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Solar Eclipse: Why the Sun Is Not Responsible for Recent Climate Change

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An annular solar eclipse in progress graces the sky at Dog Beach in San Diego, California, USA, 1992. N J Gargasz / Alamy

By Zeke Hausfather

With a total solar eclipse sweeping across North America, everyone is suddenly paying attention to the sun. One of the most common skeptical arguments against human-caused climate change is that changes in solar activity, rather than just CO2, is playing the biggest role.

At first glance, it seems to make intuitive sense: The sun is a massive nuclear fusion reactor a million times larger than Earth, it is responsible for almost all the energy reaching our planet, and in the past few decades scientists have learned that solar activity varies significantly over time. Indeed, changes in the distribution of sunlight reaching the Earth clearly change the temperature dramatically on a daily and annual timescale.


However, since 1970 global temperatures have shot up by almost 0.7 C, while the amount of solar energy reaching the Earth has actually declined. Similarly, the upper atmosphere is cooling while the lower atmosphere warms, a clear fingerprint of warming from greenhouse gases rather than the sun.

This evidence suggests we can rule out a major solar influence on recent warming.

Moving in Opposite Directions

Satellites have been directly monitoring the amount of the sun's energy reaching the Earth since the late 1970s. Before that, researchers kept careful records of the number of "sunspots," dark patches on the surface of the sun that are strongly related to solar output.

Combining older sunspot measurements with modern satellite observations, scientists have put together estimates of the sun's output—called Total Solar Irradiance or TSI—for the past 400 years. There is still some debate around how much solar output changed in the past, with some reconstructions suggesting more variation than others.

The plot below shows the solar TSI reconstruction from Naval Research Laboratory Total Solar Irradiance-2 (NRLTSI2) model (red line)—one of the ones with larger changes in solar output over the past 150 years—alongside the surface temperature record jointly produced by the UK Met Office Hadley Centre and the Climatic Research Unit at the University of East Anglia (black line).

Annual global mean surface temperature from HadCRUT4 in black in degrees C, along with NRLTSI2 TSI data in watts per meter squared. Lowess-smoothed curves are shown via dashed lines. Chart by Carbon Brief using Highcharts.

The temperature and TSI values shown in this plot are not intended to be directly comparable. Dr. Gavin Schmidt, director of NASA Goddard Institute of Space Studies, told Carbon Brief that it would take around a seven watts per meter squared change in TSI to result in 1C warming, meaning that the observed rise in solar activity between 1880 and 1980 would result in only 0.1C warming.

There are indirect effects that need to be accounted for as well. Increases in solar UV output increase the formation of ozone, which is itself a greenhouse gas. This could at most double solar's contribution to warming, taking it to 0.2C.

This shows that solar has only had a small impact of global temperatures over the last century or so, said Schmidt:

"Just as for the other drivers of change (such as deforestation, air pollution and greenhouse gases) we can calculate the fingerprint for these variations in time throughout the climate system from the surface to the mesosphere [in the upper atmosphere]. When we match that up with what we have observed over time though, the solar contribution is small—close to zero over the last 50 years, and perhaps as large as 10% since the late 19th century."

A Slight Decrease in Solar Activity

It is also worth noting that almost all of the minor warming contribution from fluctuations in the sun's output occurred before 1970.

In recent decades, when global temperatures have risen most steeply, TSI has been flat or even slightly declining, said Schmidt:

"The period of greatest warming—since about 1975—has coincided with a slight decrease in solar activity."

Solar output in the satellite era, when we have much higher confidence in the records, is shown in the figure below. Each black dot represents daily total solar irradiance, while the red line is a longer-term average.

Satellite-based daily Total Solar Irradiance (TSI) in watts per metre squared from 1976-2016 via PMOD. Red line represents a lowess-smoothed fit. Chart by Carbon Brief using Highcharts.

There is a clear cycle in solar activity of around 11 years. This has some effect on short-term climate, though it tends to average out over longer time periods. For example, the unusually low solar output in after 2009 may have contributed to slower warming of the Earth's surface between 1998 and 2013.

Atmospheric 'Fingerprint'

The lack of an increase in solar activity after 1970 is one major argument against a solar role in modern warming. Another is the cooling in a layer of the upper atmosphere known as the stratosphere.

If changing solar output were driving warming, the whole atmosphere would warm due to the addition of incoming solar radiation. In contrast, if warming was due to greenhouse gases, the lowest layer of the atmosphere—the troposphere—and surface would warm, while the upper atmosphere would cool as greenhouse gases trapped heat and prevented it from escaping the troposphere.

The figure below shows what has actually happened since 1950. The upper chart shows a clear cooling trend in the stratosphere, while the lower chart shows the warming of the troposphere and Earth's surface. This is the "fingerprint" of warming from CO2 and other greenhouse gases, though recent declines in stratospheric ozone also play a large role in stratospheric cooling.

Global lower stratosphere (top) and troposphere (bottom) temperatures between 1958 and 2012. Figure from the UK MET Office HadAT. The CO2 cooling signal is clearer and more differentiable from ozone-driven stratospheric cooling in higher levels of the stratosphere.

Schmidt describes this evidence as "the biggest mismatch." He told Carbon Brief:

"If the warming at the surface was related to solar forcing, the upper atmosphere would also be warming. But it hasn't been—it has been cooling, exactly as predicted from the effects of CO2 increases."

Grasping at Cosmic Rays

With no discernible increase in solar activity, proponents of solar influence on modern warming have turned to other possible explanations. One that has gained traction in recent years is the idea that galactic cosmic rays may play a role in the Earth's climate.

Galactic cosmic rays (GCRs) are high energy particles from beyond our solar system that regularly bombard the Earth. When solar activity is high, the "solar wind"—a stream of particles emitted from the sun—acts to reduce the number of GCRs that enter the Earth's atmosphere.

Some research has found that GCRs in the atmosphere can play a role in cloud formation, with higher levels of GCRs potentially leading to more low-altitude clouds. These low-altitude clouds can influence the Earth's climate by reflecting incoming sunlight back into space.

This has led some to suggest that changes in solar activity could influence the Earth's climate by changing cloud formation.

However, the GCR hypothesis suffers from the same fundamental problem as total solar irradiance: It is moving in the wrong direction. Since 1960, the amount of GCRs reaching the Earth has increased, as shown in the figure below. If GCRs were a major influence on climate, this would result in cooling, not warming, over the past 50 years.

Daily Galactic Cosmic Ray (GCR) counts from the neutron monitor at the McMurdo Station in Antarctica. Yellow line represents a lowess-smoothed fit. Chart by Carbon Brief using Highcharts.

Other recent research has also cast doubt on the role of GCRs as a major factor in the Earth's climate, suggesting that their effect on cloud formation is far too weak to make much of a difference.

Taken together, these three lines of evidence show that solar variations are not driving modern climate change, said Dr. Mike Lockwood, a solar physicist at the University of Reading. As he concluded for Carbon Brief:

"Most-importantly, the observed height profile is all wrong: a total solar irradiance increase would drive higher temperatures at all heights in the atmosphere, not just the surface, whereas the data show that while the lower atmosphere (and surface) have warmed, the stratosphere has cooled. The only mechanism that predicts this is greenhouse gas trapping of thermal infrared radiation from Earth's surface.

Secondly, the long-term trend in solar activity since 1985 has been weakly downward whereas that in surface temperatures has been a strong rise. This also eliminates other proposed mechanisms, such as high cloud production by cosmic rays.

And the third is that you simply cannot put the observed levels of CO2 into the atmosphere without causing warming of about the magnitude observed."

Reposted with permission from our media associate Carbon Brief.

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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. Niq Steele / Getty Images

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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Democratic presidential hopefuls Joe Biden and Senator Bernie Sanders greet each other with a safe elbow bump before the start of the Democratic Party 2020 presidential debate in a CNN Washington Bureau studio in Washington, DC on March 15, 2020. Mandel Ngan / AFP / Getty Images

By Jake Johnson

Unity Task Forces formed by presumptive Democratic presidential nominee Joe Biden and Sen. Bernie Sanders unveiled sweeping party platform recommendations Wednesday that—while falling short of progressive ambitions in a number of areas, from climate to healthcare—were applauded as important steps toward a bold and just policy agenda that matches the severity of the moment.

"We've moved the needle a lot, especially on environmental justice and upping Biden's ambition," said Sunrise Movement co-founder and executive director Varshini Prakash, a member of the Biden-Sanders Climate Task Force. "But there's still more work to do to push Democrats to act at the scale of the climate crisis."

The climate panel—co-chaired by Rep. Alexandria Ocasio-Cortez (D-N.Y.) and former Secretary of State John Kerry—recommended that the Democratic Party commit to "eliminating carbon pollution from power plants by 2035," massively expanding investments in clean energy sources, and "achieving net-zero greenhouse gas emissions for all new buildings by 2030."

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.

"It has always been a crisis that tens of millions of Americans have no or inadequate health insurance—but in a pandemic, it's potentially catastrophic for public health," the task force wrote.

Dr. Abdul El-Sayed, a former Michigan gubernatorial candidate and Sanders-appointed member of the Healthcare Task Force, said that despite major disagreements, the panel "came to recommendations that will yield one of the most progressive Democratic campaign platforms in history—though we have further yet to go."

 

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.