What Does A Six-Degree Rise In Average Global Temperature Mean, Anyway?

Mon, Dec 14, 2015

When people talk about global warming, they say things like “models predict that Earth will warm between 2 and 6 degrees Celsius in the next century”. But what does that mean? I can’t tell the difference between 74° F and 76° F, or between 23° C and 25° C. Is a two-degree change in global temperature really that important?

Yes.

We’ll look at two periods in time when the global temperature was within 10 degrees (Celsius) of what it is now – the Ice Age and the Cretaceous.

The Ice Age

Scientists can estimate global temperatures by examining ice cores taken from the South pole. They estimate that during the Ice Age, the Earth was 4 to 7 degrees (Celsius) cooler than it is today.

Here’s what that four to seven degree change in temperature gave us:

• Europe, now largely glacier-free, had glaciers extending into modern Poland and Germany during the last ice age.
• In North America, glaciers reached into what is now Arizona.
• In South America, there were glaciers in Venezuela, and an ice sheet covered the Southern Andes up to the modern location of the Northern Patagonian Ice Field.
• Global dust levels were 25 times higher during the last ice age.
• Sea levels were low enough that Australia, Tasmania, and New Guinea were one landmass, which geologists call Sahulland.
• North America had cheetahs and lions¹. Herds of mammoths lived in modern Russia and across North America, and they went far enough south that they were caught in the La Brea tar pits, along with saber-toothed tigers.

When the global temperature rose, glaciers in North America receded to form the Great Lakes and Niagara Falls. Animals that lived in tundra conditions could no longer survive in what is now Southern California.

Again: all of these changes were accompanied by a global rise in temperature of four to seven degrees Celsius. It’s a small enough change that I wouldn’t touch my thermostat.

The Cretaceous

The Cretaceous period, at its warmest, was 8 to 10 degrees (Celsius) warmer than today, and during more moderate periods was 6 to 8 degrees warmer.

During the Cretaceous:

• Forests extended into the North and South Poles. There were even polar dinosaurs.
• Sea levels were so high that much of the modern United States was underwater.
• The Western Interior Seaway connected the modern Canadian Arctic sea with what is now the Gulf of Mexico.
• There was nearly twice as much carbon dioxide in the atmosphere as there is today.

The Cretaceous also had wildly different lifeforms than the modern Earth, but it is unlikely that climate change was the only reason they went extinct.

Conclusion

Given that efforts to stem climate change are severely underfunded, I recommend beating the rush and:

• buying a summer home in Siberia
• starting a farm in Nunavut
• building beachside resorts in Kentucky and Montana
• learning how to be self-sufficient while living in a houseboat

A six-degree change in global temperature is very, very bad.