Enhanced Weathering for Climate Protection: Is It Possible To Lower Global Temperatures by Blending Crushed Rock With Arable Soil?

Our planet continues to get hotter, and the consequences have manifested worldwide. Looking back on the past, global warming can be seen as a common event in Earth's geological history.

During the Paleocene-Eocene Thermal Maximum (PETM) period around 56 million years ago, the global temperature rose by an average of 5 to 8 degrees Celsius. This is most likely due to increased volcanic activities that resulted in the release of vast amounts of carbon dioxide into the atmosphere. The high atmospheric temperature persisted for about 200,000 years.

Achieving Climatic Recovery

In 2021, Professor Philip Pogge von Strandmann from Johannes Gutenberg University Mainz (JGU) investigated the events that led to global cooling after the PETM warming of Earth. It was found that the combination of rainwater with the carbon dioxide in the atmosphere caused carbonic acid formation. This has led to enhanced rock weathering followed by calcium and magnesium release.

The rivers transported the calcium, magnesium, and carbonic acid into the oceans, forming insoluble limestone. According to Strandmann, the accelerated chemical rock weathering process due to high temperatures reduced carbon dioxide levels in the atmosphere and allowed the climate to recover.

Another global warming event occurred 16 million years after the PETM during the Middle Eocene Climatic Optimum (MECO). This time, it took longer for the climate to restabilize as the warming effect lasted for 400,000 years.

Pogge von Strandmann and his co-authors attempted to understand why the recovery was so slow during this period. They searched for answers by analyzing 40-million-year-old oceanic carbonates and comparing them to similar samples from 56 million years ago.

The team discovered that there was also intensified weathering and erosion in the MECO, just as during the PETM. However, less exposed rock was on the Earth's surface 40 million years ago. During this time, our planet was covered by a global rainforest with soil largely composed of clay minerals. Unlike rocks, clay does not weather. Even in high temperatures, the clay soil prevented rocks from being weathered in soil shielding.

Protecting the Climate Through Enhanced Chemical Weathering

Experts try to find ways to influence our present climate positively. One option is boosting the chemical weathering of rocks, which can be achieved by plowing finely crushed rocks into the fields. As the fine particles of rock rapidly erode, it would bind atmospheric carbon dioxide and enable the climate to recover.

However, weathering can result in clay formation, making the process less efficient. As Pogge von Strandmann discovered, clay retains the calcium and magnesium, which would otherwise be transported into the ocean. The carbon dioxide will continue to flow into the oceans without being able to escape back into the atmosphere.

In short, enhanced chemical weathering can be a viable approach to lowering global temperatures. However, it would first be necessary to determine the amount of clay formed during the weathering process at each potential location.