If currently popular scientific theories and hypotheses about the Earth's historical climate are correct (and they very well may not be), then:
- From the time the Earth was formed (when it was purportedly covered with molten lava) until now, the Earth has cooled.
- Around 650 million years ago, during the "Snowball Earth" period, the Earth was believed to have been covered in ice from pole to pole. Since that time, the Earth has warmed.
- During the time of the dinosaurs, which spanned around 180 million years until about 65 million years ago, temperatures were largely warmer. So, since that time, the Earth has cooled.
- Since the last ice age (around 12-20 thousand years ago), the Earth has warmed.
- Since the Medieval Warming Period (around 800–1300 AD), the Earth has cooled.
- Since the mini-ice age (around 1350-1850 AD), the Earth has warmed.
- Since around 1995, the Earth has cooled a little bit or at worst leveled off.
So, if you want to answer the question: Is the Earth cooling or warming, you first have to pick a starting point from where you are going to start your measurement.
Which starting point do you pick? Based on that, has the Earth warmed or cooled? Because either answer could be correct depending on when you start your measurement.