A suffocating temperature rise

Some 96% of all marine animal species were wiped out when Earth’s temperature rose by 10+ degrees over a short period of time. The cause is unknown – perhaps volcanic eruptions or meteor strikes – and scientists have been unsure if it was the heat or its secondary effects that made the world uninhabitable. Now a new computer simulation shows that ocean warming may have led to massive oxygen depletion, causing mass suffocation of many species.

It may come as a surprise to discover that although today’s CO emissions, temperatures and ocean levels are rising at an alarming speed, all three are at almost their lowest levels in 600 million years. Earth’s climate could be considered as being close to ‘zero’.

But we are nevertheless in a climate crisis, as never before have these three factors followed each other so closely to reach rock bottom at the same time. The central question now is what happens when things go the opposite way?

Most scientists agree that the ongoing climate change is due to a severe rise in the atmosphere’s CO2 content, which is causing temperatures to rise, making the poles melt and ocean levels rise. This will turn animals' and plants' living conditions – and so also our food sources – upside down, and will flood cities, making millions homeless.

Over the past millions of years, such CO2 , temperature and ocean level fluctuations have had repeatedly major effects on animals and plants, in some cases triggering mass destruction. Climate researchers are now focusing on periods of Earth’s history which are much like the present to get an idea of what the future of the world might be – and how things might be prevented from going so wrong again.

Temperatures could rise by 7°C

For the last almost 10,000 years, Earth’s average temperature has been very constant. But something started to happen in 1900. Over a period of only 100 years, temperatures rose by 1 degree as a result of industrial development. Over the next 100 years a rise of

another 1-2 degrees is expected. Hopefully, more accelerated temperature rises can be prevented, but the worst case scenario might see still higher temperature rises. If another seven degrees were added by 2300, the average temperature would reach 22 degrees. The temperature itself is one thing, but it is the speed of change which is most alarming. Such a rapid rise temperature rise would be almost unprecedented in Earth’s history.

Most other temperature fluctuations have happened gradually over millions of years. One exception to the rule occurred during the PETM period 56 million years ago. Temperatures rose by eight degrees over a period of 20,000 years, ending at a level of 25.5 degrees – 11 degrees warmer than now. The temperature rise was probably triggered by emissions of the methane greenhouse gas from the ocean floor, and the rising heat might have begun a self-sustaining process.

In 2019, California Institute of Technology climate researcher Tapio Schneider introduced a theory of how a temperature rise could dissolve cloud cover and so take the climate beyond a critical point. Without

SHUTTERSTOCK 70% of all vertebrates died out, including the 2m-long lystrosaurus. Heat = oxygen depletion Warm water holds less oxygen than cold. Yet the heat intensified animal metabolism, so more oxygen was required. The Equator made it More species survived near the Equator where they had already adapted to an environment of warm oxygen-poor water.

C L A U S L U N A U NORTH POLE Death at the poles More species became extinct near the poles, where animals had difficulties adapting to the warmer water.