Earth's previous thriving during a period
of climate change has given scientists
hope that it could survive current
warming.
Image: iStockphoto

At a time when global warming is a major international issue, leading scientists from Australia and overseas attended a groundbreaking symposium in Melbourne on 25 September to discuss an extreme period of climate change that occurred on Earth millions of years ago, the kick-start it seemed to give to the evolution of early life, and what it can tell us about the longer-term climate cycles that Earth may experience in the future.

Approximately 750-550 million years ago – hundreds of millions of years before dinosaurs roamed the Earth – one of the most extraordinary climatic periods of Earth’s history occurred.

During this time, the Earth was alternately subjected to the most severe ice age conditions (‘Snowball Earth events’) the planet has ever witnessed (with ice present even around the equator), and then to similarly widespread tropical greenhouse conditions.

“During these ice age events, any parts of Australia and the world that weren’t at that time submerged under the ocean would most probably have been barren, icy wastelands – including destinations that are today considered to be tropical getaways” said Associate Professor Stephen Gallagher, immediate past-Chairman of the Geological Society of Australia’s Victoria Division and convenor of the Geological Society of Australia (Victoria Division) Selwyn Symposium and Lecture 2008.

“Should you have been living back then, instead of taking a beach towel to these destinations, you would instead have been taking a very thick parka, a pair of woolly socks and an ice axe. But of course, back then, it was still hundreds of millions of years before humans would evolve.

“The extreme climates of the Snowball Earth period, together with the sudden and widespread appearance of very primitive multi-cellular lifeforms in a window of tropical climate between the period’s two major ice age events, make this one of the most important and enigmatic episodes in Earth’s history.

“A key question for scientists today is how these primitive lifeforms not only survived the extremely hostile temperatures of Snowball Earth’s ice age periods, but actually seemed to thrive during the wild fluctuations from ice age to tropical conditions and back to ice age.

“Indeed, it is thought that the extreme climates of this period may actually have provided the real kick-start that nature needed to get the process of evolution underway.

“Today’s national symposium will bring together leading researchers – including the internationally renowned Professor Paul Hoffman from Harvard University – to examine the causes and effects of these extreme climatic events and the evolution of early life, and the longer-term perspectives this period offers on the current debate on climate change.

“What the Snowball Earth period shows us is that while the extent of climate change we are experiencing today is extremely worrying when considered against the short timescale of human life – and has immense potential to cause real problems such as longer droughts, hotter temperatures, and rising sea levels – it is certainly not as extreme as periods of climate change that Earth has experienced in its first 5 billion years, and it will probably not be as extreme as the climate change that Earth will experience in the 5 billion years remaining before it and the Sun explode.

“Indeed, given the surface temperature of Earth could ultimately reach 500 degrees Celsius in the final millions of years before its decline, humankind would first have to survive for many billions of years longer than expected – and second, undergo a significant process of evolution – to exist in those conditions.”