According to an analysis by a group of leading climate scientists, the unprecedented heat wave that hit the western United States and Canada in late June would be “near impossible” without man-made climate change. The World Weather Attribution Organization stated that global warming caused by greenhouse gas emissions has increased the likelihood of heat waves by at least 150 times.
The temperature in the Pacific Northwest of the two countries reached a record number of degrees. Among them, Leiden Village in Canada reached a record 49.6 degrees Celsius. Most of the village was later destroyed by forest fires. To find out whether climate change is working, scientists analyzed historical observations and computer simulations to match the current climate after global warming of 1.2 degrees Celsius (2.2 degrees Fahrenheit) since the beginning of the 19th century for comparison.
They found that the observations are so extreme that they far exceed the temperature observed in history, but given the current climate, it is estimated that this event may occur once in a thousand years. Looking to the future, this kind of heat wave will occur every five to ten years. If the earth heats up by 2 degrees Celsius (3.6 degrees Fahrenheit), this kind of heat wave will be even more regular. At the current rate, this may happen in the 2040s.
Researchers have offered two broad explanations for how climate change increases the likelihood of extreme heat waves. The first is that although climate change increases the likelihood of events, it is still very unusual. In the statement, climate change exacerbated previous droughts, which deprived the area of evaporative cooling, and a slowly moving high-pressure system in the atmosphere called a “heat dome.” If there is no impact of climate change, according to this theory, the maximum temperature would be about 2 degrees Celsius lower.
The second hypothesis is even more pessimistic: the climate system has exceeded the threshold at which low global warming now causes extreme temperatures to rise faster than previously observed. “Everyone is very worried about the consequences of these events, because no one expected them and no one thought it was possible,” said co-author Geert Jan van Oldenborgh from the Royal Netherlands Meteorological Institute.