Earth is about 4.5 billion years old but the existence of multi-cellular life on the planet has only occurred during the last 524 million years (the phanerozoic aeon.) Earth's temperature has fluctuated between ice ages (temperatures down to 6℃ cooler than the present) and climate maxima (temperatures up to 14℃ warmer than now) with four such cycles during the current aeon. We are now living in the quaternary ice age.
Within each ice age there are fairly regular glacial and inter-glacial periods where the temperature fluctuates by about 8℃. We're currently in the holocene epoch (starting about 12000 years ago) where the planet's temperature has been broadly static after initially rising out of the last glacial period. Note that these glacial periods within an ice age are sometimes termed 'ice ages' in popular terminology, hence some confusion!
There is evidence to suggest that Earth is descending back into another glacial period since the planet's temperature has actually cooled a degree or so over the last 5000 years. However, the human influence of global warming may counter this trend to some extent and it remains to be seen what effect humans will have on the long-term, geological time-frame trends of the planet.
The information here is taken from a Wikipedia page which explains the source of the data and provides many more details of the Earth's historical temperature record.
Before anyone suggests that the extensive fluctuations in the Earth's temperature over geological timeframes mean we shouldn't care about climate change and the role humans have played in it, be under no illusions that the forces that shape our planet over long timescales 'care' two hoots about any of Earth's species, us included. These are big events taking place over long timescales. The planet will still be here regardless of whether we make it more or less conducive to the continued existence of the current set of animals, plants and other forms of life that inhabit it.
At some point in the future the current ice age will come to an end and average temperatures on the planet will rise by 10 to 14℃ into the next thermal maxima. Further still into the future, all life on Earth will be extinguished as the Sun dies. Our own galaxy will eventually be sub-sumed into Andromeda and, after an unimaginable amount of time, the whole universe and even time itself will simply fade into nothing (according to the current best theory.)