Scientists are always trying to understand Earth’s history. Also, they hope to learn how, or if, it gives indications of what we can expect today. While carbon dioxide levels historically have always been in flux, humans were not present for the majority of it. That said, currently, we have much less volcanic activity or massive meteors creating onslaughts of environmental and geological change in comparison to millions of years ago.
With these two variables in mind, can we still expect to find the same climate changes if carbon dioxide reaches the same levels? What can account for the same carbon levels if those two variables do not exist in one of two scenarios? Recently, scientists reveal that carbon dioxide levels are as high as they were 3 million years ago. What can that tell us?
Understanding carbon dioxide levels from the last 3 million years to 25 thousand years ago.
Three million years ago, Earth was in the later years of the period labeled the Pliocene Epoch. The Pliocene Epoch was from 5.3 million years ago to 2.6 million years ago. This period preceded the Pleistocene Epoch, otherwise known as the Great Ice Age. Many of us learned about this period in school, where the great wooly mammoths died, and homo sapiens crossed continents that had recently merged.
What people may not realize is the Pliocene Epoch was a time of fluctuating temperatures, with its warmest time happened about 3-4 million years ago. This warming included the Arctic. At that time, the Arctic was about 60 degrees F during the summer months, and studies have also shown that it was a warm and wet climate with consistent vegetation. That is 20 degrees warmer than Greenland was this summer of 2019, which raised many alarm bells. Interestingly enough, scientists estimate that 3.6 million years ago, the carbon dioxide levels were between 380-450 ppm. Our current carbon dioxide levels are within the same levels as 3 million years ago. In 2019, carbon dioxide levels were measured to be at 407 ppm.
A brief history of the Pliocene Epoch
The Pliocene epoch was instrumental in creating the geography as we know it today. The previous era had been warm, and as the Pliocene epoch began, the temperatures fluctuated until they began to cool toward the ending years. Due to the warm weather, in the beginning, there were no ice caps at the poles, making the sea level 30 meters higher than today. As the weather cooled and became dryer, grasslands began to take over the forests. This climatic shift created a change in the appearance of many grazing mammals who eventually displayed longer legs, longer teeth, and mammals, like the apes, came down from the trees.
A time of forming Earth’s landmarks
During this time is when the continents began to merge, such as the plates of North and South America. Notably, it also included the Caribbean shift, which resulted in the land bridge across the Isthmus of Panama. This formation changed migratory patterns of the animals who could now cross into new territories. There was also a change in marine life as now the oceans were split into today’s Pacific and Atlantic Oceans.
Mountain ranges that we are familiar with today formed during this time. India and Asia collided and created the Himalayas, while tilts in the Americas lifted the Rockies and Appalachians, among other areas. Many more tectonic plate movements created changes across the globe.
Towards the end of this period, temperatures began to progressively cool and continue to get dry. This cooling caused the Mediterranean Sea to dry up and remain grassland for millions of years. The making of Antarctica as we know it began during this time by starting the formation of ice caps.
Scientists are not sure what caused this sudden cooling. There are multiple theories:
- The rise in greenhouse gases
- The oceans didn’t circulate heat as well
- The formation of the Himalayans.
A brief history of the Pleistocene epoch
The Pleistocene Epoch is the time of Earth’s history that most of us have learned about, most recognized as The Great Ice Age. It started roughly 2.6 million years ago and ended 11.7 thousand years ago. This is the time in which homo sapiens evolved from our ancestors about 2.3 million years ago. By the end of the epoch, we had spread out across the globe.
Fauna of the time
Mammals such as the wooly mammoth, saber tooth tiger, and giant ground sloths roamed with apes, cattle, deer, rabbits, and bears, among several other familiar mammals today. Reptiles such as snakes, crocodiles, and lizards existed along with ducks, geese, hawks, and eagles.
At about 13,000 years ago, the wooly mammoths, saber-tooth tigers and other mammals went extinct en masse. Scientists are still attempting to discover the cause. Here’s an important note. This epoch did not cause the mass extinction of the dinosaurs. That event happened 60 million years prior.
Ecology of the Pleistocene Epoch
The planet was dry, and vegetation was minimal due to the cold temperatures. Water was frozen, decreasing rainfall to about half of what it is today. Temperatures were about 9-18 degrees F lower than our average most frigid temperatures. While summer and winter did exist, it never reached warm enough to melt all of the snow.
This was when the land became covered by massive ice sheets and glaciers. These icy structures encompassed 30% of the landmasses on our planet. The primary focus was in the Northern Hemisphere, and fluctuations were allowing for partial melting and then freezing occurring again. This flux in ice and snow melting and then freezing also created changing sea levels. While frozen, the sea level could be 100 feet below current levels, and after the ice melted, it could be at what is considered normal levels by today’s standard.
There was a multitude of effects on the landmasses and lakes and rivers, which differed in each region due to different soil, compactness, on-going tectonic plate movement, and more.
Carbon Dioxide and the Ice Sheets
The oceans absorb up to about 30% of carbon dioxide in the atmosphere. The question of how the freezing and thawing of the oceans and the contained carbon dioxide affects the acidity of the sea and the carbon in the atmosphere is of particular importance right now. Our carbon levels are 407 ppm, like that of the Pliocene Epoch, which leads to the Pleistocene Epoch, or the Great Ice Age.
Scientists did a study off of the east coast of New Zealand by analyzing boron isotopes of the planktic foraminifera Globigerina bulloides from two core samples. Planktic foraminifera are multichambered amoebas with a type of shell surrounding them commonly found in an ooze-like substance at the bottom of the ocean.
Researchers commonly use these samples to determine the time frames of earth events. These particular samples dated back to 25000 years ago and demonstrated that ocean pH levels were 8.2 at that peak period. They also discovered that at about 14,000-16,000 years ago, the pH level dropped and rose again to about 8.1 at the end of the era. The period 17,000 to 11,000 years ago was the end of another ice age during that epoch.
The evidence appears to point to the fact that while glaciers were melting, the ocean was releasing stored carbon dioxide. The scientists compared their records with previous records from other locations. They noted that during periods of deglaciation, the seas were venting out the carbon dioxide. This finding seems to verify that the South Pacific and South Atlantic Oceans are carbon contributors, not absorbers. This may have also explained why, in our current epoch, there appeared an increase in carbon emissions despite no change in atmospheric carbon levels.
Studying the influence of oceans on the Earth in regards to climate, weather, and carbon dioxide are crucial to understanding what we can expect in the coming years. There is still much we don’t know, and it will take the continued effort of scientists to discover the answers. Scientists revealed that carbon dioxide levels are as high as 3 million years ago. This fact means our carbon levels are increasing 100 times faster than the times of the last ice age. Now we must question the role the oceans may have played in Earth’s history or will play in the future.