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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). On top of the trend are oscillations that last about thirty years in each direction. In 2009 we are where the green arrow points [on graph showing said oscillations- SkS], with temperature leveling off. The pattern suggests that the world has entered a period of slight cooling until about 2030."  (David Evans)

At a glance

Where were you in 2009? It seems an age ago now. Climate science denial was everywhere. Skeptical Science was just two years old. It was like whack-a-mole - as one myth was dealt with, more would pop up.

Among the talking-points emerging around that time was the one that global warming was simply the planet recovering from the Little Ice Age (LIA). The LIA was a period of regionally cold conditions, usually said to have occurred between 1350 and 1850. Glaciers in the European Alps reversed their decline and advanced. In London, UK, the tidal Thames froze over sufficiently for 'frost-fairs' to be held on the ice, between 1608 and 1814. Their frequency is often exaggerated; roughly one winter in ten would be a realistic estimate.

Why was it so cold? Here, time travel would be wonderful. In the absence of that, we have had to develop more ingenious ways of reconstructing what happened.

A key factor is the LIA's regional nature. Its most dramatic effects were in Europe and North America. That suggests there was an element of 'internal climate variability' involved. The latter term refers to how heat is moved around within Earth's climate system, as opposed to being added to or removed from it.

During the LIA there were 'external forcing' factors too - these are things that do add or remove heat from the climate system. There was an extended period of minimal Solar activity, known as the Maunder Minimum. However, the Maunder Minimum took place between 1637 and 1719, more than 200 years into the LIA. It cannot have caused the initial cooling.

There were several colossal volcanic eruptions during the LIA, such as Laki in 1783 and Tambora in 1815. The Samalas eruption on the Indonesian island of Lombok was also huge, but occurred in 1257, almost a century before the LIA started. Volcanogenic cooling episodes typically last just a few years, but they wouldn't have helped: Laki and Tambora likely prolonged the cold conditions.

Recent research is instead hinting that the LIA was triggered by a dramatic weakening of the Gulf Stream. That was caused by warm ocean currents penetrating far into the Arctic, causing a dramatic breakup of the sea-ice. Resultant ice-floes were 'exported' en-masse out into the North Atlantic, where they melted, generating cool freshwater. This process peaked around the year 1350. The overloading by all that cool freshwater disrupted ocean circulation patterns and a rapid regional cooling followed.

At the other end of the LIA, what warmed things back up? Firstly, the 1850 end-date is not necessarily reflected in temperature datasets. These show a steady warming trend that only emerged after 1910, steepening and becoming less interrupted after 1970. That is not a regional but global pattern, suggesting that unlike the LIA, an external forcing was dominant. There's one obvious one - our pumping out of greenhouse gases.

The year 2009 was full of predictions from well-known deniers that we were entering a cooling trend. Fourteen years on, there's no sign of that!

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!


Further details

Some climate science deniers like to insist that because the climate has changed dramatically in the past without man’s intervention, the current changes are also a natural event. You may be familiar with paintings depicting Londoners skating on the frozen River Thames. These mostly date from a period when Northern Hemisphere winters were more severe. The beginning and end of this cold period are subject to various interpretations, but the period is referred to as the Little Ice Age (LIA) and it occurred between the 14th and 19th centuries.

Limited History

If we are to understand the LIA, we need to figure out what caused it. Scientists have examined a number of important strands of evidence about the LIA. These include key natural drivers of climate change such as Solar activity, volcanoes, the Arctic and ocean heat circulation.

The activity of the Sun can be assessed by looking at proxies – processes that we know to be affected by the Sun’s activity. One of these is the formation of the radioactive isotope Carbon-14 (C14) in the atmosphere. The half-life of the C14 isotope is 5730±40 years. Radioactive carbon is mainly produced by cosmic particles reaching Earth's upper atmosphere. These particles vary in abundance through time. During times of high Solar activity, the Solar wind shields the Earth, whereas when activity is low, that shield is weaker. Thus, it is possible to deduce past Solar activity from changes in the concentration of C14 in the atmosphere. Because plants can absorb C14, past levels can be deduced by measuring C14 in tree rings and in other accurately age-constrained biogenic materials. Hence, we can estimate how active the Sun was in the past. A graph showing the Sun’s activity over the last few thousand years is presented in fig. 1.

Long-term sunspot-number reconstruction from C14 data.

Fig. 1: Long-term sunspot-number reconstruction from C14 data. All data are decade averages. The Maunder Minimum is visible near the far right of the reconstruction. Source: Usoskin (2017).

Marked deviation from the norm in Solar activity may be expected to have effects on the climate. The Maunder Minimum, a long period when the Sun was particularly inactive, lasted from 1637 to 1719 (Owens et al. 2017). If the 1350 onset of the LIA is accepted, it cannot have been initiated by the Maunder Minimum, although it may well have helped prolong it.

Volcanic activity was high during this period of history. We know from modern studies of volcanism that major eruptions can have strong cooling effects on the climate, albeit for a limited number of years. Notably violent eruptions occurred during the LIA, such as that of Laki in Iceland in 1783 and Tambora, on the island of Sumbawa in present-day Indonesia, in 1815. These were big enough to be detected in ice-cores as sulphate-rich layers caused by sulphuric acid aerosol fall-out. They cannot have caused the LIA but they would almost certainly have prolonged it.

Going further back in time, the Samalas eruption, on the Indonesian island of Lombok, was colossal. It too left a sulphate-mark in ice-cores. The only thing is that the Samalas eruption occurred in 1257, almost a century before the accepted start of the LIA.

Socioeconomic factors may be relevant. Sudden and major population decreases occurred at this time, due to the Black Death and other pandemics. In turn, that would have resulted in a decrease of agriculture and reforestation of agricultural land. Such changes might have had a role, but how big is uncertain.

Since the original version of this rebuttal was published, advances in tracking the former extent of Arctic sea-ice have been dramatic. They are starting to provide important clues regarding the onset of the LIA. Miles et al. (2020) presented a reconstruction of sea ice export from the Arctic Ocean over the past 1400 years, using a spatial network of proxy records. They found robust evidence for a previously unknown period of extreme export of sea ice that commenced abruptly around the year 1300 and terminated in the late 1300s. The pulse of ice along East Greenland resulted in downstream increases in polar waters and ocean stratification that was sustained during subsequent centuries. Such an intense injection of fresh water into the North Atlantic Ocean could have so disrupted the ocean's circulation that the warm water currents of the Gulf Stream were weakened. That would have inhibited their moving so much heat around the Northern Hemisphere. Such a change would in turn have cooled countries adjacent to the North Atlantic, in a regional cooling phenomenon - which the LIA certainly was.

Can We Draw a Conclusion?

To some extent, the climatic shift of the LIA remains subject to speculation. Variable output from the Sun was most marked long after the LIA onset. From the end of the LIA to the 1950s, the Sun’s output increased, so its role may have been important. But since then, the Sun has slowly grown quieter, yet the temperature on Earth has continued to go up (fig. 2). This shows that whilst the Sun has an obvious role as an external climate forcing agent, it's not the only one out there. Modern global warming is mostly the result of adding manmade greenhouse gases to the atmosphere as the result of fossil fuel combustion.

 TSI vs T

Fig. 2: Annual global temperature change (thin light red) with 11 year moving average of temperature (thick dark red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year moving average of TSI (thick dark blue). TSI from 1880 to 1978 from Krivova et al. 2007. TSI from 1979 to 2015 from the World Radiation Center (see their PMOD index page for data updates). Plots of the most recent solar irradiance can be found at the Laboratory for Atmospheric and Space Physics LISIRD site.

Instead, internal climate variability, driven by abrupt and drastic changes to Arctic sea-ice, are increasingly being pointed at as the trigger for the LIA. Such an event has now been detected and will come under further scrutiny in the coming years. The end of the LIA coincided with recovering Solar output plus increasing greenhouse gas emissions with growing industrialisation. Like many changes in climate, there's no single cause and different mechanisms can dominate at different times. Today, there's no doubt about the chief agent of rising temperatures and it's not the Sun!

Last updated on 5 May 2024 by John Mason. View Archives

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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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