The recent heat wave that scorched the Pacific Northwest of the United States and Canada was unprecedented in its intensity and duration, killing hundreds of people and shattering temperature records.
According to a new study, such extreme heat events are becoming more frequent and severe due to human-caused climate change.
The Role of the 'Heat Dome' and the 'Wet Bulb' Temperature
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The study, published in the journal Nature Climate Change, found that the heat wave was a rare and unlikely event, but it was made much more probable by the global warming that has increased the average temperature of the Earth by about 1.2°C since the pre-industrial era.
The researchers used a technique called "extreme event attribution" to compare the observed temperatures with simulations of a world without human influence on the climate.
They found that the heat wave would have been virtually impossible without climate change, and that it was about 2°C hotter than it would have been otherwise.
They also estimated that such heat waves are now about 150 times more likely to occur than they were in the past.
One of the factors that contributed to the extreme heat was the presence of a high-pressure system, also known as a "heat dome", that trapped hot air over the region and prevented it from escaping.
The heat dome was unusually strong and persistent, and it was influenced by the jet stream, a band of fast-moving air that circles the globe and affects weather patterns.
Another factor that made the heat wave more deadly was the high humidity, which reduced the ability of the human body to cool itself through sweating.
The researchers used a measure called the "wet bulb" temperature, which combines temperature and humidity, to assess the risk of heat stress.
They found that the wet bulb temperature reached dangerous levels of above 35°C in some locations, which can be fatal for humans within hours.
The researchers projected that by the end of the century, under a high-emissions scenario, such heat waves could occur every five to 10 years, and be about 4°C hotter than they are now.
They also cautioned that the current climate models may be underestimating the frequency and severity of such events, and that the impacts could be worse than expected.
They urged for more research and adaptation measures to prepare for the increasing threat of extreme heat.
There is also a need for urgent and ambitious action to reduce greenhouse gas emissions and limit the global temperature rise to 1.5°C, as agreed in the Paris Agreement.
This would substantially reduce the risk of such heat waves, and prevent many deaths and damages.
They also called for more public awareness and education on the dangers of heat waves, and the best ways to cope with them.
They suggested that people should stay hydrated, avoid strenuous activities, seek shade or air-conditioned places, and check on vulnerable groups such as the elderly, the sick, and the homeless.
They also recommended that governments and authorities should invest in more cooling infrastructure, such as public fountains, pools, and shelters, and improve the resilience of buildings, transportation, and energy systems.
They also advocated for more green spaces, such as parks and trees, that can provide natural cooling and reduce the urban heat island effect.
Heat wave was a wake-up call for the world to take action on climate change, and to adapt to the new reality of more frequent and intense heat waves. They said that the heat wave was a "harbinger of the future", and that "we are not prepared for it".
