This would be very bad news - many more people die in cold events than in hot ones. Most of those deaths have historically been from starvation, and there's really nothing to suggest that anything is fundamentally different today. Sure, world wide transport is easy, but world food stocks are the lowest they've been in decades. So it is much to be hoped that the American Astronomical Society is wrong.
William of Occam tells us why. Occam's Razor tells us that if you have two theories that both explain the same thing, the simpler of the two is almost certainly correct. The classical lesson in scientific reasoning here involves the Ptolemaic Earth-centered view of the Solar System vs. the Copernican Sun-centered view. The Ptolemaic theory had to resort to ever more rococo ad hoc tweaks like epicycles to explain the orbits of the planets. Johann Kepler explained the Copernican system simply and elegantly with his mathematical laws.
Occam's Razor says that simple and elegant beats complicated and crufty 999 times out of 1000.
And so to sun spots and climate. We have quite good records of sunspot activity going back to 1700 A.D. We have decent records of the price of wheat going back much further - pretty good ones to 1500 A.D., and sporadic records all the way back to 1250 A.D. (!). The reason is that bread is the staff of life - no bread, and people starved.
In short, grain prices are a pretty good proxy for climate, in the days before thermometers. Certainly better than, say, bristle cone pine tree rings. This is important for two reasons, and the combination is very bad news indeed for people who cling to the "Carbon Dioxide is killing Mother Gaia" theory.
First, the price of grain and the number of sunspots have been known to be very closely correlated for hundreds of years. William Herschel (who discovered the planet Uranus) first published this, back around 1800. When there are a lot of sun spots, he said, the price of grain is low - harvests are good. When there are few sun spots, harvests fail and the price of grain soars.
Remember, we have records on this that are so old that this has been known for literally hundreds of years. You might say that, err, the Science is Settled.
Second, there's a theoretical foundation that explains why these two are linked. Henrik Svensmark has proposed that Cosmic Rays are linked to clouds. Specifically, the very high energy (ionizing radiation) rays generate aerosols when they strike high altitude molecules in the atmosphere, and that these aerosols form the nucleation points for high altitude clouds. These clouds reflect incoming solar radiation back into space, cooling the earth.
Everybody knows that when the Sun's magnetic field is strong, fewer Cosmic Rays reach Earth. And when the magnetic field is strong, we see lots of sun spots.
The Svenmark Hypothesis was recently experimentally confirmed at CERN, where artificial Cosmic Rays were crashed into an atmosphere. And aerosols were born. Pretty cool when a scientific prediction is confirmed.
To understand why this is so incredibly bad for the warmist crowd, you need to compare and contrast with the theory of Anthropogenic Global Warming (Carbon Dioxide heating the planet). The theoretical underpinning of AGW predicts a warm zone in the mid-Troposphere (say, 8 miles up or so) in the tropics. Essentially, this is a heat pump that cycles captured heat from the increased Greenhouse effect down to lower atmospheric levels (rather than radiating out to space).
The only problem is that with maybe a million weather balloons looking for the hot spot, nobody's found it. Let's call this Epicycle #1. But the plot thickens. We're told that the correlation between CO2 and warming is clear. It's not:
If I adopt this 10:1 ratio by looking at the last 100 years worth of data I find 1910-1940 temperatures rising while CO2 was not. 1940 to 1975 temperatures falling while CO2 rising, 1975 to 1998 temperatures rising while CO2 rising and 1998 to 2009 temperatures falling while CO2 rising. Three quarters of the period shows no correlation or negative correlation with CO2 and only one quarter shows positive correlation. I do not understand how one can claim a hypothesis proven when ¾ of the data set disagrees with it. To me it is the clearest proof that the hypothesis is wrong.That's Epicycle #2. But wait - we're not done yet. CO2 is a very weak greenhouse gas. There are a lot of GHGs, the most powerful of which is Methane, at 1400 times more powerful than CO2. But the real action is with water vapor, which makes up 90% of all greenhouse warming. So what's with all the focus on CO2?
We're told that it's positive forcings, where some CO2 leads to increased temperature, which creates more moisture in the air, which makes more greenhouse warming, which makes more moisture, and so on.
So why didn't we see this out of control increase in past warm periods, like the Medieval Warm Period which was at least as warm as now and likely warmer. Why didn't it spin out of control into Thermageddon, instead of crashing into the Little Ice Age?
Epicycle #3, right there. And the temperatures are diverging pretty spectacularly from the Climate Models' predictions:
At this point, you should hear William of Occam whispering in the back of your head. The simpler explanation is better.
Or it could be shouted at you. The most famous failed scientific experiment of all time was the Michaelson-Morley Experiment, which tried to measure the Luminiferous Aether. The problem of the day was that light was known to be a wave, but space was known to be a vacuum. A wave needs a medium to propagate through, like waves through water. Obviously, there was no water in space (or air, for that matter), and so the Luminiferous Aether was proposed. It was a mathematical formulation, and its properties were derived from the observed properties of light. Those properties meant that it had to be an exceptionally rigid vacuum.
Ernst Mach (of supersonic fame) was contemptuous of the whole idea. The whole edifice was constructed from cardboard and tape (err, or nineteenth century words to that effect), and anyone could see that it was wrong. Michaelson and Morley set out to directly measure the Aether, and failed. Completely.
Because Mach was right: there is no Aether. Looking back, this is obvious, and scientists of the day should have thought that a simpler explanation would be forthcoming, as indeed it was (the photon).
And so back to the matter at hand. William of Occam politely (as befits a church man) suggests that AGW is overly complex. Ernst Mach sneers that it's plain as the nose on your face. CERN shows aerosol formation.
Of course, I'm one of those Deniers (Epicycle #5) who don't recognize that the Science Is Settled® (Epicycle #6), and who should be locked up as an Enemy Of The State™ (Epicycle #7).
Or perhaps e pur si muove: and yet it moves. Instead of a bunch of epicycles, you can look at an elegant hypothesis backed up by experimental confirmation and 300 years of correlated observations.
The house of cards is only held together with tape after all.
UPDATE 19 December 2017 09:42: Updated model vs. temperature diagram and link due to Internet bit rot devouring the original version.