‘What is happening today is unique from a historical geological perspective’
By Summit Voice
SUMMIT COUNTY — Simultaneous warming in the southern and northern hemispheres hasn’t occurred in at least 20,000 years, and possibly longer, according to a Swedish researcher who says his findings refute one of the more common arguments against global warming.
“What is happening today is unique from a historical geological perspective,” said Svante Björck, a climate researcher at Lund University.
Björck directly addressed the argument that climate has always changed in cycles by showing that, in the past, when when, for example, the temperature rises in one hemisphere, it falls or remains unchanged in the other.
“My study shows that, apart from the larger-scale developments, such as the general change into warm periods and ice ages, climate change has previously only produced similar effects on local or regional level,” says Svante Björck.
To make his findings, Björck examined global climate archives, searching for evidence that any of the climate events that have occurred since the end of the last Ice Age 20,000 years ago generated similar effects on both the northern and southern hemispheres simultaneously.
He used the Little Ice Age as an example, explaining that, while Europe experienced some of its coldest centuries, there is no evidence of corresponding simultaneous temperature changes and effects in the southern hemisphere.
Climate records, in the form of core samples taken from marine and lake sediments and glacier ice, serve as a record of how temperature, precipitation and concentration of atmospheric gases and particles have varied over the course of history, and are full of similar examples.
Instead it is during ‘calmer’ climatic periods, when the climate system is influenced by external processes, that the researchers can see that the climate signals in the archives show similar trends in both the northern and southern hemispheres.
“This could be, for example, at the time of a meteorite crash, when an asteroid hits the earth or after a violent volcanic eruption when ash is spread across the globe. In these cases we can see similar effects around the world simultaneously”, says Svante Björck.
Björck draws parallels to today’s situation. The levels of greenhouse gases in the atmosphere are currently changing very rapidly. At the same time, global warming is occurring.
“As long as we don’t find any evidence for earlier climate changes leading to similar simultaneous effects on a global scale, we must see today’s global warming as an exception caused by human influence on the earth’s carbon cycle,” Björck said.
“This is a good example of how geological knowledge can be used to understand our world. It offers perspectives on how the earth functions without our direct influence and thus how and to what extent human activity affects the system.”
Filed under: climate and weather, Environment, global warming Tagged: | climate, climate change, Environment, global warming, Lund University, Northern Hemisphere, Southern Hemisphere, Summit County News, Svante Björck