Global warming today mirrors conditions leading to Earth’s largest extinction event, UW study says

A melting iceberg floats along a fjord leading away from the edge of the Greenland ice sheet near Nuuk, Greenland, in 2011. By this century’s end, if emissions continue at their current pace, humans will have warmed the ocean about 20 percent as much as during the Permian extinction event, newly published research says. (Brennan Linsley / The Associated Press)

If humans continue to pump greenhouse gases at our current rate, “we have no reason to think it wouldn’t cause a similar type of extinction,” said Curtis Deutsch, a UW professor and author of the research.

More than two-thirds of life on earth died off some 252 million years ago, in the largest mass extinction event in Earth’s history.

Researchers have long suspected that volcanic eruptions triggered “the Great Dying,” as the end of the Permian geologic period is sometimes called, but exactly how so many creatures died has been something of a mystery.

Now scientists at the University of Washington and Stanford believe their models reveal how so many animals were killed, and they see frightening parallels in the path our planet is on today.

Models of the effects of volcanic greenhouse-gas releases showed the earth warming dramatically and oxygen disappearing from its oceans, leaving many marine animals unable to breathe, according to a study published Thursday in the peer-reviewed journal Science. By the time temperatures peaked, about 80 percent of the oceans’ oxygen, on average, had been depleted. Most marine animals went extinct.

The researchers tested the model’s results against fossil-record patterns from the time of the extinction and found they correlated closely. Although other factors, like ocean acidification, might have contributed some to the Permian extinction, warming and oxygen loss account for the pattern of the dying, according to the research.

By this century’s end, if emissions continue at their current pace, humans will have warmed the ocean about 20 percent as much as during the extinction event, the researchers say. By 2300, that figure could be as high as 50 percent.

“The ultimate, driving change that led to the mass extinction is the same driving change that humans are doing today, which is injecting greenhouse gases into the atmosphere,” said Justin Penn, a UW doctoral student in oceanography and the study’s lead author.

Curtis Deutsch, a UW associate professor of oceanography and an author of the research, said if society continues to pump greenhouse gases at our current rate, “we have no reason to think it wouldn’t cause a similar type of extinction.”

Massive eruptions

The earth 252 million years ago was a much different place. The continents as we know them today were still mostly one landmass, named Pangea, which looks like a chunky letter “C” on a map.

The climate, however, resembled Earth’s now, and researchers believe animals would have adapted many traits, like metabolism, that were similar to creatures today. Nearly every part of the Permian Ocean, before the extinction, was filled with sea life.

“Less than 1 percent of the Permian Ocean was a dead zone — quite similar to today’s ocean,” Deutsch said.

The series of volcanic events in Siberia that many scientists believe set off the mass extinction “makes super volcanoes look like the head of a pin,” said Seth Burgess, a geologist and volcanologist with the United States Geological Survey.

“We’re talking about enough lava erupted onto the surface and intruded into the crust to cover the area of the United States that if you looked at the U.S. from above was maybe a kilometer deep in lava,” he said.

Burgess, who has researched the Siberian Traps volcanic events but did not work on the new Science paper, said scientists believe magma rising from the earth released some extinction-causing greenhouse gases.

In addition, sills of magma still inside the earth heated massive deposits of coal, peat and carbonate minerals, among others, which vented even more carbon and methane into the atmosphere.

“That’s how you drive the Permian mass extinction, by intruding massive volumes of magma into a basin rich in carbon-bearing sediments,” he said.

The UW and Stanford research “takes the next step in figuring out why things died at the end of the Permian,” Burgess said. “It couples what we think was happening in the climate with the fossil record, and it does it elegantly.”

Animals couldn’t breathe

It took a supercomputer more than six months to simulate all the changes the volcanic eruptions are suspected of causing during the Permian period. The computer models go into remarkable detail — simulating things like clouds, ocean currents and marine plant life — in describing what temperatures and conditions were like on Earth.

The researchers knew that surface temperatures rose about 10 degrees Celsius in the tropics because of previous scientific analysis of the fossilized teeth of eel-like creatures called conodonts.

To run their model, researchers pumped volcanic greenhouse gases into their simulation to match temperature conditions at the end of the Permian period.

As temperatures climbed toward the 10-degree mark, the model’s oceans became depleted of oxygen, a trend scientists are evaluating in today’s oceans, too.

To measure how rising temperatures and less oxygen would affect animal species of the Permian period, the researchers used 61 modern creatures — crustaceans, fish, shellfish, corals and sharks. The researchers believe these animals would have similar temperature and oxygen sensitivities to Permian species because the animals adapted to live in similar climates.

Warming’s effects were twofold on the creatures, the researchers found. In warmer waters, animals need more oxygen to perform bodily functions. But warm waters can’t contain as much dissolved oxygen, which means less was available to them.

In other words, as animals’ bodies demanded more oxygen, the ocean’s supply dropped.

In their model, the researchers were able to quantify the loss of habitat as species faced increasingly challenging ocean conditions. Surface-temperature rise and oxygen loss were more substantial in areas farther from the equator. Extinction rates also increased at higher latitudes.

Animals in the tropics were already accustomed to warmer temperatures and lower oxygen levels before the volcanic eruptions shifted the climate, according to the research. As the world warmed, they could move along with their habitat.

Marine creatures that favored cold waters and high oxygen levels fared worse: They had nowhere to go.

“The high latitudes where it’s cold and oxygen is high — if you’re an organism that needs those kind of conditions to survive, those conditions completely disappear from Earth,” Deutsch said.

In modern oceans, warming and oxygen loss have also been more pronounced near the poles, researchers said, drawing another analogue between the shift in climate some 252 million years ago and what’s happening today.

“The study tells us what’s at the end of the road if we let climate [change] keep going. The further we go, the more species we’re likely to lose,” Deutsch said. “That’s frightening. The loss of species is irreversible.”

Original post: https://www.seattletimes.com/

Evan Bush: 206-464-2253 or ebush@seattletimes.com; on Twitter: @EvanBush.

California drought likely a fixture, says Stanford study

Two piers lay on the shoreline at Shadow Cliffs Regional Recreation Area in Pleasanton, Calif., on Friday, Jan. 9, 2015. The man-made lake’s water level remains at historically low levels, about 10 feet below normal for the winter season. (Doug Duran)

Human-caused climate change is increasing drought risk in California — boosting the odds that our current crisis will become a fixture of the future, according to a major report Stanford scientists released Monday.

The finding comes as cities across the Bay Area wrap up the warmest three-month stretch of winter on record.

The new study looked at data from the past and simulations foretelling the future to understand the influence of greenhouse gases on California.

“What has happened in California has been a clear warming trend over the historical record … that probably would not have happened without humans,” said Stanford climate scientist Noah Diffenbaugh.

The continuation of global warming “will result in more frequent occurrences of high temperatures and low precipitation that will lead to increased severe drought conditions,” said Diffenbaugh. The research was published in the March 2 issue of the journal Proceedings of the National Academy of Sciences.

Low precipitation, alone, doesn’t cause a drought — what matters is whether it happens in a warm year, according to members of the Stanford team. They don’t offer specific recommendations but say their findings could help California plan for the future.

The news comes on the eve of this winter’s third manual snow survey, taken atop the Sierra on Highway 50. Other readings reveal that statewide, the snowpack water content is just 19 percent of the historical average for the date.
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Reinforcing the drought’s threat, one weather agency is reporting that many Bay Area cities have broken records for the warmest winter in history. Average temperatures for December through February were 54.44 degrees in San Jose, up from the 54.42 degree record of 1996; 52.62 degrees in Livermore, up from the 51.72 degree record of 1996; and 57 degrees in San Francisco, up from the 55.70 degree record of 1970, according to Jan Null of Golden Gate Weather Services.

The Stanford study supports the growing recognition that warming temperatures can worsen a drought that is driven by declining precipitation, noted Richard Seager of Columbia University’s Lamont-Doherty Earth Observatory, who was not involved in the research.

“This is happening all over the world — there is nothing unusual in terms of California,” said Seager.

The Stanford team previously reported that the conditions behind our current drought — a high pressure system parked over the Pacific Ocean, diverting storms away from California — are much more likely to occur amid concentrations of greenhouse gases.

The new study goes further. Using a recently released trove of 120 years of historical data, the researchers found more than a doubling of the frequency of drought years. There were six droughts in past 20 years (1995-2014), compared to 14 in the previous 98 years (1896-1994.)

What’s happening? Imagine flipping two coins, one for precipitation and one for temperature, said Diffenbaugh, associate professor of Environmental Earth System Science at Stanford.

Until recently, precipitation and temperature occurred independently.

But climate change means that the temperature coin is landing on warm weather most of the time. So even as precipitation varies, the combination of both warm and dry is more common. We see little rain, snow melts earlier, and soil and plants lose more water.

“Low precipitation isn’t enough to create a drought. The key difference is temperature,” said Diffenbaugh. And that’s what is changing.

Seager agrees that climate change will produce warmer weather, although he contends that our recent extreme heat is due to natural variations in sea surface temperatures, “far in excess of what you would expect from background greenhouse gases,” based on his National Oceanic and Atmospheric Administration-sponsored research.

He agrees that California “will also face tremendous water problems as the climate changes, because of warmer temperatures, less snow, shorter and sharper winters, and warming that takes moisture out of the soil.”

The Stanford team doesn’t have data for the future, of course, and it’s impossible to run a real-world experiment. So they created climate simulations to peer into the future.

Their models show that the warming trend is likely to continue, boosting the odds that a heads-tails coin toss — co-occurring warm and dry years, creating drought — will climb in the coming decades.

Droughts have occurred throughout California’s pre-human history, just as the coin toss example would predict, they say. And nature creates its own variability, with volcanic eruptions and solar fluctuations.

But steadily rising temperatures — caused by burning fossil fuels and clearing forests — increases the probability of such conditions, they found.

“Continued global warming will result in more frequent occurrences of high temperatures and low precipitation,” said Diffenbaugh, “leading to more of the severe drought conditions that we’ve been experiencing.”

Read the original post: MercuryNews.com | By Lisa M. Krieger