The Pandemic vs. The Maunder Minimum

Skeptics of Global Warming (GW) like to point to the Little Ice Age as being caused by the lack of sunspots as evidence of how the sun, more than anything, can affect climate. Covering roughly 400 years and ending around 1650, the Little Ice Age is well documented in studies of glacier advances, ships' logs, and paintings of anomalous winter scenes, among others. Overlapping the Little Ice Age is the Maunder Minimum, a period of decreased sunspot activity that lasted some fifty years, breaking from the traditional 11 year solar cycle. So, hardcore GW deniers will try to convince you that the Maunder Minimum caused the Little Ice Age, explaining that a lack of sunspots means less solar intensity and therefore less heating of the Earth.

While this may be true on its face, they are exaggerating the contribution (or lack thereof) of solar intensity variability with sunspots. And they also conveniently forget that the period of the Little Ice Age was also accompanied by increased volcanic activity which served to veil the Earth in a thin cloud of ash, vastly outweighing the effects of reduced solar activity. Finally, the Maunder Minimum comes at the tail end of the Little Ice Age, so even though it may have contributed in some small way, it certainly did not cause the Little Ice Age.

Now, another contender has entered the arena, vying for its place in history as the cause of the Little Ice Age: the pandemic. Richard Nevle and Dennis Bird of Stanford have examined sediment cores and soil samples dating back 5000 years and noted a precipitous drop in charcoal ash following periods of major pandemics. This indicated a massive decrease in the clearing of forests by burning to create more land for crops. While the population recovered (remember, Europe lost 20-30 million people in the span of six years), abandoned land began to regrow. Whole new forests sprouted, sucking CO2 out of the atmosphere, effectively removing layers from the Earth's thermal blanket. Moreover, their data aligns nearly perfectly (or so they say) with other information (heavy/light carbon isotope ratios) detailing the drop in atmospheric CO2 at the same time.

This is not to say that pandemics are THE cause of the Little Ice Age. Rather, it looks like they are possibly a serious contributor. And, as far as I'm concerned, this holds as much water as the Maunder Minimum correlation. GW deniers have yet to provide a workable theory beyond a few gesticulations as to how the Maunder Minimum could so significantly affect the environment.

See the Standford University News Release for more.


Anonymous said...

Water vapour is the most important green house gas followed by methane. The third most important greenhouse gas is CO2, and it does not correlate well with global warming or cooling either; in fact, CO2 in the atmosphere trails warming which is clear natural evidence for its well-studied inverse solubility in water: CO2 dissolves in cold water and bubbles out of warm water. The equilibrium in seawater is very high, making seawater a great 'sink'; CO2 is 34 times more soluble in water than air is soluble in water.
Correlation is not causation to be sure. The causation has been studied, however, and while the radiation from the sun varies only in the fourth decimal place, the magnetism is awesome. As I understand it, the hypothesis of the Danish National Space Center goes as follows:
Quiet sun → reduced magnetic and thermal flux = reduced solar wind → geomagnetic shield drops → galactic cosmic ray flux → more low-level clouds and more snow → more albedo effect (more heat reflected) → colder climate
Active sun → enhanced magnetic and thermal flux = solar wind → geomagnetic shield response → less low-level clouds → less albedo (less heat reflected) → warmer climate
That is how the bulk of climate change might work, coupled with (modulated by) sunspot peak frequency there are cycles of global warming and cooling like waves in the ocean. When the waves are closely spaced, the planets warm; when the waves are spaced farther apart, the planets cool.
Using a box of air in a Copenhagen lab, physicists traced the growth of clusters of molecules of the kind that build cloud condensation nuclei. These are specks of sulphuric acid on which cloud droplets form. High-energy particles driven through the laboratory ceiling by exploded stars far away in the Galaxy - the cosmic rays - liberate electrons in the air, which help the molecular clusters to form much faster than climate scientists have modeled in the atmosphere. That may explain the link between cosmic rays, cloudiness and climate change.
The ultimate cause of the solar magnetic cycle may be cyclicity in the Sun-Jupiter centre of gravity. We await more on that. In addition, although the post 60s warming period is over, it has allowed the principal green house gas, water vapour, to kick in with humidity, clouds, rain and snow depending on where you live to provide the negative feedback that scientists use to explain the existence of complex life on Earth for 550 million years. The planet heats and cools naturally and our gasses are the thermostat. Check the web site of the Danish National Space Center.
Keeping in mind that windmills are hazardous to birds, be wary of the unintended consequences of the all-knowing environmental lobby groups.

The skepTick said...

You are establishing relations among greenhouse gases without definition. What do you mean by "most important green house gas"? There is no doubt water vapor has a direct effect on GW, yet we don't calculate its global warming potential because it is so short-lived in the atmosphere and the concentration varies directly with temperature. If the bulk of our emissions was water vapor and if water vapor had a long half-life in the atmosphere, then we would treat it as a contributor to global warming.

By listing methane as the next "most important green house gas", I assume you're looking at its radiative cross-section. What you should be concerned with is its overall contribution to the global warming problem. To do that, look at the radiative forcing of each gas you're considering, which depends not only on molecular properties but also atmospheric concentration. The RF of CO2 is 1.66 W m-2, while RF for CH4 is 0.48 W m-2. These numbers are as of 2005 and there is high confidence in them. Furthermore, CO2 continues to increase while CH4 has held steady or may in fact be decreasing.

Regarding the cosmic ray flux contribution, this theory was proposed and immediately latched onto by skeptics of GW. The proof would be in the experiment. Well, the experiment has been performed. You can find a quick layman's take on it here: http://www.physorg.com/news148751093.html (which I hope to do a post on soon).

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