Little rock nuggets record climate

This is a non-technical summary I prepared for the following scientific manuscript:

Fischer-Femal, B. J. & Bowen, G. J. Coupled carbon and oxygen isotope model for pedogenic carbonates. Geochim. Cosmochim. Acta 294, 126–144 (2020). 10.1016/j.gca.2020.10.022


Figure 1 from the manuscript, illustrating how pedogenic carbonate (e.g., the rock nugget in the bottom center) can record climate.

In this paper, the authors show a new, promising way to predict changes in climate (like average annual rainfall and temperature) for locations around the world. They combine hundreds of measurements made by other scientists on modern soil samples. These soils are special because they contain a unique type of rock, which can be as small as a pea and as large as a grapefruit. This extraordinary rock forms when water evaporates from the soil. It’s similar to the process that happens when salt forms into tiny crystals when water evaporates. The soil rocks contain the elements carbon and oxygen (like how salt has sodium and chloride), and special forms of these elements record the average climate of where they are from. For example, a soil rock from here in Utah would record an overall hot and dry climate.

With the new approach that the authors show here, our ability to predict and understand changes in climate over past times of warming (that can tell us more about modern climate change) is greatly improved. Specifically, the authors combine carbon and oxygen measurements of soil rocks and, in doing so, this provides a more constrained estimate of what the climate is like. By doing this on modern soil samples, they can compare their results to data observed over the past ten thousand years. This process really allows them to nail down their new method. It’s kind of like reading multiple reviews before buying a new car… by combining independent reviews (or, in the authors’ case, climate recorders), you can get a better idea of what the car is like (or in the authors’ case, the climate!). Then, by test-driving it, you know if the car is good or not (or, in the authors’ case, does the method work? [answer: yes!]). Now, other researchers can use the method that the authors created to better understand climate change in the past and, potentially, the future.

Published by Courtney Wagner

Soon-to-be postdoctoral research scientist at the Smithsonian National Museum of Natural History.

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