3-3.3 million years ago global average temperature was 2-3 °C higher than today. The sea level was 25 meters higher and there was hardly any ice sheet in the northern hemisphere. Just as in predictive models, in the paleaontological data you also see a larger difference with today’s temperatures in the northern hemisphere than in tropical regions and southern hemisphere.
Carbon dioxide concentration during the mid-Pliocene has been estimated at around 400 ppm (yes, the 400 ppm that we have crossed in 2016 for the first time in 3 million years).
The climate was not only warmer, but also wetter, resulting in a northward shift of the taiga (boreal forest) and tundra and a spread of tropical savannahs and woodland in Africa at the expense of deserts (am I reading this correctly: less desert?!)