The Daily Maverick: 'South African seas up to 30m higher show a wet planet under siege'

Published 28 September 2020 in Insights

The Daily Maverick

'South African seas up to 30m higher show a wet planet under siege'

By Tiara Walters

The Daily Maverick

Published 28 September 2020

The last time atmospheric carbon dioxide matched present-day levels, Earth’s oceans were remarkably high. It’s a warning to act, ground-breaking international research on the Cape coasts reveals.

Welcome to the Pliocene – an ancient proxy for a future world in which big carbon can rewrite global temperatures and expanding oceans can swallow liveable land.

To catch a glimpse of how such a hostile planet could become a reality for modern humans, a major new analysis published by the American Geophysical Union urges us to travel several million years into the deep past. Back then, the atmosphere’s carbon dioxide needle hovered around 400 parts per million, roughly the same as today – and what’s more, these very conditions churned up sea levels many metres higher than modern oceans, the paper suggests.

As a natural pressure cooker, this epoch has intrigued climate modellers for years, but they lacked data for how the Pliocene’s motherload of CO2 fed into other big-picture drivers of potentially catastrophic change, such as melting ice caps and rising sea levels.

Supported by a $4.25-million grant from the US National Science Foundation to cover a research period of five years, an expert group of geologists, glaciologists, climatologists and crust modellers set out to help solve this puzzle. They dubbed their grant “Pliomax”, short for “Pliocene maximum sea level”.

Team Pliomax’s mission? Using the Republic of South Africa as a prime natural laboratory to see just how high sea levels can soar in a 400ppm world like ours.