Enlarge (credit: Aurich Lawson | Getty Images)

The Great Oxygenation Event , which occurred around 2.4 billion years ago, was one of the biggest transformations of our planet. Before it, there was practically no oxygen in the atmosphere; after, there was.

Conventionally, the rise of oxygen is seen as life triumphantly terraforming a passive planet. But we’re learning now that Earth was an active participant, and it took two more big lifts of oxygen over the succeeding 2 billion years before it reached breathable levels. So which was more responsible for oxygen’s rise on Earth: the evolution of life or the evolution of the planet? Nature or nurture? And does the same answer apply to all of the rises of oxygen in Earth’s past?

It’s a question beyond curiosity about our past, as it also affects how we might interpret signs of life on exoplanets.

Enlarge / Deployment of LSPM junction box 1. (credit: IN2P3/CNRS)

In 1962, one of the world's first underwater research laboratories and human habitats was established off the coast of Marseilles, France, at a depth of 10 meters. The Conshelf 1 project consisted of a steel structure that hosted two men for a week.

Now, more than 60 years later, another underwater laboratory is being set up not far from Marseilles, this time to study both the sea and sky. Unlike the Conshelf habitat, the Laboratoire Sous-marin Provence Méditerranée (LSPM) won't be manned by humans. Located 40 km off the coast of Toulon at a depth of 2,450 meters, it is Europe’s first remotely operated underwater laboratory.

Physics under the sea

Currently, three junction boxes capable of powering several instruments and retrieving data are at the heart of LSPM. The boxes, each measuring 6 meters long and 2 meters high, are connected to a power system on land via a 42-kilometer-long electro-optical cable. The optical portion of this cable is used to collect data from the junction boxes.

Enlarge / If this road is your only route to the outside world, it might not matter that your house didn't flood. (credit: Maurice Alcorn / EyeEm )

Climate change produces lots of risks that are difficult to predict. While it will make some events—heatwaves, droughts, extreme storms, etc.—more probable, all of those events depend heavily on year-to-year variation in the weather. So, while the odds may go up, it's impossible to know when one of these events will strike a given location.

In contrast, sea level rise seems far simpler. While there's still uncertainty about just how quickly ocean levels will rise, other aspects seem pretty predictable. Given a predicted rate of sea level rise, it's easy to tell when a site will start ending up underwater. And that sort of analysis has been done for various regions.

But having a property above water won't be much good if flooding nearby means you can't get to a hospital or grocery store when you need to or lose access to electricity or other services. It's entirely possible for rising seas to leave a property high, dry, but uninhabitable as rising seas cut connections to essential services. A group of researchers has analyzed the risk of isolation driven by sea level rise, and shows it's a major contributor to the future risks the US faces.

Enlarge / Is it natural, or is it us? (It's us.) (credit: Andriy Onufriyenko/Getty Images)

It starts as a reasonable question: If the Earth's climate changed before humans existed, how can we be so sure the current change is due to us and not something natural?

To answer that question, we need to understand what caused the natural changes of the past. Fortunately, science has a good handle on the causes of Earth’s natural climate changes going back hundreds of millions of years. Some were cyclical; others were gradual shifts or abrupt events, but none explain our changing climate today.

A zombie claim

With energy policy and elections in the news, the claim by some politicians that climate change is natural is once again bubbling up from the disinformation swamp. So I asked some scientists a very unscientific question: What would they buy if they had a dollar for every time they heard it?

Enlarge / A slice through a crystal of Feldspar (gray, center of view), a key mineral in the weathering process. (credit: Chmee2/Wikimedia CC-by-SA)

Scientists have understood for years that silicate minerals react with CO ₂ and water to remove CO ₂ from the atmosphere, acting as a thermostat that kept Earth’s climate broadly stable over billions of years. But how sensitive is that thermostat? To find out, scientists need to scale up lab measurements to fit the real world, but it has been impossible to reconcile the lab work with the real-world measurements made in soils and rivers.

This gap in our understanding has hampered efforts to model Earth’s long-term carbon cycle and climate, making it hard to predict exactly how effective silicate weathering, both natural and artificial, would be at removing CO ₂ from our atmosphere.

In a paper in the journal Science , professor Susan Brantley and her team from Penn State University have found a way to quantify silicate weathering’s response to temperature consistently at all scales, from lab measurements and real-world measurements in landscapes to the whole world. In doing so, they have identified the kind of landscape that has the most influence on Earth’s thermostat.

Enlarge (credit: Victor Leshyk)

The end-Triassic extinction, which happened 201 million years ago, was Earth’s third most severe extinction event since the dawn of animal life. Like today, CO ₂ rise and global warming were present, but the similarities don’t end there. As with today, it was a time of wildfires, deforestation, downpours, erosion, ocean acidification, marine dead zones, vanishing coral reefs, sea-level rise, and even insect plagues. There was also pollution by mercury, sulfur dioxide, halocarbons, and methane —and possibly even a damaged ozone layer.

“Something very violent occurred 201 million years ago, with great similarity in terms of CO ₂ with what we see is happening now,” said Dr. Manfredo Capriolo of the University of Oslo. That would seem to make it a good model to understand what’s going on now. But there are glaring differences—most notably the lack of humans.

Instead of the human pollution of today, the end-Triassic saw massive volcanic eruptions that emitted prodigious amounts of greenhouse gases and pollutants. There were other differences as well. During the Triassic, there was just one continent, called “Pangea,” and the climate started warmer and ice-free, with CO ₂ levels much higher than those of today. Dinosaurs had yet to dominate the planet, and there was no grass or flowers.

Enlarge / Map of major earthquakes and aftershocks in Turkey on Monday. (credit: US Geological Survey)

A major earthquake and a series of strong aftershocks shook Southern Turkey and other parts of the Middle East on Monday. The most powerful of these registered 7.8 magnitude on the Richter scale, placing it among the five most powerful earthquakes recorded during the 21st century in the world.

This first earthquake, at 4:17 am local time in Turkey (Sunday evening in the United States), was followed later in the day by another powerful temblor hundreds of kilometers away, at magnitude 7.5, as well as additional aftershocks. These earthquakes appeared to be occurring along the East Anatolian Fault, which divides the Eurasian tectonic plate to the north from the Anatolian plate to the south.

Earthquakes of this magnitude produce violent shaking of the ground and landslides and can level buildings. They are terrifying and deadly events for people living nearby. Early death counts, as of Monday, had already exceeded 1,600 people, The New York Times reports .

Enlarge (credit: MOF )

Currently, the major oil companies appear to have settled on an awkward compromise with the reality of climate change: They generally acknowledge that their product is helping drive it but plan to continue to produce as much of that product as they can. But that reflects a major change for these companies, which up until recently were funding think tanks that minimized the risks of climate change and, in many cases, directly denying the validity of the science.

In the case of ExxonMobil, that includes denying its own science. Thanks to documents obtained by the press, we now know that Exxon sponsored its own climate researchers who did internal research, collaborated with academic scientists, and came to roughly the same conclusions about carbon dioxide that the rest of the scientific community had—and executives were made aware of it.

But how rough were the conclusions that Exxon's scientists gave its executives? It's a question that goes to the heart of how misleading the executives were being when they downplayed the risks. A new study answers that question pretty definitively: Exxon's scientists were as good (and sometimes better) than the scientific community as a whole at projecting the climate changes created by fossil fuel use.

Enlarge / Scientists about to sink an Ocean Bottom Seismometer to the Atlantic seabed in 2021.

Scientists have scanned a section of the North Atlantic and revealed the remnants of what had been a huge pulse of hot rock that initiated a rapid climate warming event 56 million years ago.

The climate event, known as the Paleocene-Eocene Thermal Maximum (PETM), warmed the already-hot climate of the time by about 5.6° C due to a jump in atmospheric CO ₂ . Levels of that greenhouse gas rose from about 1,120 parts per million to about 2,020 ppm —much higher than today’s 417 ppm . Although it didn’t trigger a major extinction, it still exterminated some deep-sea creatures and tropical plants . Scientists want to understand the PETM better, because it’s an example of how the Earth reacted to a rapid rise in atmospheric CO ₂ a bit like we’re currently experiencing, albeit starting from a hot, ice-free climate.

Finding a cause

Although the cause of PETM has been debated since it was discovered in the 1990s , more and more evidence has accumulated that points to massive quantities of CO ₂ and methane emitted due to volcanic activity in the North Atlantic as the primary cause. This activity created what’s now known as the North Atlantic Igneous Province— the same kind of enormous volcanic phenomenon linked to climate disruption and extinctions at other times in Earth’s past, like the end-Triassic , the end-Permian , the early Jurassic , and others .