From NSF and the 66 million year old mud department comes yet another hockey stick making proxy. So far, the reliability of proxies has been questionable at best, and it seems to me they found exactly what they expected to find. They are using climate models to estimate lead/lag times, so the obvious question is, what models and how good are they? They also don’t seem to have an SI with data that I was able to find on the journal page, so verifying the work might be difficult, if not impossible. Here’s a graphic showing the Paleocene–Eocene Thermal Maximum (PETM) for reference:
Humans responsible for carbon release 10 times faster than any event since age of dinosaurs
The earliest measurements of Earth’s climate using thermometers and other tools start in the 1850s.
To look further back in time, scientists investigate air bubbles trapped in ice cores, expanding the scope of climate records to nearly a million years. But to study Earth’s history over millions of years, researchers examine the chemical and biological signatures in deep-sea sediments.
New research published today in the journalNature Geoscience by geoscientist Richard Zeebe of the University of Hawai’i at Manoa and colleagues looks at changes in Earth’s temperature and atmospheric carbon dioxide (CO2) since the end of the age of the dinosaurs. The evidence is in sediment cores retrieved from beneath the seafloor by geologists working aboard the ocean drillship JOIDES Resolution.
“In studying one of the most dramatic episodes of global change since the dinosaurs, the researchers show that we are currently in uncharted territory in the rate carbon is being released into the atmosphere and oceans,” said Candace Major, program director in the National Science Foundation (NSF) Division of Ocean Sciences, which funded the research.
The findings suggest that humans are responsible for releasing carbon about 10 times faster than during any time in the past 66 million years.
The research team developed a new approach and was able to determine the duration of the onset of an important past climate event, the Paleocene-Eocene Thermal Maximum (PETM), 56 million years ago.
“As far as we know, the PETM had the largest carbon release during the past 66 million years,” Zeebe said.
Zeebe and co-authors Andy Ridgwell, of the University of Bristol and University of California, and James Zachos, of the University of California, combined analyses of chemical properties of sediment cores dating back to the PETM with numerical simulations of Earth’s climate and carbon cycle.
The new method allowed them to extract rates of change from a sediment record.
Applied to the PETM, they calculated how fast the carbon was released, how fast Earth’s surface warmed, and what constrained the time scale of the onset, which was across 4,000 years.
The rate of carbon release during the PETM was much smaller than the current input of carbon to the atmosphere from human activities.
Carbon release rates from human sources reached a record high in 2014 of about 37 billion metric tons of CO2. The researchers estimated that the maximum sustained carbon release rate during the PETM was less than four billion metric tons of CO2 per year — about one-tenth the current rate.
“Because our carbon release rate is unprecedented over such a long time period in Earth’s history, it also means that we have effectively entered a ‘no-analogue’ state,” said Zeebe. “This represents a big challenge for projecting future climate change because we have no good comparison from the past.”
Whereas large climate transitions in the past may have been relatively smooth, there is no guarantee for the future, the scientists said. The climate system is non-linear, which means that its response to inputs, such as CO2 emissions, is a complex process involving multiple components.
“If you kick a system very fast, it usually responds differently than if you nudge it slowly but steadily,” Zeebe said. “It is likely that future disruptions of ecosystems will exceed the relatively limited extinctions observed at the PETM.”
The PETM suggests that the consequences of our massive burning of fossil fuels will have much longer-lasting effects, said Zeebe.
“Everyone is focused on what happens by 2100, but that’s only two generations from today,” he said. “It’s very clear that over a longer time scale there will be much bigger changes.”
The scientists are continuing their work on the PETM to study other aspects of the event — for example, determining how severe ocean acidification was during that time and what effect it had on calcifying organisms in the ocean. The results will provide insights about what to expect in the future as Earth’s climate likely continues to warm and oceans keep acidifying.
Anthropogenic carbon release rate unprecedented during the past 66 million years
Richard E. Zeebe, Andy Ridgwell & James C. Zachos
Carbon release rates from anthropogenic sources reached a record high of ~10 Pg C yr−1 in 2014. Geologic analogues from past transient climate changes could provide invaluable constraints on the response of the climate system to such perturbations, but only if the associated carbon release rates can be reliably reconstructed. The Palaeocene–Eocene Thermal Maximum (PETM) is known at present to have the highest carbon release rates of the past 66 million years, but robust estimates of the initial rate and onset duration are hindered by uncertainties in age models. Here we introduce a new method to extract rates of change from a sedimentary record based on the relative timing of climate and carbon cycle changes, without the need for an age model. We apply this method to stable carbon and oxygen isotope records from the New Jersey shelf using time-series analysis and carbon cycle–climate modelling. We calculate that the initial carbon release during the onset of the PETM occurred over at least 4,000 years. This constrains the maximum sustained PETM carbon release rate to less than 1.1 Pg C yr−1. We conclude that, given currently available records, the present anthropogenic carbon release rate is unprecedented during the past 66 million years. We suggest that such a ‘no-analogue’ state represents a fundamental challenge in constraining future climate projections. Also, future ecosystem disruptions are likely to exceed the relatively limited extinctions observed at the PETM.