The reporter directly attacked the serious air pollution incident in the United States： everything is full of doomsday feeling, and no one can escape.

On June 10th, after 7: 00 a.m. Eastern Time in North America, I woke up uneasily and felt a little hoarse. After drinking a few mouthfuls of water, I quickly opened the curtains and looked at the sky outside the window. Fortunately, the sky is still blue, but I feel a little cloudy, and I can’t see the white clouds in the past. Turn on the weather forecast on the mobile phone, "london, Ohio, AQI air quality index 90", which is in a yellow area and belongs to medium air quality. The prompt is "the air quality is acceptable, but people who are extremely sensitive to PM2.5 particles may have respiratory diseases."

This is the fifth day of the worst air pollution in recent decades in the northeastern United States due to wildfires in Canada. Since June 6, major cities in the eastern United States have been haunted by smoke from wildfires. On June 7th and 8th, new york’s AQI (Air Quality Index) exceeded 300, and sometimes even exceeded 400. According to the data of the Air Quality Index of the US Environmental Protection Agency, on the morning of June 8, the air quality in North American cities was the worst in the world.

At this time, the air quality in new york has returned to a good level, and Philadelphia and Washington are still on the edge of the yellow area; With the drift of smog, Indiana and Ohio in the central United States have become the most polluted areas. Newcastle, Indiana has an AQI index of 156, which is rated as unhealthy and may affect everyone’s health. It is currently the highest pollution index in the United States.

Newcastle, Indiana, is where we drove through last night! I suddenly remembered the popular word "running poison" in the circle of American Chinese friends in recent days.

We are on a trip to the East of America at the wrong time. At 11 o’clock last night, when driving through Newcastle, we didn’t know we were in the center of poisonous smoke. I smelled an obvious burning smell in the car and began to cough involuntarily. Street lamps illuminate the air at night, and it seems that you can see smoke and dust repeatedly. Open the weather forecast software, AQI153! We had planned to park next to Newcastle for the night, but we were choked and had to drive for more than 100 miles. It was not until after midnight that we rushed out of the orange pollution area.

The average air quality index of the United States in 2022 is 37, and the average index of Oak Ridge, Ohio, the most polluted city, is 96. By contrast, it is not difficult to understand the panic that the American people feel about this air pollution. Among them, I interviewed L and S, citizens of new york, and Dr. Jacob Bendix, honorary professor of the School of Geography and Environment of Syracuse University, who has been tracking wildfires for a long time, trying to interpret the climate metaphor brought by this sudden wildfire crisis.

On June 7, 2023, a man looked at the George Washington Bridge through the smog and made a phone call. Image source: vision china "I have experienced the worst air quality in new york for three days!"

"There is an obvious burning smell, choking voice, red smoke sky, and everything is full of doomsday." L, who moved to new york from the north of China, recalled his experience a few days ago. "From June 6th to 8th, it was undoubtedly the three days with the worst air quality in new york!"

On June 7th, L went out without wearing a mask, only to find that most new york people in the street were wearing medical masks left over from the COVID-19 epidemic. "Medical masks actually have no effect on PM2.5 The New York City Government issued N95 masks at the subway entrance, and many people went to collect them." L told me that both the New York State Government and the municipal government issued notices to remind sensitive people to stay indoors, and the school cancelled outdoor activities, but did not suspend classes. Urban public services have not been affected, and the number of street people has not decreased significantly.

However, some outdoor public activities were forced to be cancelled. On Broadway, the performances of Hamilton and Camelot were cancelled on June 7th, and Jodie Comer, the star of The Surface, left the matinee 10 minutes later because of breathing difficulties. Shakespeare in the park canceled the performance of Hamlet on Thursday and Friday. Major League Baseball’s new york Yankees and Philadelphia Phillies postponed the game.

On June 8, Washington issued a rare code purple alert-which means that air quality is "very unhealthy" for everyone, not just those with respiratory diseases. The National Zoo of the United States was also forced to close, and animals, including three giant pandas, were taken indoors for refuge. Harmful air stretches all the way to Virginia and Indiana.

On TikTok, the most clicked videos these days include some videos that teach people how to make their own air purifiers with tape. The self-made filter stuck on the air inlet side of box fan with adhesive tape works very well, and the price is only 10 dollars. It is better to stick four filters together.

"Many people who have been living in the United States still have a great reaction to this air pollution. Hiding in the room with the air purifier on is a way of refuge." L said that these days, I have been driving a purifier at home.

Marshall Burke, an associate professor of earth system science at Stanford University, said on Twitter that the scale of smog events in new york this week was bigger than any time in the past two decades, and the PM2.5 value had reached off the charts. Although air pollution in eastern cities such as new york has temporarily eased, as long as Canadian wildfires are still burning, billowing smoke may come back at any time.

Zack Taylor, a meteorologist with the National Weather Service, warned that although air pollution in the northeastern United States may be suspended, smog may come back this summer. "The direct source of all this is obviously the fire in Canada. Until these fires are better controlled, smoke will continue to drift into the atmosphere. Depending on the wind direction and weather patterns-some of them may sometimes fall into the United States. "

The neglected truth: PM2.5 emission from wildfire or superman as the emission source.

How did it happen? The main source of this round of air pollution in the United States comes from wildfires in Canada.

At present, there are more than 400 forest fires burning all over Canada. Since last month, the smoke from the fire in Canada has been spreading to the United States, but it has been aggravated with the recent fire in Quebec. Last week alone, there were 150 wildfires in Quebec, and about 100 fires were considered completely out of control.

Due to climate change, the fire season in Canada came earlier and lasted longer than before. All 10 provinces in Canada are extremely dry or experiencing a total drought, which means that there is a lot of fuel ready to be ignited by the inevitable spark. The area burned by fires all over Canada is 12 times of the 10-year average at this time of year. The United States has sent more than 600 firefighters and equipment to Canada, and other countries are also providing help, but the fire is not decreasing. Canadian officials say this will be the worst wildfire season in the country’s history.

The worst wildfire season in history has also brought the worst air pollution in history. For a long time, people have pointed the finger at industrial pollution and exhaust emissions, ignoring the threat of wildfire to air pollution.

Wildfire, also known as forest fire, jungle fire and wasteland fire, is an unplanned, uncontrolled and unpredictable fire in combustible vegetation region. A lot of combustible materials, drought and high temperature usually cause serious wildfires. Wildfire will release a large amount of carbon dioxide, black carbon and brown carbon particles, as well as ozone precursors such as volatile organic compounds and nitrogen oxides (NOx) into the atmosphere, and these emission areas can cross national boundaries and continental boundaries.

Dr. Nidhi Kumar, a cardiovascular expert, wrote that we are now in a high concentration of pollutants and toxins. The concentration of carbon monoxide in the atmosphere is so high that it will not only cause heart problems of patients, but also cause lung problems and general inflammation of the body.

Wolfgang Knorr, a Swedish scientist, wrote in the paper "The Impact of Climate and Population on the Air Pollution Hazards of Wildfire in the 21st Century", "Wildfire poses great risks to human life and health due to the emission of toxic smoke. At present, in most parts of the world, the emission of PM2.5 from wildfires exceeds that from human sources, while the emission from deforestation or peat fires is a secondary source. This means that controlling man-made emissions will not be enough to achieve the World Health Organization’s air quality goals. "

The United States has always been seriously affected by air pollution caused by wildfires. Jia Coco Liu analyzed the level of fine particulate matter (PM2.5) directly caused by wildfires in 561 counties in the western United States during the fire season from 2004 to 2009 in the paper "Particulate air pollution caused by wildfires in the western United States under climate change". They found that wildfires contributed an average of 71.3% of the total PM2.5 in the days when PM2.5 regulatory standards were exceeded in these six years.

Why did this Canadian mountain fire have such a severe impact on the air in North America? Professor Jacob Bendix told me that, first of all, the unusually hot and dry weather conditions led to unprecedented fire outbreaks, both in quantity and scale. Secondly, we encountered a rare but not unprecedented weather pattern, which gave us a few days of strong north wind and brought the smoke from those fires to the eastern United States. The combination of these events produced an unusually large amount of smog, and most of it was transported to densely populated areas.

Under the global climate change, no one can escape the "smoky sky"

"Welcome to a smoky day!" S had been living and working in the Bay Area before, and moved to new york last year. For a Californian, she is familiar with the weather in new york these days. "Red sky? Do you have black smoke secretion when you blow your nose? We all went through it in California. I moved from the west to the east to avoid smoking. Ironically, it seems that the smoky days have followed me. "

Every summer and autumn, arid California will experience a difficult wildfire season. In 2020, 4.3 million acres of land in California were burned. Researchers at Stanford University estimate that in 2020, smoke inhalation caused 1,200 additional deaths in California. When the same story happened in new york, a global metropolis, people’s attention to wildfire was pushed to a new height.

Since the industrial age, the world has warmed by about 1.2 degrees Celsius, and climate change has increased the probability of hot and dry weather that may contribute to wildfires. A 2021 study supported by the National Oceanic and Atmospheric Association found that climate change has been the main reason for the increase of hot and dry fire weather in the western United States.

A United Nations report last year warned that the intensity of global wildfires is expected to increase by 57% by 2090 due to climate change. Jia Coco Liu estimates that under the future climate change, from 2046 to 2051, the frequency and intensity of more than 82 million people experiencing wildfire smoke will increase by 57% and 31% respectively. Northern California, western Oregon and the Great Plains may suffer the worst fire smoke exposure in the future. In the changing climate, extreme events may have a significant impact on human health.

"This is a good metaphor for how complex and interconnected the global climate system is." Illinois climatologist Trent Ford said. Wildfire smoke can spread hundreds or thousands of miles, and can cross national boundaries and even continents. In the face of mountain fires in other countries and illusory smoke, what people can do seems to be very limited except hope for wind and rain. "Destiny community" and "common powerlessness" came together.

Professor Jacob Bendix told me that some smoke from this wildfire in Canada will even reach Asia. "It is expected that the concentration will be very low at that time and will not cause major problems. However, he mentioned that what is more worrying is that Siberia has also experienced more and more serious wildfires in recent years. As this trend continues in the future, it is likely that enough smog will reach the northeast of China, which will have a significant impact on health.

Is there anything else we can do? In the United States, the latest "less sparks, less wildfires" action is obviously still in force, but it has not yet reached its goal. Studies have shown that 80% of wildfires in the United States are caused by human carelessness. "Less sparks, less wildfires" calls on people to put out campfires, tighten trailer chains to prevent them from sparking on asphalt pavement, cut grass as soon as possible, do not cut grass where blades can hit rocks, prepare fire-fighting tools to deal with debris burning, and shoot at safe targets.

In the long run, we must make greater efforts to mitigate climate change. Jacob Bendix said that although there are many factors leading to wildfire disaster, including past and present forest management methods, where people live and the way they build houses and other buildings, natural or man-made fire sources and so on. However, there is one factor that will lead to the increase of disasters in various environments, and that is climate change. So far, the most important thing we can do is to reduce greenhouse gas emissions.

Jacob Bendix told me that because climate change is increasing the frequency and severity of heat waves and droughts, it is almost certain that the number and scale of wildfires in most parts of the world will increase in the coming decades.

"We have seen this growth trend and have every reason to believe that it will continue. These fires will directly harm human society by destroying houses and infrastructure, destroying wood resources, generating smoke that restricts human activities and endangers human health, and occasionally killing people who cannot escape from the flames. There will also be collateral damage, because the fire itself will release carbon into the atmosphere, which will lead to climate change. In addition, the smoke from North American fires may darken Greenland’s glaciers, making them absorb more sunlight and melt faster. Melting glaciers cause sea levels to rise, thus creating additional problems. "

Professor Jacob Bendix said that all these impacts remind us of the urgency of mitigating climate change. Although it may be too late to stop some of these effects, our actions can at least prevent the situation from getting worse. At least, it’s never too late to try to reduce the damage.