Back To The Pliocene - Re. Atmospheric CO2, We've Gone Back At Least 2.6 Million Years In Time

[hatrack]

Trees growing near the South Pole, sea levels 20 metres higher than now, and global temperatures 3C-4C warmer. That is the world scientists are uncovering as they look back in time to when the planet last had as much carbon dioxide in the atmosphere as it does today. Using sedimentary records and plant fossils, researchers have found that temperatures near the South Pole were about 20C higher than now in the Pliocene epoch, from 5.3m to 2.6m years ago.

Many scientists use sophisticated computer models to predict the impacts of human-caused climate change, but looking back in time for real-world examples can give new insights.

The Pliocene was a “proper analogy” and offered important lessons about the road ahead, said Martin Siegert, a geophysicist and climate-change scientist at Imperial College London. “The headline news is the temperatures are 3-4C higher and sea levels are 15-20 metres higher than they are today. The indication is that there is no Greenland ice sheet any more, no West Antarctic ice sheet and big chunks of East Antarctic [ice sheet] taken,” he said.

Fossil fuel burning was pumping CO2 into the atmosphere extremely rapidly, he said, though it took time for the atmosphere and oceans to respond fully. “If you put your oven on at home and set it to 200C the temperature does not get to that immediately, it takes a bit of time, and it is the same with climate,” Siegert said, at a Royal Meteorological Society meeting on the climate of the Pliocene.

He added that global temperature had already risen by 1C since the industrial revolution, when CO2 levels were 280 parts per million (ppm). CO2 was now at 412ppm and rising, suggesting the planet would be locked into rises of 3C-4C in the next few centuries. Ice melting, he said, took even longer and the huge sea level rises indicated by the Pliocene evidence would probably take a few millennia to come about.

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https://www.theguardian.com/science/2019/apr/03/south-pole-tree-fossils-indicate-impact-of-climate-change?CMP=share_btn_tw

[NNadir]

1. Don't worry, be happy...

I heard that in Hawaii, 500 acres of a former sugar plantation is about to be covered with semiconductor solar cells.

Personally, I think that sugar bagasse, a waste product, offers an opportunity to remove carbon dioxide from the atmosphere, and many scientific papers along this line have been written, but I'm stupid and just didn't get how all these solar schemes have saved the world.

[OKIsItJustMe]

2. More CO2 than ever before in 3 million years, shows unprecedented computer simulation

https://www.pik-potsdam.de/news/press-releases/more-co2-than-ever-before-in-3-million-years-shows-unprecedented-computer-simulation

More CO2 than ever before in 3 million years, shows unprecedented computer simulation

03/04/2019 - CO2 greenhouse gas amounts in the atmosphere are likely higher today than ever before in the past 3 million years. For the first time, a team of scientists succeeded to do a computer simulation that fits ocean floor sediment data of climate evolution over this period of time. Ice age onset, hence the start of the glacial cycles from cold to warm and back, the study reveals, was mainly triggered by a decrease of CO2-levels. Yet today, it is the increase of greenhouse gases due to the burning of fossil fuels that is fundamentally changing our planet, the analysis further confirms. Global mean temperatures never exceeded the preindustrial levels by more than 2 degrees Celsius in the past 3 million years, the study shows – while current climate policy inaction, if continued, would exceed the 2 degrees limit already in the next 50 years.

“We know from the analysis of sediments on the bottom of our seas about past ocean temperatures and ice volumes, but so far the role of CO2 changes in shaping the glacial cycles has not been fully understood,” says Matteo Willeit of the Potsdam Institute for Climate Impact Research, lead author of the study now published in Science Advances. “It is a breakthrough that we can now show in computer simulations that changes in CO2 levels were a main driver of the ice ages, together with variations of how the Earth’s orbits around the sun, the so-called Milankovitch cycles. These are actually not just simulations: we compared our results with the hard data from the deep sea, and they prove to be in good agreement. Our results imply a strong sensitivity of the Earth system to relatively small variations in atmospheric CO2. As fascinating as this is, it is also worrying.”

Studying Earth’s past and its natural climate variability is key to understanding possible future pathways of humanity. “It seems we’re now pushing our home planet beyond any climatic conditions experienced during the entire current geological period, the Quaternary,” says Willeit. “A period that started almost 3 million years ago and saw human civilization beginning only 11,000 years ago. So, the modern climate change we see is big, really big; even by standards of Earth history.”

Learning from Earth’s past to understand the future

Building on previous research at PIK, the researchers reproduced the main features of natural climate variability over the last few million years with an efficient numerical model – a computer simulation based on astronomical and geological data and algorithms representing the physics and chemistry of our planet. The simulation was driven only by well-known changes in the ways the Earth circles the sun, the so-called orbital cycles, and different scenarios for slowly varying boundary conditions, namely CO2 outgassing from volcanoes. The study also lookedt into changes in sediment distribution of the Earth surface, since ice sheets slide more easily on gravel than on bedrock. It has also accounted for the role of atmospheric dust, which makes the ice surface darker and thereby contributes to melting.

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https://dx.doi.org/10.1126/sciadv.aav7337