New research by Birkbeck academic shows how rocks can rebalance our climate
New research shows how rocks may help the earth recover from CO2 emissions.
Dr Philip Pogge von Strandmann, a new appointment to Birkbeck’s Department of Earth and Planetary Sciences, has led a research team at Oxford University’s Department of Earth Sciences looking at a global warming event that took place 93 million years ago. Their study, published in the journal Nature Geoscience, suggests that the Earth can recover from high carbon dioxide emissions but that the process takes around 300,000 years after emissions fade.
The project studied rocks from locations at Beachy Head, near Eastbourne, and South Ferriby, North Lincolnshire, to investigate how chemical weathering of rocks ‘rebalanced’ the climate. In chemical weathering CO2 from the atmosphere, dissolved in rainwater, reacts with rocks such as basalt or granite, so that this atmospheric carbon then flows into the oceans, where a large proportion is ‘trapped’ in the bodies of marine organisms.
Photograph shows 'black band' of shale indicating the mass extinction in the record from South Ferriby.
What chemical weathering can reveal
The team tested the idea that, as CO2 warms the planet, the reactions involved in chemical weathering speed up, causing more CO2 to be ‘locked away’, until, if CO2 emissions decline, the climate begins to cool again. They looked at evidence from the ‘Ocean Anoxic Event 2’ in the Late Cretaceous when volcanic activity spewed around 10 giga-tonnes of CO2 into the atmosphere every year for over 10,000 years. During this period chemical weathering increased, locking away more CO2 as the world warmed and enabling the Earth to stabilise to a cooler climate within 300,000 years, up to four times faster than previously thought.
Reconstructing a record of past chemical weathering is challenging because of how plants and animals take carbon out of the environment. To get around this the team used a recently-developed technique involving studying lithium isotopes in marine limestone (this lithium could only come from weathering and is not changed by biological organisms).
Dr Philip Pogge von Strandmann commented: ‘Our research is good news, showing that the Earth can recover up to four times faster than we thought from CO2 emissions, but even if we stopped all emissions today this recovery would still take hundreds of thousands of years. We have to start doing something soon to remove CO2 from the atmosphere if we don’t want to see a repeat of the kind of mass extinctions that global warming has triggered in the past.’
The research was supported by the UK’s National Environment Research Council (NERC).