Sediments in Lake Malawi are helping us to understand ancient climates

Lake Malawi. Photo: Shutterstock

Understanding climate change requires more than just looking at recorded data from the last 150 years. That data shows us that yes, the planet is warming and the climate is changing, but the more we understand about ancient climates and how the planet’s climate has changed, the better we can understand what is happening now. This will give us tools to understand how we might mitigate, prevent, or even reverse those changes.

One researcher, assistant professor Melissa Berke from the University of Notre Dame, is trying to do exactly that, and has been doing research at Lake Malawi in southeast Africa. She has been studying layers of sediment, collected in the lake over millions of years, to see how the climate has changed.

Sediment layers can tell us a lot about what the climate was like when the layers were put down, and these have shown her something rather startling: contrary to the long-held savanna hypothesis, Africa has been getting wetter over the last 1.3 million years, not drier.

This doesn’t necessarily mean that the savannah hypothesis is wrong, just incomplete. The savannah hypothesis data has come from northern Africa, which is noticeably different than the southern part of the continent. Africa is a huge continent featuring a number of different ecosystems and climates. It’s not just possible but probable that different parts of Africa would see different kinds of climate change over millions of years.

Berke is currently working on research focused on the Indian Ocean, looking at sediments up to 7 million years old, which can give us an understanding of the global climate on an even longer timeline. The planet has had hotter periods than the one we’re entering, but it was a very different place then. Having a better understanding of ancient climates could give us insight into how the planet’s current climate might change over the next century or so.