A common figure the Left likes to trot out in the climate debate is that 2000 to 2009 were the hottest years on record. This is a meaningless number, the earth is 4.5 billion years old and the way it naturally changes and shifts is readily observable if you know where to look.
Humanity has not been recording climate data for that long: 1880 is the year most point to for the start of proper record keeping when it comes to the climate.
Warming periods (with hotter temperatures than today) are known unequivocally to have occurred during the heyday of the Roman Empire and the Middle Ages – to say nothing of the time of the dinosaurs.