Pondering Maunder

“Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.”

–Richard Feynman, in "What is and What Should be the Role of Scientific Culture in Modern Society", lecture at the Galileo Symposium in Italy, (1964)

Global warming denialists got a shot in the arm in the last few weeks, with news that several prognosticators now believe that we are headed for a new Maunder Minimum type event vis-à-vis solar sunspot activity.  The implication, of course, is that rather than facing catastrophic global warming, we are actually headed (by as soon as the year 2030 C.E., no less) towards a repeat of “The Little Ice Age” which lasted from about 1550 C.E. until roughly 1850 C.E.

Solar weather in the news -- Sun spots are theorized to affect climate.

The conservative blogosphere has, to put it simply, gone giddy with these prognostications.  Unfortunately, the conclusion that warming is going to be magically dissipated is misguided at best, and is more likely calamitously, catastrophically wrong.

To explain why, we will attempt to deliver a crash course in space weather, vulcanology, paleometeorology, the bias of  recent observation, and the nature of ice ages.  After that, we will be making tea, and perhaps taking a nap.

First things first, what is this “Maunder Minimum” of which the news feed speaks?

The phenomenon known as a “sun spot” is a well known solar event similar in nature to a large cyclonic weather system on Earth – basically, it’s a big storm system on the surface of the sun.  We say “big” of course, because it is large enough to be spotted through telescopes and solar spectrometers, but compared to the overall surface of the sun, they are actually pretty small, hence “spots”.

The number of sun spots at any given time is a fairly variable data point.  In modern times, the average is between 40,000 – 50,000. 

During the “Maunder Minimum” there were fewer than 50 observed sun spots at any given time.

And since the “Maunder Minimum” occurred in the middle of the “Little Ice Age” there have been numerous climatologists over the last century and a half who have attempted to draw correlations between the two events.

Wouldn't you just love to be able to explain away the dips
and valleys in this chart?  Too bad it's not that easy.

There are several problems with this analysis, of course.  For one thing, the start of the minimum event was roughly 1645 C.E. – almost a centuryafter the onset of the Little Ice Age.  That alone is cause for healthy skepticism regarding claims of strong correlation between solar weather and planetary climate.  There is still some wiggle room for the possibility of the effect of sun spots on global temperatures, but without even diving into the data, it is easy to see that there is not an overwhelming one-to-one relationship.

Moreover, sun spot activity during the Maunder Minimum was only marginally lower than that seen during the Spörer Minimum, which lasted from roughly 1460 until 1550 – the Little Ice Age began when sun spot activity was coming out of a minimum, not when it was going into one.

To make matters more complicated still, observations of historical climate data are strongly dependent on subjective observations more susceptible to error than would be true of more objective measurements – to whit, the fact that in London the River Thames froze over during several winters in the time period in reference certainly sounds convincing… and evidence from ice core samples suggests that on average, winters in Northern Europe were, in fact, somewhat colder during this time period than for most of the Holocene… but these two facts in isolation do not mean much.   The Thames has undergone so much engineering over the last 500 years that there is no comparing the river today to that of the 16^th and 17^thcenturies – the water was slower moving when the “old bridge” was still in place, so it was easier to freeze.  In the 19^th century, it was removed; no more freezes.  And as for those ice cores?  Yes, they demonstrate that winter was colder… but they also show that summers were right at the statistical mean for the Holocene.

In short, if the Maunder Minimum had any impact, it was only felt for half the year.  Summer was just as warm as ever

The "Little Ice Age" was cold... in winter... (recency bias at its best)

during the Little Ice Age.  The Intergovernmental Panel on Climate Change Third Assessment Report of 2001 noted that “…the conventional terms of ‘Little Ice Age’ and ‘Medieval Warm Period’ appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries… [Viewed] hemispherically, the ‘Little Ice Age’ can only be considered as a modest cooling of the Northern Hemisphere during this period of less than °1 C relative to late twentieth century levels.”

There is another potential cause for the cooldown observed from 1550 through 1850 which would go a long way toward explaining this strange dichotomy – and which makes much more sense when accounting for all the data points.

In late spring or summer of 1257 C.E., Mt. Rinjani, on Lombok Island in Indonesia,  shook the world with one of the largest volcanic eruptions in the modern record.  To be precise, prior to this explosion, there were twin peaks on the island – Gunung Samalas and Gunung Rinjani.  After the explosion, there was only Rinjani, with a massive caldera.  Gunung Samalas  was spread throughout the upper atmosphere, along with a sizable chunk of Rinjani.  Deposits found in ice cores from the Arctic Circle suggest that the dust cloud from this explosion would have lasted for several years, dimming the amount of sunlight reaching the surface of the Earth, and quite probably having not just short-term impacts such as crop failure and changes to precipitation patterns, but also quite likely leading to shifts in long-term cyclic behavior in ocean currents.

Mt. Rinjani during a recent eruption.

Most notably among the ocean currents affected, of course, would be the thermohaline circulation in the North Atlantic where the warm water of the Gulf Stream travels towards the North Pole, cooling as it travels northward, finally sinking to form North Atlantic Deep Water, which then flows into the various basins of the deep Atlantic, only to upwell in the Southern Ocean to be heated again.  This ocean conveyor belt is the single greatest driver of climate in Western Europe, and as most of modern history has been written by Western Europeans, their natural biases in described weather will be directly related to changes in the North Atlantic thermohaline circulation.

The Mt. Rinjani explosion certainly qualified as an event capable of altering the North Atlantic conveyor belt; several other volcanic eruptions during the same time frame were equally likely to have impacted European winters:  Bárðarbunga (Iceland) blew in 1477;  Kuwae in Vanuatu (South Pacific) in 1452-53; Huaynaputina in South America in 1600; Santorini (Greece) in 1650; Grímsvötn (Iceland) in 1783; Mount Tambora (Indonesia) in 1815.  In fact, the Tambora eruption was directly responsible for the 1816 “Year Without a Summer”.

As it turns out, even short term changes to local conditions can have dramatic consequences for New England, Canada, Greenland, Iceland, Britain (and, if the change is dramatic enough, the rest of Europe).  The North Atlantic Oscillation is strongly susceptible to either a rise in temperature, which causes excessive ice melt in Greenland, spilling freshwater into the North Atlantic, decreasing the density of the surface water, causing the Gulf Stream to subside (that is, “dive” further south than it ought, basically turning off Great Britain’s natural space heater), or to a decrease in temperature, which forms a denser layer of surface water, which disperses the heat from the Gulf Stream too quickly, achieving the same effect.

The lake that used to be Samalas... Rinjani's twin mountain

Note that in either case, the total amount of heat transmitted to the planet is more or less the same as it had always been, but the effects on local climate are night-and-day different.  In a plot twist worthy of the most cynical of locally oriented climate denialists, there is a fairly good chance that global warming may actually make several countries (including but not limited to Iceland and the U.K., and possibly the New England states in the U.S.) much, much colder in the future.  No certainties on this score, of course, but it is one of the possibilities in play.

Which brings us to the impending solar minimum of the 21^st century.  The causality of impacts on Earth weather from sun spot activity are still theoretical at best, but even accepting for a moment the idea that the Maunder Minimum caused all of whatever cooling happened during the Little Ice Age… the IPCC finding was that the cooling in question amounted to less than 1°C over a three century time frame.

During the Little Ice Age, carbon-dioxide concentrations in the atmosphere were around 250 parts per million.  During the Industrial Revolution, those numbers rose to the 300s.  The estimated warming for the 21^st century in a “best case scenario” has involved a 350 ppm cap on carbon-dioxide, resulting in a 2°C increase in temperatures.  At best the upcoming minimum event might reduce the rate at which warming is accelerating, and not even by half, at that.

However, we are already well past 350 ppm carbon-dioxide.  We are soon going to be looking at 400 ppm in the rearview mirror.

In short, catastrophic warming is every bit as much on the menu as it was before all this sun spot ice age talk started.  Don’t let propagandists take your mind off of the actual science.

Now then, not to leave y’all on a down note….

For those who prepare, climate change is going to present some incredibly awesome gardening opportunities.  We’ll tell y’all about them some time, but for right now, we have a cup of tea and a hammock calling our names.

Happy farming!