There has been much speculation on possible relationships between global warming and the covid19 pandemic with causation proposed in both directions as in the pandemic reduced fossil fuel emissions in a kind of climate action and also the reverse hypothesis that warming made the pandemic more likely and more deadly.

The warming to pandemic causation hypothesis is seen for example in the works of the Harvard School of Public Health (HSPH) where we find this hypothesis: “We don’t have direct evidence that climate change is influencing the spread of COVID-19, but we do know that climate change alters how we relate to other species on Earth and that matters to our health and our risk for infections. As the planet heats up, animals big and small, on land and in the sea, are headed to the poles to get out of the heat. That means animals are coming into contact with other animals they normally wouldn’t, and that creates an opportunity for pathogens to get into new hosts. Many of the root causes of climate change also increase the risk of pandemics. Deforestation, which occurs mostly for agricultural purposes, is the largest cause of habitat loss worldwide. Loss of habitat forces animals to migrate and potentially contact other animals or people and share germs. Large livestock farms can also serve as a source for spillover of infections from animals to people. Less demand for animal meat and more sustainable animal husbandry could decrease emerging infectious disease risk and lower greenhouse gas emissions. We have many reasons to take climate action to improve our health and reducing risks for infectious disease emergence is one of them.} In essence they are saying YES global warming causes pandemics but the hypothesis is worded carefully with caveats for the flexibility needed to avoid accountability for science fraud or circular reasoning. LINK to HSPH: https://www.hsph.harvard.edu/c-change/subtopics/coronavirus-and-climate-change/

In this context, we should note that the Black Plague, that killed 25 million people in Europe in the period 1346AD to 1353AD, did not occur during the previous Holocene warm period known as the Medieval Warm Period from 950AD to 1250AD but well after that and well into the the Little Ice Age (1303-1860) cold period. In violation of the warming driven climate-pandemic causation hypothesis proposed by HSPH above, we see a pandemic that did not occur during an intense warm period but in a cold period.

In that case, the pandemic is causally related to the cold climate of the Little Ice Age in the reverse direction because the timing suggests the reverse causation. It is proposed that the pandemic caused the cold period by way of dead people’s abandoned farms going back to forest, sucking out atmospheric CO2, and causing cooling. However, as seen in the chart above, Europe’s forest cover has been on a downlward trend since 1000 BC. There appears to be a brief upward jump at 1320AD before the black plague and not after. More about this chart in a related post: LINK: https://tambonthongchai.com/2021/01/09/a-european-emphasis-on-forest-preservation-in-the-amazon/

In all such causation hypotheses, where the hypothesis is derived from history, there is no way to test the hypothesis because a hypothesis derived from the data cannot be tested with the same data.

That kind of hypothesis test contains the the so called Texas Sharpshooter fallacy, also understood as circular reasoning and confirmation bias. Therefore, given that the covid pandemic has occurred during global warming it is possible to propose their various possible causal relationships post hoc but there is no way to test these post hoc theories. That would have been possible had the pandemic been forecast on the basis of global warming theory before it had occurred.

As often seen in circular reasoning hypotheses, the proposed causation relationship between global warming and the pandemic is also seen in reverse because in all such cases causation is suggested by a shared time span and not by statistical evidence of responsiveness. Here it is observed that the pandemic had greatly reduced economic activity in terms of canceled airline flights and the virtual elimination of travel, tourism, and recreation. In that context it is suggested that the pandemic had imposed nature’s climate action such that fossil fuel emissions have sharply declined. However, as seen in the the analysis presented in a related post, the assumed responsiveness of atmospheric composition to fossil fuel emissions is not seen in the case of the pandemic’s effect on fossil fuel emissions: LINK: https://tambonthongchai.com/2020/05/18/12479/ . A more in-depth test of the assumed causation relationship between fossil fuel emissions and atmospheric composition is presented in yet another related post on this site: LINK: https://tambonthongchai.com/2020/12/29/climate-scientist-explains-the-carbon-budget/

WE CONCLUDE FROM THE ABOVE ANALYSIS THAT THERE IS NO EVIDENCE OF A CAUSATION RELATIONSHIP IN EITHER DIRECTION BETWEEN ANTHROPOGENIC GLOBAL WARMING AND THE COVID19 PANDEMIC BUT THAT THE USE OF CIRCULAR REASONING CAN READILY CREATE THESE RELATIONSHIPS IN EITHER DIRECTION.

POSTSCRIPT: THE HSPH ASSESSMENT : Does climate change affect the transmission of coronavirus?
We don’t have direct evidence that climate change is influencing the spread of COVID-19, but we do know that climate change alters how we relate to other species on Earth and that matters to our health and our risk for infections. As the planet heats up, animals big and small, on land and in the sea, are headed to the poles to get out of the heat. That means animals are coming into contact with other animals they normally wouldn’t, and that creates an opportunity for pathogens to get into new hosts. Many of the root causes of climate change also increase the risk of pandemics. Deforestation, which occurs mostly for agricultural purposes, is the largest cause of habitat loss worldwide. Loss of habitat forces animals to migrate and potentially contact other animals or people and share germs. Large livestock farms can also serve as a source for spillover of infections from animals to people. Less demand for animal meat and more sustainable animal husbandry could decrease emerging infectious disease risk and lower greenhouse gas emissions. We have many reasons to take climate action to improve our health and reducing risks for infectious disease emergence is one of them. Does air pollution increase the risk of getting coronavirus? Does it make symptoms worse? Recent research from Rachel Nethery, Xiauo Wu, Francesca Dominici and other colleagues at Harvard Chan has found that people who live in places with poor air quality are more likely to die from COVID-19 even when accounting for other factors that may influence risk of death such as pre-existing medical conditions, socioeconomic status, and access to healthcare. This finding is consistent with prior research that has shown that people who are exposed to more air pollution and who smoke fare worse with respiratory infections than those who are breathing cleaner air, and who don’t smoke. In places where air pollution is a routine problem, we have to pay particular attention to individuals who may be more exposed or vulnerable than others to polluted air, such as the homeless, those who don’t have air filtration in their homes, or those whose health is already compromised. These individuals may need more attention and support than they did even before coronavirus came along. For those interested in research papers on air pollution and virus transmission: Exposure to air pollution and COVID-19 mortality in the United States (Harvard University, preprint, 2019). This study found that a small increase in long-term exposure to PM2.5 leads to a large increase in COVID-19 death rate.
Measuring the impact of air pollution on respiratory infection risk in China (Environmental Pollution, 2018). This study found that worse air quality in China may increase transmission of infections that cause influenza-like illnesses. The association between respiratory infection and air pollution in the setting of air quality policy and economic change (Annals of the American Thoracic Society, 2019). A study of nearly 500,000 New York residents found that higher particulate matter air pollution levels increased the chances of hospitalization for pneumonia and emergency deparment visits, especially for influenza. Airborne transmission may have played a role in the spread of 2015 highly pathogenic avian influenza outbreaks in the United States (Scientific Reports, 2019). Researchers have found that several viruses, including adenovirus and influenza virus, can be carried on air particles. This recent paper finds that particulate matter likely contributed to the spread of the 2015 avian influenza. Relationship between ambient air pollution and daily mortality of SARS in Beijing (Biomedical and Environmental Sciences, 2005). During the SARS epidemic in 2003, this study found that increases in particulate matter air pollution increased risks of dying from the disease. SARS is a coronavirus, like COVID-19. Will warmer weather slow the spread of coronavirus? We don’t yet have a sense of what the changing weather will mean for COVID-19 and so we shouldn’t rely upon warmer weather to curtail transmissions. We need to do everything we can right now to slow the spread of this disease, and that means we need to follow the advice that public health experts are telling us and practice social distancing and good hand hygiene, among other actions. How likely are we to see infectious disease spread as a result of climate change? Climate change has already made conditions more favorable to the spread of some infectious diseases, including Lyme disease, waterborne diseases such as Vibrio parahaemolyticus which causes vomiting and diarrhea, and mosquito-borne diseases such as malaria and dengue fever. Future risks are not easy to foretell, but climate change hits hard on several fronts that matter to when and where pathogens appear, including temperature and rainfall patterns. To help limit the risk of infectious diseases, we should do all we can to vastly reduce greenhouse gas emissions and limit global warming to 1.5 degrees. Why are emerging infectious diseases on the rise? We have seen a trend of greater emergence of infectious diseases in recent decades. Most of these diseases have entered into people from animals, especially wild animals. This trend has many causes. We have massive concentrations of domesticated animals around the world, some of which can be home to pathogens, like the flu, that can make people sick. We also have massive concentrations of people in cities where diseases transmitted by sneezing may find fertile ground. And we have the ability to travel around the globe in less than a day and share germs widely. But a look at the origins of COVID reveals that other forces may be in play. In the past century we have escalated our demands upon nature, such that today, we are losing species at a rate unknown since the dinosaurs, along with half of life on earth, went extinct 65 million years ago. This rapid dismantling of life on earth owes primarily to habitat loss, which occurs mostly from growing crops and raising livestock for people. With fewer places to live and fewer food sources to feed on, animals find food and shelter where people are, and that can lead to disease spread. Another major cause of species loss is climate change, which can also change where animals and plants live and affect where diseases may occur. Historically, we have grown as a species in partnership with the plants and animals we live with. So, when we change the rules of the game by drastically changing the climate and life on earth, we have to expect that it will affect our health. What actions can we take to prevent future outbreaks? We can make many smart investments to avert another outbreak. Federal, state, and local agencies can support public health leadership and science, we can provide more funding for needed research, early response to outbreaks, and supplies for testing. And we can do much more to control the illegal wildlife trade. We also need to take climate action to prevent the next pandemic. For example, preventing deforestation—a root cause of climate change—can help stem biodiversity loss as well as slow animal migrations that can increase risk of infectious disease spread. The recent Ebola epidemic in West Africa probably occurred in part because bats, which carried the disease, had been forced to move into new habitats because the forests they used to live in had been cut down to grow palm oil trees. Rethinking our agricultural practices, including those that rely on raising tens of millions of animals in close quarters, can prevent transmissions between animals and spillover into human populations. Reducing air pollution caused by burning fossil fuels like coal, oil and natural gas also helps keep our lungs healthy, which can protect us from respiratory infections like coronavirus. To combat climate change, we need to drastically decrease greenhouse gas emissions. Generating electricity from low-carbon energy sources like wind and solar decreases harmful air pollutants such as nitrogen oxides, sulfur dioxide, and carbon dioxide that lead to more heart attacks and stroke as well as obesity, diabetes, and premature deaths that put further strains on our health care systems. Preparation for pandemics is also about keeping people healthy at baseline. If we have a population in the U.S. where a third of our population are obese, and 5-10% of people have diabetes, we’re going to be immensely more vulnerable. And if you look at why people in the U.S. are not healthy at baseline, it has to do with our diets, pollution, and climate change. We have an opportunity here to recognize that prevention is by far the best approach to protecting health. When COVID-19 eases, and we are ready to restart our economy, we can make our workforce healthier and more climate-resilient through scaling-up our investments in low-carbon technologies. Can you identify the communities most at-risk, and how and why both COVID-19 and climate change harms them? People with chronic health conditions, lower-income, and communities of color are disproportionately impacted by both COVID-19 and climate change, and pollution is at the heart of both problems as a new Harvard T.H. Chan School of Public health study confirms. We know that African American communities are disproportionately exposed to air pollution and we’re now seeing this pollution driving higher mortality rates from COVID-19. We owe it to everyone to improve health, and we do that by reducing the sources of pollution that drive a large burden of disease both in the United States and around the world. Why is it so important for health officials to talk about climate change now? Having taken care of children and families who are deeply concerned about how they can protect their children from this disease, I can tell you that we need to wash our hands and we need to socially distance. But if we really care about preventing this kind of problem in the future, we need to think hard about climate change and the biodiversity crisis. I was actually in a room with a child and a family when I first thought that this is exactly the time that we need to think more about the broader issues that we face. We simply cannot afford to deal with a crisis like this pandemic on top of another climate-related crisis—like a hurricane, tornado, wildfire, or heatwave—when we absolutely know how to implement climate solutions, and can put them into action right now. Doing so will make us healthier today and protect our future. Climate change and global health policy are largely treated as separate issues by the public and media. Do we need to adjust our thinking?
Yes. The separation of health and environmental policy is a ​dangerous delusion. Our health entirely depends on the climate and the other organisms we share the planet with. We need to bring these communities together. Some progress has been made in addressing the risk of pathogen spillover from animals into people. But largely we still view the environment, and life on earth, as separate. We can and must do better if we want to prevent the next infectious pandemic. That means we must combat climate change and do far more to safeguard the diversity of life on earth, which is being lost at a rate not seen since the dinosaurs—and more than half of life on earth—went extinct 65 million years ago. COVID-19 is killing people now and climate change is killing people now. The scale of actions to combat them are starkly different. Why? Infectious diseases are scary because they are immediate and personal. They radically and rapidly change how we lead our lives, and they are an immediate threat to our friends and families. They hit all of our “go” buttons. Climate change seems to many an armageddon in slow motion and its dangers can feel impersonal and its causes diffuse. It’s easy to think “I didn’t cause this” or that “it doesn’t directly affect me.” But there’s another way to look at it. Like COVID-19, if you’re concerned about climate change, you can take actions right now to improve your health and the health of your friends and loved ones. We can learn from this pandemic that people are motivated by the personal and the actionable. At Harvard Chan C-CHANGE, our research shows that the actions we need to combat climate change are the same actions we need to make people healthier right now, especially for diseases causing huge burdens on our health like obesity, heart disease, and cancer. We need to do much more to talk about the “burden of disease” that’s preventable, and the things we can do now to prevent it. Is climate change too expensive to fix? We spend just over $3 trillion every year in the United States on health care. And by some estimates, more than half the deaths in the United States are preventable, largely because of pollution, diet, exercise, and lifestyle habits like smoking. So think about the money we could save simply by reducing air pollution, eating less meat, and building exercise into our day by walking or biking more often. We could use the savings to invest in preventing climate change, among other things like education, and paying fair wages. When you look at this question purely from a financial standpoint, air pollution is a drag on economic growth and solutions to address have been enormously cost-effective in the United States. In 2011, a study by the Environmental Protection Agency that looked at the costs and benefits of the Clean Air act found that every $1 invested to reduce air pollution returns up to $30 in benefits. The only thing our health and our economy can’t afford is climate inaction.