Lessons From A Hot Past

This short editorial published recently in Nature Geoscience is worth reading and thinking about. It summarizes our findings of past climate change and how earth systems such as sea level, glaciers, and the biosphere responded to these climate swings. 

Reconstructing temperatures going back to the Eocene (~50 million years ago) and later in the Miocene (~ 15 million years ago) reveal a very different world. These finding do come with a caveat. The rates of change are averaged over thousands of years, while we today stare at an unfolding catastrophe in our lifetimes. 

There is data though from more recent times that can tell us in finer temporal detail how climates fluctuated. Carbon dioxide trapped in Antarctica ice sheets points to changing atmospheric composition on a centennial scale and tree ring data informs us about seasonal changes in rainfall.

The current level of CO2 in the atmosphere of about 415 ppm (parts per million) are the highest since the Pliocene, more than 3 million year ago. We are also pumping CO2 at rates which are unprecedented in geologic memory, a shift from about 280 ppm to our present levels in just about 150 years The past may not provide a perfect analogue for the rapid changes we are experiencing, but it does send us a sobering warning that civilization's envelopes of comfort will be breached not so far in the future.

Nature Geoscience Editorial: Lessons From A Hot Past.