The Global Temperature Cycle: Are humans really causing global warming?

Relative to the rest of Earth’s history, the climate at the moment  is pretty cold as Earth is just coming out of an ice age. So over time the gradual increase in temperature is quite normal. The Earth’s climate has undergone these ups and downs in global temperature throughout its entire lifetime with different species flourishing at different times. But even with these ups and downs the Earth’s temperature has been pretty stable and consistently habitable when compared to Venus or Mars.

So how does Earth maintain this consistent habitability?

It’s all about the exchange of elements and molecules! And this is what I learnt last term in the geochemistry module.

CO2 is important: Too much in the atmosphere and Earth’s gets too warm (like Venus) and not enough in the atmosphere and it freezes (like Mars). Earth is like the ‘Goldilocks planet’ not too hot, not too cold, but just right

How to maintain CO2 (a very basic model): Earth produces a lot of CO2, from respiration, volcanic emissions, dissolving limestone in the ocean etc. You’d think the latter was of least importance, but really it is the crux of the matter – limestone (CaCO3) is where the Earth stores most of the CO2 so as not to have it catching the sun’s rays in the atmosphere and warming the Earth up. As global temperatures increase more weathering occurs, shaving off bits of mountains and sending more elements, such as Calcium into the oceans. If there is more Calcium (Ca) in the oceans the Earth can make more Limestone (CaCO3) and thus remove more CO2 from the atmosphere which in turn decreases global temperatures. Et voila: a perfect self-sustaining global temperature cycle (which happens much the same the other way around too).
Obviously lots of other things factor into this cycle as well such as photosynthesis of trees and algae, ocean pH, how many mountains there are, the changes in shape of the orbital path the Earth takes around the sun, how quickly the tectonic plates are moving and much more.

So the Earth is very good at dealing with CO2 when considering only natural sources – the question is; do human emissions thrust the amount of CO2 out of the manageable range? Will we spiral into a global oven complex from which there is no return?

Perhaps when we consider that normal CO2 concentration  in the atmosphere (what the Earth system strives for) is around 270ppm and the number we have today is 400ppm, there is cause for concern.

So to answer whether or not humans are causing global warming is: no we are certainly not causing it as it is a natural cycle and would be warming anyway. BUT we are in grave danger of meddling with it too much for Earth to recover and do need to think seriously of how not to further upset the preciously delicate balance of the Earth’s global temperature system.


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About Eleri

Eleri has now graduated from the University of Leicester. Hello! My name is Eleri Simpson and I'm a 4th (and final!) year geology student at the University of Leicester. The parts of my course that I love the most are: mapping, igneous and metamorphic processes, geochemistry and volcanology. Outside of learning I'm part of the First Aid society and the University concert band, where I play the clarinet. I enjoy evenings at the pub, cooking, walking in the countryside and a good cup of tea.

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4 responses to “The Global Temperature Cycle: Are humans really causing global warming?”

  1. Dan Pangburn

    An unfunded engineer discovered the two primary drivers of average global temperatures that explain the reported up and down measurements since before 1900 with 90% accuracy and provide credible estimates back to 1610.

    The science is settled, CO2 change is NOT one of the drivers.

  2. Naomi

    That was very interesting, and I have a few questions:
    Do environmentally friendly behaviours make any difference?
    eg: recycling, eating less meat, using less petrol, putting on layers not heating, turning off electrical appliances when not in use etc.
    Does this make any difference? Is there any point in it? Or is the Earth going to heat up naturally so we might as well enjoy all the things?

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