2023-08-12 03:30:00
Matthew Patterson, University of Oxford
Temperatures in some areas of Chile and northern Argentina have shot up to 10°C-20°C above average in the last days. The cities of the Andes mountain range have reached the 38°C or higher, while in the Argentine capital, Buenos Aires, temperatures above 30°C were recorded, exceeding its previous August record by more than 5°C. In the city of rivadavia maximum temperatures of 39 °C were reached.
Keep in mind that we are in the middle of winter in this part of the world. And it’s far enough south that seasonal variations have a substantial impact on temperatures. Buenos Aires, for example, is as far south as Japan, Tibet, or Tennessee is to the north.
In terms of deviation from temperatures that would be expected at a given location and time of year, this heat wave is comparable to, if not greater than, recent heat waves in southern Europe, the United States, and China. In Vicuña, one of the cities in the Chilean Andes that recently hit 38°C, a typical day in August might be 18°C or so – imagine it’s 20°C warmer than normal wherever you are right now.
Not surprisingly, some climatologists have already suggested that this might be one of the most extreme heat waves ever recorded.
What is causing the extreme heat?
For the past six days, a persistent high pressure area, or anticyclone, has lingered east of the Andes. Also known as “high lockout”, it seems to be the main cause of the intense heat.
Blocking anticyclones can cause heat waves in three main ways. First, they draw warmer air toward them from near the equator. The system also compresses and traps the air, heating it up, as was the case with the 2021 heat wave in the Pacific Northwest, which broke the Canadian temperature record by nearly 5°C. Finally, the high pressures mean that there is little rising air and, therefore, little cloudiness. This allows the sun to heat the land continuously during the day, accumulating heat.
However, scientists need to take a closer look at the meteorology of this unprecedented event to gain a fuller understanding.
El Nino made it more likely
The heat wave between Chile and Argentina may have been more likely due to the development of El Niño in the Pacific Ocean. El Niño events, which typically occur regarding every four years, are characterized by warm sea surface temperatures in the central and eastern tropical Pacific. Currently, temperatures in the central Pacific are approximately 1°C above average for the time of year.
These warmer ocean temperatures cause air to float more over the central Pacific, causing the air to rise. This causes changes in atmospheric circulation patterns beyond. El Niño-induced changes in atmospheric circulation typically result in higher pressure and warmer winter temperatures for this part of South America.
Climate change made it worse
The locking system that caused the extreme heat would likely have resulted in warm temperatures even in the absence of anthropogenic climate change. However, the rapid warming caused by climate change allowed the heat wave to become truly unprecedented.
Climate scientists expect to see temperature records broken as our planet continues to warm. This is because the distribution of possible temperatures is shifting higher and higher.
Chile has already recently experienced the effects of climate change through a severe heat wave in February – in late summer – that led to several deaths from forest fires, as well as a decade-long mega-drought. The country recently rejected a new draft of the constitution that would have forced its government to take action once morest the natural and climate crises.
The long-term impact of a winter heat wave
Higher temperatures appear to have largely subsided in the Andes. However, temperatures are still well above average in northern Argentina, Bolivia and Paraguay, and will remain so for the next five days.
The effects of winter heat waves are less well known than those of summer heat waves. For Chile, the most likely impact is on snow cover in the mountains, which provides water for drinking, agriculture and power generation. The melting of the snow cover will likely affect the diverse flora and fauna of the Andes as well.
Overall, this heat wave is a striking reminder of how humans are changing the Earth’s climate. We will continue to see these unprecedented extremes until we stop burning fossil fuels and putting greenhouse gases into the atmosphere.
Matthew Patterson, Postdoctoral Research Assistant in in Atmospheric Physics, University of Oxford
This article was originally published on The Conversation. Read the original.
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