Recent global warming trends are inconsistent with very high climate sensitivity

Credit: CC0 Public Domain

Research published this week in Earth System Dynamics reports that the most sensitive climate models overestimate global warming during the last 50 years.

Recent developments in cloud modeling have produced models that portray very large sensitivity to rising .

A subset of models even showed that a doubling of CO2 could lead to over 5°C of , questioning whether the goals of the Paris agreement are achievable even if nations do everything they can.

The lead author of the study, Ph.D. candidate Femke Nijsse from the University of Exeter, said: “In evaluating the climate models we were able to exploit the fact that thanks to clean air regulation, air pollution in the form of climate-cooling aerosols have stopped increasing worldwide, allowing the greenhouse gas signal to dominate recent warming.”

The amount of warming that occurs after CO2 concentrations in the atmosphere are doubled is called the equilibrium climate sensitivity.

The study found that based on the latest generation of climate models the equilibrium climate sensitivity is likely between 1.9 and 3.4 °C.

Co-author Mark Williamson, of Exeter’s Global Systems Institute, added: “Global warming since 1970 also provides even better guidance on the rate of climate change in the future.

“We find a likely range for the ‘Transient Climate Response’ of 1.3-2.1 °C, whether we use the latest models or the previous generation of models.”

The new study is only one piece of the puzzle.

A recent review paper found that low estimates of climate sensitivity can be excluded because they are, in general, not consistent with climate changes in Earth’s past.

Co-author Professor Peter Cox explains the significance of these findings: “It is good to see that studies are now converging on a range of equilibrium  sensitivity, and that both high and low values can be excluded.

“For over forty years,  have tried to pinpoint this quantity and it seems that we’re finally getting close.”

Explore further

More sensitive climates are more variable climates, research shows

A Drop in Sulfate Emissions During the Coronavirus Lockdown Could Intensify Arctic Heatwaves

Lower greenhouse gas emissions slow climate change, but declines of sulfate aerosols that reflect heat away from the planet may bring short-term warming.


JUN 8, 2020

The Arctic underwent an unprecedented heat wave this spring. Credit: Kathryn Hansen/NASA

In mid-May, a pocket of scorching hot air flowed north from Siberia and fanned out across the Arctic Ocean, reaching as far as Greenland and triggering an unprecedented heatwave. In Khatanga, a Russian village above the Arctic Circle that normally remains below freezing in the spring, the mercury hit 77 degrees Fahrenheit, smashing the previous record by 23 degrees. According to temperature records which go back to 1958, no other year has been hotter in the Arctic for this same time period.

This weather anomaly has since ignited significant wildfires in Russia and contributed to the rapid melt-out of sea ice in the Arctic Ocean—possibly jumpstarting this year’s melt season. Indeed, sea ice is currently at its fourth lowest extent for this time of year since record-keeping began in the 1970s.

“Overall, this winter wasn’t particularly warm, but now that’s flipped around in the last month and we’re really seeing the effects,” says Mark Serreze, director of the National Snow and Ice Data Center (NSIDC). “Big holes are opening up along the Siberian coast where it’s been the warmest.”

This Central Arctic heatwave may not be a one-off event only occurring in spring 2020, researchers suggest. Rather, if levels of global industrial air pollutants continue to fall due to the Covid-19 pandemic, the current Arctic warmth could be a bellwether of what’s to come later this summer when sea ice melt annually kicks into high gear.

According to a recent study in Nature Climate Change, daily global greenhouse gas emissions dropped by 17 percent in early April compared to last year’s numbers. If maintained, a decline in carbon pollution is a good thing for global climate stability and for avoiding the most severe consequences of climate change.

But in the short-term, a drop-off in atmospheric pollutants can actually cause a slight increase in global warming. That’s because heat-trapping gases such as carbon dioxide and methane aren’t the only thing released by burning fossil fuels. Sulfate aerosols are also spewed into the air, and these aerosols are known to produce a cooling effect on the planet, mitigating some of the warming from greenhouse gases. If aerosol emissions are going down, it’s possible we could see a slight upward temperature bump this spring and summer, which could speed up Arctic sea ice melt.

“Ultimately we need to eliminate sulfur pollution and sulfate aerosols, which cause lots of other problems too, such as acid rain,” says Michael Mann, a renowned climatologist and director of the Earth System Science Center at Pennsylvania State University. “But it is a ‘Faustian bargain’ in the sense that [reductions in aerosols] unmasks some of the global warming that had been hidden for decades by the sulfate aerosol pollution.”

Sulfate Aerosols Can Cool the Planet, but Not for Long

Unlike greenhouse gases which can remain in our atmosphere for years, sulfate aerosols are relatively short-lived. They’re typically washed out of the troposphere in a matter of weeks, and therefore need to be constantly replenished by industry to maintain their cooling benefits.

Sulfate aerosols counteract planetary warming in two different ways. For one thing, they’re highly reflective.

“They reflect a lot of sunlight back into space, rather than have it absorbed and warming the earth,” explains Michael Diamond, an atmospheric scientist at the University of Washington. “They can also change cloud properties. Clouds aren’t just pure water—they need a seed or a nuclei to form.”

Sulfate aerosols provide such nuclei for water to condense around, creating a greater abundance of clouds, and more reflective clouds as well—an effect known as “cloud brightening.”

“It’s like a lot of little mirrors reflecting sunlight back to space,” says Diamond.

The United Nations Intergovernmental Panel on Climate Change has long struggled to quantify the exact cooling impact of sulfate aerosols. According to Mann, aerosols have likely been responsible for offsetting about 0.7 degrees Fahrenheit of global surface warming, and a much larger amount—more than 1.8 degrees—in the mid-latitude regions during summer when there is more sunlight to reflect back.

An AGU Advances study published in March 2020 sought to further quantify the aerosol impact on cloud brightening, with researchers zeroing in on a shipping lane in the southeast Atlantic. Diamond, who served as lead author of that study, found that sulfate aerosols from shipping were responsible for reducing warming by two watts per meter squared. To put that in perspective, greenhouse gases are responsible for warming of about 4 watts per meter squared.

When Diamond and his team calculated the global cooling effect from all industrial activity around the world, on land and at sea, they found that sulfate aerosol-seeded clouds masked about a third of all warming from greenhouse gases.

And Then Came Covid-19

Researchers around the world are now trying to parse out how Coronavirus lockdown measures have affected global emissions. In the Nature Climate Change study published last month, an international team of scientists found that daily CO2 emissions dropped by 17% at the peak of the coronavirus shutdown.

However, emissions are creeping back up as shelter in place measures are relaxed. By year’s end it’s expected 2020 CO2 emissions will end up between 4 and 7% lower than 2019—the biggest drop since World War II.

Another study published in Geophysical Research Letters in May found that nitrogen dioxide pollution over China, Western Europe and the United States decreased by as much as 60% in early 2020 compared to the same time last year. And a study focused on northern China found that levels of particulate matter known as PM 2.5, a notable human health hazard, decreased by approximately 60 percent in January and February.

But Diamond says the picture is a bit more muddied when it comes to aerosols. His research group has been examining emission levels from China in February 2020.

“In the clouds over the South China Plain and East China Sea, you don’t see any difference in the size of those cloud droplets,” he says, indicating there hasn’t been a significant change in the level of sulfate aerosols in the atmosphere.

One explanation could be that though passenger traffic has fallen during the pandemic, electricity generation for industrial combustion is only down by about 10%, according to data from the Chinese government.

However, coincidentally, in January 2020, the United Nations International Maritime Organization implemented a policy banning ships from using fuels with a sulfur content above 0.5 percent, a seven-fold reduction from the 3.5 percent allowed previously.

“Any signal we’re seeing in international shipping right now is a combination of this policy and the pandemic,” says Diamond.

Sulfate aerosols have been decreasing in the United States under the Clean Air Act as well, says Patricia Quinn, atmospheric chemistry leader at the U.S. National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Lab. Since the 1980s, sulfate aerosols have likely declined by between 30 and 50 percent.

“It’s not serving as big as a mitigator [of warming] as it once was,” Quinn said. “Coal-fired power plants—a major source—aren’t being used as much as they were a few years ago because it’s a more expensive form of energy production now.”

Indeed, in a 2017 study, scientists posited that the sulfate aerosols released due to human activity masked the decline in Arctic sea ice in the mid-20th century, before the Clean Air Act went into effect, and actually led to periods of ice growth.

A Riddle, Wrapped in a Mystery, Inside an Enigma

So how might a reduction in sulfate aerosol levels affect the Arctic during the coronavirus pandemic?

Quite a lot—maybe. Juan Acosta Navarro is an environmental scientist at the Barcelona Supercomputing Center. He says that, “the Arctic appears to be quite sensitive to changes in emissions of sulfate aerosols.”

Using earth system computer modelling, his simulations showed that sulfate aerosol reductions in Europe since 1980 could potentially explain a significant fraction of Arctic warming over that period. Specifically, the Arctic received approximately 0.3 watts per meter squared of energy, warming by 0.9 degrees Fahrenheit on average as Europe’s sulfur emissions declined.

“We conclude that air quality regulations in the Northern Hemisphere, the ocean and atmospheric circulation, and the Arctic climate are inherently linked,” his 2016 Nature Geoscience study stated.

But weather variability and climate system chaos—as always—still provide an obstacle to making any long-term predictions about the sea ice outcome this year, or any year.

“Patterns of the atmospheric circulation are going to play a huge role in what summer looks like,” says NSIDC’s Serreze. “Could we be looking at a record high global temperature this year? Maybe. We’re kind of on track for that right now. What’s going to happen with the sea ice? We know it’s well below average right now, but [weather variability] can counter the effects of greenhouse gases” in the short term.

Still, he’s energized—certainly not by Covid-19, but by the prospect of being able to test the role of sulfate aerosols on global warming.

“Here we are, in a serendipitous sense, presented with this incredible global experiment. We can perhaps see what the effects are [of sulfate aerosol reduction] and how this relates back to the sea ice.”

“Every cloud has a silver lining,” he concludes.

Gloria Dickie is a freelance journalist based in British Columbia, Canada. Her work appears in The New York Times, The Guardian, Scientific American, National Geographic and Wired. Follow her on Twitter @GloriaDickie or read more of her work at

This article was first published in Mongabay

Scientists Create a Prototype ‘Air Plasma’ Engine That Works Without Fossil Fuels

main article image
(RgStudio/Getty Images)

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6 MAY 2020
…the prototype was able to launch a one-kilogram (2.2-pound) steel ball 24 millimeters (almost one inch) into the air.

A prototype jet engine can propel itself without using any fossil fuels, potentially paving the way for carbon-neutral air travel.

The device compresses air and ionizes it with microwaves, generating plasma that thrusts it forward, according to research published Tuesday in the journal AIP Advances. That means planes may someday fly using just electricity and the air around them as fuel.

There’s a long way to go between a proof-of-concept prototype and installing an engine in a real plane. But the prototype was able to launch a one-kilogram (2.2-pound) steel ball 24 millimeters (almost one inch) into the air. That’s the same thrust, proportional to scale, as a conventional jet engine.

“Our results demonstrated that such a jet engine based on microwave air plasma can be a potentially viable alternative to the conventional fossil fuel jet engine,” lead researcher and Wuhan University engineer Jau Tang said in a press release.

230879 webSchematics of the prototype and images of the bright plasma jet at different microwave powers. (Jau Tang and Jun Li)

Air travel represents a small but not insignificant portion factor of climate change. The New York Times reported in September that commercial air is responsible for 2.5 percent of all greenhouse gas emissions – though that excludes military jets.

“The motivation of our work is to help solve the global warming problems owing to humans’ use of fossil fuel combustion engines to power machinery, such as cars and airplanes,” Tang said in the release.

“There is no need for fossil fuel with our design, and therefore, there is no carbon emission to cause greenhouse effects and global warming.”

This article was originally published by Futurism. Read the original article.

2°C crossed

FRIDAY, MARCH 13, 2020

It’s time to stop denying how precarious the situation is.

Remember the Paris Agreement? In 2015, politicians pledged to hold the global temperature rise to well below 2°C above pre-industrial levels and pledged they would try and limit the temperature rise to 1.5°C above pre-industrial levels. Well, an analysis by Sam Carana shows that it was already more than 1.5°C above pre-industrial when the Paris Agreement was reached.

In Sam Carana’s analysis, the year 1750 is used as the baseline for pre-industrial. The analysis shows that we meanwhile have also crossed the 2°C threshold (in February 2020) and that the temperature rise looks set to rapidly drive humans and eventually most if not all species on Earth into extinction.

Yet, our politicians refuse to act!

Accelerating temperature rise

Indeed, there are indications that the recent rise is part of a trend that points at even higher temperatures in the near future, as also discussed at this analysis page. Polynomial trends can highlight such acceleration better than linear trends. The 1970-2030 polynomial trend in the image below is calculated over the period from 1880 through to February 2020. The trend points at 3°C getting crossed in 2026.

In above image, the January 2020 and February 2020 anomalies are above the trend. This indicates that the situation might be even worse.

A polynomial trend calculated over a shorter period can highlight short-term variation such as associated with El Niño events and can highlight feedbacks that might otherwise be overlooked. The 2010-2022 trend in the image below is calculated with 2009-Feb.2020 data. The trend indicates that 2°C was crossed in February 2020, and looks set to keep rising and cross 3°C in 2021, more specifically in January next year, which is less than a year away.

Such a steep rise is in line with unfolding developments that are causing the aerosol masking effect to fall away, such as a decrease in industrial activity due to COVID-19 fears. The image below shows a potential rise of 18°C or 32.4°F from 1750 by the year 2026.

Above image was posted more than a year ago and illustrates that much of this potentially huge temperature rise over the next few years could eventuate as a result of a reduction in the cooling now provided by sulfates. In other words, a steep temperature rise could result from a decline in industrial activity that is caused by fears about the spread of a contagious virus, as also discussed in the video at an earlier post.

The situation is dire and calls for immediate, comprehensive and effective action, as described in the Climate Plan.


• Analysis: Crossing the Paris Agreement thresholds

• A rise of 18°C or 32.4°F by 2026?

• How much warming have humans caused?

• Arctic Ocean January 2020

• Climate Plan

In the video below, Guy McPherson discusses the situation.

Reducing sunlight unlikely to cool earth – scientists


Idea that we can address global warming by engineering the atmosphere rebuffed by scientists in USA and Germany

(Pic: NASA)

(Pic: NASA)

By Tim Radford

Two German scientists have just confirmed that you can’t balance the Earth’s rising temperatures by simply toning down the sunlight.

Reducing sunlight unlikely to cool earth – scientists

It may do something disconcerting to the patterns of global rainfall.

Earlier this year a US-led group of scientists ran sophisticated climate models of a geo-engineered world and proposed the same thing. Now Axel Kleidon and Maik Renner of the Max Planck Institute for Biogeochemistry in Jena, Germany, have used a different theoretical approach to confirm the conclusion, and explain why it would be a bad idea.

The argument for geo-engineering goes like this: the world is getting inexorably warmer, governments show no sign of drastically reducing greenhouse gas emissions, so why not control the planetary thermostat by finding a way to filter, block, absorb or reflect some of the sunlight hitting the Earth?

Such things can be done by pumping soot or aerosols into the stratosphere to dim the skies a fraction, or even floating mirrors in Earth orbit to reflect some of the sunlight back into space.

Either way, the result is the same: you have global temperature control, tuned perhaps to the average at the beginning of the last century, and you can then go on burning as much petrol or coal as you like.

But now the two biogeochemists at Jena report in the journal Earth System Dynamics that they used a simple energy balance model to show that the world doesn’t work like that. Water simply doesn’t respond to atmospheric heat and solar radiation in the same way.

No simple fix

If you make the atmosphere warmer, but keep the sunlight the same, evaporation increases by 2% per degree of warming. If you keep the atmosphere the same, but increase the levels of sunlight, evaporation increases by 3% per degree of warming.

Kleidon uses the simple analogy of a saucepan on a kitchen stove. “The temperature in the pot is increased by putting on a lid, or by turning up the heat – but these two cases differ by how much energy flows through the pot,” he says.

A stronger greenhouse effect would act as a kind of tighter-fitting atmospheric lid. In the kitchen a lid keeps the water from escaping from the saucepan and at the same time reduces the energy cost. But planetary energetics are not really comparable to kitchen economics.

That is because evaporation itself, and the traffic of water vapour around the planet, plays a powerful role in the making of climate. To change the pattern and degree of evaporation would inevitably disturb weather systems and disrupt agriculture, with unpredictable and potentially catastrophic consequences.

The authors say: “An immediate consequence of this notion is that climate geo-engineering cannot simply be used to undo global warming.”

This article was produced by the Climate News Network

Why there’s more greenhouse gas in the atmosphere than you may have realised

The Cape Grim observatory, home of the ‘world’s cleanest air’… and rising greenhouse gases. CSIROAuthor provided

This week brought news that atmospheric carbon dioxide (CO₂) levels at the Mauna Loa atmospheric observatory in Hawaii have risen steeply for the seventh year in a row, reaching a May 2019 average of 414.7 parts per million (ppm).

It was the highest monthly average in 61 years of measurements at that observatory, and comes five years after CO₂ concentrations first breached the 400ppm milestone.

But in truth, the amount of greenhouse gas in our atmosphere is higher still. If we factor in the presence of other greenhouse gases besides carbon dioxide, we find that the world has already ticked past yet another milestone: 500ppm of what we call “CO₂-equivalent”, or CO₂-e.

Read more: Forty years of measuring the world’s cleanest air reveals human fingerprints on the atmosphere

In July 2018, the combination of long-lived greenhouse gases measured in the “cleanest air in the world” at Cape Grim Baseline Atmospheric Pollution Station surpassed 500ppm CO₂-e.

As the atmosphere of the Southern Hemisphere contains less pollution than the north, this means the global average atmospheric concentration of greenhouse gases is now well above this level.

What is CO₂-e?

Although CO₂ is the most abundant greenhouse gas, dozens of other gases – including methane (CH₄), nitrous oxide (N₂O) and the synthetic greenhouse gases – also trap heat. Many of them are more powerful greenhouse gases than CO₂, and some linger for longer in the atmosphere. That means they have a significant influence on how much the planet is warming.

Southern Hemispheric radiative forcing relative to 1750 due to the long-lived greenhouse gases (carbon dioxide, methane, nitrous oxide and synthetic greenhouse gases), expressed as watts per square metre, from measurements in situ at Cape Grim, from the Cape Grim Air Archive, and Antarctic firn air. CSIRO

Atmospheric scientists use CO₂-e as a convenient way to aggregate the effect of all the long-lived greenhouse gases.

As all the major greenhouse gases (CO₂, CH₄ and N₂O) are rising in concentration, so too is CO₂-e. It has climbed at an average rate of 3.3ppm per year during this decade – faster than at any time in history. And it is showing no sign of slowing.

Cape Grim/Antarctic carbon dioxide equivalent (CO₂-e) calculated from the long-lived greenhouse gas radiative forcing data shown in the figure above with CO₂ data shown for reference, annual data through to 2018. Inset panel shows the monthly mean CO₂-e data for Cape Grim from 2015 through to March 2019, showing CO₂-e surpassing 500ppm in July 2018. CSIRO

This milestone, like so many others, is symbolic. The difference between 499 and 500ppm CO₂-e is marginal in terms of the fate of the climate and the life it sustains. But the fact that the cleanest air on the planet has now breached this threshold should elicit deep concern.

Warming on the way

The Paris climate agreement is aimed at limiting global warming to less than 2℃ above pre-industrial levels, to avoid the most dangerous effects of climate change. But the task of predicting how human greenhouse emissions will perturb the climate system on a scale of decades to centuries is complex.

The best estimate of long-term global warming expected from 500ppm CO₂-e is about 2.5℃. But so far, since pre-industrial times, the global climate (including oceans) has warmed by only 0.7℃.

This is partly because industrial smog and other tiny particles (together called aerosols) reflect sunlight out to space, offsetting some of the expected warming. What’s more, the climate system responds slowly to rising atmospheric greenhouse gas concentrations because much of the excess heat is taken up by the oceans.

The amount of heat each greenhouse gas can trap depends on its absorption spectrum – how strongly it can absorb energy at different wavelengths, particularly in the infrared range. Despite its simple molecular structure, there is still much to learn about the heat-absorbing properties of methane, the second-biggest component of CO₂-e.

Studies published in 2016 and 2018 led to the estimate of methane’s warming potential being revised upwards by 15%, meaning methane is now considered to be 32 times more efficient at trapping heat in the atmosphere than CO₂, on a per-molecule basis over a 100-year time span.

Considering this new evidence, we calculate that greenhouse gas concentrations at Cape Grim crossed the 500ppm CO₂-e threshold in July 2018.

This is higher than the official estimate based on the previous formulation for calculating CO₂-e, which remains in widespread use. For instance, the US National Oceanic and Atmospheric Administration is reporting 2018 CO₂-e as 496ppm.

The graph below shows the two curves for the time evolution of CO₂-e in the atmosphere as measured at Cape Grim, using the old and new formulae.

Cape Grim monthly CO2-e from 2015 until Sept 2018 calculated using the old and new formulae. CSIRO

Some greenhouse gases, such as chlorofluorocarbons (CFCs), also deplete the ozone layer. CFCs are in decline thanks to the Montreal Protocol, which bans the production and use of these chemicals, despite reports that indicate some recent production of CFC-11 in China.

But unfortunately their ozone-safe replacements, hydrofluorocarbons (HFCs), are very potent greenhouse gases, and are on the rise. The recently enacted Kigali Amendment to the protocol means that consumption controls on HFCs are now in place, and this will see the growth rate of HFCs slow significantly and then reverse in the coming decades.

We can change

Australia is at the forefront of initiating measures to curb the impact of HFCs on climate change.

Methane is another low-hanging fruit for climate action, while we undertake the slower and more difficult transition away from CO₂-emitting energy sources.

The significant human methane emissions from leaks in reticulated gas systems, landfills, waste water treatment, and fugitive emissions from coal mining and oil and gas production can be monitored and reduced. We have the science and technology to do this now.

Both in the oil and gas sectors and in urban areas, there are many examples of how methane “hot spots” can be identified and tackled.

It’s a classic win-win that saves money and reduces climate change, and something we should be implementing in Australia in the near future.

Climate change: Scientists test radical ways to fix Earth’s climate

A villager walks on a dried up dam in West Java province, Indonesia. Photo: September 2018Image copyrightGETTY IMAGES
Image captionJust cutting carbon emissions will not be enough to prevent damaging climate change, scientists warn

Scientists in Cambridge plan to set up a research centre to develop new ways to repair the Earth’s climate.

It will investigate radical approaches such as refreezing the Earth’s poles and removing CO2 from the atmosphere.

The centre is being created because of fears that current approaches will not on their own stop dangerous and irreversible damage to the planet.

The initiative is the first of its kind in the world and could lead to dramatic reductions in carbon emissions.

The initiative is co-ordinated by the government’s former chief scientific adviser, Prof Sir David King.

“What we do over the next 10 years will determine the future of humanity for the next 10,000 years. There is no major centre in the world that would be focused on this one big issue,” he told BBC News.

Some of the approaches described by Sir David are often known collectively as geoengineering.

The Centre for Climate Repair is part of Cambridge university’s Carbon Neutral Futures Initiative, led by Dr Emily Shuckburgh.

She, said the initiative’s mission would be to “solve the climate problem”.

“It has to be. And we can’t fail on it,” she said.

It will bring together scientists and engineers with social scientists.

“This really is one of the most important challenges of our time, and we know we need to be responding to it with all our efforts,” Dr Shuckburgh told BBC News.

Refreezing the poles

One of the most promising ideas for refreezing the poles is to “brighten” the clouds above them.

The idea is to pump seawater up to tall masts on uncrewed ships through very fine nozzles.

This produces tiny particles of salt which are injected into the clouds, which makes them more widespread and reflective, and so cool the areas below them.

Graphic: How unmanned ships could be used to 'brighten' clouds and reflect sunlight

Recycling CO2

Another new approach is a variant of an idea called carbon capture and storage (CCS).

CCS involves collecting carbon dioxide emissions from coal or gas fired power stations or steel plants and storing it underground.

Prof Peter Styring, of the University of Sheffield, is developing a carbon capture and utilisation (CCU) pilot scheme with Tata Steel in Port Talbot in South Wales which effectively recycles CO2.

Graphic: How CO2 can be recycled into fuel

The scheme involves setting up a plant on-site which converts the firm’s carbon emissions into fuel using the plant’s waste heat, according to Prof Styring.

“We have a source of hydrogen, we have a source of carbon dioxide, we have a source of heat and we have a source of renewable electricity from the plant,” he told BBC News.

“We’re going to harness all those and we’re going to make synthetic fuels.”

Ocean greening

Other ideas the centre would explore include greening the oceans so they can take up more CO2.

Such schemes involve fertilising the sea with iron salts which promote the growth of plankton.

Previous experiments have shown that they don’t take up sufficient CO2 to make the scheme worthwhile and might disrupt the ecosystem.

Graphic: How 'ocean greening' could work

But according to Prof Callum Roberts of York University, approaches that are currently thought beyond the pale now have to be considered and, if possible, made to work.

This is because the alternative of damaging and potentially irreversible climate change is considered beyond the pale.

“Early in my career, people threw their hands up in horror at suggestions of more interventionist solutions to fix coral reefs,” Prof Roberts said.

“Now they are looking in desperation at an ecosystem that will be gone at the end of the century and now all options are on the table”.

The options include genetically engineering heat-resistant coral or dumping chemicals into the sea to make the sea less acidic.

“At the moment, I happen to think that harnessing nature to mitigate climate change is a better way to go. But I do see the legitimacy of exploring [more radical] options as a means of steering us towards a better future,” Prof Roberts said.

Thinking the unthinkable

Such ideas have many potential downsides and may prove to be unfeasible.

But Peter Wadhams, a professor of ocean physics at Cambridge University, said that they should be properly assessed to see if the downsides can be overcome, because he believes that reduction of CO2 emissions on its own won’t be enough.

“If we reduce our emissions all we are doing is making the global climate warmer a bit more slowly. That is no good because it’s already too warm and we have already got too much CO2 in the atmosphere,” Prof Wadhams said.

“So climate repair can actually take it out of the atmosphere. We can get the level down below what it is now and actually cool the climate bringing it back to what it was before global warming,” he added.

We’re altering the climate so severely that we’ll soon face apocalyptic consequences. Here are 9 last-ditch ways we could hack the planet to reverse that trend.

Clouds above earth
If warming continues, subtropical stratocumulus clouds could disappear altogether.
 Aleksandar Georgiev/Getty Images
  • Geoengineering is a term that refers to technology that can alter Earth’s natural cycles to cool down the planet. It’s being increasingly discussed as a potential way to address climate change.
  • Putting mirrors in space, capturing carbon dioxide, and seeding clouds with particles are all ways of manipulating weather or the atmosphere.
  • But some scientists and politicians think geoengineering could damage the planet or lead to war.
  • Here are 11 strategies researchers have put forth to hack the planet and combat climate change.

Oceans are hotter than they’ve ever been in recorded history. Ice Sheets are melting at unprecedented rates. Sea-level rise threatenscountless species, coastal cities, and local economies.

As researchers’ warnings about the consequences of climate change get more dire, some scientists and politicians are suggesting we do more than just curb our greenhouse-gas emissions — they want tohack our climate.

The technical term for this is geoengineering.

The concept evokes fantastical images of weather-controlling satellites, giant space mirrors, and carbon-sucking tubes. But some techniques for modifying Earth’s atmosphere aren’t in the realm of fantasy.

In fact, discussions about manipulating the atmosphere to cool the planet are growing increasingly mainstream. Climeworks, a company that captures carbon dioxide from the air, opened its first commercial plant in Switzerland in 2017. Y Combinator, Silicon Valley’s largest incubator, has requested proposals from geoengineering-focused start-ups. And some political candidates, including presidential hopeful Andrew Yang, think the US needs to beat other countries to these technologies.

Read More:Longshot presidential candidate Andrew Yang thinks rogue geoengineering could cause a war

But other experts are less than convinced that these planet hacks are a good idea.

“The side effects may be almost as bad as the disease you’re trying to cure,” author and environmental activist Bill McKibben told Business Insider. What’s more, McKibben said, geoengineering does little to address other problems that arise from greenhouse-gas emissions, such as ocean acidification.

Here are 11 potential geoengineering methods that have been proposed so far.

There are two main types of geoengineering. The first is carbon capture, which entails removing carbon dioxide from the atmosphere.

There are two main types of geoengineering. The first is carbon capture, which entails removing carbon dioxide from the atmosphere.
Smoke rises from the chimneys of a power plant in Shanghai, December 5, 2009.
 Aly Song/Reuters

Carbon capture and storage (CSS) is becoming widely accepted as a safe and potentially effective climate-change-fighting tool. Many people see it as a way to simply undo the changes that human activity is already causing.

Power plants in the US and Canada have already started utilizing CSS to lower their emissions. In the fall of 2014, the Boundary Dam Power Station near Estevan, Saskatchewan became one of the first power stations in the world to successfully use the technology.

According to the Center for Climate and Energy Solutions, 21 commercial-scale carbon capture projects are operating around the world, and 22 more were in developmentas of 2017.

In some cases, CSS technology can also prevent carbon emissions from entering the atmosphere at all. Instead, carbon dioxide that’s created when coal burns or electricity is generated can be captured in a plant, then transported and stored somewhere else.

Some companies are already developing promising carbon-capture technologies.

Some companies are already developing promising carbon-capture technologies.
A view of the GassNova headquarters in Porsgrunn, Norway, August 9, 2017.
 Lefteris Karagiannopoulos/Reuters

Norway’s state-owned carbon-capture technology coordinator, GassNova is facilitating financial support for the development, demonstration, and pilot studies of CCS technologies in the country.

A New York-based start-up, Global Thermostat, uses carbon sponges to absorb carbon dioxide directly from the atmosphere, smokestacks, or both.

The company is building its first commercial-scale direct-air carbon-capture plant in Huntsville, Alabama. Global Thermostat cofounder Graciela Chichilnisky told Grist that once the plant is up and running, it will suck “up to a million tons of CO2 per year or more — all removed from air,”

Carbon Engineering, a British Columbia-based company owned in part by Bill Gates, is also striving to open commercial plants to pull carbon dioxide directly out of the the air.

One of the biggest issues with these carbon-capture technologies, however, is figuring out where to put the carbon dioxide after it's captured.
The Nesjavellir Geothermal Power Plant in Þingvellir, Iceland.
 Gretar Ívarsson/Wikimedia Commons

According to the Carbon Capture and Storage Association, storage sinks for captured carbon are typically deep underground in depleted oil and gas fields.

A Saskatchewan-based carbon storage effort, the Weyburn-Midale CO2 Monitoring and Storage project, has successfully moved and injected stored carbon into two depleted oil fields.

In 2008, a facility on an island in the Barents Sea stored nearly 4 tons of carbon in an offshore subsurface reservoir.

Captured carbon could also get stored in containers filled with carbon-dioxide-eating or converting algae and bacteria.

Captured carbon could also get stored in containers filled with carbon-dioxide-eating or converting algae and bacteria.
Tubular bioreactors are filled with green algae fixing CO2 in Costa de la Luz, Andalusia, Spain.
 Santiago Urquijo/Getty Images

These storage units are sometimes called bioreactors. A company in Quebec City, Canada called CO2 Solution has genetically engineered E. coli bacteria to produce enzymes that convert the carbon dioxide into an alternative form called bicarbonate.

According to a 2010 study, algae ponds are also effective at naturally capturing carbon through photosynthesis.

Some companies are trying to turn the carbon they capture into useful materials.

Some companies are trying to turn the carbon they capture into useful materials.
A Climeworks facility for capturing carbon dioxide from the air in Hinwil, Switzerland July 18, 2017.
 Arnd Wiegmann/Reuters

In May 2017, the Zurich-based company Climeworks opened its first commercial carbon-capture plant, which compresses captured carbon dioxide and turns it into fertilizer.

A company called Blue Planet converts carbon dioxide into bicarbonate then uses that to make building materials.

A company called Blue Planet converts carbon dioxide into bicarbonate then uses that to make building materials.
San Francisco International Airport.
 Justin Sullivan/Getty Images

Blue Planet takes carbon dioxide that has been captured from factories — like California’s largest power plant in Moss Landing— and turns it into into a limestone coating that covers the company’s proprietary concrete building material.

Blue Planet’s products aren’t yet available in big enough quantities for large-scale projects, according to Caltrans, but the company is currently developing a larger production facility in the San Francisco Bay Area.

Despite the fact that Blue Planet’s products aren’t on the commercial market yet, its bicarbonate rocks were included in the construction of part of San Francisco International Airport.

Another major planet-hacking strategy is solar geoengineering, which involves injecting particles or clouds into the sky that reflect sunlight back into space.

Another major planet-hacking strategy is solar geoengineering, which involves injecting particles or clouds into the sky that reflect sunlight back into space.Ian Waldie/Getty Images

This is also called solar radiation management or albedo modification. (Albedo is the term for how much light or radiation is reflected back from Earth’s surface.)

Ultimately, solar geoengineering aims increase the amount of solar radiation that gets reflected out into space from Earth in order to cool down the planet.

But none of these technologies have gotten off the ground yet, so to speak. In fact, most are so controversial that they haven’t even been tested.

The idea for solar geoengineering is inspired by the effects of volcanic eruptions.

The idea for solar geoengineering is inspired by the effects of volcanic eruptions.
The Anak Krakatoa volcano erupts on December 23, 2018 in the Sunda Straits off the coast of southern Sumatra.
 Nurul Hidayat/AFP/Getty Images

When volcanoes fill the skies with sulfur and ash, that causes more sunlight to be reflected away from the planet, and the Earth cools.

Nearly 200 years ago, Mount Tambora in Indonesia underwent the most deadly volcanic eruption in recorded history, according to NASA. Some scientists believe the eruption was responsible for a severe summertime cold snap the following year that triggered killer frosts in New England and Europe.

This volcanic effect could be mimicked via a technique called stratospheric aerosol scattering. This involves injecting the upper atmosphere with tiny reflective particles like sulfuric acid or aerosols.

The idea is that these particles would reflect some sunlight away from Earth and back into space.

Harvard University’s solar geoengineering research program is currently trying to model how clouds of such particles in the atmosphere would behave using small, steerable balloons.

The research program also suggests that we could brighten marine clouds so they reflect more sunlight. (The closer an object’s color is to white — or the brighter it is — the more light it reflects.)

Mirrors, of course, also reflect sunlight. So some scientists have floated the idea of putting giant mirrors in space.

Mirrors, of course, also reflect sunlight. So some scientists have floated the idea of putting giant mirrors in space.SVF2/Getty Images

In the 2000s, a scientist named Lowell Wood from Lawrence Livermore National Laboratory suggested that a giant space mirrormade of aluminum mesh could combat climate change. But he warned that the device would need to be 600,000 square miles in area — about the size of Greenland — to do any good. That would probable be prohibitively expensive.

“It would be like a window screen made of exceedingly fine metal wire,” Wood explained to Popular Science in 2005.

More than a decade later, the idea of a space mirror is still hypothetical.

Eliminating or thinning some cirrus clouds —a type of cloud that sits high in the atmosphere and absorbs radiation — could be another way to send heat back into space.

Eliminating or thinning some cirrus clouds —a type of cloud that sits high in the atmosphere and absorbs radiation — could be another way to send heat back into space.Aleksey Sagitov/Shutterstock

This effort would involve reducing high-altitude cirrus clouds by seeding them with water-depleting aerosols.

These wispy clouds don’t do much to reflect sunlight, but they do a lion’s share of radiation trapping. So thinning them could theoretically help cool the Earth because that would provide more pathways for planet-warming solar radiation to escape into space.

One technology that manipulates the clouds is already in use today. It doesn’t really address climate change, but it does allow us to make it rain when and where we want.

One technology that manipulates the clouds is already in use today. It doesn't really address climate change, but it does allow us to make it rain when and where we want.
Dark clouds hang over Frankfurt, Germany on March 7, 2019.
 Michael Probst/Associated Press

Cloud seeding is a way to make it rain or snow by dropping silver ions into the atmosphere. Rainstorms happen when enough moisture collects around particles in the air, so these ions provide additional particles for moisture to glom onto.

The technology has already been tested by the governments of China, Russia, and the United Arab Emirates.

According to Pacific Standard Magazine, the technique has been in use for 75 years, and even helps with drought relief in the western US. In 2015, Texas experienced a 34% uptick in the length of rainfall thanks to cloud seeding.

Instead of focusing on clouds, some researchers are looking into ways to save melting Arctic ice. Ice sheets are responsible for reflecting lots of sunlight into space, so less ice means less heat leaving the planet.

Instead of focusing on clouds, some researchers are looking into ways to save melting Arctic ice. Ice sheets are responsible for reflecting lots of sunlight into space, so less ice means less heat leaving the planet.Jeremy Potter/NOAA OAR/OER

A 2018 study showed that the 75% loss of Arctic ice volume that we’ve seen since 1979 — and the related loss of sunlight-reflecting surfaces — has significantly contributed to our warming planet.

A nonprofit called Ice911 wants to spread tiny glass beads around the Arctic that mimic ice’s reflective abilities.

A nonprofit called Ice911 wants to spread tiny glass beads around the Arctic that mimic ice's reflective abilities.
The Greenland Ice Sheet is melting four times faster than it was 16 years ago.
 Chasing Ice

Ice911‘s glass microsphere beads are tiny, hollow, and made from sand. They look like snow.

Leslie Field, the founder of Ice911, wants to spread the beads all over the Arctic in the hopes of making the polar ice more reflective and less prone to melting.

“Multi-year ice, the reflective ice in the Arctic, was historically the Earth’s heat shield,” Field recently told Fast Company. “It’s not there to do that anymore.”

The group is still testing its technology near Barrow, Alaska. In 2017, Ice911 covered more than three football fields of ice in glass beads, and in 2018, the organization deployed an additional 161,000 square feet of beads. Early results were promising: Treated areas showed higher reflectivity and less ice melt than untreated areas.

Alternatively, some researchers are pushing to shore up melting ice from the bottom up.

Alternatively, some researchers are pushing to shore up melting ice from the bottom up.
Patagonia’s glaciers are melting rapidly.
 Mario Tama/ Getty Images

A recent article in the journal Nature suggested using geoengineering to preserve continental ice sheets by targeting the places where the ice meets warming ocean water.

One proposed technique is to raise artificial ridges to protect the weakening margins of glaciers. But scientists warn that such a projectcould cost billions of dollars.

Beyond all of these options, researchers and investors are also thinking about geoengineering strategies that sound like something out of science fiction.

Y Combinator, a prestigious incubator that boasts alums like Dropbox and Airbnb, issued a request last year for start-ups focusing on what they call “frontier technology ideas” for geoengineering.

“It’s time to invest and avidly pursue a new wave of technological solutions to this problem — including those that are risky, unproven, even unlikely to work. It’s time to take big swings at this,” the company wrote in an announcement on their website.

Examples of these frontier solutions include developing genetically engineered phytoplankton that take in carbon dioxide via photosynthesis, and flooding deserts to create micro-oases that serve as carbon sinks.

Such concepts “straddle the border between very difficult to science fiction,” the company wrote.

Wilder still is a proposal to create a cloud of asteroid dust in space that would shield the Earth from sunlight.

Wilder still is a proposal to create a cloud of asteroid dust in space that would shield the Earth from sunlight.
NASA’s OSIRIS-REx spacecraft took this image of the asteroid Bennu on November 16, 2018, from a distance of 85 miles (136 kilometers).
 NASA/GSFC/University of Arizona

group of Scottish scientists suggested this idea in 2012.

Their plan called for pushing an asteroid to a specific point in space where it would feel equal gravitational pulls from the Earth and sun, so would remain anchored in place. Then a spacecraft would land on the asteroid and hurl asteroid dust into space.

The researchers said their plan would reduce the amount of sunlight hitting Earth by almost 2%, which would be enough to offset some 5 degrees Fahrenheit of warming.

Needless to say, the plan has many downsides, including the risk that the asteroid could accidentally get directed towards Earth.

In general, any geoengineering project or proposal that involves tweaking the delicate chemistry of Earth’s atmosphere and its cycles faces enormous opposition.

Many scientists are particularly concerned about solar geoengineering experiments because most models predict that the effects will be felt differently around the globe, even in spots far from the initial location. For example, if solar geoengineering technology gets deployed in the southern hemisphere, that could impacts ocean temperature and wind speeds, leading to more hurricanes in the northern hemisphere.

Plus, a failed geoengineering technology could leave Earth’s atmospheric chemistry irreversibly altered. We could end up damaging the ozone layer, for example, which protects us from harmful ultraviolet radiation.

However, a recent study asserted that it is possible to tweak the atmosphere in a way that would prevent other parts of the planet from experiencing weather backlash.

However, a recent study asserted that it is possible to tweak the atmosphere in a way that would prevent other parts of the planet from experiencing weather backlash.
Planes or drones could scatter small doses of aerosols into the atmosphere.

The study, published in the journal Nature Climate Change, modeled a scenario in which small amounts of geoengineering would decrease temperatures all over the world. Although such an initiative would perturb the climate in new ways, the authors wrote, those disturbances would be negligible compared to the havoc that climate change is already wreaking via droughts and rising sea-levels.

They suggested forming an international research program to investigate this option further.

Yet some scientists and politicians are already warning that geoengineering could lead to war.

“I’ve got a list of 27 reasons we shouldn’t do it,” Alan Robock, an environmental science professor at Rutgers and an expert on geoengineering, previously told Business Insider.

He worries a rogue country could pull the trigger on an atmospheric-transformation project that affects the entire world. The resulting conflicts with other nations could ultimately could escalate to nuclear war, Robock said.

Andrew Yang echoed similar concerns. If China start playing with atmospheric modifications on its own, rather than as part of a global initiative, Yang said, he expects the worst.

SEE ALSO: How a last-ditch ‘planet-hacking’ plan could keep Earth habitable for longer

“Silver buckshot” isn’t enough to fix the climate

Clayton Moore as the Lone Ranger in 1965. His “silver” bullets were actually made from aluminum.Clayton Moore as the Lone Ranger in 1965. His “silver” bullets were actually made from aluminum.

“There are no silver bullets, only silver buckshot.”

I don’t know whether author and environmental activist Bill McKibben was the first to coin the term, but “silver buckshot” is now the solution du jour to climate change. With Congress debating a Green New Deal, and Washington Gov. Jay Inslee running for president on a climate platform, the phrase is spreading faster than a wave of late-season flu.

Defeating climate change is certainly going to require more than one killer energy technology. Trouble is, even if the world deploys every single energy technology at its disposal—a shell crammed full of pellets—that still won’t be enough. Fixing the climate requires new policies as well as technologies; systemic changes to the economy; and perhaps most important of all, a shared sense of purpose. Buckshot might bring down a deer, but it isn’t powerful enough to break through the walls erected by the defenders of Business As Usual. That’s going to require battering rams and a determined siege.

One Big Thing. Many people still haven’t given up on finding a silver bullet. Some dream of a new generation of nuclear reactors, others of “clean coal” or artificial photosynthesis. And then there are the journalists who take it upon themselves to tell everyone about the One Big Thing ordinary people can do to solve climate change.

One analysis claims that “avoiding meat and dairy products is the single biggest way to reduce your environmental impact on the planet,” noting that beef production emits far more greenhouse gases per pound than cultivating tofu and that giving up meat is better than giving up your car.

Another says that flying on an airplane “is the most carbon-intensive activity we can do,” and the New York Times advises readers that “the most effective way to reduce your carbon footprint is to fly less often.”

And then there’s the mother of all solutions: family planning. The carbon footprint of having a child in a developed country dwarfs the impacts of dietary and transportation choices. (If you want to have a low-impact child, just don’t be rich).

Of course, most people aren’t the least bit interested in an all-or-nothing lifestyle change. But they might consider making a bunch of less dramatic changes: having one less child, skipping meat one night a week, driving fewer miles, putting solar panels on their roof, and so forth. That’s the buckshot approach. The hope is that lots of smaller, more practical changes will add up to a bigger end result than One Big Thing. If the climate is dying by a thousand cuts, maybe a thousand Band-Aids can help.

There is much to like about the buckshot approach. It reminds people there is no simple, either-or solution to the wicked problem of climate change. Renewable energy is critical for addressing global warming, but even in the most optimistic projections renewable energy can only meet about 80 percentof recent US electricity demands by 2050—and that doesn’t include energy used in other sectors of the economy, such as transportation. As its proponents have explained, buckshot must also include shifts in attitude and behavior, like reducing food waste and walking more. With the shotgun approach, even your climate-change-denying Uncle Pete may find some policies he likes.

Silver-tongued politicians. The trouble with “silver buckshot” is that nobody ever says exactly what it is. It obviously includes “clean energy,” whatever that means. Unlike the Green New Deal, which gets criticized for not being specific enough, silver buckshot isn’t even a set of policies that have been written down and distributed for discussion.

Buckshot is similar to the “stabilization wedges” first described by Princeton University researchers Robert Socolow and Stephen Pacala 15 years ago: a wedge of emissions reduction via wind power, a wedge of vehicle fuel efficiency, a wedge of avoided deforestation, and so forth. The beauty of the wedges approach was that it offered a quantitative pathway to the amount of carbon dioxide emissions needed for a stable climate. Silver buckshot is basically a catchier name for wedges—except that it doesn’t attempt to name all the wedges or precisely add up their contributions to a stable climate. There is no silver-buckshot plan, only silver buckshot.

In short, silver buckshot is better suited to politicians than to scientists. It’s every bit as meaningless as Barack Obama’s 2012 “all-of-the-above” energy strategy—but somehow manages to sound more effective and less desperate.

Even the US Chamber of Commerce is paying lip service to silver buckshot. That alone suggests that yesterday’s ammo has already been melted down and retooled into today’s trinkets. After all, this is the same organization whose president and CEO last month wrote that “the dream of making fossil fuel go the way of the dinosaur is hardly the most absurd element” of the Green New Deal.

Bigger caliber. To be successful, climate action must include policy changes as well as energy technologies, and it must get a lot more ambitious than “buckshot” suggests. A bunch of little things aren’t going to do the trick. The climate fix doesn’t require new technology, but it does require massive coordination, effort, and willpower—something more like a Manhattan Project than a potluck dinner.

I have no doubt that humans and their governments can come up with a diversified set of solutions to stabilize the climate, but the real question is whether Earth’s residents are willing to cooperate with each other on the global scale required. Many Americans have had to battle their neighbors just to install a rain barrel or hang laundry outdoors.

This “silver” bullet, used as a prop on the television series The Lone Ranger, is actually made from aluminum. Credit: National Museum of American History.
This “silver” bullet, used as a prop on the television series The Lone Ranger, is actually made from aluminum. Credit: National Museum of American History.

In the wrong hands, “silver buckshot” could become an excuse for thinking small. Large changes are needed if human society is to prevent catastrophic warming, and they must be systemic changes—not just individual choices.

Unless it is better defined and immediately developed, silver buckshot probably won’t do anything to fix the climate. What the world really needs are legions of Lone Rangers: people who seek justice for all, believe that they have it within themselves to make the world a better place, and carry silver bullets as a reminder that life is precious and not to be wasted. And for every Lone Ranger, a Tonto, because fighting climate change can be a lonely job.

The case for spraying (just enough) chemicals into the sky to fight climate change

A new study says geoengineering could cut global warming in half — with no bad side effects.

A motorcyclist wears a mask after a volcanic eruption in Indonesia. Geoengineering takes its inspiration from volcanoes, which spray sulfur particles into the sky.
NurPhoto via Getty Images

If you think pumping the sky full of chemicals sounds like a weird way to fight climate change, you’re not alone. Solar geoengineering — the idea of injecting aerosols into the high atmosphere to reflect sunlight back into space and make for a cooler planet — is very controversial. And not just because it seems so offbeat.

Although geoengineering is not yet being deployed in the real world, past computer modeling studies have suggested it could produce unintended effects like droughts. Some have worried that it might create new climate inequities, worsening the weather in some regions even as it improves conditions in others. It’s incurred so much backlash that until recently it’s been taboo among scientists, and even today, much less attention is devoted to exploring this strategy than to cutting emissions.

But a study published this week in Nature Climate Change argues that the strategy could be highly successful — it’s all a matter of how much geoengineering we use. Yes, spraying a huge quantity of aerosols aimed at totally eliminating global warming can produce unwanted effects. Yet applying the right “dose” — just enough to cut global warming in half — could do the trick without causing negative side effects, the scientists say.

“The analogy is not perfect, but solar geoengineering is a little like a drug which treats high blood pressure,” said lead author Peter Irvine of Harvard University. “An overdose would be harmful, but a well-chosen dose could reduce your risks.”

In the study, Irvine and his co-authors used a high-resolution computer model to simulate what would happen if we deployed geoengineering with the goal of halving global warming, in a scenario where the carbon dioxide levels in our atmosphere have doubled preindustrial levels. (Currently, we’re at about 1.4 times those earlier levels.) Whereas most previous research only looked at temperature and precipitation, this study also examined other things that matter to people, like water availability.

The results? Geoengineering cooled the planet and reduced the intensity of extreme weather events like hurricanes. Importantly, this held true across the entire globe. There weren’t regional winners and losers, just winners. If anything, the researchers noted, the regions that suffered most from climate change were the most likely to see it reduced.

Critics of geoengineering have worried that although it may benefit the rich, it could harm low-income people, who may be less equipped to cope with unpredicted weather changes if things go awry, and who won’t get as much say in deployment. But David Keith, a senior author on the study and a Harvard physics professor, told me he believes it would be a net benefit for low-income people.

“The poorest people tend to suffer most from climate change because they’re the most vulnerable. Reducing extreme weather benefits the most vulnerable the most. The only reason I’m interested in this is because of that,” he said.

The study has significant limitations

Don’t get too excited just yet. The study — a collaboration between Harvard, MIT, and Princeton — is based on a highly idealized scenario.

The researchers chose to use a scenario where atmospheric CO2 levels have doubled preindustrial levels by the time geoengineering is deployed. “Double” may sound like a lot, but some climate scientists believe our CO2 levels will be woefully higher than that by the middle of this century. And we’re not even close to ready for any large-scaledeployment of geoengineering. So by using this scenario, the study may be setting itself up for an unrealistically optimistic result.

It’s also important to note that the study doesn’t actually model what happens when you shoot aerosols into the sky. It models what happens if the sun’s rays are dimmed. Although that’s a fairly common proxy, Rutgers University climate expert Alan Robock objects that it doesn’t precisely capture the impact of spraying aerosols, which could have other effects, like messing with atmospheric circulation.

The team behind the study agrees that modeling aerosols is also important but believes that asking one model to do everything isn’t necessarily the best option, according to Keith. “The climate models treat aerosols pretty badly, so it’s not clear you can trust the results. In our opinion it makes more sense to use this model, and then separately do models that have very good representations of aerosols. It’s like building a bridge from two sides,” he told me.

The study’s findings are nowhere near certain enough that policymakers should be making decisions off them — as the researchers themselves are the first to point out. For example, even though the model indicated that no regions would be significantly worse off with geoengineering than without it, Keith said, “I think if this is in the real world, there will be some regions or activities that are worse off. Because nothing in the real world is without risk.”

He added, “I think it would be ridiculous to have any deployment until after there’s been a much wider-open international research effort — with research groups specifically focused on critiquing ideas — and only after there’s an adequate governance system in place.”

Explaining why he wants other researchers to pressure-test his group’s ideas, Keith was unusually candid for a scientist discussing controversial new work on the record. “I think there’s a real risk of groupthink at this point, what with such a small number of researchers, including me [studying geoengineering]. We might just be deluded.”

Why do people get so nervous about geoengineering?

Solar geoengineering is an idea for meddling with nature that comes from observing nature itself. As my colleague Dylan Matthews details in a great podcast episode, scientists got the idea for this technique by watching volcanoes. They noticed that when volcanic eruptions sprayed sulfur particles into the sky, it temporarily caused a reduction in temperatures on Earth. They started to wonder: What would happen if we basically mimicked the impact of volcanoes?

Their critics, however, seem to feel that nature spraying chemicals into the sky is one thing, but human beings doing that deliberately is a different story.

In a recent paper titled “Geoengineering Justice,” Jonathan Symons, a senior lecturer in international relations at Macquarie University, hypothesizes that “the prohibition on intentional interference in nature — a defining norm of modern environmentalism — deters discussion of solar geoengineering’s potential benefits.” He explains:

In his expansive history The Progressive Environmental Prometheans, William Meyer traces the roots of this prohibitionFor centuries, the Promethean belief in humans’ ability to enhance their biophysical environment was primarily associated with the political left. With the advent of modern environmentalism in the 1960s, this progressive Prometheanism was reversed. Greens now emphasized the “danger of undesirable consequences produced by meddling in the complex system of nature.” As a result, Prometheanism came to be associated with the environmental movement’s conservative opponents.

This sociological perspective goes some way toward explaining why scientists who support geoengineering have received such intense backlash.

“What [critics] I think are sometimes implicitly saying is that they’d rather not see research,” Keith said. “Yes, there’s some kind of research that we should suppress — like how to make smallpox in your basement — but I think the case for repressing research in this case is pretty weak. There’s a lot of evidence from many studies that geoengineering could significantly reduce environmental risks.”

In addition to (very legitimately) worrying about safety issues that could result if geoengineering is deployed recklessly, critics also worry that research on this topic risks accidentally inducing complacency about cutting emissions.

Regardless of whether we end up using geoengineering, we absolutely still have to cut emissions — otherwise, we’ll keep making the climate crisis worse. But cutting emissions doesn’t solve the problem of the CO2 already in the air. That’s why scientists propose geoengineering as a supplement to cutting emissions, not a replacement.

Keith himself is concerned about the risks of complacency. “I’m very worried that corporations and other entities with interests will exploit the work we do to argue against emissions cuts — that Big Fossil will overclaim about how solar geoengineering will be available someday,” he said. “On the other hand, I don’t think it means they’ll win. And I don’t think it’s a reason not to research this.”