We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
WHAT IS THE "CORRECT" AVERAGE TEMPERATURE? Don’t we need to know this first before we can determine what deviance is detrimental?
This is a question that used to have been answered. There is a period known as the "Climate Optimum" http://en.wikipedia.org/wiki/Holocene_climatic_optimum around 9,000 – 5,000 years ago. The temperature was up to 4 C warmer than now and the Sahara was fertile, supporting, if cave paintings in the central Sahara are to be believed, all sorts of animals including hippopotamus.
Holocene might be pleasant enough, but I don't even get the idea of a planetary average because, with so many climates on earth, and so many human-influenced microclimates, I would think an average would lack meaning.
A global temperature is a easily measurable metric, uses only simple math to assemble. It is useless for making decisions.
A useful metric would be the quantity of potentially arable land, based on rainfall, growing season, high/low daily temperatures. Establish a world base flatland arable area, then add or subtract each year at the edges. Establish a relation between rain/temp and protein/acre or calories/acre, and now you're talking real information.
You're quite right about the "global temperature" being easy to assemble and useless. It's also easy to manipulate, it turns out.
Your more useful metric would be very difficult indeed to put together and, more important, it probably would help to falsify the "progressive" narrative of human industry ruining the planet's weather.