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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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What ended the Little Ice Age?

What the science says...

Select a level... Basic Intermediate Advanced

The sun was warming up then, but the sun hasn’t been warming since 1970.

Climate Myth...

We're coming out of the Little Ice Age

 

"The global temperature has been rising at a steady trend rate of 0.5°C per century since the end of the little ice age in the 1700s (when the Thames River would freeze over every winter; the last time it froze over was 1804) ...

 

...

 

The IPCC blames human emissions of carbon dioxide for the last warming. But by general consensus human emissions of carbon dioxide have only been large enough to be significant since 1940—yet the warming trend was in place for well over a century before that."  (David Evans)

 

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.

Basic rebuttal written by GPWayne


Update July 2015:

Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial

Last updated on 5 July 2015 by skeptickev. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

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Comments 26 to 50 out of 76:

  1. cruzn246, nobody claimed the Earth is in equilibrium. The sentences you quoted are expository.
  2. "cruzn246, nobody claimed the Earth is in equilibrium. The sentences you quoted are expository. " Then naturally we should be heating or cooling. Right? Which one should we be doing now? "@cruzn246: I don't think you understand what equilibrium means in this context." Archie, explain it to me.
  3. @cruzn246: "Archie, explain it to me." Why should I? You'll only ignore what I say and/or change the subject yet again. You've proved time and time again you're not interested in learning. Here's a hint for you, though: equilibrium is not a "hard thing to achieve" in a system, it's what a system naturally tends to. Also, a thermal equilibrium isn't necessarily livable. Venus is in a thermal equilibrium (i.e. it's temperature is stable), but it's the closest thing we have to Hell.
  4. @cruzn246: "Archie, explain it to me." "Why should I? You'll only ignore what I say and/or change the subject yet again. You've proved time and time again you're not interested in learning. Here's a hint for you, though: equilibrium is not a "hard thing to achieve" in a system, it's what a system naturally tends to. Also, a thermal equilibrium isn't necessarily livable. Venus is in a thermal equilibrium (i.e. it's temperature is stable), but it's the closest thing we have to Hell." Well, with Venus you have a completely different situation. It's like comparing apples and oranges. That type of equilibrium, static, is next to impossible in our atmosphere system . We have what is called a dynamic equilibrium. I'll ask you the question that Tom doesn't seem to want to answer. Naturally, without anthropogenic influence, should we be heating up or cooling now?
  5. Eliminating anthropogenic influence is the first issue. Do you mean all the changes since the land use changed by the introduction of agriculture, or the whole of the industrial revolution, or just the last 60 odd years of accelerated industry, land use and population changes? It makes a difference, you know.
  6. adelady "Eliminating anthropogenic influence is the first issue. Do you mean all the changes since the land use changed by the introduction of agriculture, or the whole of the industrial revolution, or just the last 60 odd years of accelerated industry, land use and population changes? It makes a difference, you know." Of course it does. Lay a number on it.
  7. I'll take a punt but you need to ask over what timescale so I will look at post-1975 out to now. For natural effects TSI very slightly down since 1975. Milankovitch forcings are obviously dependent on latitude but glacial cycle tracks NH effects which are very very slowly going down. Aerosols slightly up. Overall barely perceptable change with maybe some cooling. Of course this is in AR4 WG1, FAQ 9.2, Fig 1.
  8. "I'll take a punt but you need to ask over what timescale so I will look at post-1975 out to now. For natural effects TSI very slightly down since 1975. Milankovitch forcings are obviously dependent on latitude but glacial cycle tracks NH effects which are very very slowly going down. Aerosols slightly up. Overall barely perceptable change with maybe some cooling. Of course this is in AR4 WG1, FAQ 9.2, Fig 1." So you think we should have stayed in about the same climate patterns we were having from the the 40s to the mid 70s?
  9. Speaking of anachronistic climate patterns, personally I think throwing a substantial and irretrievable additional lagged input into a system dominated by hysteresis without thoroughly predicting the novel perturbation's effects is reckless. We're a little late off the mark with integrating our own activities with those of nature. Does our belated realization mean we should thus ignore our activities, remain fixated on natural phenomena, pretend we don't exist? Perhaps such a comment would better fit in the topic of models, however.
  10. cruzn246 - given the Milankovitch cycle (sp?), solar irradiance, and the fact that our CO2 emissions (which should add up to 4ppm/year) are adding 2ppm/year, it should be cooling now without anthropogenic influence. Next question?
  11. Folks, click on the basic tab above and look at the charts in the Limited History section. The carbon data is all over the place clearly showing the Little ice age big time, but hockey stick Mann claims it wasn't a NA event. Please. Note another thing. The LAST part of that carbon chart shows the highest levels of carbon 14! The funny thing is it really took off in the latter part of the 19th century. that pretty much coincides with the warm-up from that time till the mid 40s. It says the graph stops in 1950. WHY? Are they afraid to show what happened with carbon 14 after that? I would say yes. they then go to a lame sunspot cycle. This is not the same as a carbon measurement. Why the switch? Because if they would have continued with a carbon graph you would have seen something like this. I know this is not a carbon 14 measure, but this closely follows the same of pattern carbon 14 readings. If someone finds the chart for carbon 14 readings since 1950 I would sure like to see them.
  12. @cruzn246: "Well, with Venus you have a completely different situation. It's like comparing apples and oranges. That type of equilibrium, static, is next to impossible in our atmosphere system . We have what is called a dynamic equilibrium." Okay, now it's obvious you have no idea what you're talking about. "I'll ask you the question that Tom doesn't seem to want to answer. Naturally, without anthropogenic influence, should we be heating up or cooling now?" Cooling, most probably. The fact temperatures are still increasing tells you how large the anthropogenic influence is. "The funny thing is it really took off in the latter part of the 19th century. that pretty much coincides with the warm-up from that time till the mid 40s. It says the graph stops in 1950. WHY? Are they afraid to show what happened with carbon 14 after that? I would say yes." Are we back to conspiracy theories, now? The evil scientists are hiding the data, is that it? "I know this is not a carbon 14 measure" In other words, it is completely irrelevant. You just wanted to add a graph to give your innocuous post some credibility.
  13. As I stated, my comments about what the natural trend should be were from 1975 to now. However the figure I referenced shows the natural forcing from 1900. If you are trying a "its the sun" argument, argue it in the right place but also note all the detail there about it isnt. You wont find a C14 past 1950 that can tell you anything about solar - the atmospheric nuclear test regime overprints everything else, but now we have direct measurement of TSI anyway. Please try to stick to peer-reviewed science - that way you avoid the people who trying to fool you.
  14. cruzn246 #36: As usual, you seem to be basing your conclusions on fiction. "The carbon data is all over the place clearly showing the Little ice age big time, but hockey stick Mann claims it wasn't a NA event. Please." Mann doesn't say that the LIA was a non event. It is very clearly evident in the Mann 2008 reconstruction; "WHY? Are they afraid to show what happened with carbon 14 after that? I would say yes." Congratulations, your official wacky conspiracy theorist tin foil hat is in the mail. Carbon 14 ratio was a reasonable proxy for solar irradiance prior to the point that we started putting tons of fossil carbon into the atmosphere and releasing bursts of radiation with atomic explosions. Of course, we've been able to measure solar irradiance directly for decades so we don't need proxies any more. We've been in a pronounced solar minimum for a few decades now... while temperatures have been going through the roof. "I know this is not a carbon 14 measure, but this closely follows the same of pattern carbon 14 readings." Ummm... what? They aren't even close. Total atmospheric carbon levels barely changed at all between 1000 AD and 1800 AD while Carbon 14 ratio was going up and down like a roller coaster along with TSI. Since then total atmospheric CO2 has risen at a steadily increasing rate while Carbon 14 has continued to roller coaster.
  15. Is there a tipping point with solar values? In other words, once they exceed a certain value warming will continue regardless of whether it is increasing? I would think so. It has average above above 1366 for well over 5 decades. Prior to 1880 it was averaging well under 1335 for sure for over 500 years. Think of this. I a semi-closed system, which we have, there must be a point where you will keep warming as long as you are above a tipping point. Who is to say that we, being at the highest average solar output in over 2,000 years, have not passed that tipping point? No one can say. We do not know where that point is.
  16. cruzn246 writes: Prior to 1880 it was averaging well under 1335 for sure for over 500 years. Er, no. Not even remotely. Did you miss this graph? Figure 1: Reconsructed total solar irradiance (Delaygue and Bard 2010) Note the Y axis. The running mean of solar irradiance (after smoothing out the 11-year cycle) has varied by less than 1 W/m2 over the past 1300 years. If it had actually dropped by 30 W/m2 for "over 500 years" we'd have glaciers running amok all over the place.
  17. "Er, no. Not even remotely. Did you miss this graph?" I can see it. I meant 1365. The graph is mostly under 1365, on average from about 800 AD to almost 1900 AD. from During the LIA it was averaging about 1364.75. Even the minimum around 1975 was higher than anything the previous 100 years.
  18. #40: "Is there a tipping point with solar values?" Did you miss the 2008 announcement that solar wind strength is decreasing? The average pressure of the solar wind has dropped more than 20% since the mid-1990s. ... The change in pressure comes mainly from reductions in temperature and density. The solar wind is 13% cooler and 20% less dense. And yet, we still see higher temperatures. Why would that be?
  19. cruzn246 writes: I meant 1365. The graph is mostly under 1365, on average from about 800 AD to almost 1900 AD. from During the LIA it was averaging about 1364.75. OK, so we're talking about an 0.25 W/m2 forcing in a plane perpendicular to the Earth-Sun axis. That's an 0.0625 W/m2 forcing when distributed over the spherical top of the atmosphere, and about 0.044 W/m2 after taking into account the Earth's albedo. In comparison, the IPCC TAR gives the total current forcing from greenhouse gas emissions (relative to 1750) as 2.10 W/m2. (And of course this is increasing every year). So, you think that a (natural) 0.044 W/m2 forcing might just have happened to push us over some kind of tipping point, but you're completely unconcerned about a (anthropogenic) forcing that's 48 times larger and growing? This kind of thing makes it very hard to take "skeptics" seriously. It's like the old joke about lawyers straining at gnats and swallowing camels.
  20. cruzn246 - "is there a tipping point for solar" - Well yes, on it way to a red dwarf, the sun will eventually boil the seas and that surely is tipping point. Not one that need concern us much however. This sounds like a continued effort to explain warming from solar effects. Lets try the science approach. What would we predict to occur, from considerations of past solar warming and from basics physics? Warming more pronounced in tropics; warmer days rather than warmer nights; summers warming faster than winters; and the biggy - the stratosphere warming not cooling. Observation dont match these predictions but they do match the predictions for GHG-driven warming.
  21. No Little Ice Age in Japan? http://zacost.zamg.ac.at/phaeno_portal/was-so-los-ist.html In the end of the page: "Kirschblüte in Japan" In this chart there are dates of full-flowering of cherry trees in Kyoto of years 700 to 2000. No LIA, but the recent warming is visible. http://tinyurl.com/39nqn7m Flowering of cherry trees in Japan does no reveal any LIA: https://www.cfa.harvard.edu/~wsoon/MiyaharaHiroko08-d/AonoKazui07-Aug23-KyotoSpring.pdf http://www.envi.osakafu-u.ac.jp/atmenv/aono/KyoPhenoTemp4.html
  22. Has anyone done a critique of Syun-Ichi Akasofu's paper "On the recovery from the Little Ice Age"? At first glance it looks interesting, and provides a possible alternate to some of the warming. http://www.scirp.org/journal/NS/
  23. PaulPS, I am in the process of doing a critique on my new blog: Part 1 Part 2 Part 3 is still to come.
  24. No responce from PaulPS, so I assume his was a flyby shooting. But, nonetheless, part 3 of my responce to Akasofu is now posted at bybrisbanewaters.blogspot.com
  25. It often strikes me that the argument 'we are recovering from the LIA' is given as a physical reason for heating. Complete nonsense of course. A cup of hot water is cooling when you put it on the table not because 'it is recovering from its hot temperature' but because there is an energy transfer from the hot system (your hot water) to the environment. THAT is a reason. The fact that 'your cup is recovering from its hot temperature' is a CONSEQUENCE of that energy transfer. If however you put the table on fire, your cup will not cool despite its desire to 'recover from its hot temperature'.

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