Tierney and others. The.
a The study was published in PNASUniversity of Arizona professor Jessica Tierney and colleagues have created the most comprehensive global map of carbon-induced warming that occurred during the Paleocene-Eocene Thermal Maximum (PETM) 56 million years ago.
Although there are some similarities in the current PETM period with warming, the new work has some unexpected consequences – the climate’s response to carbon dioxide.2 It was twice stronger than the current best estimate by the Intergovernmental Panel on Climate Change (IPCC). But changes in precipitation patterns and increased warming at the poles remarkably correspond to recent trends, although in an entirely different world at the time.
different world
The warming of the Petam period was caused by rapid geological release Who2in the first place magma spasms In the crust where Iceland is now. Magma invaded the oil-rich sediments in the North Atlantic, bringing carbon dioxide to a boil2 and methane. It really required a rise in CO22 Climate and tens of thousands of years pushed it, prompting some deep sea creatures And Some tropical plants for destruction. Mammals evolved youngAnd there were a large number of them Migrations Across continents, creatures like crocodiles, hippopotamuses and Palm trees They all thrive within 500 miles of the North Pole Antarctica There was no snow.
As our climate warms, scientists Looking Increasingly To Past Times To visions, but temperature uncertainty, CO2 Phases and exact timing of transitions – Previous work on PETM had an uncertain temperature of 8-10°C. Now Tierney’s team has reduced this uncertainty range to just 2.4 °C, showing that PETM warmed by 5.6 °C, compared to the previous estimate of ~5 °C.
“We were able to lower that estimate compared to previous work,” Tierney said.
The researchers also calculated carbon dioxide2 Levels before and after the BTM period were derived from boron isotopes measured in fossil plankton shells. They found CO2 It was 1,120ppm just before the PETM period, and it rose to 2020ppm at its peak. In comparison, pre-industrial CO2 I was 280ppmWe are here now 418ppm. The team was able to use the new temperature and carbon dioxide2 Values to calculate how much the planet is warming in response to the doubling of carbon dioxide2 values, or “equilibrium sensitivity to climate” for PETM.
hypersensitivity
The IPCC’s best estimate of the climate sensitivity of our time is 3°C, but that comes with a significant degree of uncertainty – it could be anything in between. 2° to 5°CBecause of our imperfect knowledge Feedback in the Earth system. The higher the sensitivity, the more we warm up to a certain amount of emissions. The Tierney study’s PETM sensitivity was 6.5 °C – twice the IPCC’s best estimate.
Tierney told me that the large number “wasn’t too surprising” because previous search Earth’s specific response to carbon dioxide2 Stronger at higher carbon dioxide2 Earth’s past states. Our climate sensitivity wouldn’t be that high: “We don’t expect we’ll have a 6.5°C climate sensitivity tomorrow,” Tierney explained.
However, if we keep raising CO2, their paper suggests2 levels, it will result in a temperature response to that CO2 More “We can expect some level of climate sensitivity in the future, especially if we release more greenhouse gases,” Tierney said.
Climate mapping through “data ingestion”.
A new, more accurate picture emerges of how Tierney’s team has dealt with a perennial problem for geologists: we don’t have data for every place on the planet. PETM’s geological data is limited to sites where sediments from that period are preserved and accessible. Any conclusions about global Climate must be measured from these scattered data points.
“It’s a really difficult problem,” Tierney noted. “If you want to understand what’s going on there, it’s very difficult to do that from geographical data alone.” So Tierney and his colleagues borrowed a technique from weather forecasting. “What people do in the weather is they run a weather model, and as the day goes on, they take wind and temperature measurements, and then they integrate that into their model … and then run the model again to improve the forecast,” Tierney said.
Instead of using a thermometer, his team used temperature readings from microbial and plankton remains preserved in 56 million-year-old sediments. Instead of a climate model, they used a climate model of Eocene geology and ice-free climates to simulate the climate before, and at, the peak of PETM warming. They ran the model several times, changing the CO2 Locations and orbital configuration of the Earth due to its uncertainty. They then used the microbial and plankton data to choose the simulation that best fit the data.
“The idea is to take advantage of the fact that the model simulations are spatially complete. But they are models, so we don’t know if they are correct. The data knows what happened, but it’s not complete,” Tierney explained. “So by mixing it up, we get the best of both worlds.”
To see how their compound product matched reality, they checked it against independent data obtained from pollen and leaves, as well as from sites not included in the compounding process. “They fit really well, which is fairly comfortable,” Tierney said.
“The novelty of this study is that it uses a climate model to work out precisely which climate condition the data best fit before and after the PETM period, providing a better estimate of mean global temperature change and patterns of climate change worldwide.” Dr Tom Dunkley-Jones from the University of Birmingham, who was not part of the study, said.