Temperature below 10º in Cuiabá, snow in Santa Catarina and record cold in São Paulo. The low temperatures definitely drew attention this week. Scientists already know that the climate crisis especially exacerbates heat waves, droughts and torrential rains, but cold can also enter the equation.
That is, according to studies, in some places and times, extreme cold can also be associated with the climate crisis. It is important to emphasize that it is not simple to point out the relationship between a specific phenomenon – such as the current cold wave – and the climate crisis.
“In this phenomenon [onda de frio] it’s too early to say. We have to wait for the event to end and then we start doing research”, says José Marengo, climatologist and coordinator of the National Center for Monitoring and Alerts for Natural Disasters, about the climate crisis.
Exactly to try to solve this, the so-called attribution studies were developed. They try to identify what weight climate change has on extreme events such as droughts and cyclones. Thus, scientists are able to point out whether global warming has made a certain event more likely.
For this, these attribution studies make climate models that compare and simulate the world climate, with and without crisis, allowing the observation of the incidence of certain extreme events. Due to the complexity, this type of research is not necessarily fast, making it difficult to analyze ongoing phenomena.
“It’s not that climate change explains this cold wave”, says climatologist Paulo Artaxo, vice president of the SBPC (Brazilian Society for the Progress of Science) and a member of the IPCC (UN Intergovernmental Panel on Climate Change).
But, in any case, it is known that the climate crisis is related to extreme events of the most diverse types. An example already studied is extreme winters in the USA. A recent study published in the journal Science showed how the warming of the Arctic — a result of climate change —, at certain times, interferes with and weakens the Arctic polar vortex, in the north of the planet. When this occurs, extremely cold air can escape southwards and cause intense cold in North America and Asia. The most recent and impressive example of this was the freezing wave that hit Texas in 2021.
Despite an extreme example like this, in general, the climate crisis is expected to reduce cold waves and their intensity around the globe. However, in some cases, they can be more extreme.
At the same time, thanks to global warming, says Artaxo, we can expect more frequent and intense heat waves and droughts. “What we are changing is the statistics, the probability of these events occurring”, says the researcher.
Artaxo highlights that it is necessary to prepare properly for climatic extremes and to think about the most vulnerable populations in cities, such as homeless people.
In São Paulo, Isaías de Faria, 66, a homeless person, died on Wednesday (18) at the São Martinho de Lima community center, in the Belém neighborhood, in the east side of São Paulo. According to information, he had spent the night on the street and died shortly after entering the coexistence center, around 8 am.
According to the CGE (Centre for the Management of Climatic Emergencies of the City of São Paulo), it was the coldest dawn (reaching 7°C, with lower thermal sensations, due to the wind) for a month of May since the beginning of the measurement, in 2004, 18 years ago.
A question that may arise for some people is: if warming is global, why do we have cold waves? Former presidential aide and Senate pre-candidate Arthur Weintraub questioned climate change on his social media this week, including. “Globalists spoke of ‘global warming’ to justify their actions. It was very cold. So now the threat they say exists is ‘climate change,'” he wrote.
Global warming refers to an increase in the average temperature of the planet, which does not mean that some places and moments cannot have moments of colder, even intense. On average, however, the years keep getting warmer and warmer.
The data show that the average global temperature has already risen by more than 1.1°C compared to the pre-industrial era. The cause of this increase is the emission of greenhouse gases, such as COtwowhich retain the heat generated in the atmosphere and make the planet warm.
Thus, if these emissions are not reduced, extreme events, such as droughts, heat waves, and floods, tend to worsen.
“Extremes get more extreme,” says Marengo. “Sceptics always come around saying ‘wow, we’re freezing to death, where’s the warming?’ They always take advantage. But when we talk about global warming extremes are more extreme and a cold snap is an extreme.”
The current cold wave in the country has an unusual touch, with cold air invading the equatorial area and covering a considerable part of Brazil and other South American countries.
Francisco de Assis Diniz, head of the weather forecast center at Inmet (National Institute of Meteorology), says that such a widespread occurrence of this level of cold has rarely been seen. He cites some years when similar cases occurred, such as 1955, 1975, 1985 and 2000. Last year, there were two similar occurrences.
According to him, extensive and intense cold weather like the one seen in Brazil this week — there were places with historical records — are more common in La Niña years, like the current one. The phenomenon causes an abnormal cooling of the surface waters of the Tropical Pacific Ocean and, in addition to temperatures, it also influences the rainfall regime.
The head of the weather forecast center at Inmet says that the current cold spread across the country is also due to the subtropical storm Yakecan, which intensified an already strong mass of cold air and ended up pushing it towards the most central region of the continent.
