One thing I never saw mentioned in the stories of how the earth is warmer now than in the past 400 years was the fact that 400 years ago we were smack in the middle of this thing called the Little Ice Age, which ran roughly from 1300 - 1850.
In Eurpoe there were a few minor effects credited to the LIA:
Quite a few bad crop years leading up to the mid 1300s weakened the population. The colder weather also drove people indoors with the rats, which contributed to the Black Death spreading like wildfire.
The wine grape industry in Northern Europe failed year after year (leading to the dramatically increased popularity of beer and hard spirits, since they can be made with more 'cold tolerant' crops. Even today the 'northern line' of the region where grapes are grown is 350 miles south of where it used to be. Also, since the U.S. was settled originally by northern europeans, the cultural behavior was transported and the alcohol industry here is 93% beer & hard spirits (mostly beer), 7% wine.
The Viking colonies in Greenland were driven back to Europe by the harsh conditions.
The adoption of a certain cold-weather-tolerant breed of potato as a staple crop in many areas (>90% of the diet of an average person, Ireland for example) leading to the potato famine when that one crop was ravaged by disease.
The Year Without A Summer (look it up).
Anyway, there are many more effects. All tied to this 500-year LIA. There are several theories of the causes of the LIA. There were were a lot of volcanos going off, and solar activity was different than it was before or since.
Isn't it interestig that none of the news stories chose to mention the LIA when reporting that the earth is warmer now than it was 400 years ago?