Scheme: Wolfson Research Merit Awards
Organisation: University of Bristol
Dates: Aug 2011-Jul 2016
Summary: One of the most profound questions facing scientists is 'How much will the Earth's surface warm for a given increase in carbon dioxide concentrations'. This is a question that has taken on particular resonance as we pass an atmospheric CO2 concentration of 400 ppm. Climate models are powerful tools for interrogating this issue but predict a range of climate responses. Therefore, it is valuable to use the past history of our planet to test our ideas; one particularly important test is the determination of Earth’s past temperatures and comparing them to estimated CO2 concentrations. This is no easy task! Robust temperature and CO2 records preserved in ice cores extend back less than one million years, and that entire record is characterised by CO2 levels lower than they are today. To understand the climate of a warmer Earth requires records from much deeper in Earth history.
If direct records do not exist then proxy records are required - geochemical or biological signatures that directly reflect a given climate variable. Our work has been devoted to understanding and applying such proxies, and many challenges remain. We investigate them in the past but also in today’s oceans to help us understand what they are really telling us. As our understanding has increased, so has our confidence in our interpretation of the geological record, and this has yielded important but concerning insights. They suggest that the Earth’s temperature is very sensitive to carbon dioxide levels; for example, carbon dioxide levels three million years ago were less than or similar to 400 ppm, but the climate was very warm. Moreover, this warming was particularly strong at high latitudes and such polar amplification could have important consequences for the long term stability of ice sheets and permafrost. We are continually expanding our investigations, using the geological record to better understand not just how much warmer climate was but also how that affected the entire Earth system.