A bit more than ten thousand years ago, a “Glaciation” ended and the climate warmed significantly. Since then, the global climate, while fluctuating, has been warmer than today’s temperatures. How do I know?
Well, there was a great scientific endeavor called the Greenland Ice Sheet Project (GISP) that core-drilled the continental ice sheet to produce a sequence of cylindrical chunks of ice that were sampled for oxygen isotope ratios which are dependent on the temperatures when that ice was first deposited as snow. Later, of course the snow was compressed into ice. Those readings indicated a clear record of temperature changes over many millennia. This is what is called a proxy and it is an accurate one. These data have been confirmed by other such studies in other parts of the world.
There were three upward fluctuations that peaked at (roughly) 1000, 2000 and 3300 years ago that today are called the Medieval, Roman and Minoan Warm Periods, respectively. There were two major downward fluctuations, one after the Roman Warm Period and one after the Medieval. The latter is referred to as the Little Ice Age. In all of the 10,000 years of the Holocene there were cold fluctuations (one at 8200 years ago) but never such an extended cold period as the Little Ice Age. Today we live in another warm fluctuation that is cooler than the Medieval warm period. It is cooler than the Roman Warm period by about another degree Celsius. The Minoan Warm period was warmer yet. Please see figure A. I should add that those warm periods are confirmed by historical accounts.
Figure A: (upper graph) Greenland ice core temperature proxies for the last 10500 years
The lower graph is a proxy measure of Carbon Dioxide concentration. But, that is another fact.