Above, Joe Rogan raises a point of contention about climate change, pretending to have read about a study in The Washington Post that, he says, raises questions about human caused climate change.
In the video, Dr Michael Mann follows up and gently points out that if Rogan had indeed read the article, (on a study that Mann himself had reviewed) – then perhaps Rogan’s reading comprehension needs remediation.
An ambitious effort to understand the Earth’s climate over the past 485 million years has revealed a history of wild shifts and far hotter temperatures than scientists previously realized — offering a reminder of how much change the planet has already endured and a warning about the unprecedented rate of warming caused by humans.
The timeline, published Thursday in the journal Science, is the most rigorous reconstruction of Earth’s past temperatures ever produced, the authors say. Created by combining more than 150,000 pieces of fossil evidence with state-of-the-art climate models, it shows the intimate link between carbon dioxide and global temperatures and reveals that the world was in a much warmer state for most of the history of complex animal life.
At its hottest, the study suggests, the Earth’s average temperature reached 96.8 degrees Fahrenheit (36 degrees Celsius) — far higher than the historic 58.96 F (14.98 C) the planet hit last year.
The revelations about Earth’s scorching past are further reason for concern about modern climate change, said Emily Judd, a researcher at University of Arizona and the Smithsonian specializing in ancient climates and the lead author of the study. The timeline illustrates how swift and dramatic temperature shifts were associated with many of the world’s worst moments — including a mass extinction that wiped out roughly 90 percent of all species and the asteroid strike that killed the dinosaurs.
“We know that these catastrophic events … shift the landscape of what life looks like,” Judd said. “When the environment warms that fast, animals and plants can’t keep pace with it.”
At no point in the nearly half-billion years that Judd and her colleagues analyzed did the Earth change as fast as it is changing now, she added:
“In the same way as a massive asteroid hitting the Earth, what we’re doing now is unprecedented.”
The timeline encompasses almost all of the Phanerozoic — the geologic eon that began with the emergence of multicellular, non-microscopic organisms and continues today.
It portrays a global climate that was more dynamic and extreme than researchers had imagined, said Jess Tierney, a climate scientist at the University of Arizona and co-author of the study. Compared with graphs based solely on climate models, which tend to depict smaller and slower swings in temperatures, the new timeline is full of sudden spikes and abrupt shifts.
But, in keeping with decades of past research on climate, the chart hews closely to estimates of carbon dioxide in the atmosphere, with temperatures rising in proportion to concentrations of the heat-trapping gas.
“Carbon dioxide is really that master dial,” Tierney said. “That’s an important message … in terms of understanding why emissions from fossil fuels are a problem today.”
At the timeline’s start, some 485 million years ago, Earth was in what is known as a hothouse climate, with no and average temperatures above 86 F (30 C). The oceans teemed with mollusks and arthropods, and the very first plants were just beginning to get a toehold on the land.
Temperatures began to slowly decline over the next 30 million years, as atmospheric carbon dioxide was pulled from the air, before plummeting into what scientists call a coldhouse state around 444 million years ago. Ice sheets spread across the poles and global temperatures dropped more than 18 degrees Fahrenheit (10 degrees Celsius). This rapid cooling is thought to have triggered the first of Earth’s “big five” mass extinctions — some 85 percent of marine species disappeared as sea levels fell and the chemistry of the oceans changed.
An even more dramatic shift occurred at the end of the Permian period, about 251 million years ago. Massive volcanic eruptions unleashed billions of tons of carbon dioxide into the atmosphere, causing the planet’s temperature to shoot up by about 18 F (10 C) in roughly 50,000 years. Acid rain fell across the continents; marine ecosystems collapsed as the oceans became boiling hot and depleted of oxygen.
“We know it to be the worst extinction in the Phanerozoic,” Tierney said. “By analogy, we should be worried about human warming because it’s so fast. We’re changing Earth’s temperature at a rate that exceeds anything we know about.”
The study also makes clear that the conditions humans are accustomed to are quite different from those that have dominated our planet’s history. For most of the Phanerozoic, the research suggests, average temperatures have exceeded 71.6 F (22 C), with little or no ice at the poles. Coldhouse climates — including our current one — prevailed just 13 percent of the time.
This is one of the more sobering revelations of the research, Judd said. Life on Earth has endured climates far hotter than the one people are now creating through planet-warming emissions. But humans evolved during the coldest epoch of the Phanerozoic, when global average temperatures were as low as 51.8 F (11 C).
Without rapid action to curb greenhouse gas emissions, scientists say, global temperatures could reach nearly 62.6 F (17 C) by the end of the century — a level not seen in the timeline since the Miocene epoch, more than 5 million years ago.
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PBS Terra also did a deep dive on the study and the graph.