55 million years ago, the temperature on our planet rose sharply. This has become one of the most dramatic examples of climate change. The world could never be the same.
In the late 1980s, many governments began to look closely at the issue of climate change. The mud at the bottom of the ocean off the coast of Antarctica was a surprise. It turned out that the Earth had already suffered global warming before.
What is thermal maximum
About 55 million years ago, global temperatures rose sharply. As now, this has led to an increase in ocean levels and acidity, as well as the extinction of many species.
Not surprisingly, scientists view this event, known as the Late Paleocene Thermal Maximum (PETM), as a potential treasure trove of useful information to help understand current climate change.
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We now know that this was the fastest and most dramatic case of climate change in the history of the Earth. Its causes are still controversial, but scientists draw eerie parallels with modern conditions. But it is known for sure: the effect of such a change had far-reaching consequences. It is possible that these events changed the course of life on the planet.
What are the isotopes of oxygen and carbon talking about?
Geologists who studied the said Antarctic deposits in 1980 published their findings in 1991. They reported that the presence of tiny planktonic fossils in the mud indicated rapid changes in temperature.
More precisely, these were oxygen isotopes "locked" in these shells. About 55 million years ago, the amount of heavy oxygen-18 in shells increased significantly relative to light oxygen-16.
The abundance of oxygen-18 is a sure sign that conditions were warmer. Water evaporates more easily at higher temperatures, and oxygen-16 with it. This means that the warm water contained more oxygen-18, and the plankton living in it had more of this element in their shell.
These findings turned out to be useful for another reason. They pointed out why the ocean temperature began to rise. This was due to the carbon in the water.
Like oxygen, carbon exists in different isotopic forms. While the plankton was enriched with oxygen-18, it also had an increase in carbon-12 compared to carbon-13. This means that its supply has increased in the oceans.
The greenhouse effect millions of years ago
This usually occurs after the massive release of carbon-rich greenhouse gases - carbon dioxide or methane - into the atmosphere. In other words, the thermal maximum was caused by the greenhouse effect, just like modern climate change. But current global warming is not just a repeat of a thermal maximum. 55 million years ago, the Earth was completely different.
One of the biggest problems today is that Antarctic ice sheets are shrinking due to climate change. 55 million years ago, this was not a problem, as ice did not exist then. Even before the PETM, global temperatures were several degrees higher than they are now.
How quickly the climate changed
Some researchers believe that the rate of climate change at that time also differs from the current one. The reason for this opinion was a controversial study published in 2013.
Scientists have studied additional finds that formed on the ocean floor 55 million years ago, but this time in the northwestern Atlantic Ocean. They found streaks of mud that were thought to have formed in annual cycles. When they looked at the amount of oxygen and carbon isotopes associated with PETM, they found they were only found in 13 bands. This means that temperature changes have occurred in just 13 years.
This does not yet prove that the thermal maximum increased and then decreased in a little over a decade. All researchers agree that an unusual rise in temperature, at least 5 degrees above average, lasts about 170 thousand years. But this means that the global temperature during PETM has changed by 5 degrees over 13 years. In modern times, global temperatures have increased by 1 degree compared to the late 19th century.
Possible Causes of Thermal High
If climate change millions of years ago really happened so quickly, some event must have happened that would have caused such a warming. To trigger such a rapid rise in global temperature, the atmosphere must fill with greenhouse gases in record time.
Perhaps the reason lies in the release of gases from the melting of a huge comet rich in carbon, which flew too close to Earth. Climate change today is not that dramatic. But it is important to emphasize: many researchers strongly deny that such global changes have occurred in just 13 years.
Disadvantages of the 13-year climate change hypothesis
This idea has many disadvantages. Most importantly, the ocean is physically incapable of heating up so quickly. The world's oceans contain a huge amount of water, and it takes enough time to warm it up. Even if there was a massive release of CO2 into the Earth's atmosphere, the oceans simply would not have had time to warm up in 13 years. The atmosphere heats up relatively quickly, but it will take millennia for the same to happen to the oceans.
Other researchers have suggested that the 13 stripes on the rock should mean centuries, rather than individual years, if they are authentic. It is possible that they were the result of a drilling process that scientists used to extract mud.
Most researchers are confident that the PETM warming did take place for a long time, but how long it lasted remains to be seen. A 2011 estimate suggests that carbon has been released into the atmosphere over 20,000 years.
This slow release is very different from the modern one. This could mean that the greenhouse gases were caused by volcanic activity.
What do the finds in the soil say?
Another study was conducted in 2014. Scientists have studied carbon isotopes that have been preserved in soil formed 55 million years ago in what is now America. If oceanic precipitation indicates PETM conditions in the water, then the soil can clarify the atmospheric situation that is responsible for the rapid climate change.
The increased amount of carbon-12 mentioned earlier has also been noted in the soil. In this case, all indications are that carbon has been released into the atmosphere for 1500 years. It looks more like modern changes. Scientists estimate that approximately 1 billion tons of carbon is released into the atmosphere each year. The current level of emissions is 9.5 billion tons per year. In this light, PETM looks like a more reasonable model for today's climate change.
