Energy > Climate Change
Carbon dioxide has warmed the planet before
This article is the eighth in a series focused on the causes and consequences of a warming planet
The greenhouse effect has been contributing to changes in the Earth’s temperature for millions of years. Here are a couple of examples.
The Earth is currently in a 100,000 year cycle of warming and cooling, commonly known as ice ages. These long-term cycles are related to change in the earth’s path as it revolves around the sun. Some ice ages were so severe that ice sheets stretched to the tropics. During the last ice age, layers of snow and ice covered much of Canada and the northern portions of the United States, reaching as far south as Des Moines, Iowa.
Glacial periods are punctuated by warm periods such as the one we are living in now. The temperature difference between the warm period we are currently experiencing and the last period of glaciation is only about 10-15 degrees Fahrenheit. So, a relatively small change in temperature can have an enormous impact on climate.
Although not triggered by carbon dioxide, ice ages are impacted by changes in carbon dioxide. Over the last 800,000 years, the rise and fall of the Earth’s temperature closely mirrors the rise and fall in atmospheric levels of carbon dioxide.
Left to itself, the Earth will continue the glaciation cycle of the past with a very slow cooling of the Earth over the coming tens of thousands of years. But we are currently experiencing something much different. Instead of very gradual cooling, the Earth is rapidly warming.
Another example of the power of carbon dioxide is mass extinctions. Millions of years ago, sudden changes in climate caused mass extinctions of life on Earth. The most prominent is the Permian–Triassic Extinction of 248 million years ago when 90-96% of life on earth perished.
Scientists believe many of these mass extinctions in Earth’s distant past were caused by giant volcanic eruptions. These behemoths of the past make current volcanic eruptions pale in comparison. These eruptions are believed to have continued for thousands of years with lava covering vast areas of the planet.
As these volcanoes erupted, they spewed enormous amounts of carbon dioxide into the atmosphere which caused a large increase in global temperature resulting in the extinction of many species.
So, we can see that the Earth has undergone huge temperature and climate swings in the past driven by carbon dioxide and the greenhouse effect. The only difference is that today’s carbon dioxide emissions are coming from oil derricks and coal mines rather than massive volcanic eruptions.
Don Hofstrand, retired extension agricultural business specialist, email@example.com
Reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University