Is Buenos Aires already tropical?

The resounding rains that fell like buckets on Buenos Aires during March left tragedy and two things clear: umbrellas hardly stop at all and water hurts a lot when it accumulates in places where it is not needed.

The endless storm, the mosquitoes threatening to transmit more dengue and the memory of prolonged heat waves of recent summers lead us to wonder if these phenomena are temporary or we will have to get used to living in a “tropical” Buenos Aires, with the effects of climate change (anticipated for years) already being felt on the skin.

In 2012, Argentine climatologist Osvaldo Canziani told Clarion who was convinced that this was the destiny of Buenos Aires. “In the last 100 years the average temperature of the City rose 1.8°C. But what is most significant is the 2.7° increase in minimum temperatures from 1962 onwards. If we add to this that since that year, in addition, Rainfall increased by almost 20 percent, there is no longer any margin for error; “It can be concluded that we are witnessing a radical change in the city’s climate, we are becoming tropicalized,” said the scientist who was part of the Intergovernmental Panel on Climate Change (IPCC), which won the Nobel Prize in Peace in 2007.

The city’s climate is temperate humid, but the highest incidence of severe rains and historical dengue fever peaks They warn that something has changed and will continue to change.

“Indeed, climate change, as a phenomenon on a global scale but with local impacts, is being observed in the City of Buenos Aires and is affecting the health of the people of Buenos Aires. On the one hand, through extreme weather events, such as heat waves or very heavy rainfall that have become more frequent and intense. For example, this summer the City has experienced two heat waves of 3 and 5 days duration (30/1 to 3/2 and 6/2 to 8/2), and last summer (2022-2023) there were nine. heat waves that were recorded between November and March. A study revealed that during heat waves mortality in the City increases by 14 percent, but in the longer heat waves like the one experienced in December 2013, the increase is greater: mortality reached 43 percent that year,” he details to Viva Francisco Chesini, from the Ibero-American Society of Environmental Health (SIBSA) and professor at the National University of José C. Paz.

For the coming years, the data indicate that between now and 2040, a increase in average temperature close to 1º C. According to another predictive model, for 2081-90, this increase would be between 2º and 3.5°.

The greatest increases would be seen in spring and winter, with a simultaneous increase in maximum and minimum temperatures. That poses a new panorama.

Globally, the World Health Organization (WHO) announced more common and lasting heat waves for the planet, and a warmer climate that will increase reproduction, resistance and distribution of vector-borne diseases (for example, dengue fever).

What exactly will happen in the Argentine capital? The City of Buenos Aires, which is located on the southern coast of the Río de la Plata estuary, has an area of ​​203 square kilometers and a humid temperate climatewith hot summers and cool winters.

“Temperature records from recent decades show that summers tend to be longer and extend into the falland winters show a tendency to be more moderate,” states a research work by biologists Patricia Himschoot and María Mar Areco on Buenos Aires and climate change.

Matilde Rusticucci, doctor in Atmospheric Sciences, principal researcher at Conicet and professor at the University of Buenos Aires (UBA), tells Viva that “over time, we observed that summer runs from October to April and that is due to climate change.”

Rusticucci, who recognizes these effects of global warming, prefers not to strictly use the word tropicalization to refer to the phenomenon that affects the City because “the tropics have a climate characterized by their little temperature variability throughout the year and we still continue to have very marked winters and a circulation characterized by certain variabilities such as the passage of cold fronts, which do not reach the tropics,” he details.

In any case, with a summer that would last seven months, the feeling of “tropics” seems to settle beyond definitions.

The City, according to atmospheric studies, is exposed to the effect of the pampero winds (cold and dry southwest) that cause strong storms and sometimes hail falls) and sudestada (persistent wind from the southeast that generally causes light rains). That, naturally.

“Due to climate change, it is observed that the Río de la Plata is experiencing an increase in its average level due to both the increase in average sea level and the change in the direction of the predominant seasonal winds. An increase in the frequency of storm waves is also observed. According to the intensity and persistence of the southeastflooding of varying degrees occurs on the coast of the City of Buenos Aires and the coastal districts of AMBA,” details the report by biologists Himschoot and Areco.

Patricia Himschoot, co-author of this extensive survey and one of the experts on the effects of climate change in the City, explains to Viva that “one could say that a 1.7° increase in the City is very little, but no: it is a lot. That is enough for a disease like dengue to establish itself in the Capital. Dengue requires certain temperatures“We are talking about the mosquito that transmits it, of a certain duration in which certain minimum and maximum temperatures must prevail.”

“Well, that’s already happening,” says Himschoot. There are scientific studies carried out by the expert Inés Camilioni that say that we are going to have more heat waves and they are going to be longer, more durable, in Buenos Aires. So the temperatures would be different. That’s why we have dengue in the City, something we didn’t have 30 years ago. Several events that were announced decades ago are already happening, and more quickly.”

“Global warming is one of the causes of the increase in dengue cases in areas that are further south on the globe, such as Argentina. He Temples of the Egyptians is well adapted to live in temperatures above 25°its ideal is between 28 and 30 degrees,” he confirms to Viva Diogo Chalegre, del World Mosquito Program (WMP), from Brazil, where they try to promote mosquito populations that cannot transmit harmful viruses to humans.

“To talk about the rains in the City, we must take into account and add the local effects of the El Niño phenomenon, which in its warm phase translates into higher rainfall in the region and that explains to some extent the extreme rainfall that has affected the City in recent weeks,” explains the expert Chesini.

And he adds: “Climate change, through the increase in average temperatures, also affects slow evolving processes, such as the ecology of disease vectors. Different studies have shown that the mosquito Temples of the Egyptians (transmitter of Zika, dengue and chickungunya) is surviving even during the Buenos Aires winters (which are increasingly shorter and milder); This means that there is an abundance of mosquitoes for longer periods of the year, which favors transmission. Dengue has become a major public health problem. Each epidemic has surpassed the previous one in cases and deaths are being added to this, which already total 10 cases for this season in the City (at the close of this edition).”

The effects of temperatures and rains are increasingly noticeable. “You are beginning to see those storms that occur with great intensity. Maybe, the total water that falls in the year is the same, the problem is that it falls all at once. They are like showers, rains that come quickly. A lot of water falls in a short period of time, which is why they cause flooding. This is happening more and more frequently. They are consequences of climate change,” says Himschoot.

In the City, in addition to the aforementioned scenarios, the Urban Heat Island phenomenon occurs. “It occurs in many metropolises. Cities accumulate more heat because there is a greater concentration of people; there is more cement and pavement that absorb more heat. The number of air conditioning units also influences, we all know that everything is fine inside, but the unit throws heat outside, that heat has to go somewhere. All of this makes the most densely populated places hotter than the rest,” explains Himschoot.

What to do in the face of this new Buenos Aires? Chesini summarizes it like this: “Adaptation measures at the individual level have to be accompanied by public policies. Regarding extreme events such as heat waves and extreme precipitation, it is essential to be informed of the early warnings issued by the National Meteorological Service. Alerts save lives. On the other hand, it will be necessary to think about how we adapt our routines to extreme heat. For its part, the State will have to incorporate greener in urban planning (as Paris is doing), as well as preventive measures in work environments and strengthening the response capacity of the health system. “A good policy that the City has adopted is climate shelters.”

Change Buenos Aires. A lot.