Pollen data shows humans reversed natural global cooling | John Abraham

Current temperatures are hotter than at any time in the history of human civilization

In order to understand today's global warming, we need to understand how Earth's temperatures varied in the past. How does the rapid warming we see now compare with past natural climate changes? Also, how long have humans been having an impact on the climate? These are some questions that can be answered through paleoclimate studies. Paleoclimate research uses natural measurements of the Earth's temperature. Clever scientists are able to estimate how warm or cold the Earth was far back in time, way before we had thermometers.

Readers of this column are probably familiar with some of these paleoclimate techniques that may use ice cores or tree rings to infer temperature variations. A different method that uses plant distribution was a technique used in a very recent study published in Nature. That technique used pollen distribution to get an understanding of where plant species thrived in the past. Those distributions gave them insights about the temperatures. On the surface, it's pretty straightforward. Tropical plants differ in major ways from plants that live in, say, the tundra. In fact, plants that thrive where I live (Northern USA) differ from plants that populate landscapes further south.