The early part of the COVID pandemic led to a significant reduction in air pollution in many parts of the world. With lockdowns, travel restrictions and decreased economic activity, there was a noticeable drop in the emission of air pollutants, such as nitrogen dioxide (NO₂) and particulate matter (PM) that is fine enough to be inhaled.

Changes in air pollution varied depending on the location and the type of pollutant, but reductions were particularly noticeable in cities and industrial areas, where emissions from transport and industrial activities are typically high. In many areas though, air pollution levels quickly increased again as restrictions eased and activity resumed.

Along with having harmful effects on the environment, it’s well established that air pollution can have negative effects on human health, including increasing the risk of respiratory and heart problems and cancers. Emerging research suggests air pollution may also affect the brain and be linked to certain developmental issues in babies. The severity of these health effects can depend on the type and concentration of pollutants, as well as individual factors that affect a person’s susceptibility.

While there has been much focus on the way the pandemic affected air quality, it has also become apparent that air quality affects COVID risk – both in terms of the likelihood of contracting COVID and how sick people get with the infection.

How does air quality increase COVID risk?

Research has shown that long-term exposure to air pollution, particularly fine particulate matter under 2.5 micrometres (PM2.5) and NO₂, may increase the risk of COVID infection, hospitalisation, and death.

A study in England, for example, showed long-term exposure to PM2.5 and NO₂ is associated with 12% and 5% increases in COVID cases, respectively, for every additional microgram of PM2.5 or NO₂ per cubic metre of air.

One of the primary ways that air pollution may increase the risk of COVID is by weakening the respiratory system’s defences against viral infections. We know long-term exposure to fine particulate matter that is inhaled can reduce the lungs’ immune responses and cause damage to them, which can make people more vulnerable to respiratory infections like COVID.

Read more: Long COVID linked to air pollution exposure in young adults – new study

Air pollution can also impact the immune system’s ability to fight off viral infections. Exposure to particulate matter, such as PM2.5, has been linked to increased levels of cytokines and inflammation in the body.

Cytokines are signalling molecules that help the immune system fight infections. But high levels can cause a “cytokine storm”, where the immune system overreacts and attacks healthy cells in addition to the virus. Cytokine storms have been associated with severe COVID and a higher likelihood of dying from the disease.

And notably, COVID binds to ACE2 receptors to enter a cell. In studies of animals, PM2.5 exposure has been linked to a significant increase in ACE2 receptors. PM2.5 may therefore increase the probability of COVID entering cells in humans.

Further, air pollution may increase the severity of COVID symptoms by exacerbating underlying health conditions. Exposure to air pollution has been linked to increased rates of conditions such as diabetes and heart disease, which have been identified as risk factors for severe COVID.

Air pollution may also increase COVID transmission rates by acting as a carrier for the virus. Researchers continue to debate the potential of respiratory droplets from infected people attaching to particulate matter in the air and travelling long distances, potentially increasing the virus’s spread.

How can I reduce exposure to air pollutants?

With all this in mind, reducing air pollution levels may be an important strategy for mitigating the impact of COVID and protecting public health.

This requires a combination of individual actions and collective efforts to address the sources of pollution. There are several ways you can decrease your and others’ exposure to air pollution, including:

Limit outdoor activity during high-pollution days. Check air quality forecasts and limit outdoor activities on “high” days. Try to go outside at times of the day when pollution levels are lower, such as early morning or late evening.

Think about your mode of transport. Using public transport, walking or riding a bike instead of driving can help to reduce pollution levels. If you do drive, try to carpool or use an electric or hybrid vehicle.

Read more: Wuhan's lockdown cut air pollution by up to 63% – new research

Use indoor air filters. Having air filters in your home can help reduce indoor pollution levels. Hepa filters can remove many pollutants, including fine particulate matter. Further, the use of Hepa air systems can successfully filter COVID virus particles from the air.

Samuel J. White advises on air quality and receives funding from Fédération Equestre Internationale.

Philippe B. Wilson 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.

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In the days after Elon Musk took over Twitter in October 2022, the social media platform saw a “surge in hateful conduct,” which its then safety chief put down to a “focused, short-term trolling campaign.” New research suggests that when it comes to antisemitism, it was anything but.

Rather, antisemitic tweets have more than doubled over the months since Musk took charge, according to research that I and colleagues at tech firm CASM Technology and the Institute for Strategic Dialogue think tank conducted. Between June and Oct. 26, 2022, the day before Twitter’s acquisition by Musk, there was a weekly average of 6,204 tweets deemed “plausibly antisemitic” – that is, where at least one reasonable interpretation of the tweet falls within the International Holocaust Remembrance Alliance’s definition of the term as “a certain perception of Jews, which may be expressed as hatred towards Jews.”

But from Oct. 27 until Feb 9, 2023, the average was 12,762 – an increase of 105%. In all, a total of 325,739 tweets from 146,516 accounts were labeled as “plausibly antisemitic” over the course of our study, stretching from June 1, 2022 to Feb. 9, 2023.

Finding antisemitism with AI

To identify plausibly antisemitic tweets, my co-authors and I combined 22 published hate speech-identifying algorithms into a single mechanism and used even more machine learning to see which combinations of decisions led to the correct result. We then passed through all tweets – over a million in total – that contained any one of 119 words, phrases, slurs and epithets related to antisemitism.

No such process is perfect. We estimate our model to make a correct decision about 75% of the time. We also no doubt missed some antisemitic tweets not containing any of those 119 key words, as well as those taken down before early December when we collected the data.

We then used an algorithm to draw out 10 different themes of antisemitism seen in the tweets. Some centered around the use of specific antisemitic derogatory epithets. Others alluded to conspiracy theories concerning hidden Jewish influence and control.

Antisemitic tweets directed at Jewish investor and philanthropist George Soros warranted its own category. He was mentioned more than any other person in our data, over 19,000 times, with tweets claiming he was a member of a hidden globalist, Jewish or “Nazi” world order.

Another theme were tweets defending the rapper Ye, formerly Kanye West, who had made a number of antisemitic remarks after he had his account briefly reinstated by Musk.

Our research, which has not yet been peer-reviewed, also found around 4,000 of the antisemitic tweets were focused on the Russian invasion of Ukraine. These variously claimed that the conflict was caused by Jews, or that Jews secretly caused the U.S. to support Ukraine. They also contained direct antisemitism directed against the Ukrainian president, Volodymyr Zelenskyy, who is Jewish.

Musk rolls back content moderation

Musk’s acquisition of Twitter came on the back of what I have observed as a decadelong trend among tech giants to take more responsibility for hate speech, harassment, incitement, disinformation and other harms lurking in the information flowing through their platforms. Over that period, companies such as Facebook and Twitter gradually enacted policies to respond to extremism, hate speech and harassment, or increase “civility,” as Twitter itself described it in 2018, and built out the teams and tools to enforce them.

Musk, a self-professed “free speech absolutist,” pointed the platform in a different direction after taking control. In short order, Twitter’s independent Trust and Safety Council was dissolved, previously banned accounts were reinstated and over half of Twitter’s staff was laid off or simply left – including many of those responsible for enforcing the company’s hate speech policies.

As someone who has tracked hate speech on places like Twitter for around 10 years, I believe the changes to Twitter’s moderation practices are only partly to blame for the jump in antisemitism on the platform.

The media spectacle surrounding Musk’s takeover, along with his very vocal views on free speech, likely also encouraged exactly those people to join or rejoin the platform who had fallen foul of its previous attempts to confront hate. Our research gives some backing to this theory. Some 3,855 accounts we identified as posting at least one plausibly antisemitic tweet joined Twitter in the 10 days after Musk took over. This is, however, only a small proportion of the 146,516 accounts that sent at least one antisemitic tweet over the course of the entire study.

Little effect on curbing hate speech

A surge in hate speech on Twitter was flagged by researchers in the weeks after Musk took over, concerns the billionaire dismissed as “utterly false,” having earlier vowed to “max deboosted & demonetized” hateful tweets.

If Twitter has been de-amplifying antisemitism, our research shows almost no evidence of it. Before Oct. 27, antisemitic tweets received an average of 6.4 “favorites” and 1.2 retweets. Since then, they have averaged 6 “favorites” and 1 retweet. Although such engagement isn’t a perfect measure for visibility, tweets made much less visible to users would generally receive less engagement.

We also attempted to measure takedowns of antisemitic tweets. On Feb. 15, 45 days after we initially collected the data, we tried to re-collect all the tweets we identified as antisemitic. Tweets can be unavailable for lots of reasons, and Twitter’s enforcement is only one of them. Imperfect though this is, it does give us a tentative glimpse of what might be happening in regard to the removal of antisemitic posts. And across those dates, 17,589 antisemitic tweets were taken down – 8.5% of the total.

Rising tide of antisemitism

Our findings come at a time when many fear growing threats to Jewish communities. In 2021, the Anti-Defamation League tracked the highest number of antisemitic incidents – including harassment, vandalism and assaults – in the U.S. since they started tracking numbers in 1979. And this is not just a U.S. phenomenon; in the U.K., the Community Security Trust has recorded a similar spike in anti-Jewish activity, while in Germany, anti-Jewish crimes surged by 29% over the pandemic.

Studying social media has shown me again and again just how powerfully it helps to form the cultures and ideas that underlie its users’ behavior. Ultimately, the proliferation of tweets that hold Jews responsible for all the world’s ills, that circulate dark conspiracies of control and cover-up, or that fire derogatory attacks directed toward Jews, can only support antisemitism online – and in the real world.

Carl Miller is a Partner of CASM Technology and a Senior Fellow at the Institute for Strategic Dialogue. They conduct a wide range of public-interest social media research on online harms for a range of philanthropic, foundation and public sector institutions.

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Reading the latest international climate report can feel overwhelming. It describes how rising temperatures caused by increasing greenhouse gas emissions from human activities are having rapid, widespread effects on the weather, climate and ecosystems in every region of the planet, and it says the risks are escalating faster than scientists expected.

Global temperatures are now 1.1 degree Celsius (2 degrees Fahrenheit) warmer than at the start of the industrial era. Heat waves, storms, fires and floods are harming humans and ecosystems. Hundreds of species have disappeared from regions as temperatures rise, and climate change is causing irreversible changes to sea ice, oceans and glaciers. In some areas, it’s becoming harder to adapt to the changes.

Still, there are reasons for optimism – falling renewable energy costs are starting to transform the power sector, for example, and the use of electric vehicles is expanding. But the change isn’t happening fast enough, and the window for a smooth transition is closing fast, the Intergovernmental Panel on Climate Change report warns. To keep global warming below 1.5 C (2.7 F), it says global greenhouse gas emissions will have to drop 60% by 2035 compared with 2019 levels.

That’s 12 years from now.

In the new report, released March 20, 2023, the IPCC summarizes the findings from a series of reports written over the past eight years by hundreds of scientists who reviewed the latest evidence and research.

Here are four essential reads by some of the co-authors of those reports, each providing a different snapshot of the transformational changes underway.

1. More intense storms and flooding

Many of the most shocking natural disasters of the past few years have involved intense rainfall and flooding.

In Europe, a storm in 2021 set off landslides and sent rivers rushing through villages that had stood for centuries. In 2022, about a third of Pakistan was underwater, and several U.S. communities were hit with extreme flash flooding.

The IPCC warns in the sixth assessment report that the water cycle will continue to intensify as the planet warms. That includes extreme monsoon rainfall, but also increasing drought, greater melting of mountain glaciers, decreasing snow cover and earlier snowmelt, wrote UMass-Lowell climate scientist Mathew Barlow, a co-author of the assessment report examining physical changes.

“An intensifying water cycle means that both wet and dry extremes and the general variability of the water cycle will increase, although not uniformly around the globe,” Barlow wrote.

“Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies.”

Read more: The water cycle is intensifying as the climate warms, IPCC report warns – that means more intense storms and flooding

2. The longer the delay, the higher the cost

The IPCC stressed in its reports that human activities are unequivocally warming the planet and causing rapid changes in the atmosphere, oceans and icy regions of the world.

“Countries can either plan their transformations, or they can face the destructive, often chaotic transformations that will be imposed by the changing climate,” wrote Edward Carr, a Clark University scholar and co-author of the IPCC report focused on adaptation.

The longer countries wait to respond, the greater the damage and cost to contain it. One estimate from Columbia University put the cost of adaptation needed just for urban areas at between US$64 billion and $80 billion a year – and the cost of doing nothing at 10 times that level by mid-century.

“The IPCC assessment offers a stark choice,” Carr wrote. “Does humanity accept this disastrous status quo and the uncertain, unpleasant future it is leading toward, or does it grab the reins and choose a better future?”

Read more: Transformational change is coming to how people live on Earth, UN climate adaptation report warns: Which path will humanity choose?

3. Transportation is a good place to start

One crucial sector for reducing greenhouse gas emissions is transportation.

Cutting greenhouse gas emissions to net-zero by mid-century, a target considered necessary to keep global warming below 1.5 C, will require “a major, rapid rethinking of how people get around globally,” wrote Alan Jenn, a transportation scholar at the University of California Davis and co-author on the IPCC report dealing with mitigation.

There are positive signs. Battery costs for electric vehicles have fallen, making them increasingly affordable. In the U.S., the 2022 Inflation Reduction Act offers tax incentives that lower the costs for EV buyers and encourage companies to ramp up production. And several states are considering following California’s requirement that all new cars and light trucks be zero-emissions by 2035.

“Behavioral and other systemic changes will also be needed to cut greenhouse gas emissions dramatically from this sector,” Jenn wrote.

For example, many countries saw their transportation emissions drop during COVID-19 as more people were allowed to work from home. Bike sharing in urban areas, public transit-friendly cities and avoiding urban sprawl can help cut emissions even further. Aviation and shipping are more challenging to decarbonize, but efforts are underway.

He adds, however, that it’s important to remember that the effectiveness of electrifying transportation ultimately depends on cleaning up the electricity grid.

Read more: Revolutionary changes in transportation, from electric vehicles to ride sharing, could slow global warming – if they’re done right, IPCC says

4. Reasons for optimism

The IPCC reports discuss several other important steps to reduce greenhouse gas emissions, including shifting energy from fossil fuels to renewable sources, making buildings more energy efficient and improving food production, as well as ways to adapt to changes that can no longer be avoided.

There are reasons for optimism, wrote Robert Lempert and Elisabeth Gilmore, co-authors on the IPCC’s report focused on mitigation.

“For example, renewable energy is now generally less expensive than fossil fuels, so a shift to clean energy can often save money,” they wrote. Electric vehicle costs are falling. Communities and infrastructure can be redesigned to better manage natural hazards such as wildfires and storms. Corporate climate risk disclosures can help investors better recognize the hazards and push those companies to build resilience and reduce their climate impact.

“The problem is that these solutions aren’t being deployed fast enough,” Lempert and Gilmore wrote. “In addition to pushback from industries, people’s fear of change has helped maintain the status quo.” Meeting the challenge, they said, starts with embracing innovation and change.

Read more: Climate change will transform how we live, but these tech and policy experts see reason for optimism

Editor’s note: This story is a roundup of articles from The Conversation’s archives.

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