A human’s life may only last 80 years, but life on Earth has lasted for much longer. And during life’s exciting ride, our planet’s temperature has remained within a comfortable range. This is in part due to the Earth's natural temperature control system - The Rock Thermostat. This system uses rocks to regulate Earth's temperature and maintain stability.
Rocks? It may seem crazy; how in the world can inanimate boulders control the Earth’s temperature? It all comes down to one thing, chemical weathering. We all know how carbon dioxide in our atmosphere works as a greenhouse gas to trap heat, and chemical weathering can help decrease the amount of carbon dioxide in our atmosphere. In chemical weathering, carbon dioxide reacts with rocks and is ultimately trapped on the seafloor. The chemical weathering feedback loop works like this:
Carbon dioxide is released by volcanoes (and now humans and our various endeavors).
It is then dissolved in rainwater.
It then reacts with silicone-rich continental rocks (the actual process of chemical weathering refers to).
Finally, the runoff flows into the ocean, and the carbon dioxide is trapped in the seafloor.
And voila! The amount of carbon dioxide in our atmosphere decreases and the Earth gradually cools.
According to our previous theories based on this process, as temperatures rise, the rate of chemical weathering should also increase, resulting in a feedback loop that keeps the long-term temperature in a specific range.
But it turns out that this mechanism is a lot more temperamental than we originally expected. It takes a huge increase in temperature for a significant change in rate to occur, and it relies on specific weather conditions to work, something that is increasingly inconsistent in today’s climate. In short, the increase in the rate at which chemical weathering occurs is not equal to the rate at which the Earth is heating up, meaning while the Earth may have this natural thermostat, its effectiveness is questionable.
An example of this system's effectiveness (or lack of) can be seen in past changes in climate. 183 million years ago, when a major extinction event of the dinosaurs happened, temperatures went up. We would expect the rate of chemical weathering to increase greatly to compensate for the higher temperatures. However, based on geological records, the rate of chemical weathering’s correlation with temperature was lower than expected.
After further investigation, it turns out that the relationship between carbon dioxide, temperature, ocean chemistry, and chemical weathering is weaker than formerly hypothesized. Scientists initially thought that for the rate of weathering to double, the temperature would have to increase by 7C while new findings show that it takes triple that, an increase of 24C.
Despite the questionable effectiveness of chemical weathering, the Earth was still able to cool down 183 million years ago. One possible explanation for the reason the Earth was still able to cool down may have been the formation of the Tibetan Plateau. Its steep sides may have been the real cause for increased rates of chemical weathering (rather than the heating up of the Earth) which caused the cooling of Earth to its current temperature.
So, rather than the increased rate of chemical weathering and cooling of Earth being attributed to the higher temperatures, it was possibly actually due to circumstantial causes.
To conclude, we cannot rely on Earth’s rock thermostat to solve our climate change crisis anytime soon. Even if chemical weathering was able to make a significant impact on the Earth’s climate, we have to remember that the process of chemical weathering is a slow one, and takes millions of years to significantly cool the planet, meaning that it will not counteract our rapid contributions to global warming in the time we need it to. The Earth's natural processes are important, but they are not enough to address the current crisis. Therefore, we must continue to work towards reducing our carbon footprint and finding sustainable solutions to our energy and environmental problems. We remain the only ones that are able to take action to ensure that our planet remains habitable for future generations.
Works Cited:
Brantley, S. L., Shaughnessy, A., Lebedeva, M. I., & Balashov, V. N. (2023). How temperature-dependent silicate weathering acts as Earth’s geological thermostat. Science, 379(6630), 382–389. https://doi.org/10.1126/science.add2922
Earle, S. (2015, September 1). 5.2 Chemical Weathering. Opentextbc.ca; BCcampus. https://opentextbc.ca/geology/chapter/5-2-chemical-weathering/
Haughney, K. (2017, August 1). FSU Research: Chemical weathering could alleviate some climate change effects. Florida State University News. https://news.fsu.edu/news/science-technology/2017/08/01/fsu-research-chemical-weathering-alleviate-climate-change-effects/
Hickey, H. (2017, May 22). Weathering of Rocks a Poor Regulator of Global Temperatures. UW News. https://www.washington.edu/news/2017/05/22/weathering-of-rocks-a-poor-regulator-of-global-temperatures/
Hilton, R. G. (2023). Earth’s persistent thermostat. Science, 379(6630), 329–330. https://doi.org/10.1126/science.adf3379