[RayChuang88]

The problem is that we've had much more serious temperature extremes within the last 1500 years. People forget that from the time the Roman Empire fell up to the middle 1300's, Europe was much warmer than now, and enjoyed such long agricultural seasons that famines were rarely an issue during the so-called Dark Ages. But then, winters in Europe turned really cold, and that combined with the arrival of the bubonic plague ended up killing 1/3 of the European population between 1346 and 1354.

We know that the Sun hugely determines Earth's climate. Thanks to record taking of sunspots after Galileo invented the modern refracting telescope at the beginning of the 17th Century, we know that between 1645 and 1715, there was essentially NO sunspots seen on the Sun, and that perfectly coincided with the famous Maunder Minimum that resulted in winters so cold that the Thames and Seine Rivers in Europe easily froze over during the winter.

[HiTech RedNeck]

Prior to modern means of measuring solar output nobody would be able to know if it really changed, absent something like being able to probe the equivalent of meteorological artifacts on other planets. I wonder if lurking somewhere on, say, Saturn is evidence like this. That might show that oh, Saturn was having a (relative) ice age while Earth was having one too. That would point a finger right at Old Sol.