2010-08-30 00:24:04Basic rebuttal 32: We're coming out of the Little Ice Age
gpwayne
Graham Wayne
graham@gpwayne...
217.44.86.17
The Little Ice Age: Sceptics skating on thin ice

Argument 32: We're coming out of the Little Ice Age

Climate change sceptics suggest that because the climate has changed dramatically in the past – and without man’s intervention – it is possible that current changes to the Earth’s climate are also a natural event.

You may be familiar with paintings depicting Londoners skating on the frozen River Thames, when winters, at least in the northern hemisphere, were more severe. The beginning and end of this period are subject to various interpretations, but the period is referred to as the Little Ice Age (LIA) and occurred between the 16th to 19th centuries.


Limited History

If we are to understand the LIA, we need to figure out what caused it. Scientists have examined several important strands of evidence about the LIA, including the activity of the sun, of volcanoes, and ocean heat circulation, principle drivers of natural climate change.

The activity of the sun can be assessed by looking at proxies – processes we know are affected by the sun’s activity. One of these is the formation of the radioactive isotope Carbon-14 in the atmosphere, which plants then absorb. By measuring carbon-14 in tree rings and other materials we know are from a certain period, we can estimate how active the sun was at the time. This graph shows the sun’s activity over the last millennium:

The carbon-14 data used in this graph go up to 1950. The graph below gives a fuller picture, showing that in the last three decades, the sun's normal cycle of activity has remained steady, while temperatures have shot up:

Yet while the dips in solar activity correlate well with the LIA, there are other factors that, in combination, may have contributed to the climate change:

  • Volcanic activity was high during this period of history, and we know from modern studies of volcanism that eruptions can have strong cooling effects on the climate for several years after an eruption.
  • The ‘ocean conveyor belt’ –  thermohaline circulation – might have been slowed down by the introduction of large amounts of fresh water e.g. from the Greenland ice cap, the melting by the previous warm period (the Medieval Warm Period).
  • Sudden population decreased caused by the Black Death may have resulted in a decrease of agriculture and reforestation of agricultural land.


Can We Draw a Conclusion?

In truth, not really. The Little Ice Age remains for the present the subject of speculation. The most likely influence during this period is variable output from the sun combined with pronounced volcanic activity. We know that from the end of the LIA to the 1950s the sun’s output increased. But since WW2 the sun has slowly grown quieter, yet the temperature on Earth has gone up.

The sceptical argument that current warming is a continuation of the same warming that ended the LIA is unlikely. There is a lack of evidence for a suitable forcing (e.g. the sun) and numerous correlations with known natural forcings that can account for the LIA itself, and the subsequent climate recovery. Taken in isolation, the LIA might cast doubt on the theory of climate change. Considered alongside the empirical evidence, model predictions and a century of scientific research into the climate, recovery from the LIA is not a plausible theory to explain the observed evidence and rate of global climate change.

2010-08-30 03:15:44minor nits
nealjking

nealjking@gmail...
84.151.45.10

-     "the significance of a climate event like this: was this a global phenomenon"

=> "the significance of a climate event like this: Was this a global phenomenon"

 

-     "Carbon 14"

=> "Carbon-14"

 

- "There is a lack of evidence for a suitable forcing (e.g. the sun)": In particular, solar luminosity has not changed as much as 1 part in 1000 over the last 20 years or so, according to satellite measurements.

 

Neal

2010-08-30 05:12:28Comment
Robert Way

robert_way19@hotmail...
142.162.188.138
I very much agree with your statement "The ‘ocean conveyor belt’ –  thermohaline circulation – might have been slowed down by the introduction of large amounts of fresh water e.g. from the Greenland ice cap, the melting by the previous warm period (the Medieval Warm Period)."

A tree ring analysis recently done shows that Liderholm et al. 2010 very clearly shows that the AMO (which is essentially the proxy for the THC) was positive during the MWP meaning a stronger THC.

"The reconstruction suggests
anomalously warm North Atlantic SSTs from ca. AD 900 to 1050, coinciding with the “Medieval Warm Period”,
as well as a phase between 1100 and 1400 with relatively little interdecadal variability. There is a prolonged negative
phase of AMO from ca. 1600-1860, i.e. during the “Little Ice Age” (LIA). The multidecadal variability of
approximately 40-80 years remains constant throughout the record, except around ca 1500-1700, i.e. during the
LIA, when it breaks down."


A little side note, I would not include the IPCC phrase on the MWP and LIA. The evidence DOES suggest a global LIA and a warm period at the time of the MWP but it just doesn't reach current levels (more like 1940s). To include the IPCC's statement that the LIA wasn't global will be a lightening rod for criticism I think.
2010-08-30 06:28:50
doug_bostrom

dbostrom@clearwire...
184.77.83.151

I really like this. It's circumspect, acknowledging our lack of perfect information on this matter.

If I were writing this I'd emphasize the distinction between the LIA and our present influence on the climate, reiterating to the general effect that if you're on a bike and run over a nail with your front tire, repair it and then drive over a collection of tacks thereby deflating both of your tires you cannot conclude from your experience with a nail that you may continue cycling as usual.

2010-08-30 16:34:05THE TITLE IS CUT OFF.
villabolo

villabolo@yahoo...
76.93.65.8
You only have the first word of the rebuttal title.
2010-08-30 16:47:34Miscellaneous thoughts
James Wight

jameswight@southernphone.com...
58.105.164.221

I think the current version might be a bit too long and detailed for a basic rebuttal. In fact, I think it might be longer than the intermediate version of this rebuttal.

As for the point about solar activity having levelled off since 1950, it might be a good idea to include that in the graph if possible.

Also, I would change "the LIA might cast doubt on the theory of climate change" to "the LIA might cast doubt on the theory of anthropogenic climate change".

2010-08-31 12:00:19GP, you can edit the rebuttal title by editing the Summary line of the first post
Jim Meador

jimm58@gmail...
67.101.213.181

(I made the same mistake.)

"Try to learn from the mistakes of others, that way you don't have to make them all yourself." 

2010-08-31 16:26:00Responses
gpwayne
Graham Wayne
graham@gpwayne...
217.44.86.17

Neal - only proper nouns and acronyms are capitalised after a colon - I'm not American.

Robert: agreed - IPCC stuff removed.

Doug - don't really understand the analogy, but the length is already pushing the limits, so I'm resisting adding more to it.

James - I really think that when we talk these days about climate change, even the dullest denier gets we're talking about the anthropogenic kind. Also, I have not agreed that 'basic' means short: to me it means language and explanations suited to lay people (although I did cut a bit out anyway).

And why the bloody titles keep getting truncated is beyond me. I keep putting them back, they keep buggering off again. Weird...

2010-09-01 04:48:04
doug_bostrom

dbostrom@clearwire...
184.77.83.151

Graham, my tortured analogy was to the effect that "So what if it was warmer in the Middle Ages? What does that have to do with the new physical effects we've introduced w/C02? One style of warming from long ago does not mean we can ignore a new mode today." 

But not essential to the argument.


2010-09-01 05:55:38
Nicholas Berini

nberini@gmail...
24.189.119.236
Not your fault, but I wish the graph did show the decline in solar output after 1950.  It almost hurts the argument as is... Very well written, thumbs up.
2010-09-01 20:24:30New Graph
gpwayne
Graham Wayne
graham@gpwayne...
217.44.86.17
OK chaps - I found a graph that brings the solar forcing up to date. Sorry the two don't quite join up, to show the diminuition after the 50s - couldn't find anything that quite did the job.
2010-09-03 05:16:12Comment
Robert Way

robert_way19@hotmail...
142.162.188.138
May I suggest you not use Hadley for the temperature graph as it has been shown that they have underestimated the warming of the 21st century...
2010-09-03 05:29:39graph
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.249

The Max Planck Institute has a useful graph that I often reference.

Max Planck solar vs temp

Also the Stanford Solar Center.

stanford solar center

I'd also suggest mentioning that the LIA was probably a combination of solar, volcanic, thermohaline, etc.  But overall it looks good.

2010-09-03 16:36:03Responses
gpwayne
Graham Wayne
graham@gpwayne...
81.152.234.172

Robert - surely if Hadley are giving the most 'undramatic' figures, we should use them in preference so as not to be accused of exaggeration or cherry picking?

Dana - hello and thanks. Only thing is, I was concerned my rebuttal was already a bit 'technical'. I don't feel the graphs you've provided (which I reviewed when writing the piece) are simple enough, so I'll stick with what I have now. Thanks for the suggestion though - and keep them coming.

2010-09-04 02:41:13okay
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.249
Fair enough.  I'd still clarify that the LIA was caused by a combination of factors and that it's not solar or volcanic or thermohaline, etc.
2010-09-04 03:16:29Comment
Robert Way

robert_way19@hotmail...
142.162.188.138
Oh I understand why one would use hadley for just keeping skeptics mouth shut but we consistently on this website show how 1998 is not the warmest on record and yet there we use a dataset which shows it is... in the intermediate for 1998 is the warmest it shows a link where a real analysis shows that hadleys sampling underpredicts warming during the 2000s therefore  I think it is very easy to defend the use of another index. We cant constantly be saying one thing and then be using the same index that we claim is not appropriate for recent warming... oh and ps only 0.06 difference now in UAH between 1998 and 2010... too close to call for a record!
2010-09-04 03:39:54Source of the C-14 graph?
Jim Meador

jimm58@gmail...
67.101.147.179

The main message of the intermediate rebuttal is that the sun (+volcanoes) brought us out of the LIA, but since the 1940s, the S+V factor has gone down and recent warming is due to AGW.

To me the C-14 chart shows solar activity rising in the 20th century, with no sign of flattening out. It appears from first glance at the visuals that recent warming would be due to a continually warming sun. (Yes the second chart makes this point, but it is too isolated from the first chart.)

The C-14 chart does not correlate well with dana1981's chart for sunspots in the 20th century. (Which published work states that  C-14 is a good proxy for solar activity? Wouldn't this need to be adjusted to account for anthropogenic C-14 changes since the industrial age?)

I think that if you show historical solar activity, it needs to be linked with recent solar activity more clearly. So I agree with others that a different chart would be better, and among the suggestions above I don't see a clearly superior choice. There must be a definitive record of the historical-to-present solar influence out there somewhere...

2010-09-04 03:57:05
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.249

The C-14 chart stops in the early-mid 20th century, prior to solar activity flattening out.  That's why graham added the second figure to fill in that gap, or at least part of it.

I've read that around WWII when we started detonating nuclear bombs, it increased the atmospheric carbon-14 level, so that's probably why the graph stops there.

2010-09-04 18:04:59Consistency
gpwayne
Graham Wayne
graham@gpwayne...
81.152.234.172

I feel I must make the point again that all my rebuttals are based on, and consistent with, the intermediate versions. We seem to be debating issues here outside of the remit I have adopted - which isn't to debate the issues (better places elsewhere to do that, I think) but to re-write the inters to make them more approachable. This is what my basic version is - a re-write of the inter, which uses the same argument and graph (albeit the other way round).

The additional points raised here are testament to a greater issue. This item languished in the author's list while everything around it was claimed. I think nobody wanted to take it on because it cannot be nailed. We can beat around the bush, debate solar measurements till the cows come home, but nothing except a time machine will definitively sort this out because, like the MWP, it's history. This is why I made a point of admitting we really can't draw a conclusion. I also think the last paragraph is as close as I could get to rebutting the argument - because irrespective of what caused the LIA, what brought us out of it etc, the real issue to me is that the LIA does not bear on the current climate changes, and that's the point I've tried to make clear. All suggestions made here seem to me to make things less clear and more complex, even if strictly speaking the points raised may be more 'accurate' overall.

2010-09-04 18:36:14Comment
dansat
dannysatterfield@mac.com
15
24.214.40.2

I would think this is perfect for an intermediate. It does seem a bit complex for a basic explanation. Dana's suggestion on graphics would get a thumbs up from me. (Am just getting started here by the way). Perhaps mine was too basic ;)

 

 

2010-09-04 19:15:24Complex?
gpwayne
Graham Wayne
graham@gpwayne...
81.152.234.172
Hi Dan - bit surprised you think it's at the 'inter' level. Have you read the actual intermediate version? I laboured over this one, and I can't see how I can make it any simpler, but if you have any suggestions I'd be glad to hear them. (I must say too that Dana's graphics might be pretty scary for lay people - surely this kind of graph is what we should avoid as much as possible in the basic versions?)
2010-09-04 19:20:08Dana - I missed it!
gpwayne
Graham Wayne
graham@gpwayne...
81.152.234.172

Sorry - forgot to sort out the combination issue. This is what I have now:

"Yet while the dips in solar activity correlate well with the LIA, there are other factors that, in combination, may have contributed to the climate change..."

Anyway, good call. Hope that gets it.

2010-09-05 00:25:38
doug_bostrom

dbostrom@clearwire...
184.77.83.151

I second (again, see "circumspect" above) Graham's point about this being one of those matters that is not resolved to a fare-thee-well. Meanwhile an attempt at an air-tight argument on the LIA leads to the bleeding edge of research and thus is fundamentally incompatible w/simplicity.

I'm sounding like a stuck record here but hermetic arguments concerning all but the simplest climate phenomena cannot be simple because simple arguments create ambiguity; skipping detail axiomatically leaves detail unexplained.  

This LIA thing is arcane, attracts skeptics like flies to dung but probably does not figure large in the mind of John Q. Citizen, who will read this rebuttal and its concluding remarks about other evidence and conclude something to the effect of "that's reasonable." 

2010-09-05 07:25:14We should consider
nealjking

nealjking@gmail...
84.151.49.66

if this topic cannot be knocked squarely out of the park, why are we trying to handle it as a "basic" argument?

Is a skeptic or even a naive reader going to come away with a better understanding of AGW from this?

Maybe it would be better if we just had Intermediate & Advanced level on this one; perhaps the work that has gone into this can be used to improve the I & A versions.

 

Neal

2010-09-05 18:31:45
gpwayne
Graham Wayne
graham@gpwayne...
81.152.234.172

Neal: "if this topic cannot be knocked squarely out of the park, why are we trying to handle it as a "basic" argument?"

It's a rebuttal to an argument that is, in fact, equally basic. The fact that we must address uncertainty is a fact of life, about which we must be candid. If you want tidy science, you have to turn to maths based work like classical physics. All climate science is messy, because it is the study of chaos - all loose ends, and no scissors - and everything about it is inferential because there is no 'control' Earth, no blind tests, no consistent phenomena.

Will skeptics or naive readers get a better understanding. Well, if they take on board the nature of uncertainty and stop using it like a club with which to beat up science, then yes.

2010-09-06 00:36:55The question is
nealjking

nealjking@gmail...
91.33.109.141

whether we're going to come out ahead after the typical reader has read the article.

If not, we're not helping.

 

2010-09-07 04:41:59Basic Rebuttal 32: thumbs up
jimalakirti

jimalakirti@gmail...
70.56.240.163

1) I think it is a good thing to provide the basic data and reasoning about an issue, even with the conclusion being "We can't really tell for sure." Or "The issue is irrelevant. Look at the real data!" That's science for ya'. No quick and easy answers.

2) We have to say something on this issue because it is a favorite of people who either don't believe because they don't understand, they don't believe because they don't want to (they are more comfortable believing something else, or they will not admit they believe because they are using climate warming denial for political, economic, or religious purposes and don't give a damn about the science. I think this basic explanation can be understood by the big three denial groups. 

3) I don't believe it is too complex for anybody with a high-school science course (if those are still available in the US) and I doubt anybody with less education is likely to be reading this site. 

2010-09-09 04:30:52Ok
nealjking

nealjking@gmail...
84.151.34.204
approve.
2010-09-09 08:20:57
Michael Searcy

scentofpine@yahoo...
72.91.223.97

Sounds good to me.  Nice job as usual.  A few minor tweaks...

"including the activity of the sun, of volcanoes, and ocean heat circulation"

Perhaps change to "including solar activity, volcanic eruptions, and ocean heat circulation"


Check consistency on capitalization of "Carbon-14"


"Sudden population decreased caused by the Black Death..."

Perhaps change to "Sudden population declines caused by the Black Death "

2010-09-09 23:50:48Published
John Cook

john@skepticalscience...
121.222.93.62
I know this will offend your UK sensibilities but I changed sceptic to skeptic :-)