Climatology's Piltdown Man?

I am really suspicious about this Global Warming rage. First off, I hope that the earth actually IS getting warmer. It would mean more vegetation growing, and more oxygen in the air we breathe. Unless, of course, it kept getting warmer and didn’t know when to stop. Oven dried plants don’t photosynthesize.

But here are some of the things that bother me. What is the ideal temperature for the earth?  Maybe we are still colder than that. When I read of some of the foods to be had in England early in the last millennium, I have to think that the place was warmer than it is today. It cooled considerably as Europe entered a new ice age in the late fifteenth century. Some people act like they think that the earth’s temperature was static until recent times, but climate has constantly been changing throughout history.

How can anyone know the temperature of the earth? Are official recordings (I mean the ones that give rise to the conclusion that the earth is growing warmer) taken in enough places so as to represent a statistically significant sample?  And what happens when thermometers need replacing? Are the new ones calibrated exactly like the old? Or are they even different models? Given that the temperature is reputed to have changed less than a degree in one century, this could introduce a very significant bias, it seems to me.

I read that since 1880, average temperatures have risen .85 degrees. It’s gone from 286 degrees Kelvin to 287 degrees. So what? Is a change of 3 hundredths of one percent such a big deal? Average temperature in any one spot can change far more than that, up or down, from year to year without major consequences.

These are some of the issues that lead me to wonder if global warming isn’t the Piltdown Man of climatology.