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Solar Geoengineering Could ‘Fail to Prevent Damage to Crop Yields’

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Scattered rainfall over dry season fields before harvest in the Sahel near Bahn Yatenga Burkina Faso Africa. The region is regularly affected by droughts. Getty Images

By Daisy Dunne

Releasing aerosols into the atmosphere in order to limit the rise in global temperature would not stave off damage to crop yields, a new study suggests.

Scientists have suggested that intentionally releasing aerosols into the atmosphere—a type of "solar geoengineering"—could help to limit global warming by reflecting away incoming sunlight in a similar way to a volcanic eruption.


The new research uses historical data to investigate how past major volcanic eruptions have impacted global crop yields. It finds that, following past eruptions, global crop yields have been negatively impacted by a reduction in direct sunlight—which impairs the ability of plants to photosynthesize.

The findings suggest that, if ever used, solar geoengineering could benefit crops by cooling temperatures and reducing the risk of heat stress. However, this positive effect could be largely offset by the negative impacts associated with a reduction in sunlight, the authors say.

However, the new research is "limited" and does not take into account the differences that are likely to exist between volcanic eruptions and solar geoengineering, other scientists tell Carbon Brief. Therefore, they say, it should not be used to draw "solid conclusions."

Artificial Volcanoes

Solar geoengineering is a term used to describe a set of still-hypothetical technologies that could limit global warming by reflecting more sunlight away from Earth.

The most commonly proposed technology is "stratospheric aerosol injection," a technique where reflective solid particles known as aerosols—such as sulphur dioxide—would be released high up in the stratosphere using, for example, a high-altitude balloon or plane.

Because the technique has never been tested, it is still unclear what its impacts would be.

However, previous research using modeling suggests that releasing aerosols could limit temperature rise and restore rainfall to pre-industrial conditions. This could benefit crop production, which is likely to face threats from heat stress and drought as the climate warms.

Yet, other scientists have postulated that solar geoengineering could be harmful to crops. This is because the presence of reflective aerosols reduces the amount of direct sunlight reaching plants. Plants absorb sunlight and use it to create energy during photosynthesis.

The new research, published in Nature, is the first to look at the potential impacts of solar geoengineering via the use of "real world" analogues—two previous volcanic eruptions.

When a volcano erupts, it spews out ash, dust, CO2 and sulphur dioxide high into the atmosphere. The sulphur dioxide combines with water to form sulfuric acid aerosols, which—along with the ash and dust—temporarily cool the planet by reflecting away sunlight.

The two eruptions include Mexico's El Chichón in 1982 and Mount Pinatubo in the Philippines in 1991—the latter of which, in its aftermath, released enough aerosols to cause average global temperatures to dip by 0.5°C, according to the researchers.

Mount Pinatubo eruption, June 12, 1991, Luzon, PhilippinesDave Harlow, USGS / Wikimedia Commons

The findings of the research suggest that, if solar geoengineering were to be used, its impact on incoming sunlight would "wash out" any potential benefits the technology would have for agriculture, lead author Jonathan Proctor, a Ph.D. student at the Global Policy Laboratory at the University of California, Berkeley, told a press briefing. He said:

"The implications of this are that solar geoengineering, using sulphate-based aerosols like we saw emitted from these volcanic eruptions, may be an ineffective way to mitigate the damages that climate change poses to global agricultural production."

Yielding Results

For the study, the researchers used historical data taken from the United Nations Food and Agricultural Organization (FAO) to explore how the yields of several crops, including wheat, maize and rice, were affected in the aftermath of each eruption.

The chart below shows changes to several variables, including aerosol cover, average global temperature and average global crop yields between 1980 and 2010. On the chart, the dashed lines show when the eruptions of El Chichón and Mount Pinatubo occurred.

Chart shows: (a) the average aerosol cover; (b) average temperature change caused by the natural climatic event El Niño; (c) global average temperature change; (d) global average rainfall change; (e) global average cloud cover; and (f) the change in global average crop yield for maize (orange), wheat (grey), soy (blue) and rice (green), from 1980-2010. The dashed lines show when the eruptions of El Chichón and Mount Pinatubo occured. Source: Proctor et al. (2018). The charts show how, around the time of each volcanic eruptions, global crop yields tend to decline abruptly.

The researchers estimate that the impact of the Mount Pinatubo eruption on sunlight caused global yields of maize to fall by 9 percent and global yields of wheat, soy and rice to fall by an average of 5 percent.

The El Chichón eruption had a "significant" impact on maize yields, but only a small effect on yields of other crops, the research shows.

One reason maize could have been impacted the most is that it is a "C4" plant (meaning that during photosynthesis it produces a sugar compound that has four carbon atoms), while the other crops are "C3" plants (meaning they produce a sugar that has three carbon atoms).

Research shows that C3 plants require less sunlight to reach optimum levels of photosynthesis than C4 plants—meaning they are likely to be less affected by the solar dimming caused by aerosol release.

Geoengineered World

To understand how solar geoengineering could impact crop yields, the researchers applied their results to a climate model.

The model looked at changes to crop yields under two future scenarios—one with "moderate" climate change ("RCP4.5") and one with the same level of emissions, but also an injection of aerosols. The scenario assumes that the amount of aerosols released is enough to offset the temperature change caused by all emissions occurring after 2020.

The modeling results show that, in the solar geoengineering scenario, cooler global temperatures boost average maize yields by 6 percent, when compared to the climate change scenario.

However, the reduction of direct sunlight in the same scenario reduces maize yields by 5 percent over the same period. Yields are also slightly decreased as a result of the impact of aerosol release on rainfall and cloud cover.

The findings show that, in comparison to a scenario with climate change alone, solar geoengineering "has no statistically discernible effect on yields once we have accounted for optical effects," the researchers said in their paper.

The researchers also found that solar geoengineering had an "insignificant" effect on yields of soy, rice and wheat—in comparison to the climate change scenario.

Food for Thought

The findings suggest that, on balance, solar geoengineering could "fail" to prevent the damage to global crop yields expected under climate change alone, said Proctor.

The new research could offer a new avenue for solar geoengineering researchers, said co-author professor Solomon Hsiang, a policy researcher from the University of California, Berkeley. He told a press briefing:

"A key innovation of this study was to find a way to study the potential side-effects of geoengineering without actually deploying it."

However, although the research is "useful and important" to understanding more about how the dimming of sunlight could affect agriculture, it does not provide "solid evidence" of how solar geoengineering would impact crops, said professor David Keith, director of the Solar Geoengineering Research Program at the University of Harvard, who was not involved in the research. He told Carbon Brief:

"Solar geoengineering would likely differ from volcanoes in two crucial respects. First, and most important, solar geoengineering would be a relatively continuous application of aerosols rather than a single pulse that lasts less than a year. The climate response to continuous and pulsed radiative forcing—science speak for dimming the sun—would be very different.

"Second, most serious proposals for solar geoengineering assume that it would be designed to have roughly even pole-to-pole radiative forcing. A volcano, in contrast, tends to produce a quite asymmetric radiative forcing. That asymmetry again produces a climate response quite different from what would likely happen under solar geoengineering."

The new research also does not consider how solar geoengineering could influence the occurrence of extreme events, such as heatwaves and droughts, which are likely to be important to crop production, said Dr. Anthony Jones, a research fellow from the University of Exeter, who was also not involved in the research. He told Carbon Brief:

"I suspect that the crop yields are sensitive to changes to extremes – for instance, droughts and heatwaves – that may be ameliorated by SRM and which are not accounted for in this model."

The methods used by the research team are "interesting" and provide "new results," said professor Alan Robock from the the department of environmental sciences at Rutgers University. He told Carbon Brief:

"But they are based on agricultural practices from 30 years ago. More study of whether modern and future farming, including new equipment, seeds, and fertilizers, would react the same way is needed."

The study takes an "important" step forward in understanding the potential socio-economic impacts of solar geoengineering, said professor Govindasamy Bala, from the Divecha Centre for Climate Change at the Indian Institute of Science. He told Carbon Brief:

"However, I do not think this is the last word on this subject. More similar studies would be needed to narrow down the uncertainty in process modeling."

Agreeing with Bala, professor Douglas MacMartin, an engineering researcher from Cornell University, who contributed to a hearing on geoengineering at the U.S. House of Representatives, said the results should provide "motivation" for more research. He told Carbon Brief:

"The study is important for looking at a possible impact of solar geoengineering that no one has yet explored. But because the data that goes into the study is so limited and so noisy, one shouldn't read too much into it, at least not yet. Instead, this should be taken simply as motivation for doing more research and only reaching conclusions after more studies have looked at this question."

Reposted with permission from our media associate Carbon Brief.

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By Sherry H-Y. Chou, Aarti Sarwal and Neha S. Dangayach

The patient in the case report (let's call him Tom) was 54 and in good health. For two days in May, he felt unwell and was too weak to get out of bed. When his family finally brought him to the hospital, doctors found that he had a fever and signs of a severe infection, or sepsis. He tested positive for SARS-CoV-2, the virus that causes COVID-19 infection. In addition to symptoms of COVID-19, he was also too weak to move his legs.

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We are neurologists specializing in intensive care and leading studies related to neurological complications from COVID-19. Given the occurrence of Guillain-Barre Syndrome in prior pandemics with other corona viruses like SARS and MERS, we are investigating a possible link between Guillain-Barre Syndrome and COVID-19 and tracking published reports to see if there is any link between Guillain-Barre Syndrome and COVID-19.

Some patients may not seek timely medical care for neurological symptoms like prolonged headache, vision loss and new muscle weakness due to fear of getting exposed to virus in the emergency setting. People need to know that medical facilities have taken full precautions to protect patients. Seeking timely medical evaluation for neurological symptoms can help treat many of these diseases.

What Is Guillain-Barre Syndrome?

Guillain-Barre syndrome occurs when the body's own immune system attacks and injures the nerves outside of the spinal cord or brain – the peripheral nervous system. Most commonly, the injury involves the protective sheath, or myelin, that wraps nerves and is essential to nerve function.

Without the myelin sheath, signals that go through a nerve are slowed or lost, which causes the nerve to malfunction.

To diagnose Guillain-Barre Syndrome, neurologists perform a detailed neurological exam. Due to the nerve injury, patients often may have loss of reflexes on examination. Doctors often need to perform a lumbar puncture, otherwise known as spinal tap, to sample spinal fluid and look for signs of inflammation and abnormal antibodies.

Studies have shown that giving patients an infusion of antibodies derived from donated blood or plasma exchange – a process that cleans patients' blood of harmful antibodies - can speed up recovery. A very small subset of patients may need these therapies long-term.

The majority of Guillain-Barre Syndrome patients improve within a few weeks and eventually can make a full recovery. However, some patients with Guillain-Barre Syndrome have lingering symptoms including weakness and abnormal sensations in arms and/or legs; rarely patients may be bedridden or disabled long-term.

Guillain-Barre Syndrome and Pandemics

As the COVID-19 pandemic sweeps across the globe, many neurologic specialists have been on the lookout for potentially serious nervous system complications such as Guillain-Barre Syndrome.

Though Guillain-Barre Syndrome is rare, it is well known to emerge following bacterial infections, such as Campylobacter jejuni, a common cause of food poisoning, and a multitude of viral infections including the flu virus, Zika virus and other coronaviruses.

Studies showed an increase in Guillain-Barre Syndrome cases following the 2009 H1N1 flu pandemic, suggesting a possible connection. The presumed cause for this link is that the body's own immune response to fight the infection turns on itself and attacks the peripheral nerves. This is called an "autoimmune" condition. When a pandemic affects as many people as our current COVID-19 crisis, even a rare complication can become a significant public health problem. That is especially true for one that causes neurological dysfunction where the recovery takes a long time and may be incomplete.

The first reports of Guillain-Barre Syndrome in COVID-19 pandemic originated from Italy, Spain and China, where the pandemic surged before the U.S. crisis.

Though there is clear clinical suspicion that COVID-19 can lead to Guillain-Barre Syndrome, many important questions remain. What are the chances that someone gets Guillain-Barre Syndrome during or following a COVID-19 infection? Does Guillain-Barre Syndrome happen more often in those who have been infected with COVID-19 compared to other types of infections, such as the flu?

The only way to get answers is through a prospective study where doctors perform systematic surveillance and collect data on a large group of patients. There are ongoing large research consortia hard at work to figure out answers to these questions.

Understanding the Association Between COVID-19 and Guillain-Barre Syndrome

While large research studies are underway, overall it appears that Guillain-Barre Syndrome is a rare but serious phenomenon possibly linked to COVID-19. Given that more than 10.7 million cases have been reported for COVID-19, there have been 10 reported cases of COVID-19 patients with Guillain-Barre Syndrome so far – only two reported cases in the U.S., five in Italy, two cases in Iran and one from Wuhan, China.

It is certainly possible that there are other cases that have not been reported. The Global Consortium Study of Neurological Dysfunctions in COVID-19 is actively underway to find out how often neurological problems like Guillain-Barre Syndrome is seen in hospitalized COVID-19 patients. Also, just because Guillain-Barre Syndrome occurs in a patient diagnosed with COVID-19, that does not imply that it was caused by the virus; this still may be a coincident occurrence. More research is needed to understand how the two events are related.

Due to the pandemic and infection-containment considerations, diagnostic tests, such as a nerve conduction study that used to be routine for patients with suspected Guillain-Barre Syndrome, are more difficult to do. In both U.S. cases, the initial diagnosis and treatment were all based on clinical examination by a neurological experts rather than any tests. Both patients survived but with significant residual weakness at the time these case reports came out, but that is not uncommon for Guillain-Barre Syndrome patients. The road to recovery may sometimes be long, but many patients can make a full recovery with time.

Though the reported cases of Guillain-Barre Syndrome so far all have severe symptoms, this is not uncommon in a pandemic situation where the less sick patients may stay home and not present for medical care for fear of being exposed to the virus. This, plus the limited COVID-19 testing capability across the U.S., may skew our current detection of Guillain-Barre Syndrome cases toward the sicker patients who have to go to a hospital. In general, the majority of Guillain-Barre Syndrome patients do recover, given enough time. We do not yet know whether this is true for COVID-19-related cases at this stage of the pandemic. We and colleagues around the world are working around the clock to find answers to these critical questions.

Sherry H-Y. Chou is an Associate Professor of Critical Care Medicine, Neurology, and Neurosurgery, University of Pittsburgh.

Aarti Sarwal is an Associate Professor, Neurology, Wake Forest University.

Neha S. Dangayach is an Assistant Professor of Neurology and Neurosurgery, Icahn School of Medicine at Mount Sinai.

Disclosure statement: Sherry H-Y. Chou receives funding from The University of Pittsburgh Clinical Translational Science Institute (CTSI), the National Institute of Health, and the University of Pittsburgh School of Medicine Dean's Faculty Advancement Award. Sherry H-Y. Chou is a member of Board of Directors for the Neurocritical Care Society. Neha S. Dangayach receives funding from the Bee Foundation, the Friedman Brain Institute, the Neurocritical Care Society, InCHIP-UConn Center for mHealth and Social Media Seed Grant. She is faculty for emcrit.org and for AiSinai. Aarti Sarwal does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Reposted with permission from The Conversation.


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In a series of tweets Wednesday night, Ocasio-Cortez—the lead sponsor of the House Green New Deal resolution—noted that the Climate Task Force "shaved 15 years off Biden's previous target for 100% clean energy."

"Of course, like in any collaborative effort, there are areas of negotiation and compromise," said the New York Democrat. "But I do believe that the Climate Task Force effort meaningfully and substantively improved Biden's positions."

 

The 110 pages of policy recommendations from the six eight-person Unity Task Forces on education, the economy, criminal justice, immigration, climate change, and healthcare are aimed at shaping negotiations over the 2020 Democratic platform at the party's convention next month.

Sanders said that while the "end result isn't what I or my supporters would've written alone, the task forces have created a good policy blueprint that will move this country in a much-needed progressive direction and substantially improve the lives of working families throughout our country."

"I look forward to working with Vice President Biden to help him win this campaign," the Vermont senator added, "and to move this country forward toward economic, racial, social, and environmental justice."

Biden, for his part, applauded the task forces "for helping build a bold, transformative platform for our party and for our country."

"I am deeply grateful to Bernie Sanders for working with us to unite our party and deliver real, lasting change for generations to come," said the former vice president.

On the life-or-death matter of reforming America's dysfunctional private health insurance system—a subject on which Sanders and Biden clashed repeatedly throughout the Democratic primary process—the Unity Task Force affirmed healthcare as "a right" but did not embrace Medicare for All, the signature policy plank of the Vermont senator's presidential bid.

Instead, the panel recommended building on the Affordable Care Act by establishing a public option, investing in community health centers, and lowering prescription drug costs by allowing the federal government to negotiate prices. The task force also endorsed making all Covid-19 testing, treatments, and potential vaccines free and expanding Medicaid for the duration of the pandemic.

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Observers and advocacy groups also applauded the Unity Task Forces for recommending the creation of a postal banking system, endorsing a ban on for-profit charter schools, ending the use of private prisons, and imposing a 100-day moratorium on deportations "while conducting a full-scale study on current practices to develop recommendations for transforming enforcement policies and practices at ICE and CBP."

Marisa Franco, director of immigrant rights group Mijente, said in a statement that "going into these task force negotiations, we knew we were going to have to push Biden past his comfort zone, both to reconcile with past offenses and to carve a new path forward."

"That is exactly what we did, unapologetically," said Franco, a member of the Immigration Task Force. "For years, Mijente, along with the broader immigrant rights movement, has fought to reshape the narrative around immigration towards racial justice and to focus these very demands. We expect Biden and the Democratic Party to implement them in their entirety."

"There is no going back," Franco added. "Not an inch, not a step. We must only move forward from here."

Reposted with permission from Common Dreams.