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Octopuses May Be Adapting to The Rising Acidity of Our Oceans, Study Suggests

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We know that all the excess CO2 we’re pumping into the air – alongside a host of other damaging effects – is driving up the acidity of the oceans as it sinks and dissolves into the water, but it seems as though the hardy octopus can find ways to adapt to its rapidly changing environment.


Previous research into the impact of ocean acidification on cephalopods such as octopuses, cuttlefish, and squid has shown some indication increased carbon dioxide in the water could negatively impact this type of marine life.

However, in a new study, a group of Octopus rubescens – a species of octopus common to the west coast of North America – were observed adjusting their routine metabolic rate (RMR) over a series of weeks in response to lowering pH levels in the surrounding water.

“Challenges to an organism’s physiology are often reflected in changes in energy use and therefore can be observed as changes in aerobic metabolic rate,” write the researchers in their paper.

A total of 10 octopuses were studied under controlled lab conditions, with RMR measured immediately after exposure to acidic water, after one week, and after five weeks. Critical oxygen pressure – a measure of whether not not animals are getting enough oxygen – was monitored at the same time.

To begin with, high levels of metabolic change were detected in the creatures – a sort of shock reaction that actually conflicts with earlier research into cephalopods, which had recorded a reduction in metabolic change in similar scenarios.


However, RMR had returned to normal after one week, and remained the same five weeks later, suggesting some adaptation had occurred. The increased acidity did have an impact on the ability of the octopuses to function at low oxygen levels, however.

“This response in RMR suggests that O. rubescens is able to acclimate to elevated CO2 over time,” write the researchers. “The observed increase in RMR may be the result of multiple acute responses to hypercapnia [increased CO2 in the blood], possibly including both behavioural and physiological strategies.”

Those strategies could include preparing to move to find a new stretch of water to inhabit, for example, the researchers suggest (something that wasn’t possible here). The short RMR boost might also reflect the octopuses making quick adjustments to their biological processes to suit the new acid level.

The study is the first to look at both short-term (one week) and longer-term (five week) changes in metabolism rates in cephalopods in response to ocean acidification. We know these creatures are tough, and it seems they even have coping strategies that might allow them to adapt to humans destroying the natural environment all around them.

None of this means that we should be okay with the current climate crisis though, or not be trying to make major changes to reverse it. When we don’t take proper care of the planet, it’s not just ourselves that we’re potentially dooming to extinction.

Also, these tests were done in controlled laboratory conditions that don’t take into account many other interlinking factors in the animals’ natural environment. For instance, even if the octopus themselves are able to adjust, what about their food supply?

“While this species may be able to acclimate to near-term ocean acidification, compounding environmental effects of acidification and hypoxia may present a physiological challenge for this species,” write the researchers.

The research has been published in Physiological and Biochemical Zoology.


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Our Forests Are on Track to Hit a Crucial Climate Tipping Point by 2050, Scientists Warn

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Forests and other land ecosystems today absorb 30 percent of humanity’s CO2 pollution, but rapid global warming could transform these natural ‘sinks’ into carbon ‘sources’ within a few decades, opening another daunting front in the fight against climate change, alarmed researchers have said.


Climate skeptics often describe CO2 as “plant food”, suggesting that increased greenhouse gas emissions will be offset by a massive upsurge in plant growth.

But the new study shows that beyond a certain temperature threshold – which varies according to region and species – the capacity of plants to absorb CO2 declines.

Under current greenhouse gas emission trends, plants across half the globe’s terrestrial ecosystem could start to release carbon into the atmosphere faster than they sequester it by the end of the century, researchers reported this week in Science Advances.

Ecosystems that store the most CO2 – especially tropical and boreal forests – could lose more than 45 percent of their capacity as carbon sponges by mid-century, a team led by Katharyn Duffy from Northern Arizona University found.

“Anticipated higher temperatures associated with elevated CO2 could degrade land carbon uptake,” said the study, based not on modelling but data collected over a period of 25 years.

Failure to take this into account leads to a “gross overestimation” of the role Earth’s vegetation might play in reducing global warming, the researchers warned.


“The temperature tipping point of the terrestrial biosphere lies not at the end of the century or beyond, but within the next 20 to 30 years.”

Key to understanding how this could happen is the difference between photosynthesis and respiration, two chemical processes essential to plant life that respond differently to rising temperatures.

Drawing energy from sunlight, plants absorb carbon dioxide through their leaves and water from the soil, producing sugar to boost growth and oxygen, which is released into the air.

This is photosynthesis, which can only happen when there is daylight.

By contrast, the transfer of energy to cells through respiration – with CO2 excreted as a waste product – happens around the clock.

Tipping points

To find out if there is a temperature beyond which land-based ecosystems would start to absorb less CO2, Duffy and her team analysed records from a global observation network, called FLUXNET, spanning 1991 to 2015.

FLUXNET essentially tracks the movement of CO2 between ecosystems and the atmosphere.

They found that global photosynthesis peaks at certain temperatures, depending on the type of plant, and then declines thereafter.


Respirations rates, however, increase across all types of ecosystems without appearing to reach a maximum threshold.

“At higher temperatures, respiration rates continue to rise in contrast to sharply declining rates of photosynthesis,” the study found.

If carbon pollution continue unabated, this divergence will could see the CO2 absorption drop by half as early as 2040.

“We are rapidly entering temperature regimes where biosphere productivity will precipitously decline, calling into question the future viability of the land sink,” the researchers concluded.

The findings also call into question the integrity of many national commitments under the Paris Agreement – known as nationally determined contributions, or NDCs – to reduce greenhouse gases.

“These rely heavily on land uptake of carbon to meet pledges,” the authors point out.

The study notes that capping global warming under two degrees Celsius above pre-industrial levels, the cornerstone target of the 2015 Paris climate treaty, “allows for near-current levels of biosphere productivity, preserving the majority of land carbon uptakes.”

Earth has warmed at least 1.1C so far, and is currently on track to heat up another two to three degrees by century’s end unless emissions are rapidly and drastically reduced.

In 2019, a football pitch of primary, old-growth trees was destroyed in the tropics every six seconds – about 38,000 square kilometres (14,500 square miles) in all, according to satellite data.

© Agence France-Presse


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Greenhouse Gases Still at Record Levels Despite COVID-19 Lockdowns, UN Warns

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We’ve seen evidence that COVID-19 lockdowns have reduced at least some forms of pollution, temporarily – but the overall picture remains disturbingly grim, according to new figures from the United Nations’ World Meteorological Organisation (WMO).


The WMO says that there will be a reduction in global CO2 emissions for 2020 – but that it won’t affect atmospheric levels of CO2 any more than normal year-to-year fluctuations, and maybe even less than that.

CO2 levels reached 410 parts per million in 2019, and the final figure for 2020 is expected to be higher, negating what we thought might be one bit of good news to come out of the global pandemic that has dominated this year.

While staying at home and sheltering in place has meant we’ve pumped less carbon dioxide into the atmosphere, there’s so much of it already there that this year’s reduction is unlikely to have much of a long-term impact.

“Carbon dioxide remains in the atmosphere for centuries and in the ocean for even longer,” says WMO Secretary-General Professor Petteri Taalas.

“The last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago, when the temperature was 2-3°C [3.6-5.4°F] warmer and sea level was 10-20 metres [32.8-65.6 feet] higher than now. But there weren’t 7.7 billion inhabitants.”


As scientists have been warning for decades, more CO2 in the atmosphere means more heat gets trapped – temperatures go up, ice melts, extreme weather events happen more frequently, and the oceans acidify and become less hospitable to marine life.

Since 1990, the WMO reports that greenhouse gases sticking around in the air have caused a 45 percent increase in total radiative forcing – the term given to the overall warming effect on the climate. CO2 accounts for four-fifths of this effect.

Other research agrees with the conclusion that atmospheric levels of greenhouse gases are still on an upward trend, not least because of the many factors not related to coronavirus lockdowns – such as melting permafrost, which releases long-trapped CO2 and methane into the air.

“We breached the global threshold of 400 parts per million [of CO2] in 2015,” says Taalas. “And just four years later, we crossed 410 ppm. Such a rate of increase has never been seen in the history of our records.”

That’s not to stay lockdowns, shuttered workplaces, and reduced travel haven’t made a difference: the WMO estimates that CO2 emissions were reduced by up to 17 percent at some points in the year, and could have dropped by 4.2-7.5 percent over the course of 2020 (we’re still waiting for the final figures to come in).

However, that will only temporarily tap the brakes on atmospheric CO2 level rise. The amount of CO2 in the atmosphere is likely to go up again, though not by as much as in previous years – we saw a 2.6 ppm rise from 2018 to 2019, and the one from 2019 to 2020 could be about 0.08-0.23 ppm less than that.

If there is some hope from the COVID-19 pandemic, it may be in using it as a platform to serious tackle climate change – Taalas says that only a “complete transformation” of industrial, energy, and transport systems is going to be effective when it comes to lowering atmospheric CO2.

When you consider that the widespread and significant changes we’ve seen in human behaviour this year have barely made a dent in CO2 levels, it’s clear the sort of challenge we’re up against in reversing global warming.

“The COVID-19 pandemic is not a solution for climate change,” says Taalas. “The lockdown-related fall in emissions is just a tiny blip on the long-term graph. We need a sustained flattening of the curve.”

You can read the latest WMO Greenhouse Gas Bulletin here.


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Ancient Dust From The Ocean’s Depths May Have Helped Keep The Last Ice Age Cool

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The ocean floor of the South Pacific contains traces of ancient dust that may have changed Earth’s very climate, and new research suggests it came all the way from beneath ice-age glaciers of what is now Argentina. 


Whipped up by strong westerly winds some 20,000 years ago, these microscopic minerals would have circumnavigated nearly the entire globe before finally coming to rest in the middle latitudes of the Pacific.

Importantly, they carried a nutrient that could explain a period of global cooling. That ingredient was iron.

Iron is a vital nutrient for microscopic algae in our oceans, known as phytoplankton, and these creatures are in turn a fundamental part of Earth’s climate.

That’s because phytoplankton absorb carbon during photosynthesis, thereby storing atmospheric CO2 in our oceans and driving global cooling. They might even represent “the largest biological carbon sequestration mechanism on the planet“.

Today, iron still helps fertilise our oceans, but during the peak of Earth’s last ice age, a lot more iron-containing dust was unearthed during seasonal glacier melt, and it was blown into the ocean at a much higher rate.

All this extra iron fed phytoplankton that then lowered CO2 levels in the atmosphere and could help to explain “how the Earth could have become so cold at all at that time”, says Torben Struve, a geoscientist at the University of Oldenburg in Germany.


As such, some scientists think iron fertilisation might be a useful way to increase the carbon sink of our oceans and help cool our planet down in the future.

But geoengineering of this sort is a risky and controversial strategy, and the results of this new study just go to show how much dust would be needed to have a big enough impact.

Today, human emissions have caused CO2 levels to increase from around 280 to around 415 ppm (parts per million) since the industrial revolution – a surge that is far above natural levels.

During the last ice age, however, previous models have confirmed iron-bearing dust was responsible for drawing down atmospheric CO2 by some 40 ppm.

That’s roughly half the natural variation between that ice age and the following interglacial period, and not even a quarter of our own emissions.

Nevertheless, scientists are determined to learn more about this complex feedback system in the hopes that it could one day improve our climate models or help us capture more atmospheric carbon.

Analysing 18 sediment cores from the South Pacific Ocean between Antarctica, New Zealand, and Chile, the new study has compared the chemical fingerprints of ancient dust to geological data from several different continents. 


In the end, the findings suggest up to 80 percent of iron-containing dust came from what is now north-west Argentina – and it probably blew there the long way, travelling roughly 20,000 kilometres (12,400 miles) on powerful westerly winds during the last major ice age. 

That’s a unique and interesting discovery, because today, dust input from Australia’s rivers and lakes dominates the entire study area.

Even in the past, Patagonia is usually considered the major source of far-travelled, ancient dust, not regions further north in Central South America.

“[W]e were surprised to find that the sources and transport routes of the dust were completely different from today and also different from what we would have expected,” says Struve.

“Global warming has changed the winds and environmental conditions in the source regions.”

Even something as small as dust can have global repercussions. Thirty years after we first discovered its impact on the climate system, we are still learning more about these microscopic minerals, including where they came from.

The study was published in Nature Communications.


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What You Need to Know About That Controversial New Climate ‘Tipping Point’ Study

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Even if humanity stopped emitting greenhouse gases tomorrow, Earth will warm for centuries to come and oceans will rise by metres, according to a controversial modelling study published Thursday.


Natural drivers of global warming – more heat-trapping clouds, thawing permafrost, and shrinking sea ice – already set in motion by carbon pollution will take on their own momentum, researchers from Norway reported in the Nature journal Scientific Reports.

“According to our models, humanity is beyond the point-of-no-return when it comes to halting the melting of permafrost using greenhouse gas cuts as the single tool,” lead author Jorgen Randers, a professor emeritus of climate strategy at the BI Norwegian Business School, told AFP.

“If we want to stop this melting process we must do something in addition – for example, suck CO2 out of the atmosphere and store it underground, and make Earth’s surface brighter.”

Using a stripped-down climate model, Randers and colleague Ulrich Goluke projected changes out to the year 2500 under two scenarios: the instant cessation of emissions, and the gradual reduction of planet warming gases to zero by 2100.

In an imaginary world where carbon pollution stops with a flip of the switch, the planet warms over the next 50 years to about 2.3 degrees Celsius above pre-industrial levels – roughly half-a-degree above the target set in the 2015 Paris Agreement – and cools slightly after that.


Earth’s surface today is 1.2C hotter than it was in the mid-19th century, when temperatures began to rise.

But starting in 2150, the model has the planet beginning to gradually warm again, with average temperatures climbing another degree over the following 350 years, and sea levels going up by at least three metres.

Under the second scenario, Earth heats up to levels that would tear at the fabric of civilisation far more quickly, but ends up at roughly the same point by 2500.

Tipping points

The core finding – contested by leading climate scientists – is that several thresholds, or “tipping points”, in Earth’s climate system have already been crossed, triggering a self-perpetuating process of warming, as has happened millions of years in the past.

One of these drivers is the rapid retreat of sea ice in the Arctic.

Since the late 20th century, millions of square kilometres of snow and ice – which reflects about 80 percent of the Sun’s radiative force back into space – have been replaced in summer by open ocean, which absorbs the same percentage instead.


Another source is the thawing of permafrost, which holds twice as much carbon as there is in the atmosphere. The third is increasing amounts of water vapour, which also has a warming effect.

Reactions from half-a-dozen leading climate scientists to the study – which the authors acknowledge is schematic – varied sharply, with some saying the findings merit follow-up research, and others rejecting it out of hand.

“The model used here is .. not shown to be a credible representation of the real climate system,” said Richard Betts, head of climate impacts research at the University of Exeter.

“In fact, it is directly contradicted by more established and extensively evaluated climate models.”

Mark Maslin, a professor of climatology at University College London, also pointed to shortcomings in the model, known as ESCIMO, describing the study as a “thought experiment.”

“What the study does draw attention to is that reducing global carbon emissions to zero by 2050” – a goal championed by the UN and embraced by a growing number of countries – “is just the start of our actions to deal with climate change.”

Even the more sophisticated models used in the projections of the UN’s scientific advisory body, the IPCC, show that the Paris climate pact temperature goals cannot be reached unless massive amounts of CO2 are removed from the atmosphere.

One way to do that is planting billions of trees. Experimental technologies have shown that sucking CO2 out of the air can be done mechanically, but so far not at the scale required.

© Agence France-Presse


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Catastrophic Trigger That Led to Earth’s Largest Mass Extinction Revealed in Fossils

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Scientists think they’ve finally come closer to identifying the cause of Earth’s worst mass extinction, by tracking down the geochemical trigger that may have started it all.

Known as the Great Dying, the Permian-Triassic extinction event happened around 252 million years ago. The new research is based on a study of fossil shells left behind by clam-like brachiopods in what today is the Southern Alps.


The shells record seawater pH levels which are affected by atmospheric CO2 concentrations, and it looks as though roughly 252 million years ago there was a sudden, intense injection of carbon dioxide into the atmosphere.

It was most likely from a gigantic series of volcanic eruptions in Siberia, the researchers say. The increased warming and ocean acidification would have killed off certain species very quickly, while increasingly nutrient-rich waters would then have depleted oxygen levels in the ocean over a longer time period, causing further extinctions.

“This domino-like collapse of the inter-connected life-sustaining cycles and processes ultimately led to the observed catastrophic extent of mass extinction at the Permian-Triassic boundary,” says marine biogeochemist Hana Jurikova who is now at the University of St Andrews in the UK.

The team measured different isotopes of boron and carbon in the shells to get a reading on the seawater acidity using high-precision instruments like the large-geometry secondary ion mass spectrometer (SIMS). Combined with detailed computer models, the data could be used to re-enact the Great Dying.

Scientists have long accepted that a series of volcanic eruptions in what is now Siberia were a key cause of the Great Dying, but this is the first time a reconstruction of the atmospheric circumstances has been made in such detail. This provides us with more information on the underlying mechanisms of what happened on Earth at the time, and what the consequences were over the next several thousand years


This study answers some questions about the combination of events and their sequence, clearly linking the CO2 rise with volcanic activity. The analysis and modelling also suggests that another factor – the release of large amounts of methane by microbes on the sea floor – wasn’t so important.

“With this technique, we can not only reconstruct the evolution of the atmospheric CO2 concentrations, but also clearly trace it back to volcanic activity,” says marine biochemist Marcus Gutjahr from the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany.

“The dissolution of methane hydrates, which had been suggested as a potential further cause, is highly unlikely based on our data.”

Scientists continue to piece together the story of what happened in the Permian-Triassic extinction based on geological records that are hundreds of millions of years old – not the easiest bit of detective work.

There’s still plenty more to discover about what the contributing factors were, how long they lasted, and how some species hung on. Around 96 percent of marine species and 70 percent of terrestrial vertebrate species were killed off for good.

What makes this new study exciting is that it shows how our understanding can be deepened through improved analysis techniques that are coming online, including the use of spectrometry and the study of brachiopod fossils.

“Without these new techniques it would be difficult to reconstruct environmental processes more than 250 million years ago in the same level of detail as we have done now,” says marine geochemist Anton Eisenhauer, from GEOMAR. “In addition, the new methods can be applied for other scientific applications.”

The research has been published in Nature Geoscience.


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The Ocean Is Becoming More Stable, And The Consequences May Be Dire, Scientists Warn

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Global warming is making the oceans more stable, increasing surface temperatures and reducing the carbon they can absorb, according to research published Monday by climate scientists who warned that the findings have “profound and troubling” implications.


Man-made climate change has increased surface temperatures across the planet, leading to atmospheric instability and amplifying extreme weather events, such as storms.

But in the oceans, higher temperatures have a different effect, slowing the mixing between the warming surface and the cooler, oxygen-rich waters below, researchers said.

This ocean “stratification” means less deep water is rising towards the surface carrying oxygen and nutrients, while the water at the surface absorbs less atmospheric carbon dioxide to bury at depth.

In a report published in the journal Nature Climate Change, the international team of climate scientists said they found that stratification globally had increased by a “substantial” 5.3 percent from 1960 to 2018.

Most of this stabilisation occurred towards the surface, and was attributed largely to temperature rises.

They said this process is also exacerbated by the melting of sea ice, meaning that more fresh water – which is lighter than salt water – also accumulates on the surface of the ocean.

Study co-author Michael Mann, a climate science professor at Pennsylvania State University, said in a commentary published in Newsweek that the “seemingly technical finding has profound and troubling implications.”


These include potentially driving more “intense, destructive hurricanes” as ocean surfaces warm.

Mann also pointed to a reduction in the amount of CO2 absorbed, which could mean that carbon pollution builds up faster than expected in the atmosphere.

He warned that sophisticated climate models often underestimate ocean stratification and may also be underestimating its impact.

With warmer upper waters receiving less oxygen, there are also implications for marine life.

By absorbing a quarter of man-made CO2 and soaking up more than 90 percent of the heat generated by greenhouse gases, oceans keep the population alive – but at a terrible cost, according to the Intergovernmental Panel for Climate Change (IPCC).

Seas have grown acidic, potentially undermining their capacity to draw down CO2. Warmer surface water has expanded the force and range of deadly tropical storms.

Marine heatwaves are wiping out coral reefs, and accelerating the melt-off of glaciers and ice sheets driving sea level rise.

Last year, research published in the US Proceedings of the National Academy of Sciences calculated that climate change would empty the ocean of nearly a fifth of all living creatures, measured by mass, by the end of the century.

© Agence France-Presse


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Too Much CO2 Has an Unnerving Effect on The World’s Trees, New Study Finds

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Trees that grow quickly die younger, risking a release of carbon dioxide that challenges forecasts that forests will continue to be a “sink” for planet-warming emissions, scientists said Tuesday.


Tree cover absorbs a significant proportion of carbon dioxide emitted by burning fossil fuels and plays a crucial role in projections for our ability to wrestle down CO2 levels.

Researchers said current climate models expect forests to continue to act as a carbon sink through this century, with high temperatures and concentrations of CO2 thought to stimulate tree growth and so help them absorb more carbon as they mature quicker.

But in the study, led by England’s Leeds University and published in the journal Nature Communications, they warned that this faster growth was also linked to trees dying younger – suggesting increases in the role of forests as carbon storage may be “short lived”.

The researchers examined more than 200,000 tree-ring records from tree species across the globe and found that trade-offs between growth and lifespans occurred in almost all of them, including tropical trees.

Society has benefited from the increasing ability of forests to soak up carbon in recent decades, said co-author Steve Voelker, from the State University of New York College of Environmental Science and Forestry, in a Leeds University statement.


But these CO2 uptake rates are “likely to be on the wane as slow-growing and persistent trees are supplanted by fast-growing but vulnerable trees”, he added.

“Our findings, very much like the story of the tortoise and the hare, indicate that there are traits within the fastest growing trees that make them vulnerable, whereas slower growing trees have traits that allow them to persist,” he said.

The researchers said the findings suggest that the chances of dying increase dramatically as trees reach their maximum potential size.

But they said it might also be that fast-growing trees invest less in defences against diseases or insect attacks, or are more vulnerable to drought.

Earth’s average surface temperature has risen just over one degree Celsius above pre-industrial levels, enough to boost the severity of droughts, heatwaves and superstorms made more destructive by rising seas.

Sink or source?

Commenting on the study, David Lee, professor of atmospheric science at England’s Manchester Metropolitan University, said Earth system climate models currently predict the carbon storage of forests to continue or increase.

“This study shows the opposite, that increased CO2 compromises forests as a carbon sink,” he said.


That suggests the idea that “fossil-fuel based emissions can be ‘offset’ by planting trees (or avoiding deforestation) really does not stand up to scientific scrutiny”, he added.

But Keith Kirby, woodland ecologist at the University of Oxford, said it was not necessarily the case that forests would reverse their carbon role.

“We cannot rely as much on increased growth per unit area to maintain and enhance the forest carbon sink potential, but this might be offset by slowing deforestation and increasing the expansion of the extent of forests where this can be done in a sustainable way,” he said.

Global forests – and especially the tropics – soak up 25 to 30 percent of the planet-warming CO2 humanity spews into the atmosphere.

Last year, a football pitch of primary, old-growth trees was destroyed every six seconds, about 38,000 square kilometres (14,500 square miles) in all, according to Global Forest Watch.

© Agence France-Presse


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Engineer Explains How You Can Use Ventilation to Prevent Coronavirus Spread Indoors

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The vast majority of SARS-CoV-2 transmission occurs indoors, most of it from the inhalation of airborne particles that contain the coronavirus. The best way to prevent the virus from spreading in a home or business would be to simply keep infected people away. But this is hard to do when an estimated 40 percent of cases are asymptomatic and asymptomatic people can still spread the coronavirus to others.


Masks do a decent job at keeping the virus from spreading into the environment, but if an infected person is inside a building, inevitably some virus will escape into the air.

I am a professor of mechanical engineering at the University of Colorado Boulder. Much of my work has focused on how to control the transmission of airborne infectious diseases indoors, and I’ve been asked by my own university, my kids’ schools and even the Alaska State Legislature for advice on how to make indoor spaces safe during this pandemic.

Once the virus escapes into the air inside a building, you have two options: bring in fresh air from outside or remove the virus from the air inside the building.

It’s all about fresh, outside air

The safest indoor space is one that constantly has lots of outside air replacing the stale air inside.

In commercial buildings, outside air is usually pumped in through heating, ventilating and air-conditioning (HVAC) systems. In homes, outside air gets in through open windows and doors, in addition to seeping in through various nooks and crannies.


Simply put, the more fresh, outside air inside a building, the better. Bringing in this air dilutes any contaminant in a building, whether a virus or a something else, and reduces the exposure of anyone inside.

Environmental engineers like me quantify how much outside air is getting into a building using a measure called the air exchange rate. This number quantifies the number of times the air inside a building gets replaced with air from outside in an hour.

While the exact rate depends on the number of people and size of the room, most experts consider roughly six air changes an hour to be good for a 10-foot-by-10-foot room with three to four people in it. In a pandemic this should be higher, with one study from 2016 suggesting that an exchange rate of nine times per hour reduced the spread of SARS, MERS and H1N1 in a Hong Kong hospital.

Many buildings in the US, especially schools, do not meet recommended ventilation rates. Thankfully, it can be pretty easy to get more outside air into a building.


Keeping windows and doors open is a good start. Putting a box fan in a window blowing out can greatly increase air exchange too. In buildings that don’t have operable windows, you can change the mechanical ventilation system to increase how much air it is pumping.

But in any room, the more people inside, the faster the air should be replaced.

Using CO2 to measure air circulation

So how do you know if the room you’re in has enough air exchange? It’s actually a pretty hard number to calculate. But there’s an easy-to-measure proxy that can help.

Every time you exhale, you release CO2 into the air. Since the coronavirus is most often spread by breathing, coughing or talking, you can use CO2 levels to see if the room is filling up with potentially infectious exhalations. The CO2 level lets you estimate if enough fresh outside air is getting in.

Outdoors, CO2 levels are just above 400 parts per million (ppm). A well ventilated room will have around 800 ppm of CO2. Any higher than that and it is a sign the room might need more ventilation.


Last year, researchers in Taiwan reported on the effect of ventilation on a tuberculosis outbreak at Taipei University. Many of the rooms in the school were underventilated and had CO2 levels above 3,000 ppm.

When engineers improved air circulation and got CO2 levels under 600 ppm, the outbreak completely stopped. According to the research, the increase in ventilation was responsible for 97 percent of the decrease in transmission.

Since the coronavirus is spread through the air, higher CO2 levels in a room likely mean there is a higher chance of transmission if an infected person is inside. Based on the study above, I recommend trying to keep the CO2 levels below 600 ppm. You can buy good CO2 meters for around US$100 online; just make sure that they are accurate to within 50 ppm.

Air cleaners

If you are in a room that can’t get enough outside air for dilution, consider an air cleaner, also commonly called air purifiers. These machines remove particles from the air, usually using a filter made of tightly woven fibers. They can capture particles containing bacteria and viruses and can help reduce disease transmission.

The US Environmental Protection Agency says that air cleaners can do this for the coronavirus, but not all air cleaners are equal. Before you go out and buy one, there are few things to keep in mind.

The first thing to consider is how effective an air cleaner’s filter is. Your best option is a cleaner that uses a high-efficiency particulate air (HEPA) filter, as these remove more than 99.97 percent of all particle sizes.

The second thing to consider is how powerful the cleaner is. The bigger the room – or the more people in it – the more air needs to be cleaned. I worked with some colleagues at Harvard to put together a tool to help teachers and schools determine how powerful of an air cleaner you need for different classroom sizes.

The last thing to consider is the validity of the claims made by the company producing the air cleaner.

The Association of Home Appliance Manufacturers certifies air cleaners, so the AHAM Verifide seal is a good place to start. Additionally, the California Air Resources Board has a list of air cleaners that are certified as safe and effective, though not all of them use HEPA filters.

Keep air fresh or get outside

Both the World Health Organization and US Centers for Disease Control and Prevention say that poor ventilation increases the risk of transmitting the coronavirus.

If you are in control of your indoor environment, make sure you are getting enough fresh air from outside circulating into the building. A CO2 monitor can help give you a clue if there is enough ventilation, and if CO2 levels start going up, open some windows and take a break outside.

If you can’t get enough fresh air into a room, an air cleaner might be a good idea. If you do get an air cleaner, be aware that they don’t remove CO2, so even though the air might be safer, CO2 levels could still be high in the room.

If you walk into a building and it feels hot, stuffy and crowded, chances are that there is not enough ventilation. Turn around and leave.

By paying attention to air circulation and filtration, improving them where you can and staying away from places where you can’t, you can add another powerful tool to your anti-coronavirus toolkit. The Conversation

Shelly Miller, Professor of Mechanical Engineering, University of Colorado Boulder.

This article is republished from The Conversation under a Creative Commons license. Read the original article.


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Simple Addition to Crops Could Help Soak Up 2 Billion Tonnes of CO2 Each Year

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Drastically reducing the amount of carbon dioxide (CO2) we’re pumping into the atmosphere is the best way of tackling our climate crisis, but soaking up CO2 could make a huge difference as well – and scientists have found one way to significantly boost the amount of CO2 that crops are able to absorb.


The trick is adding crushed rock dust, which triggers a reaction known as enhanced rock weathering (ERW): minerals in the tiny bits of rock chemically bind with the CO2 naturally picked up by rainwater as it falls on the ground.

The bicarbonate end product then washes away to be locked into the soil or, ultimately, the ocean.

Rock weathering happens naturally, but it speeds up when smaller rock particles are used so that it only takes months. 

The simple addition to crops would be enough to remove 2 billion tonnes of CO2 every year if it was deployed worldwide, the scientists calculated.

That’s about as much CO2 as the aviation and shipping industries pump into the atmosphere every year.

“Carbon dioxide drawdown strategies that can scale up and are compatible with existing land uses are urgently required to combat climate change, alongside deep and sustained emissions cuts,” says David Beerling, the director of the Leverhulme Centre for Climate Change Mitigation at the University of Sheffield in the UK.

“Spreading rock dust on agricultural land is a straightforward, practical CO2 drawdown approach with the potential to boost soil health and food production.”


The analysis involved creating extensive gridded maps of the world’s farmland and the weather systems that they experience. Costs, engineering challenges, and CO2 removal potential were broken down by country.

Even the quality of the local soil and the energy required to transport rock dust to each location was factored in as well, as there’s little point removing CO2 from the atmosphere if we’re going to be emitting even more in the effort to get the necessary materials to farmers in the first place.

The 2 billion tonne figure they came up with is something the researchers think we could get to by 2050, with everyone pulling together. While the approach is not without its challenges, it does have certain factors in its favour – not least that farmers already do something like it.

“The practice of spreading crushed rock to improve soil pH is commonplace in many agricultural regions worldwide,” says Steven Banwart, director of the Global Food and Environment Institute at the University of Leeds in the UK.

“The technology and infrastructure already exist to adapt these practices to utilise basalt rock dust. This offers a potentially rapid transition in agricultural practices to help capture CO2 at large scale.”


The technique has a number of bonuses. It can help stop the deterioration of topsoil, it reduces the acidity of rainwater (and also the acidity of the oceans), and we could use stockpiles of silicate rock dust left over from the mining industry as well as construction byproducts for the job.

Scientists have been exploring this idea for a number of years, but this is the first detailed report on the potential global cost and effect of ERW. The nations with the highest CO2 output, including the US and India, could suck up the most carbon dioxide the researchers say, because of their extensive agricultural industries and climates.

All that said, this would still be a huge challenge: efforts would need to be carefully coordinated across the world’s farms, any efforts would need to be well funded, and, unfortunately, adding rock dust to crops isn’t going to be nearly enough to save us on its own.

What’s more, this detailed model now needs real-world testing to back it up and check for any potential and unwanted side effects.

Still, we need options like this now more than ever.

“We have passed the safe level of greenhouse gases,” says climatologist James Hansen, from Columbia University.

“Cutting fossil fuel emissions is crucial, but we must also extract atmospheric CO2 with safe, secure and scalable carbon dioxide removal strategies to bend the global CO2 curve and limit future climate change.”

The research has been published in Nature.


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