Original article by Anthony Cohen, the Open University. Are we speeding towards future catastrophe with rapid climate change? What can we learn from the past?

Introduction

Studying how global temperature rises have caused mass extinctions in the past can give us an indicator of what we may be letting ourselves in for this century.

Measuring past environments in the layers of ancient rocks

Sections in this article

The Research

Greenhouse gas from the sea bed

The lesson for us

The Research

The Earth has faced at least two catastrophes caused by global warming in the distant past according to recent scientific research. An Oxford University team led by Dr Stephen Hesselbo has shown that the first of these two events happened some 180 million years ago, when dinosaurs dominated the continents. A second global warming event has been recognised by Professor Steve Norris of Columbia University and Dr Ursula Rohl of Bremen University. This occurred around 55 million years ago, 10 million years after the extinction of the dinosaurs.

Greenhouse gas from the sea bed

What both studies have in common is the discovery of a dramatic change in the make up of the carbon stored in marine sediment from each period. The only known source of material which could bring about this change is gas hydrate, a greenhouse gas which collects abundantly in the ocean basins. When it is released naturally, or accidentally as sometimes happens when engineers drill for oil, huge underwater explosions can occur releasing gases like methane into the atmosphere where they add to the greenhouse effect. While the effects of massive gas hydrate release have been appreciated for some time, the new research has accurately quantified the time over which release occurred, as well as providing estimates of the time taken for the environment to recover. In this way, both studies have shown that the climate perturbations coincided with "extinction events" when a substantial proportion of the Earth's flora and fauna died out.

The lesson for us

What can we learn from this research about the stability of our present climate, and of humanity's effects on it? The main lesson comes from Norris and Rohl's study. They showed that the release of gas hydrate about 55 million years ago gave rise to a global temperature rise of 5-7°C.  (The Intergovernmental Panel on Climate Change is predicting that temperatures could rise by as much as 5.8°C by the end of this century). It took only a few hundred years for this climate upheaval to occur, but the subsequent recovery took more than 100,000 years. The message for us is clear: dramatic global warming has occurred in the past regardless of human existence, yet now we face the prospect of bringing such change about through our own actions.

Where Next?

On ClimateX.org:

Read more about climate change in a comprehensive overview article: ‘Climate change'.

External links

Mark Lynas, acclaimed climate change journalist and author, examines the evidence for rapid climatic changes and the likely changes that would occur given certain amounts of warming in his new book: ‘Six degrees: Our future on a hotter planet'; see http://www.marklynas.org/