Faster global warming may bring much more heat

(Eco Business, 20 Sep 2019) Climate scientists are haunted by a global temperature rise 56 million years ago, which could mean much more heat very soon.

We could in the near future be experiencing much more heat than we now expect. As carbon dioxide levels rise, global warming could accelerate, rather than merely keep pace with the levels of greenhouse gases in the atmosphere.

This is a lesson to be drawn from new computer simulations of the conditions that must have precipitated a dramatic shift in global climate 56 million years ago, when atmospheric carbon dioxide levels rose at least 1000 parts per million (ppm) and perhaps substantially higher.

For most of human history, carbon dioxide levels stood at around 285ppm. They have now passed 400ppm. By the century’s end, if humans go on burning ever greater quantities of fossil fuels to drive global heating, then these could reach 1000 ppm.

The last time that happened, during a period known as the Early Eocene 56 million years ago, the surface temperatures became up to 9°C hotter than today. The period has been repeatedly explored as a lesson for the pattern of events that might follow from global heating by profligate combustion of fossil fuels.

The polar ice melted. Antarctic ocean temperatures reached 20°C. Sea levels rose dramatically, oceans became increasingly acidic, mammals evolved to smaller dimensions and crocodiles haunted the Arctic.

It is a principle of geology that the present is a key to the past – and it follows that the past must contain lessons for the future. So climate scientists have always taken a close interest in the Early Eocene.

External link

Eco Business, 20 Sep 2019: Faster global warming may bring much more heat