Climatic States
Throughout time Earth has transitioned between climatic states. These states were indicative of changing greenhouse gas concentrations. The fluctuating states were most noticeable by the amount of ice present on Earth. These different states have shown the success of certain mammals while the lack thereof during other periods of time. Humans, for one, are not capable of surviving in certain states.
So What Were These States?
There are three states that Earth has cycled between:
Hothouse
Greenhouse
Icehouse
Hothouse
Analogous to Dante’s Hell, a hothouse is a state on earth where human life would not be able to sustain itself. The Hothouse occurred with carbon dioxide levels around 800ppm. In contrast, today’s concentrations are around 400ppm. There was no ice on Earth and the poles were forested much to the benefit of dinosaurs inhabiting the area (The Conversation, 2018). Humans nowadays would not be able to handle this kind of environment. Luckily, if this happens it won’t be possible for several thousands of years.
Greenhouse
Nearly 70% of the previous 2.5 billion years on Earth have consisted of a warmer time period- the Greenhouse state (EarthDate, 2017). This state demonstrates higher levels of carbon dioxide, water, and methane concentrations (EarthDate, 2017). Sea temperatures are higher in the poles for an average of 0℃. This is a moderate time to exist that is quite warm and allows many species of life to not just survive but thrive.
Icehouse
We have been living in an Icehouse state which has been a major factor in enabling human life (EarthDate, 2017). The Icehouse state exhibits the presence of ice at the poles and in the form of ice sheets, a decrease in temperature in both the atmosphere and on the surface. The most intensive Icehouse experience happened during “Snowball Earth” when our planet nearly entirely froze over (EarthDate, 2017). As the name states, it was very chilly and snowy in a far greater reach than an Icehouse today.
Why Does This Matter?
There are arguments that it is natural for our planet to increasingly trend towards a warmer state of existence as historically, Earth fluctuates between warm and cold periods. This is true, but only to a degree. These fluctuations happen on their own geophysical accord (such as through Milankovitch cycles) over hundreds of thousands of years (The Conversation, 2018). Human activity overriding geological forces is not something we should be proud of; we should be ashamed of the massive, devastating impact on these forces. Human influence primarily through the burning of fossil fuels have caused atmospheric CO2 levels to increase rapidly and beyond a normal set point for an Icehouse. This increase in atmospheric CO2 has acted like an insulator as the greenhouse gas is available to retain more heat for longer periods of time, thus contributing to feedback loops that offset planetary boundaries. While Earth cycles through different states with associated levels of atmospheric carbon dioxide, human interference has influenced the next trajectory of state for the planet. This should not surprise anyone, but it should motivate everyone to change their ways of living to support an environmentally friendly lifestyle.
Sourced Information
EarthDate. (2017). Greenhouse-Icehouse Earth. https://www.earthdate.org/greenhouse%E2%80%93icehouse-earth
The Conversation. (2018). Hothouse Earth: our planet has been here before- here’s what it looked like. https://theconversation.com/hothouse-earth-our-planet-has-been-here-before-heres-what-it-looked-like-101413#:~:text=The%20last%20time%20the%20Earth,Period%E2%80%9D%20of%20the%20Pliocene%20Epoch
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