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SUNDAY SCIENCE: PREHISTORIC EARTH WAS VERY HOT. THAT OFFERS CLUES
ABOUT FUTURE EARTH.  
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Raymond Zhong
September 19, 2024
New York Times
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_ At times during the past half-billion years, carbon dioxide warmed
our planet more than previously thought, according to a new
reconstruction of Earth’s deep past. _

An artist’s impression of life on Earth during the Carboniferous
Period, 300 million years ago., Felix Images/Alamy

 

Over the past 500 million years, our planet has gone from hot to cold
to hot again. The oceans have risen and fallen. Ice caps have melted
and reformed. It is a story with several acts, and sunlight and carbon
dioxide are the main players.

The better scientists can reconstruct the climate’s story so far,
the better they might predict how it will play out in the future, now
that there’s a major new character on the scene: humans.

In a study published Thursday
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researchers presents a sweeping new account of this history, one that
combines geological evidence with predictions from computer models of
the global climate.

Their picture of Earth’s deep past is a much toastier one than other
studies have painted, particularly during periods when carbon dioxide
levels were high.

With all the carbon dioxide that humans are now pumping into the
atmosphere by burning fossil fuels, the new findings suggest that
temperatures could rise more than expected over the coming
millenniums, said the study’s lead author, Emily J. Judd, a climate
research analyst at the National Institute of Water and Atmospheric
Research in New Zealand.

“We’re not saying it’s going to heat up immediately,” Dr. Judd
said. But “in the long term, the planet will likely get warmer than
we previously thought.”

In the meantime, she said, humans are adding carbon dioxide to the
skies so quickly, nearly 40 billion tons per year, that it will have
much more catastrophic effects than the gradual, geologic shifts of
Earth’s past.

“When carbon dioxide and temperatures change rapidly, that’s when
everything on the planet just can’t keep pace,” Dr. Judd said.
“The environment is changing at a rate that’s too fast for
organisms to keep up with. And that’s when we experience mass
extinctions.”

Other researchers who weren’t involved in the study, which was
published in the journal Science
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novel methods. “It’s very innovative, and probably the way to go
in the future,” said Christopher Scotese, a geologist at
Northwestern University.

Even so, Dr. Scotese questioned whether the researchers’ hotter
account of prehistoric Earth squared with other evidence about what
the planet was like back then. The study suggests the world was
intolerably hot at certain times when life seemed to be flourishing,
he said. And it implies the planet was too warm for polar ice sheets
to grow at times when such ice apparently existed.

The past 500 million years were an eventful time for Earth. Complex
life arose. The continents broke apart. Geological processes heaved
carbon dioxide into the atmosphere, then drew it down again, causing
the climate to lurch between what scientists call greenhouse
conditions and icehouse conditions.

During this period, according to Dr. Judd and her colleagues, the
average temperature at Earth’s surface ran as cool as 52 degrees
Fahrenheit, or 11 Celsius, and as hot as 97 degrees Fahrenheit, with
plenty of ups and downs in between. The most recent “hothouse”
period was around 56 million years ago, when palm trees and alligators
thrived in the Arctic Circle.

After that, temperatures largely dropped until industrial-age
emissions of greenhouse gases put them on a rapid upswing a century
and a half ago. Today, the globe’s average annual temperature sits
at about 59 degrees Fahrenheit and climbing.

To piece together how we got here, Dr. Judd and her colleagues first
combed through previous research to compile over 150,000 pieces of
data [[link removed]], entombed in
fossils, about ancient ocean temperatures.

 

The shells and other body parts of sea creatures record invaluable
information about the ocean’s changing chemistry. But scattered
fossils only give us snapshots of what was going on worldwide.

“It’s like you have five or six pieces of a 1,000-piece jigsaw
puzzle,” Dr. Judd said. “It becomes really hard to picture what
you’re trying to put together.”

That’s why she and her colleagues then used these data points to
guide computer simulations of the prehistoric climate. They did
something akin to what meteorologists do to predict the weather: They
used models to make guesses about what the climate might have looked
like at a certain time, updated their models with fossil data, then
made better guesses.

Dr. Judd conducted the research for the study as a postdoctoral
scholar at the Smithsonian National Museum of Natural History and the
University of Arizona. Her co-authors include scientists at both of
those institutions, the University of Bristol in England and the
University of California, Davis.

Earth’s temperatures from hundreds of millions of years ago carry
grand implications for the story of animal life and evolution, said
Ethan Grossman, a professor of geology at Texas A&M University who
wasn’t involved in the study.

In a scorching climate, “you can’t have a high metabolic rate and
keep your body cool enough for the proteins to survive,” Dr.
Grossman said. That could have delayed the emergence of advanced
predators, he said. And, perhaps, humans too.

Raymond Zhong [[link removed]] reports on
climate and environmental issues for The Times.

EPA Scientists Said They Were Pressured to Downplay Harms From
Chemicals. A Watchdog Found They Were Retaliated Against.
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Sharon Lerner
ProPublica
Three reports issued by the agency’s inspector general detailed
personal attacks suffered by the scientists — including being called
“stupid,” “piranhas” and “pot-stirrers” and called on the
EPA to take “appropriate corrective action” in response.
September 18, 2024

* Science
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* Climate Change
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