Extreme weather events are not the only threat that climate change poses. Another threat is the increase in the levels of air pollutants, such as ozone, that can harm human health and the environment.
Ozone is a gas that forms when sunlight reacts with emissions from vehicles, factories, and power plants. It can cause respiratory problems, lung damage, and premature death.
When heat and ozone occur together, they can create a deadly combination that poses even greater risks to human health.
This is because high temperatures can enhance the formation of ozone, and ozone can worsen the effects of heat stress.
Therefore, it is important to monitor and predict the co-occurrence of heat and ozone extremes, especially in regions that are vulnerable to these events.
One of these regions is China, which is one of the most populous and fastest-growing countries in the world.
China has experienced rapid economic development in recent decades, which has led to a surge in energy consumption and emissions of ozone precursors.
The nation has also witnessed rising temperatures and more frequent and severe heat waves due to climate change.
These factors have contributed to the increase in the occurrence and intensity of joint heat and ozone extremes in China.
The problem of heat and ozone
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Heat and ozone are two environmental factors that can pose serious threats to human health, especially when they occur together.
High temperatures can cause heat stress, dehydration, heat stroke, and even death. Ozone is a pollutant that forms when sunlight reacts with emissions from vehicles, factories, and power plants.
It can irritate the eyes, nose, and throat, damage the lungs, and worsen respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD).
China is one of the countries that face the highest risk of joint heat and ozone extremes.
Due to its rapid economic development, China has experienced a surge in energy consumption and emissions of ozone precursors, such as volatile organic compounds (VOCs) and nitrogen oxides (NOx).
At the same time, China has also witnessed increasing temperatures and more frequent and intense heat waves, which enhance the formation of ozone.
These trends are expected to continue in the future under climate change scenarios.
The co-occurrence of heat and ozone can have devastating impacts on the population of China, especially in densely populated urban areas such as Beijing.
According to a recent study, joint heat, and ozone extremes in China could cause more than 12,000 premature deaths per year by 2050, a four-fold increase from the current level.
The study also estimated that the economic losses due to these events could reach $37 billion per year by 2050, accounting for 0.5% of China's gross domestic product (GDP).
One of the key steps is to develop an early warning system that can forecast the occurrence and severity of these events months in advance.
Such a system could help the government and the public prepare for potential risks and take appropriate actions to reduce exposure and vulnerability.
A team of researchers from the Harvard-China Project at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Hong Kong Baptist University has recently proposed a novel approach to design such an early warning system.
The researchers used machine learning techniques to reconstruct daily ozone levels in China from 2005 to 2018, based on limited observations and meteorological data.
They then identified large-scale climate patterns that could be used as predictors for joint heat and ozone extremes in China.
The researchers found that sea surface temperatures (SSTs) in three regions of the Pacific and Indian Oceans were strongly correlated with joint heat and ozone extremes in northeast China, including Beijing.
These SSTs affect the atmospheric circulation, precipitation, cloud cover, and solar radiation over China, which in turn influence the temperature and ozone levels.
By using these SSTs as predictors, the researchers were able to forecast the co-occurrence of heat and ozone extremes in China with high accuracy up to four months ahead.
The researchers suggested that their approach could be applied to other regions and pollutants as well, such as particulate matter (PM2.5) and nitrogen dioxide (NO2).
They also recommended that their method could be integrated with existing air quality models and monitoring systems to provide more reliable and timely information for decision-making.
They hoped that their research could contribute to the development of a comprehensive early warning system for joint heat and ozone extremes in China that could save lives and resources.
