Climate Change and Geologic Time: We Are Speeding the Process 

-Imagine Life Five Years Ago… 

I know for me this seems like such a long-time ago. It may be the fact that I was preparing to enter my sophomore year in high school; a crucial point in trying to figure out what to do with my life. It may be the fact that back then, I didn’t know what the words pandemic or covid meant. Either way, around this time, I decided that I would study the Earth and its atmosphere after graduation. Since then, throughout my studies, I have gained a true appreciation for the uniqueness of everything involving Earth, its climate and the science behind it all. More importantly, I’ve learned how sensitive and frail our planet and its climate systems can really be.  

-What About Life 20 Years Ago?  

Well, I was just born, and cell phones, the internet and social media were a new and emerging feat of technology. Things have noticeably changed since then. Looking back almost 80 years ago, the Second World War took place, not long after the First World War, which was a little more than 100 years ago. Before this, in the year 1879, the lightbulb was invented, and we began burning fossil fuels like coal for energy in the US around this time. As you will see in posts that follow, this period, known as the Industrial Revolution (1760-1840), will prove to be a significant turning point when it comes to Earth’s climate.  

Pittsburgh, Pennsylvania smokestacks (late 1800’s). 
-Going Back Even Farther… 

  What if we took it just as far back to when the United States was first founded about 250 years ago? Of course, during this time, the US population only consisted of about three million people, compared to today’s 330 million. Looking back at these times in history, one can only imagine the number of changes we have gone through as a human society. We have completely transformed the Earth itself, and the way we live upon it. From this point on, things may seem to get kind of blurry. 

The strong point that I want to make here is that these “large” amounts of time that we just discussed are really not as large as one may think. As a matter of fact, it’s more like the blink of an eye when compared to something like the formation of Earth, which occurred some 4.5-billion years ago, or the formation of the universe (The Big Bang), taking place around 13.8 billion years ago. These tremendous amounts of time, ranging from hundreds to thousands to millions to billions of years are all part of geologic time, or as this video calls it, deep time, and sometimes, our brains have a really hard time comprehending these things. 


Check out this really interesting video to learn about the true depth of geologic time.  

-Climate Change In the Past

Now that we’ve established the idea of geologic time, it’s important to understand that the climate has changed over a span of geologic time on multiple occasions throughout Earth’s history ( These large and gradual changes in climate have occurred way before humans even existed and Earth will likely continue to change long after we are gone. For instance, at one point in Earth’s history, during the Cryogenian Period some 720-635 million years ago, the planet was a “snowball”, with ice likely extending from the poles to the equator. On the other hand, during the Eocene (About 56-34 million years ago), there was no ice to be found anywhere on Earth’s surface and reptiles could be found living in the Arctic! In fact, according to this graph of global temperatures over the last 500 million years, the planet has gone through many climate swings during this period.  


After examining this graph, we can see that Earth has been both warmer and cooler than the present day. This is because Earth has been fluctuating between icehouse and greenhouse phases for at least 2.5 billion years. Icehouse conditions occur when there is a long-term decrease in temperature, usually accompanied by the building of polar ice caps and continental ice sheets. During an ice age, a glacial period is when glaciers build and advance, while an interglacial period is the warmer period when glaciers begin to retreat and melt into the sea. On the other hand, greenhouse conditions are characterized by a lack of continental ice sheets, mostly caused by higher temperatures due to greater levels of greenhouse gases like carbon dioxide, water vapor and methane, which do a wonderful job of reflecting heat back toward the Earth’s surface and warming the climate. Currently, we live in a mild interglacial period of the last ice age, which saw its peak glacial coverage about 20,000 years ago, when ice extended as far south as Illinois and Missouri ( Of course, these glaciers have receded over the years, all the way until the present day, where they continue to recede today. 

Charts, showing mile-high glaciers extended into the United States some 20,000 years ago and receding to the present day.

-More Recent Climate Change

Something else to consider is the fact that every number on the x-axis of the graph shown previously, is based on hundreds of millions of years. A period of 20,000 years (about 19,750 years before US was founded/when ice was still in the US), would barely appear as a small fraction of the little dot all the way at the end of the graph where “Today” is located (the blue arrow). Even a period of a million years would barely appear as that same little dot. Therefore, the graph gives a good visual representation of what scientists believe the climate was like for hundreds of millions of years before humans ever came into the picture, but it fails to show any specific trends pertaining to the present day. 

Thus, if we wanted to get a good look at how Earth has changed since humans began having an impact, we would have to observe a different, more specific, and much more recent type of data set to see current climate issues. I mentioned previously that greenhouse gases like carbon dioxide are extremely effective at warming the planet by reflecting heat back toward the Earth’s surface. As we will learn, humans have been emitting greenhouse gases into the atmosphere for hundreds of years (since the Industrial Revolution). If we observe the following images, we see that atmospheric carbon dioxide concentrations in the atmosphere are increasing unlike rates the Earth has seen in the last 800,000 years of its existence. 

Atmospheric carbon dioxide (ppm) concentrations from 60 million years ago to the present day. ( 
  • Scientists use climate proxies to figure out climate from periods before instrument data was available. 
Atmospheric carbon dioxide (ppm) concentrations for the past 2000 years. ( 
-What To Expect

These graphs prove that a massive input of carbon dioxide into the atmosphere has occurred, beginning around the year 1800, which just happens to be near the time that humans began releasing carbon dioxide through the combustion of fossil fuels on a massive scale. By investigating Earth’s climatic changes that have occurred in the past over spans of geologic time, we can get a good idea of how our climate is going to react to these changes that we are seeing today. Additionally, throughout this blog, we will learn that the rate of warming the Earth is seeing today is headed toward disaster once again, and fast… 

Almost unnaturally fast…


Keep a look-out for more posts coming soon. Thanks for reading!

-Andrew Bower

One response to “Climate Change and Geologic Time: We Are Speeding the Process ”

  1. […] I discussed in my previous post, the Earth’s climate is not only changing today, but it has changed for billions of years and […]


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