Human activities increase likelihood of extreme heat wave

Heat Wave to Affect Every Child by 2050

July 19 was recorded as the hottest recorded day in the United Kingdom when temperature shot up 40 degrees Celsius and above. Heat wave continued to grip Europe and the United States in the last many days. No doubt, human activities are the culprits and heat wave would continue.   

In the latest analysis of the atmospheric circulation patterns and human-caused emissions that led to the 2021 heat wave in North America, the researchers said that extreme heat wave events will increase by more than 30% in the coming years. The findings also have the same effects in Europe.

The findings published in Advances in Atmospheric Sciences  found that greenhouse gases are the primary reason for increased temperatures in the past and will likely continue to be the main contributing factor.

Co-corresponding author Chunzai Wang said that they looked into the physical processes of internal variability, such as atmospheric circulation patterns, and external forcing, such as anthropogenic greenhouse gases.

An extraordinary and unprecedented heat swept western North America in late June of 2021, resulting in hundreds of deaths and a massive die-off of sea creatures off the coast as well as horrific wildfires

Wang is a researcher in the Southern Marine Science and Engineering Guangdong Laboratory and head of the State Key Laboratory of Tropical Oceanography at the South China Sea Institute of Oceanology, Chinese Academy of Sciences (CAS).


Atmospheric circulation patterns describe how air flows and influences surface air temperatures around the planet, both of which can change based on natural warming from the Sun and atmospheric internal variability, as well as Earth’s rotation. Using observational data and climate models, the researchers identified that three atmospheric circulation patterns co-occurred during the 2021 heat wave: the North Pacific pattern, the Arctic-Pacific Canada pattern and the North America pattern.

“The North Pacific pattern and the Arctic-Pacific Canada pattern co-occurred with the development and mature phases of the heat wave, whereas the North America pattern coincided with the decaying and eastward movements of the heat wave,” Wang said. “This suggests the heat wave originated from the North Pacific and the Arctic, while the North America pattern ushered the heat wave out.”

But atmospheric circulation patterns can co-occur — and have before — without triggering an extreme heat wave, so how much was the 2021 event influenced by human activities? Wang and the team used the internationally curated, tested and assessed models from the World Climate Research Programme, specifically the Detection Attribution Model Comparison models of the Coupled Model Intercomparison Project Phase 6 (CMIP6).

“From the CMIP6 models, we found that it is likely that global warming associated with greenhouse gases influences these three atmospheric circulation pattern variabilities, which, in turn, led to a more extreme heat wave event,” Wang said. “If appropriate measures are not taken, the occurrence probability of extreme heat waves will increase and further impact the ecological balance, as well as sustainable social and economic development.”

Other contributors include co-corresponding author Jiayu Zheng and two students from the University of CAS: Wei Lin and Yuqing Wang.


Heatwaves, or heat and hot weather can last for several days and have a significant impact on society, including a rise in heat-related deaths. Heatwaves are among the most dangerous of natural hazards, but rarely receive adequate attention because their death tolls and destruction are not always immediately obvious. From 1998-2017, more than 166 000 people died due to heatwaves, including more than 70000 who died during the 2003 heatwave in Europe. 


Definitions  vary from one region to the other. Heat wave is usually an extended period of hot weather relative to the expected conditions of the area at that time of year, which may be accompanied by high humidity. 


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