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Changes in oxygen concentrations in our ocean can disrupt fundamental biological cycles


New research led by scientists at the University of Bristol has shown that the feedback mechanisms that were thought to keep the marine nitrogen cycle relatively stable over geological time can break down when oxygen levels in the ocean decline significantly.

Changes in oxygen concentrations in our ocean can disrupt fundamental biological cycles
On Aug. 11, 2015, a NASA satellite captured this false-color image of a large bloom of cyanobacteria (Nodularia)
swirling in the Baltic Sea. These cyanobacteria fix inorganic atmospheric nitrogen (N2) into a form available to Life,
 a process fundamental for marine ecosystems. In our paper we show that nitrogen fixation becomes even more
important when the state of oxygenation of the ocean declines [Credit: NASA Earth Observatory/USGS]
The nitrogen cycle is essential to all forms of life on Earth - nitrogen is a basic building block of DNA.

The marine nitrogen cycle is strongly controlled by biology and small changes in the marine nitrogen cycle have major implications on life. It is thought that the marine nitrogen cycle has stayed relatively stable over geological time due to a range of different feedback mechanisms.

These feedback mechanisms are called 'the nitrostat'. However, exactly how the global marine nitrogen cycle and the associated feedback mechanisms responded to past severe changes in marine oxygenation is not well understood.


The team used a data-constrained earth system model to show show that under these deoxygenated conditions the ocean can become extremely depleted in nitrogen as the total bioavailable nitrogen inventory collapses relative to phosphorous.

At the same time the ocean transitions from an oxic-nitrate ocean to an anoxic ammonium ocean. The substantive reduction in the ocean bioavailable-N inventory in response to change in marine oxygenation may represent a key biogeochemical vulnerability.

Lead author Dr David Naafs from the University of Bristol's School of Earth Sciences, said: "Our results demonstrate that changing the amount of oxygen in the ocean can have disastrous effects on vital biogeochemical cycles such as the nitrogen cycle, which is essential for all forms of Life."

Co-author Dr Fanny Monteiro, from Bristol's School of Geographical Sciences, added: "Our modelling results are in agreement with the sparsely available proxy data from the geological past."


Co-author Professor Ann Pearson from Harvard University, said: "Our modelling results show the impact of changes in ocean oxygenation on the marine nitrogen cycle for places and time periods for which we do not (yet) have sufficient proxy data."

The strength and state of the marine nitrogen cycle and biological pump in the ocean are highly susceptible to disruptions in the level of oceanic oxygen.

As oxygen levels in the oceans are currently declining and expected to decline significantly more in the coming decades due to anthropogenic activities, the results indicate that the marine nitrogen cycle might be significantly disrupted in the future.

Their findings are published in the journal Proceedings of the National Academy of Sciences.

Source: University of Bristol [November 25, 2019]

Climate change is reshaping communities of ocean organisms


Climate change is reshaping communities of fish and other sea life, according to a pioneering study on how ocean warming is affecting the mix of species.

Climate change is reshaping communities of ocean organisms
This is a black and yellow rockfish (Sebastes chrysomelas) in the Channel Islands National Marine
Sanctuary off Southern California [Credit: Claire Fackler/CINMS, NOAA]
The study, published in the journal Nature Climate Change, covers species that are important for fisheries and that serve as food for fish, such as copepods and other zooplankton.

"The changes we're observing ripple throughout local and global economies all the way to our dinner plates," said co-author Malin Pinsky, an associate professor in the Department of Ecology, Evolution, and Natural Resources in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick.


"We found dramatic evidence that changing temperatures are already reshaping communities of ocean organisms," Pinsky said. "We found that warm-water species are rapidly increasing and cold-water marine species are decreasing as the global temperature rises. Changes like this are often disrupting our fisheries and ocean food chains."

An international team of scientists also found evidence that species in some places can avoid declines by seeking refuge in cooler, deeper water - like plants on land that move to higher elevations to avoid heat, Pinsky said.

The scientists compiled the most comprehensive assessment of how ocean warming is affecting the mix of species in our oceans. They looked at fishes, invertebrates such as crabs and other crustaceans and plankton in the North Atlantic and North Pacific, across two continents and two oceans. They analyzed three million records of thousands of species from 200 ecological communities across the globe from 1985 to 2014.


Regions with stable temperatures (the Northeast Pacific and Gulf of Mexico, for example) show little change in species dominance, while warming areas (the North Atlantic, for example) are experiencing strong shifts toward the dominance of warm-water species, the study says.

Temperature is a fundamental driver for change in marine systems, with restructuring of communities in the most rapidly warming areas. Still, the data "suggest a strong prognosis of resilience to climate change for these communities," the study says.

"We're now trying to understand how the changes we see in the ocean compare with those on land and in freshwater ecosystems," said Pinsky, who is also a sabbatical professor at the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig.

Source: Rutgers University [November 25, 2019]

Antarctica likely to drive rapid sea-level rise under climate change


Scientists from The Australian National University (ANU) have shown that ice melt from Antarctica drives rapid and high sea-level rise, offering a forewarning of what to expect under human-driven climate change.

Antarctica likely to drive rapid sea-level rise under climate change
Melting ice on the coast of Adelie Land in East Antarctica
[Credit: Pauline Askin/Reuters]
The researchers examined historical and new data from the ‘last interglacial’, which took place 125,000 to 118,000 years ago and saw sea levels rise up to 10 metres above current levels.

Interglacials are periods of warmer global temperatures that can last thousands of years.

The study, published in Nature Communications, shows that sea levels rose up to three metres per century, largely driven by ice loss in the Antarctic ice sheet.


Lead author, Professor Eelco Rohling, said that the last interglacial sea-rise was due to natural climate instabilities.

“These were smaller and slower than the human-caused climate disturbance of today,” he said.

“Our study shows clearly that Antarctica, long thought a sleeping giant when it comes to sea-level rises, is in fact the key player.

“And it appears that it can change by large amounts on timescales that are highly relevant to society and in ways that would have profound effects on human infrastructure.”

The study shows for the first time by how much ice loss in the last interglacial first took place in Antarctica, followed by Greenland.


Early Antarctic ice loss was caused by Southern Ocean warming at the onset of the interglacial. Next, the meltwater from Antarctica caused changes in global ocean circulation that resulted in northern polar warming and associated Greenland ice loss.

Co-lead author, Dr Fiona Hibbert, said that in today's greenhouse-gas-driven climate change, rapid atmospheric and oceanic warming happens in both polar regions at the same time.

“This drives simultaneous ice-loss in Antarctica and Greenland,” Dr Hibbert said.

“But, what’s vital to remember is that today’s climatic disturbance is greater and develops faster than that of the last interglacial.

“As a result, rates of sea-level rise may develop over the next several centuries that are even higher than those found for the interglacial we have studied.”

Source: Australian National University [November 06, 2019]

Largest mapping of breathing ocean floor key to understanding global carbon cycle


Marine sediments play a crucial role in the global carbon cycle due to the oxygen consumption and CO2 respiration of the organisms that live in and on the ocean floor. To help predict the changing contribution of this respiration to the carbon cycle in a warming world, researchers from the Royal Netherlands Institute of Sea Research (NIOZ) and universities in Taiwan have compiled the largest open-access database available of the sediment community oxygen consumption and CO2 respiration. Their findings are published in Nature Scientific Data.

Largest mapping of breathing ocean floor key to understanding global carbon cycle
Map of all sampling stations where sediment community oxygen consumption has been measured
[Credit: Tanja Stratmann, NIOZ]
98% of the CO2 dissolved in sea water

The oceans play an important role in the global carbon cycle, with nearly 98% of the CO2 being dissolved in sea water. Also, the burial of carbon at the sea floor is an important component of the global carbon cycle.


"This large data-base is valuable. In-depth knowledge of the processes involved and the rates helps other scientists predict future scenarios for ongoing changes in climate and the oceans.", says Professor Gert-Jan Reichart of NIOZ and University of Utrecht, and coordinator of a multi-stakeholder CO2-to-Ocean research coalition about the publication, in which he did not take part.

CO2 respiration by seafloor dwelling organisms

Sediments at the bottom of the ocean host organisms such as algae that produce organic matter, but sediments also receive organic material that is formed by phytoplankton in the surface ocean and sinks to the seafloor. Part of the organic material is buried and functions as a carbon sink over geological time scales, extracting the C from the carbon cycle for millions of years.

Largest mapping of breathing ocean floor key to understanding global carbon cycle
Benthic landers on board RV Sonne. ; landers belong to Max Planck Institute for Marine Research, Germany,
and IRIS, Norway [Credit: Dr Johannes Lemburg, Alfred Wegener Institute]
However, most of the organic carbon is respired again as CO2 by microorganisms and animals that live in the top 10 to 50 cm of the sediment. The sediment community oxygen consumption (SCOC) - or put differently: -the CO2 respiration of organisms living in and on the seafloor - is considered a good proxy to understand the degradation of organic matter and to measure the flux of organic matter to the seafloor.


These rates will likely be affected by climate change and to predict their contribution to the carbon cycle in a warmer world, a sound understanding of the rates under the current climate regime is necessary. Therefore, the authors compiled the largest open-access database of SCOC that exists so far with more than 3,500 data entries from the literature and from measurements performed by the authors themselves on sea-going expeditions.

Largest mapping of breathing ocean floor key to understanding global carbon cycle
NIOZ CUBEs at seafloor [Credit: ROV KIEL 6000, GEOMAR]
Southern hemisphere still undersampled

This database shows that most of the measurements were performed in the northern parts of the Pacific and Atlantic Ocean and the Arctic Ocean. The southern hemisphere, in contrast, is undersampled and we know almost nothing about the respiration of sedimentary organisms in the Indian Ocean. Besides reporting actual SCOC values, this database can therefore also be used to plan future sampling campaigns to fill white spots on the map and improve the understanding of carbon cycling in these areas.

The 3,500 data-entries constituting the data base were based on sampling stations across the globe, but predominantly across the Northern hemisphere.

Source: Royal Netherlands Institute for Sea Research [October 29, 2019]

Humpback whale population on the rise after near miss with extinction


A population of humpback whales in the South Atlantic has rebounded from the brink of extinction. Intense pressure from the whaling industry in the 20th century saw the western South Atlantic population of humpbacks diminish to only 450 whales. It is estimated that 25,000 whales were caught over approximately 12 years in the early 1900s.

Humpback whale population on the rise after near miss with extinction
A population of humpback whales in the South Atlantic has rebounded from near extinction,
a new study shows [Credit: iStock.com/Martin Hristov]
Protections were put in place in the 1960s as scientists noticed worldwide that populations were declining. In the mid-1980s, the International Whaling Commission issued a moratorium on all commercial whaling, offering further safeguards for the struggling population.

A new study co-authored by Grant Adams, John Best and Andre Punt from the University of Washington's School of Aquatic and Fishery Sciences shows the western South Atlantic humpback (Megaptera novaeangliae) population has grown to 25,000. Researchers believe this new estimate is now close to pre-whaling numbers.

"We were surprised to learn that the population was recovering more quickly than past studies had suggested," said Best, a UW doctoral student.


The study follows a previous assessment conducted by the International Whaling Commission between 2006 and 2015. Those findings indicated the population had only recovered to about 30% of its pre-exploitation numbers. Since that assessment was completed, new data has come to light, providing more accurate information on catches—including struck-and-lost rates—and genetics and life-history.

"Accounting for pre-modern whaling and struck-and-lost rates where whales were shot or harpooned but escaped and later died, made us realize the population was more productive than we previously believed," said Adams, a UW doctoral student who helped construct the new model.

By incorporating detailed records from the whaling industry at the outset of commercial exploitation, researchers have a good idea of the size of the original population. Current population estimates are made from a combination of air- and ship-based surveys, along with advanced modeling techniques.

The model built for this study provides scientists with a more comprehensive look at the recovery and current status of the humpback population. The authors anticipate it can be used to determine population recovery in other species in more detail as well.


"We believe that transparency in science is important," said Adams. "The software we wrote for this project is available to the public and anyone can reproduce our findings."

Lead author Alex Zerbini of the NOAA Alaska Fisheries Science Center's Marine Mammal Laboratory stressed the importance of incorporating complete and accurate information when conducting these assessments, and providing population assessments without biases. These findings come as good news, he said, providing an example of how an endangered species can come back from near extinction.

"Wildlife populations can recover from exploitation if proper management is applied," Zerbini said.

The study also looks at how the revival of South Atlantic humpbacks may have ecosystem-wide impacts. Whales compete with other predators, like penguins and seals, for krill as their primary food source. Krill populations may further be impacted by warming waters due to climate change, compressing their range closer to the poles.

"Long-term monitoring of populations is needed to understand how environmental changes affect animal populations," said Zerbini.

The findings were published in the journal Royal Society Open Science.

Source: University of Washington [October 21, 2019]

Geologists reveal anoxia caused loss in biodiversity in ancient seas


Since 2016 the researchers of the Department of Geology at Tallinn University of Technology have been engaged in a research project analysing the causes of Silurian biodiversity crisis. The findings of the study are summarized in the article "Linking the progressive expansion of reducing conditions to a stepwise mass extinction event in the late Silurian oceans" published recently in the journal Geology.

Geologists reveal anoxia caused loss in biodiversity in ancient seas
Eurypterus, a common Upper Silurian eurypterid
[Credit: WikiCommons]
The international research team included scientists from the University of Florida, Tallinn University of Technology, the University of South Carolina and Lund University. A member of the research group, Professor of Bedrock Geology at Tallinn University of Technology Olle Hints says, "Our research focused on the changes in the Earth's environmental conditions and biodiversity during the Silurian period, ca 425 million years ago".

Five big mass extinctions are known from the last half a billion years of Earth's history. For example, 250 million years ago, at the end of the Permian period, 95% of the plant and animal species of that time disappeared in a short time. Today, too, we are facing major biodiversity loss and knowledge of past extinction events enables us to assess its potential course and consequences. In severe biotic crisis in the Silurian, known as the Lau Event, extinction of nearly 25% of the marine species took place. The scientists set out to determine the chronology and possible mechanisms of the event.


Information on the biota and environment of the distant past is best preserved in marine sedimentary rocks. Study of fossils enables us to document the evolution and biodiversity dynamics. Fossils also play a crucial role in constructing the geologic time scale and dating rocks. Only if precise time scale is available can it be investigated how and why environmental conditions changed and how this influenced the biosphere. For example, the atoms making up the minerals of limestone provide the evidence of the chemical composition of the ancient ocean and the atmosphere and their evolution. By combining paleontological and geochemical data, conclusions can be drawn about the relationships between biota and the environment.

In this work, the researchers focused on the study of carbon, sulphur and thallium isotopes. "What makes our research unique is that for the first time, thallium isotopes were analysed from the Paleozoic rocks indicating changes in redox conditions of the global ocean. The rock samples analysed were collected from Latvia and the island of Gotland, which once were part of the Baltic paleosea. In this region, rocks have altered very little over the last 500 million years, and thus the original information is still present. The Baltic region is a rewarding natural laboratory for geologists - there are very few places in the world where the rocky archives of the Paleozoic era are so well preserved," professor Hints says.

Geologists reveal anoxia caused loss in biodiversity in ancient seas
PhD student Chelsie N. Bowman and Professor Seth A. Young from the Florida State University collecting samples
from the 425 million years old Earth history archives that are deposited at Tallinn University of Technology
[Credit: Olle Hints]
This fact ensures that the results of the analyses are reliable. Alongside the unique rock samples, the cutting-edge analytical equipment that makes it possible to measure stable isotope ratios from small amounts of rock powders played a crucial role. Most of the geochemical analyses were carried out by Chelsie N. Bowman and Professor Seth A. Young in the National High Magnetic Field Laboratory at Florida State University, one of the most modern analytical facilities for this kind of research in the world.


The results of the analyses showed for the first time that the extinction of late Silurian species began with a progressive decrease in the oxygen content in the ocean and culminated when anoxic and likely sulphidic water masses reached the shallow seas. This change was relatively slow - it took probably 175-270 k.y. from the the initial phase until the crisis reached its peak. Among the first organisms to suffer from the environmental change were there vertebrates, represented by fish and conodonts, whose diversity decreased by nearly 70%. The environmental change had also a major impact on plankton, although it occurred somewhat later.

Professor Hints said, "What are the benefits of studying such a distant past? On the one hand, we can confirm that changes in marine redox conditions and oxygen levels have catastrophic consequences for the life in oceans and that the vertebrates are the first to be affected by the changes." This is a highly topical issue since measurements as well as models indicate progressive expansion of oceanic anoxia in the present-day oceans. Geological data prove that if a system is shifted out of equilibrium, it will take hopelessly long time from human perspective in order to return to the pre-event conditions.

"On the other hand, we can learn from this particular example, as well as from the Earth history in general, that every crisis creates the basis for evolutionary innovations, allowing better adaptable organisms to survive and new ones to emerge," Professor Hints says.

Source: Estonian Research Council [October 15, 2019]

What will the world look like in 2050?


It's 2050, and another balmy day in Los Angeles. A young woman steps outside and puts on her air filtration mask. The air is thick with smog, which aggravates her asthma. As she hurries to get into an air-conditioned, self-driving car, she wonders if the temperature will finally dip below 90 degrees today—for the first time this November.

What will the world look like in 2050?
Credit: Brian Stauffer
One hundred miles northwest, a third-generation vineyard owner finishes packing up his family and saying goodbye to the land. It has become too hot to produce his Pinot Noir grapes anymore—all the nearby vineyards now grow wheat to fit the hotter weather. He is heading to Oregon's cooler climes to start again.

Meanwhile, on the coast, a boy and his grandfather walk along the beach, careful not to touch the water. A telltale bright red stain in the waves warns them of a toxic algal bloom. The water level has risen a little bit over the years, and the grandfather wonders how much land will still be above water when his grandson reaches his age.

By 2050, climate change and its reality will no longer be up for debate. The subtle signs we're starting to see around us will be more pronounced, scientists say, and their impact will be easy to spot in everyday life. The warming trend can feel overwhelming to understand, much less confront—especially with so many factors believed to affect how the planet is changing. But there's good news: Humanity has tools to shape our future, USC researchers say, and some are already working in places across the globe.


Weather in 2050: Hot, Hotter, Hottest

"The global climate is like an aircraft carrier; turning it around is slow," says Julien Emile-Geay, an associate professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences. "If we don't start now, we'll be stuck in a very tough place in 2050." As an expert in climate dynamics, Emile-Geay has devoted his career to understanding what's coming for the planet.

The 20th century was Earth's warmest period in nearly 2,000 years, he says. Data he examined from a wide variety of sources, including ice cores, tree rings and coral reefs, show that the warming trend began after the industrial revolution—the 1850s. For most of the globe, the warmest temperatures have come within the past 100 years. He agrees with the broad scientific consensus that if the trend continues—and physics says it will—sea level rise and droughts could render areas of the planet unsafe or even uninhabitable. Refugees leaving their homes for livable climates could lead to geopolitical instability. The World Bank predicts as many as 140 million people could be displaced by 2050.

In the Southern California of 2050, Angelenos could spend a quarter of the year sweating it out in temperatures of 90 degrees or more. That's 95 days of dangerously hot weather a year, significantly higher than the 67 days we see in 2019. Air conditioning will raise energy bills, but researchers anticipate costs to health as well.

What will the world look like in 2050?
Credit: Brian Stauffer
When temperatures spike, deaths rise too, says USC Dornsife environmental economist Paulina Oliva. Research suggests that uncomfortable heat stresses the body, increasing risk of heart problems and stroke, especially in the elderly. High temperatures have also been linked to an increase in pre-term births and infant mortality. Studies on students and stockbrokers and other workers have shown that temperatures above 80 degrees slow down thinking processes, making it harder to focus and make decisions. These problems disproportionately harm people with the fewest resources to deal with the discomfort and health risks.

Several researchers raise the alarm that any climate plan has to address our society's systemic inequalities. "The pregnant mother who doesn't have a car is going to have to walk to public transportation and expose her baby to these high temperatures in utero," Oliva says. "Even though we do have means to adapt, wealthier people are going to be better able to adapt than poor people."

The climate is likely to become extreme in several ways, including an increase in both fires and floods, rainy days and droughts, cold snaps and temperature spikes. In California, unpredictable fluctuations could devastate the agricultural sector, which accounts for an eighth of the country's agricultural production. It's likely that some crops, like grapes and apples, could only be grown farther north. Farmers who opt to stay in California might switch products—say, from corn to wheat—to better match the new climate reality.

Environment in 2050: Something in the Air

We don't need to time travel to 2050 to imagine the impact of climate change on the air. In spring 2018, Los Angeles' air quality exceeded federal safety levels for 87 days, says Antonio Bento, director of the USC Center for Sustainability Solutions and professor at the USC Price School of Public Policy and the Department of Economics.

When temperatures rise, so does "bad" ozone. Don't confuse this ozone with the ozone layer in the upper atmosphere, which shields Earth from the sun's radiation. Bad ozone forms at ground level when pollutants from cars and other industrial sources react to sunlight. "Ozone is dependent on temperature, sunlight and heat waves," Bento says. "That means that higher heat brings on worse air quality."


In Los Angeles, it's one of the biggest reasons climate change endangers human health: More days above 90 degrees means more ozone, more asthma, more lung damage and more deaths. By 2050, if climate mitigation strategies and air pollution regulation don't halt rising temperatures, the skies of Los Angeles could revert to the soupy smog of the 1970s, Bento says.

That was a time before the Clean Air Act, when more than half the days in the city had unsafe levels of pollution. Angelenos couldn't see the mountains through the thick smog. "In part due to climate change, many of the benefits that we have achieved are quickly being undone," says Bento, who recently published research showing how a rollback of vehicle emissions standards would be dangerous. "We have arrived at a point where for us to prevent major damage, we would have to rely on adaptation."

For a long time, Bento was sure that leaders would take up the urgent issue of climate change based on a global consensus, so he focused his policy recommendations on broad, far-reaching solutions. But recently, he shifted his thinking. He's increasingly examining how local policy changes could benefit countries and states.

Reducing greenhouse gas emissions would not only reduce health problems related to air pollution impacts, but it also could bring along other benefits, like spurring technological innovation, improving the reliability of the power supply by diversifying energy sources, reducing fuel costs and boosting employment.

"If we account for these co-benefits of climate action, it's in the best interest of countries to act independently of what others are doing," he says. "And it's in the best interest of California to implement climate policies, because even if others don't act, we will get these additional benefits."

Bento has worked with the city of Los Angeles and other local governments in the U.S. and abroad to craft climate-mitigation strategies. By 2050, 68% of the world population will live in cities, up from 55% today, so the actions of municipal and regional governments are critical. "If cities become the unit at which we do climate policy, we end up with comprehensive climate legislation even without national leadership," he explains. "That's the future of our cities and the environment. It really depends on how we communicate the climate crisis to the public."

Bento is also researching ways to create optimal carbon pricing, which shifts responsibility back to the producers of greenhouse gas emissions. Carbon pricing works by estimating the external cost of a company's greenhouse gas emissions and issuing a tax. This puts the financial burden on businesses instead of on local and vulnerable communities, while also financially incentivizing companies to opt for cleaner technology.

"It's frustrating, because we have known how to do these things for decades, but we're not yet doing them," he says. "As we move toward 2050, we have to adapt in ways that don't put more burdens on communities that are vulnerable already."

Oceans and Water in 2050: Beneath the Surface

More than 90% of the warming created by humans since the 1970s has been absorbed by the oceans. And just as on land, there is a shift underway in the sea that will affect the global oceans of 2050, says David Hutchins, a USC Dornsife professor of marine and environmental biology. "The ocean is warming, acidifying, losing oxygen and being overfished and choked with pollutants ranging from nutrients to plastic," he says. "Nearly the entire marine environment is in flux right now."

What will the world look like in 2050?
Credit: Brian Stauffer
Numbers of large predator fish have plunged, and about half of the world's coral reefs have been lost to bleaching caused by warming temperatures, Hutchins says. By 2050, most reefs may have vanished, according to a National Oceanic and Atmospheric Administration report.

Some governments, like Australia's, are taking action, trying to protect reefs by reducing other threats to coral such as dredging and runoff from land. And scientists are identifying and growing types of resistant coral that may be better able to cope with warm water.

In Southern California, people will have to deal with rising sea levels as polar ice continues to melt. Some of California's most valuable coastal real estate may go underwater later this century, Hutchins says. Another aquatic impact: unwelcome bursts of harmful algal blooms that thrive in warmer waters and poison human and marine life.

"The climate emergency is happening now, today, not sometime in the far-off future," Hutchins says. "I'd like people to think about the kind of world we want to leave for our children and grandchildren, and to make our choices—from the way we live to the leaders we vote for—with that in mind. There is literally no time to lose."


Water distribution across the planet is a challenge, too: By 2050, more parts of the world will go through droughts, while others will be deluged with floods. It's hard to believe that a place like Phuket, Thailand, could suffer from a water shortage when about 100 inches of rain falls there per year, says Amy Childress, the Gabilan Distinguished Professor in Science and Engineering at the USC Viterbi School of Engineering. But right before the monsoon season begins, the reservoirs can get very low as reserves from the last monsoon season dwindle.

Areas like Phuket can't wait until 2050 to figure out a sustainable plan for their water supply; they need to plan now. That goes for California, too.

"In Southern California, we are simultaneously preparing for the drought scenario—alternative water supplies, expansion of the water supply portfolio—and the flood scenario, which includes dam maintenance and flood risk management," Childress says. Then there's the water we need to drink.

In the future, more people will depend on drinking water that's been recycled. The idea of drinking water that's "secondhand" from wastewater or other human uses is off-putting to many, maybe because the public prefers to think it should come from a pristine mountain stream, Childress says. That's not realistic, even today. "Typically, our drinking water comes from a source that was used upstream by others and is being reused by us," she says. "We have regulations in place to ensure that this practice is safe."

In addition to recycled water, Californians of 2050 will rely more on desalinated seawater, she predicts. Desalinating seawater is usually the last choice for a region's water supply because the process is so energy intensive, but it is a reliable supply that will become more useful in the years to come. Right now, 12 desalination plants operate in California, but ocean filtration systems operate in more than 120 countries and are especially critical in countries in the Middle East and the Mediterranean.

Lifestyle in 2050: Changes at Home

For a long time, Bento says, academics were so concerned with getting their climate change models right—and assessing broad existential threats—they failed to communicate how changes are already affecting daily life. That's no longer the case.

What will the world look like in 2050?
Credit: Brian Stauffer
Commuting, travel, shopping, eating, housing—they all may be transformed by 2050 as people come to understand their effect on the planet. Bento, for one, already drives an electric car, but he questions whether he needs one at all. "It was just such an unquestioned expectation for me, that I would get a car as a teenager," he explains. "And when electric vehicles arrived, I thought I was doing something for the environment. But now we are moving into new models. "If we could move to a system that is more efficient, and that integrates density of development with public transit and car-sharing, perhaps we could have much better outcomes."

Earth scientist Emile-Geay has cut travel to most academic conferences. Instead of flying several times a year to meet other scientists—trips that leave a big carbon footprint—he chooses just one conference to attend. "I started to ask myself: What am I getting out of these conferences and what do others get from my presence?" he says. "And so I prioritize small, more intimate gatherings where there's a real exchange of ideas."


Similarly, when people travel for pleasure in the future, more could opt to use low-carbon transportation to explore their own regions instead of taking trips to faraway countries. Besides changing his travel habits, Emile-Geay also has stopped eating meat, and tries to choose foods grown as locally as possible.

"Some like to pit a healthy planet against a healthy economy," he says. "That's a false dichotomy. It's in our power to build an economy centered on ecological and humanistic values instead. The laws of physics won't change, but our laws can." A possible low-carbon future, he says, could include less driving and more local focus, leaving more time with family and friends, which creates safer communities with stronger social bonds.

Oliva sees promise for slowing climate change, as more governments around the world seek immediate action. "And also, we're not sitting and waiting around here," she says of California. "There's quite a bit of progress being made at the state and local level." She believes the state is a model for how sustainability and business can work together. "We're showing that these climate policies really are not going to be as costly as they're being portrayed," Oliva says. "California was an early adopter of stricter greenhouse gas policies and businesses didn't all flee the state. So that gives me hope."

Emile-Geay sees an opportunity for a more civic-oriented and equitable future. Supply chains could be more efficient. Instead of shoppers ordering a product from across the Pacific, a neighborhood 3-D printer could fabricate the items people need and a bicycle courier could ferry it to their homes. He even imagines climate change spurring people to rethink the way they live.

"It's like somebody being given a diagnosis of a terminal illness. It's a wake-up call. Suddenly it makes you ask: "What am I doing with the rest of my time on Earth?"" he says. "That could be the kick we need to re-engineer our social networks and get more local, more focused on community, which is what many psychologists and social scientists say is good for us anyway."

Author: Katharine Gammon | Source: University of Southern California [October 15, 2019]

Study offers solution to Ice Age ocean chemistry puzzle


New research into the chemistry of the oceans during ice ages is helping to solve a puzzle that has engaged scientists for more than two decades.

Study offers solution to Ice Age ocean chemistry puzzle
The Southern ocean, south-east of Tasmania [Credit: IMAS]
At issue is how much of the CO2 that entered the ocean during ice ages can be attributed to the 'biological pump', where atmospheric carbon is absorbed by phytoplankton and sequestered to the seafloor as organisms die and sink.

Solving the puzzle is important to improve the accuracy of climate models and inform understanding of how ocean processes may react to future climate change.

Led by IMAS and University of Liverpool scientists and published in Nature Communications, the study found ice age phytoplankton in the tropics absorbed high levels of CO2 due to fertilisation by iron-rich dust blowing into the ocean.

Lead author Dr Pearse Buchanan said that until now models had only been able to explain a portion of the CO2 that entered ice age oceans via the biological pump.


"During past ice ages, carbon levels were lower in the atmosphere and higher in the oceans than today, but scientific models aren't able to account for all of the additional CO2 that entered the ocean," Dr Buchanan said.

"The leading hypothesis has been that iron-rich dust blown from glacial landscapes stimulated phytoplankton growth in high latitudes, but this only explained around one-third of the extra CO2 absorbed through the biological pump: the other two-thirds was effectively 'missing'.

"We used an ocean model to look at the response to iron rich dust of phytoplankton in tropical waters, particularly a group of phytoplankton called "nitrogen fixers".

"These are able to biochemically 'fix' nitrogen from the atmosphere, much like nitrogen fixing bacteria that help legume crops thrive in nutrient poor soil.

"Marine nitrogen fixers are known to be important in the marine nitrogen cycle, and now we've shown they're also critically important in the marine carbon cycle.

"When we added iron to our ocean model, nitrogen fixers thrived, and their growth and subsequent sinking to the deep ocean can account for much of the missing CO2," Dr Buchanan said.


IMAS Associate Professor Zanna Chase said this solution was first proposed in 1997 but had gained little traction over the last two decades.

"The beauty of this approach is that it can explain almost all of the additional CO2 that phytoplankton transported into the oceans during the last Ice Age," Associate Professor Chase said.

"The increased activity of the biological pump in the tropics complemented that happening in colder waters, drawing higher levels of CO2 into the oceans and locking it away in the deep ocean.

"This pathway for carbon to the deep ocean is reduced today because less fertilising iron is being circulated by the wind and phytoplankton growth, including that of nitrogen fixers, is correspondingly limited, although there are signs that it has strengthened within the Pacific since the industrial revolution.

"Taking account of these links between the cycles of iron, nitrogen and carbon in our ocean and climate change models will make them better able to explain ocean processes and predict future changes.

"But how iron fertilisation of phytoplankton will evolve is currently uncertain, undermining our ability to predict the ocean's role in drawing CO2 out of the atmosphere in the coming centuries," Associate Professor Chase said.

Source: University of Tasmania [October 10, 2019]

Grim projections for the ocean—and the life within it


The chain of causation that connects rising concentrations of greenhouse gases in the atmosphere to the marine biota has been made clearer by the Intergovernmental Panel on Climate Change (IPCC) report Special Report on Climate Change and Oceans and the Cryosphere. It was released on September 25 and examines the effects of increasing concentrations of greenhouse gases on the global oceans and the polar ice sheets.

Grim projections for the ocean—and the life within it
Credit: Earth Institute, Columbia University
While in the past the IPCC has been regarded as conservative about environmental change forced by climate change, the new summary of research has a more alarmed tone.

Sonya Dyhrman, a microbial oceanographer at Lamont-Doherty Earth Observatory and a scientist affiliated with the Center for Climate and Life, is interested in the relationship between phytoplankton, the primary producers of the sunlit depths of the ocean, and their geochemical environment.

When queried in early September, Dyhrman had not read the draft of the IPCC report leaked in August to a French news agency. But her response to the question "How has the marine phytoplankton community fared in response to changes in the physical environment that can be attributed to anthropogenic climate change?" foreshadowed the content of the report.


"There is no short answer about phytoplankton and the future ocean, but they are obviously critically important to the carbon cycle and food webs. While there are already some clear changes in ocean pH and temperature—changes in primary production and species composition are very hard to track in any comprehensive way—so detecting changes due to climate is a challenge."

In the nine-page executive summary that begins chapter five of the IPCC report, the authors state "In response to ocean warming and increased stratification, open ocean nutrient cycles are being perturbed and there is high confidence that this is having a regionally variable impact on primary producers."

For the IPCC to declare "high confidence" there must be robust evidence and much agreement among sources of data.

The IPCC report identifies two trends in the ocean, warming and acidification, as the hydrosphere absorbs both heat and carbon dioxide from the atmosphere. The authors state baldly, "The ocean has warmed unabated since 2005, continuing the clear multi-decadal ocean warming trends documented in the IPCC Fifth Assessment Report (AR5)." Not only has acidification been shown via multiple datasets and models have increased but the rate of carbon dioxide uptake to be accelerating over the past two decades as atmospheric concentrations have climbed.

Grim projections for the ocean—and the life within it
“Ocean warming in the 20th century and beyond has contributed to an overall decrease in maximum catch potential,”
the new IPCC report says. This will compound the effects of overfishing for some fish stocks
and severely impact food, culture, and livelihoods [Credit: Kevin Phillips]
As a consequence of warming and other physical and biogeochemical processes (including declining pH) the oxygen content of the open ocean is declining, very likely by 0.5 to 3.3 percent between 1970 and 2010, according to the report. The decline in available oxygen suggests that environmental changes are affecting the primary producers, which convert carbon dioxide into oxygen as a byproduct of cell maintenance and growth.

"The two main questions," said Dyhrman, "center around how much primary production will change and how will species composition change and over what timescales. Modeling-based predictions vary widely in part because there are still major knowledge gaps regarding the drivers of phytoplankton dynamics and how they will change in the future."

Dyhrman referred to a recent study of ocean color by Stephanie Dutkiewicz of MIT and several co-authors. The study used satellite observations collected since the late 1990s to model shifts in ocean color caused by changes in the phytoplankton community. By 2100 the model suggests low-latitude oceans will be bluer because of a decline in phytoplankton numbers. In contrast, continued warming will cause high-latitude oceans to become greener as more diverse and denser phytoplankton communities develop.


"Changes in species composition may sound insignificant," Dyhrman said, "but we could accidentally select for harmful species, and we can all appreciate that such a shift in primary producers on land are big deal—for example, grasslands support a very different ecosystem than a forest."

According to the IPCC report, the "observed rate of range shifts since the 1950s and its very likely range are estimated to be 51.5±33.3 kilometers (32 miles) per decade and 29.0±15.5 kilometers (18 miles) per decade for organisms in the epipelagic and seafloor ecosystems, respectively. The direction of the majority of the shifts of epipelagic organisms are consistent with a response to warming."

In addition to disruptions caused by range shifting, the IPCC report suggests, "Ocean warming and changes in primary production in the 20th century are related to changes in productivity of many fish stocks, with an average decrease of approximately 3 percent per decade in population replenishment and 4.1 percent (very likely range of 9.0 percent decline to 0.3 percent increase) in maximum catch potential. Species composition of fisheries catches since the 1970s in many shelf seas ecosystems of the world is increasingly dominated by warm-water species."

"Some models," said Dyhrman, citing a 2018 study by J. Keith Moore and others, "suggest major reductions in primary production and thus fish stocks by 2030 with a re-distribution of the nutrients that fuel primary production. This is by no means a certainty, but is arguably one more reason to view our changing climate as the crisis that it is."

Author: Bill Chaisson | Source: Earth Institute, Columbia University [October 09, 2019]

Archaea hold clues to ancient ocean temperatures


Solving a decades-old mystery, Stanford researchers have discovered proteins that enable hardy microbes called archaea to toughen up their membranes when waters are overly warm. Finding these proteins could help scientists piece together the state of Earth's climate going back millions of years to when those archaea were cruising the ancient oceans.

Archaea hold clues to ancient ocean temperatures
This image shows a cell of archaea Sulfolobus tengchongensis under a microscope that has been
 infected by viruses. New research identifies proteins in this group of archaea that could
help gauge ancient ocean temperatures [Credit: Xiangyux/WikiCommons]
"People have been looking for these proteins for 40 years," said Paula Welander, an associate professor of Earth system science in Stanford University's School of Earth, Energy & Environmental Sciences (Stanford Earth), and lead author of a study describing the finding published in Proceedings of the National Academy of Sciences.

With this finding scientists can more accurately use the lipids - or fats - found in archaeal membranes and preserved in the ocean's sediments to estimate historic ocean temperatures, Welander said.

Battening down the hatches

When under stress, archaea fuse their usually double-layered cell membranes into a single layer. Battening down the hatches in this manner firms up the membranes, which, being mostly made of fat, can get too floppy when the temperature spikes - like butter left on a kitchen counter.


Some archaea further modify the structures that fuse their membrane layers by adding on ring-like pieces that make the membranes even more compact and sturdy. These adaptations are helpful from a climatology perspective, since the membrane-linking structures - along with those sets of rings - readily preserve in marine sediments. By examining the numbers and kinds of rings, climate scientists can gauge surface water temperatures where and when those archaea lived. This technique has been used as evidence of the warmer seas of the Jurassic era, dating back more than 150 million years to the heyday of the dinosaurs.

Finding the proteins involved in making those structures resolves some uncertainties scientists have had about inferring ancient temperatures from archaeal lipids - what they call the paleotemperature proxies.

Climatologists have presumed that a single group of archaea, the Thaumarchaeota, are responsible for making lipids with rings found in open oceans and that they add those rings in response to water temperature changes. But if other environmental factors such as salinity and acidity trigger ring production in other marine archaeal groups, that could scramble how they read the temperature signals.

According to the new study, climatologists can breathe a sigh of relief. By finally nailing down the proteins in play, the Stanford researchers show that Thaumarchaeota are indeed the dominant source of the ring-bearing membrane structures in ocean waters, supporting previous ideas of ancient sea surface temperatures.

"With that critical information now in hand, we can start to constrain some of the uncertainty about this particular archaea-based paleotemperature proxy," Welander said.

Pursuing the proteins

Although not identified until the late 1970s, archaea have since been recognized as constituting a whole new third domain of life, alongside the more-familiar bacteria and eukaryotes - multicellular organisms, including humans. Although archaea superficially resemble bacteria, biochemical and reproductive differences testify to their uniqueness. Many archaea are also extremophiles, which thrive in austere environments like hot springs where other life cannot survive.


To find the ring-making proteins, the Stanford team experimented with Sulfolobus acidocaldarius, among the least difficult archaea to grow and manipulate in a lab.

"This organism is one of the very few archaea that has a genetic system where we can do the kind of work we like to do," Welander said.

Her team set out to find which proteins enabled S. acidocaldarius to attach rings to its membrane-spanning structures. The researchers first found three possible genes by looking across the genomes of archaea that do and don't construct rings. They then created mutants in the lab lacking one, two or all three genes and, ultimately, two of these genes proved integral to the ring structures.

Those genes failed to turn up in another group of archaea that share marine environments with Thaumarchaeota and were considered as a possible, additional source of ringed structures in sediment samples. With that contribution ruled out, the sea temperature estimates derived from the paleotemperature proxy in question look more robust.

Taking it global

Welander said that scientists can now look into extending the Stanford team's findings into well-sampled marine regions worldwide. Her team picked through a genetic dataset from the north Pacific Ocean, and it therefore only directly speaks to that particular biome. Other datasets from the Atlantic Ocean and the Mediterranean Sea, for example, should reveal if Thaumarchaeota are also responsible for laying down the molecular fossils of interest in those areas. These paleotemperature proxies could even be extended into lakes and other environments, Welander said, opening up still more pages in Earth's climate chronicles.

Going beyond the climatological aspects of the findings, Welander noted that figuring out how the archaeal proteins handle the arcane work of membrane fusing could reveal compelling new biochemistry for potential real-world applications, such as drug discovery and materials science.

"Microbes invent all kinds of weird biochemistry to do all kinds of weird reactions," Welander said. "Anytime you can expand that chemistry of what is possible, it's really exciting from just a basic science perspective."

Author: Adam Hadhazy | Source: Stanford University [October 07, 2019]

Longest coral reef survey to date reveals major changes in Australia's Great Barrier Reef


Coral reefs around the world are under increasing stress due to a combination of local and global factors. As such, long-term investigation is becoming increasingly important to understanding ecosystem responses.

Longest coral reef survey to date reveals major changes in Australia's Great Barrier Reef
Soft coral are now dominating large areas of the shadow reef which in 1928 had many
species of hard corals too [Credit: Professor Maoz Fine, Bar-Ilan University]
A new study -- the longest coral reef survey to date - provides an in-depth look at Australia's Great Barrier Reef over the past 91 years. Published today in the journal Nature Communications by researchers at Bar-Ilan University and Interuniversity Institute for Marine Sciences in Israel, and the University of Queensland in Australia, the study concludes that since 1928 intertidal communities have experienced major phase-shifts as a result of local and global environmental change, leaving few signs that reefs will return to their initial state in the near future.


"This is a unique opportunity to look at long-term changes on an inshore reef system," said author Prof. Hoegh-Guldberg from the University of Queensland. "Most studies are only a few decades in length - this one is just short of 100 years of study."

In 1928 the Great Barrier Reef Committee and the Royal Society of London sent an expedition to study the Great Barrier Reef. Members of the expedition, pioneers in coral biology and reef studies, lived on Low Isles for over a year. During this time they documented environmental conditions surrounding the coral reefs of the Low Isles, as well as the community structure of tidal and subtidal communities, using, for the first time, a diving helmet.

Longest coral reef survey to date reveals major changes in Australia's Great Barrier Reef
The reef-flat at the Low Isles, which was covered with living branching Acropora corals in 1928
is now mostly dead [Credit: Professor Maoz Fine, Bar-Ilan University]
"What was critical to our study was how carefully the expedition in 1928 undertook their study," said lead author Prof. Maoz Fine, of the Mina and Everard Goodman Faculty of Life Sciences at Bar-Ilan University and the Interuniversity Institute for Marine Sciences. "We were literally able to go the exact spot and identify features that the 1928 expedition saw."


Members of the expedition produced aerial photography-based mapping of the island. This highly-accurate mapping enabled researchers in the current study to follow in their footsteps and revisit and sample the exact intertidal and subtidal locations previously explored 76, 87 and 91 years later, thereby forming the longest ecological survey to date.

In the latest investigation, carried out in three phases in 2004, 2015 and 2019, researchers discovered that intertidal communities have experienced major phase-shifts over nearly a century. Species richness and diversity of these communities systematically declined for corals and other invertebrates. Specifically, massive corals have replaced branching corals, and soft corals have become much more numerous.

Longest coral reef survey to date reveals major changes in Australia's Great Barrier Reef
These are patches of branching Acropora corals during low tide at Low Isles
[Credit: Professor Maoz Fine, Bar-Ilan University]
"The degree to which reefs may shift from one state to another following environment change was overwhelming," said Prof. Fine. "The long-term implications of these changes highlight the importance of avoiding phase shifts in coral reefs which may take many decades to repair, if at all." According to Fine the multi-year study also illustrates the importance of considering multiple factors in the decline, and potential recovery, of coral reefs, and the importance of tracking changes in community structure, as well as coral abundance, over long periods.

Coral reefs are highly sensitive to environmental change. Multiple stressors, in isolation or in combination, may lead to dramatic deterioration that can result in loss of reefs and their ecological services for many years. In the future the researchers hope to use the same methods to reconstruct data from other parts of the world where historical expeditions accurately documented similar communities.

Source: Bar-Ilan University [September 27, 2019]

More than 100 dolphins die on island beach off West Africa


Authorities in the Cape Verde islands off West Africa are waiting for experts from Spain to help determine why more than 100 dolphins died on a local beach.

More than 100 dolphins die on island beach off West Africa
Dead dolphins are seen on a beach on Boa Vista Island, Cape Verde. Authorities in the Cape Verde islands are waiting
for experts from Spain to help determine why more than 100 dolphins died on a local beach. Local media report
that around 200 melon-headed dolphins were found on a beach on Boa Vista island on Tuesday. Officials,
 residents and tourists managed to drag some of them back out to sea, but many returned
[Credit: Elton Neves via AP]


Local media report that around 200 melon-headed dolphins were found on a beach on Boa Vista island on Tuesday. Officials, residents and tourists managed to drag some of them back out to sea, but many returned. Bulldozers buried 136 dead dolphins.


BIOS Cape Verde, a volunteer environmental association in the former Portuguese colony, said on its Facebook page Friday it took samples from 50 dolphins and four others were placed in deep freeze by the local council.

The group said veterinarians from the University of Las Palmas in Spain's Canary Islands are due in the coming days to perform tests.

Source: The Associated Press [September 26, 2019]

Tale of two climate crises gives clues to the present


Figuring out what lies ahead for our species and our planet is one of the most pressing and challenging tasks for climate scientists. While models are very useful, there is nothing quite like Earth's history to reveal details about how oceans, animals, and plants respond to and recover from a warming world.

Tale of two climate crises gives clues to the present
(A) During the latest Maastrichtian environmental devastation is mainly due to volcanism (ash, aerosols and greenhouse
gases), resulting in rapid climate changes, acid rains and ocean acidification that is exacerbated by the Chicxulub
 impact, thus impeding calcification by marine plankton at the base of the food chain.[Credit: Paula Mateo]

The two most recent major global warming events are especially instructive -- and worrisome, say scientists presenting new research Wednesday at the Annual Meeting of the Geological Society of America.

Ancient analogs

The two past climate crises that are comparable to today's happened 56 and 66 million years ago. The earlier one, the Cretaceous-Paleogene boundary (KPB) mass extinction, is infamous for ending the reign of the dinosaurs. The later event, called the Paleocene-Eocene Thermal Maximum (PETM) was relatively less severe, and provides clues to how the world can recover from such difficult times.


"We chose these two because they are the most recent examples of rapid climate warming and have been widely studied so we have more information about them," said Paula Mateo, a geologist at Caltech, who presented the study.

Both ancient global warming events were, like today, caused by the release of greenhouse gases -- a.k.a. carbon emissions -- into the atmosphere. The sources in the past were not fossil fuel burning however, but related to very large and long volcanic eruptions -- unlike any that have occurred during the time humans have existed.

Tale of two climate crises gives clues to the present
(B) During the latest Paleocene to early Eocene: Gradual climate warming preceding the PEB is attributed
to North Atlantic Igneous Province volcanism (NAIP), but the rapid warming of 5 °C (PETM) is linked
to methane hydrates released from continental shelves resulting in acid rain on land and
ocean acidification (~170,000 years) [Credit: Paula Mateo]
The geologic evidence suggests that the carbon emissions that preceded the dinosaurs' demise were at an average rate of about 0.2 to 3 gigatons per year. The PETM recorded carbon emissions of less than 1.1 gigatons per year, Mateo said. Those numbers are dwarfed next to humanity's emission rate of 10 gigatons per year, she added.

Dino killer?

The KPB mass extinction event is often attributed solely to the Chicxulub meteor impact in Mexico, but there is a growing body of evidence suggesting that the massive eruption of the Deccan Traps in India also played a role. That mega-eruption flowed across India in pulse after pulse, lasting about 750,000 years.

A full 280,000 years before the extinction event the oceans had warmed 3 to 4 degrees Celsius while on land the warming was of 6 to 8 degrees C because of the eruptions. Volcanic activity accelerated during the last 25,000 years before the mass extinction, Mateo said, steadily releasing more carbon dioxide into the atmosphere. Those pulses added another 2.5 degrees C to the global temperature.


"This series of mega-pulses didn't let the ecosystems adapt or even survive," Mateo said. Fossil evidence suggests that the warming and ocean acidification stressed life on land and oceans, eventually contributing to one of the five mass extinction events in the history of the planet.

Microfossils of the oceans' foraminifers, which are part of the base of the marine food chain, show signs that they were struggling leading up the end of the Cretaceous period and then 66% went extinct at the KPB, 33% survived but rapidly disappeared during the first 100,000 years after the KPB, and only one species survived in the long term. On land warming during the last 280,000 years of the Cretaceous appears to have started a decline in dinosaurs as well in early mammals, insects, and amphibians well prior to the last mega-eruptions ending with the KPB mass extinction.

Ocean-building event

The more recent PETM, for its part, was caused by the expansion of the North Atlantic Ocean basin. That involved a lot of magma rising up from below to become the new ocean crust. All that magma released a lot of carbon dioxide, which appears to have caused moderate warming that, in turn, triggered the melting of clathrates -- frozen methane hydrate deposits in the ocean floor. The methane emissions supercharged the greenhouse situation and led to a 5 degree C spike of warming.

Tale of two climate crises gives clues to the present
(C) During the Anthropocene large inputs of greenhouse gases (CO2, SO2, N2O) linked to human activities and fossil
fuel burning leads to rapid warming and ocean acidification at a rate exceeding those at the PETM and KPB
by orders of magnitude. Global carbon budget data for the Anthropocene from Le Quere et al. (2013)
[Credit: Paula Mateo]
That warming was hard on living things on land and sea, but it wasn't a series of blows, like what led to the KPB. Many animals were able to adapt or migrate and avoid the harshest conditions. It was a single blow with environmental consequences that lasted about 200,000 years but there wasn't a mass extinction event.


The best analog

Listed side-by-side, it's sobering to see how many of the same ecosystem effects of the KPB and PETM are now being played out in the oceans and on land in real time as a result of anthropogenic warming.

"The difference with today is that even though it's a very short pulse, the rate of change is very, very rapid," said Mateo. "It's happening so fast that the ecosystems are unable to catch up. There is no time for adaptation."

So while today's greenhouse warming is a single pulse, as in the PETM, it is happening orders of magnitude faster, which could be creating effects more like those of the KPB.

Neither of the past events is a perfect analog, but they are instructive. The PETM could be an analogy for our best case scenario, Mateo explained. It's something humanity could potentially survive. The KPB, on the other hand, would be our worst case scenario analogy. If we take that path it would qualify as the sixth mass extinction in the planet's history.

Source: Geological Society of America [September 24, 2019]