that.
(3) What does the increased level of greenhouse gases imply? Analysis of the large body of climate data has led to a strong consensus among climate experts that human activity which has increased atmospheric CO2, primarily the burning of fossil fuels, is responsible for most, if not all, of the global warming that has occurred in the last century. Even if sunspot activity temporarily mitigates the increase in global temperature, we still need to be concerned about the projected increases in the next few centuries.
There is a wide range of projected scenarios about what to expect, and I have been known to criticize those who overstate the case. But even mid-range scenarios project serious problems from sea-level rise, more extreme weather events (in number and intensity), the spread of tropical diseases, and disruption of agricultural patterns.
Deviations from those scenarios in a beneficial direction, as may result from changes in solar activity if the skeptics’ confidence in the causality of the Maunder minimum is correct, would be welcome. However, deviations in the opposite direction are also possible, and such deviations would be matters of great concern. Policymakers need to consider the most likely scenarios as well as the range of possible deviations in setting policy. They need to give some credence to worst case scenarios and be alert for signs that such scenarios are occurring.
In short, let’s all hope that the Sun is about to give us a reprieve from those worst case scenarios and use that reprieve, if it comes, to mitigate and eventually reverse our production of greenhouse gases. It would surely be nice to have another 70 years to solve the problem, but we would be wise to recognize that as an opportunity to change our actions, and not as an excuse to continue our risky actions.
Addendum to prevent this thread from become yet another place to rant, commenters please note: I don’t mind your disagreeing with me on the interpretation of the science if you know something about the subject, and I certainly don’t mind your disagreeing about the policies that are necessary to deal with climate change. But if this becomes a free-for-all with nonproductive rants, I will close this thread to commentary. I will also delete comments that I view as unproductive rants rather than substantive discussions.
Addendum 7 October 2010:
Nature News has an interesting article about the possibility that the decline in solar activity may be linked to the most recent warming. The article has key quotations from several scientists who view this result in the same way I do. It does not change the main conclusion that human activities are primarily responsible for changes in climate. For example:
The idea that scientists might not have quite understood the Sun’s effect on climate should not provide ammunition for climate-change sceptics, says Martin Dameris, an atmospheric scientist at the German Aerospace Center in Oberpfaffenhofen. “The findings could prove very significant when it comes to understanding, and quantifying, natural climate fluctuations,” he says. “But no matter how you look at it, the Sun’s influence on current climate change is at best a small natural add-on to man-made greenhouse warming.
Addendum, June 16, 2011:
As a scientist, I hope that we are indeed seeing a new Maunder Minimum, because then nature will be presenting us with a very interest research opportunity.
At this point, we only know that the previous Maunder Minimum was correlated with an episode of global cooling. Since we have a record of only one previous occurrence, we are unable to judge whether that correlation is due to coincidence or there is a causal effect. A second such episode should give us a better indication of the possibiliuty of causality.
If we get evidence of causality, then we need to explore what physical phenomena would tie changes in the ionosphere to changes in average global temperature. It may be time for climate scientists and atmospheric physicists to begin to explore that question and allow the changing solar behavior to provide test data for their models.
15 thoughts on “Reviving an old post: Will the Sun give us a reprieve from global warming?”
You are not even open to any other possibility for the cause of Global Warming, Climate Change or whatever the latest buzz word description is. CO2 still accounts for only two tenths of one percent of our atmosphere. It is a trace gas and every living green thing on our planet must have it to live and produce the O2 we need. Plus when you take into account just how very little of the Earth’s surface is inhabited by man, the math just does not add up.
Jules, you clearly didn’t read my article. I am open to the fact that there may be solar effects that we don’t know about, and this gives us the possibility of exploring them.
However, there is powerful science (that some people persist in denying) that supports human activity as the primary cause of climate changes that we are already seeing and are projected to become much more serious if we don’t act.
If the Maunder Minimum did indeed lead to a short period of cooling, rather than being merely coincidental with it, then nature is giving us a reprieve. We should take advantage of it to solve our problems instead of denying they exist.
There is large body of research that shows that small changes in atmospheric CO2 lead to large changes in climate. You can find many interesting books on the subject at my Science Shelf Book Review archive.
In one word. Forcing. In another two, equilibriuum thermodynamics. The planet needs to remain in radiative balance. Block some energy loss and the temperature has to increase until the radiative balance is restored, even if the path and length of time to do so is not stipulated by the same calculation or argument. Increased amount of CO2 in atmosphere traps energy in its bonds, and gets radiated back at the planet surface.
The amount of forcing needed to disrupt equilibriuum turns out to be pretty small.
It sounds like you care about this. That’s good. I urge you to look at one of two things.
The first is a course taught by Professor David Archer which is free and gets you into the physics of this process. It’s good. Archer posits an ever more elaborated series of Earth surface-ocean-atmospheric models from the simplest to a workable one, and shows why the end point needs to work the way it does, drawing conclusions from it. There’s a companion text I’d recommend.
The second is actually two books by Professor John Harte, Consider a Spherical Cow, and Consider a Cylindrical Cow. These are technically more difficult, relying upon first year college calculus in some quarters, but I think they are really worthwhile. Harte deals with many aspects of environmental science, and you may be quite surprised how quantitative these are.
I suggest taking some time and understanding a bit of the quantitative science.
It’s not like there are a whole spectrum of “reasonable hypotheses” for explaining climate change out there and people are picking out one or two in preference. There is basically one, with a lot of details needed to be worked out, since we don’t know our planet and its mechanisms as well as we should.
But basic facts are, if the conclusions of warming or change are incorrect, there’s something wrong with not geophysics or climate science, but physics at its heart. Consequently, they who challenge the science of climate not only need to explain particular observations from satellites and oceans and land and atmosphere, but where the basic physics is wrong. That’s a tall order. No such explanations are forthcoming from the critics.
I daresay, if these are wrong, then there’s a whole lot of science and engineering we should not be able to do which we clearly can do, especially at the semiconductor level.
[BLOG OWNER’S NOTE: This is more or less a standard denialist’s statement. Since it is not a rant (i.e., it does not get personal), I approved it. I will not approve others that basically repeat the same arguments. The theme is always the same. They are unwilling to accept the reports of the Intergovernmental Panel on Climate Change (IPCC) even though it has the support of the overwhelming number of active, publishing researchers.
You can find those arguments in many other places from people much more expert than I. Also, I posted this at a time where I am under deadline pressure, meaning I can’t get into extended discussions.
I will approve comments from others that further the discussion as long as they focus on the science. But I will not approve comments that merely restate arguments already made.
My personal political view is that people who make policy ought to rely on the scientific consensus, especially in cases where the consensus is as strong as it is for Anthropogenic causes of climate change, rather than favoring a fringe scientific interpretation because it suits a political agenda. A couple months ago I had a blog entry about what the US Navy was doing in response to climate change scenarios. They accepted the consensus view, and our national security is better because of it.
We now return you to the voice of commenters as moderated by yours truly.]
Your write up reveals the very flaws in the pro AGW mindset, such as:
(1) “Correlation does not mean causality..”
Ok, show me the correlation with “man made” CO2 and global warming.
Noting of course that there has been no “global warming” for the past 10 years
during a time of increasing CO2. The Hockey stick is dead.
2. “effects of increased greenhouse gases in the atmosphere will continue beyond that.”
Be specific, other than using flawed models, what are your future projections based on?
Which is a greater greenhouse gas….water vapor or Co2? Water vapor of course, while CO2 will remain a tiny percentage of the atmospheric gases and is at rather historically low levels even now. The effect of increasing CO2 is not linear and peters out as you should know.
You use the unscientific term “consensus” quite often when trying to make a point. How about coming up with facts rather than opinion (reflecting a special interest)?
Science is not about consensus…elementary my dear Watson, elementary.
” human activities are primarily responsible for changes in climate.” That is the most preposterous statement you could make….the big yellow thing in the sky that provides almost of our heat might have something to do with it, plus the oceans, orbit, natural water vapor, cosmic rays etc. The Medieval Warming period did not come about due to SUV use.
The problem Jules, is that 0.2% adds roughly 10% of the total GHG forcing of the atmosphere. Increase that 0.2%, and that forcing goes up as well. If you have a balanced input-output equation, and you start altering that balance by roughly 0.5% per year, that very small input leads to relatively large outputs.
The earth will warm from 303K to 305K. Doesn’t sound like much, does it?
Just as an aside, replace that 0.2% of the atmosphere with cyanide, see what effect that would have on life. Just because the total is small, the effect may be significant.
For addtional information on this issue, check out:
“How would a Solar Grand Minimum affect global warming?” by John Cook, Skeptical Science, June 16, 2011
Thanks, Badgersouth, for a terrific link.
You’re welcome, and thanks for all that you do.
Followed the link you posted on Skeptical Science and was pleased to find a nice resource. Thanks for your work.
You might like to look in over at Carbon Brief, Fred.
Nobody has commented on Verity’s post on this subject yet — but it won’t be long before those in denial start echoing their misinformation. Keep up the good work!
“J” made another comment essentially saying that I’ve got to be kidding about accepting the consensus view and the IPCC report. I did not approve it, because, as noted in his/her earlier comment, it repeated the same arguments as before.
For those who wish to read some more of the standard arguments that take that old and often rehashed approach, see my original Science Blog post on this topic, or search the web.
As noted in my posting, I have criticized people who have overstated the climate change case in the past. For a full set of my postings on the topic, search Science Blog for Bortz climate change. One of the posts you will find is this one called “Kilimanjaro as Poster Child,” where I take Al Gore to task for choosing the wrong glacier to serve as a global warming icon.
The globe experienced the 10th warmest May since record keeping began in 1880, as the climate phenomenon La Niña ended its 2011 cycle. The Arctic sea ice extent was the third smallest extent for May on record.
The monthly analysis from NOAA’s National Climatic Data Center is part of the suite of climate services NOAA provides government, business and community leaders so they can make informed decisions.
To read the entire NOAA report for May, go to:
“If the Maunder Minimum did indeed lead to a short period of cooling, rather than being merely coincidental with it, then nature is giving us a reprieve. We should take advantage of it to solve our problems instead of denying they exist.”
No, It would tell us that predictions of future warming were wrong and that blaming CO2 for all the past warming is just as likely wrong as well. It would tell us the sun and natural variation had a larger role in past warming than what was previously estimated. It would expose the the “scientific consensus” for the hyperbole it is.
It’s not an either/or situation. If a quiescent sun produces a cooling effect, that needs to be added to the effect of greenhouse gases. When the normal sunspot cycle returns, we will still have whatever warming those gases produce.
Wishful thinking will not solve our problems. Paying attention to the data and the projections of carefully vetted climate models is the best way to understand what we will be up against.
On track so far:
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