Brazilian big cities to get warmer and drier

. Nov 22, 2018
droughts climate change brazil global warming The empty Cantareira reservoir, in São Paulo

Last month, the Intergovernmental Panel on Climate Change (IPCC) published a special report showing a pessimistic scenario in which global warming would take average atmosphere temperatures up 4ºC by 2100. This would mean a 9ºC bump in summer temperatures, which would cut rainfall in Brazil’s largest cities São Paulo and Rio de Janeiro, and in Santos, home of the country’s busiest port. In these areas, minimum temperatures would still be 4ºC higher, with warmer winters.

These terrible projections are in a study published by Brazil’s National Institute for Space Research (Inpe), the University of Rio de Janeiro, and the Natural Disaster Monitoring and Alert Center (Cemaden). Their findings were published by the journal Theoretical and Applied Climatology. “If the current scenario of greenhouse gases remains stable, the outlook we describe becomes immensely probable,” declared André Lyra, a post-doctorate researcher at Inpe.

The Brazilian researchers made simulations of what could happen to temperatures and rainfall in these metropolitan areas considering two scenarios: one pessimistic, and one optimistic. In the latter case, emissions would stop growing by 2040. But even in this scenario, the harmful consequences for Brazil’s big cities won’t change much. Maximum temperatures in São Paulo, Rio de Janeiro, and Santos would jump by 7ºC and rainfall would be halved.[research]

Of course, there is a level of uncertainty in such projections. But the message is clear: climate change is not a hoax created by cultural Marxism, as Brazil’s future Foreign Minister believes.

The methodology of the study

The study used an improved version of the ETA regional forecast model, with a spacial resolution of 25 square kilometers—equivalent to a square with sides of 5 kilometers. The previous version of the ETA used a resolution of 400 sq km. “The new model is important to better understand the impact of climate on some aspects of topography in South America,” states meteorologist Chou Sin Chan, co-author of the paper and also a researcher at Inpe.

“A study using a resolution of 5 km is more detailed than one using 20 km.” In this version of the ETA, there are less calculation errors in climatic forecasts made in areas with steep topography. This improvement is important for working with areas close to mountainous zones, such as the Serra do Mar and Serra da Mantiqueira, found nearby the area of this study.

The climate projections in the three metropolitan regions studies were crossed with data from the historic period of the model itself, from 1961 to 1990, which served as a basis for comparison. Projections were divided into three cycles: 2011-2040, 2041-2070, and 2071-2100.

A more ‘extreme’ climate

Beyond the general trend of temperature rises and rainfall reduction, the study identifies the intensification of extreme climatic events, such as prolonged droughts and severe storms. In the Metropolitan Region of São Paulo, for instance, heatwaves could go on for over 60 days and cold snaps could last for over three by around 2100. The study also indicates a trend towards more uncomfortable days and nights in the three areas analyzed, with a higher demand for cooling equipment and an increased consumption of electricity, causing situations which can cause health risks to elderly and poor populations.

“Extremes affect our lives more,” says meteorologist Claudine Dereczynski, from the Federal University of Rio de Janeiro (UFRJ), co-author of the study. “The occurrence of more situations of this type calls more attention to climate changes than alterations to precipitation or temperature.” It is also possible, according to simulations, for extremely heavy rains to intensify around mountainous areas, causing frequent landslides, until the end of the 21st century. According to Ms. Dereczynski, future projections are more reliable with regard to temperature variations as opposed to rainfall. 

Future summer temperatures in Brazil

climate change warmer summer brazil

Governments must take action

The study emphasizes that the high population density in the metropolitan regions of Rio de Janeiro and São Paulo, home to 33 million people, causes misappropriation and intense degradation of natural resources. “Studies on climate change depend heavily on the acceptance of various economic sectors and the awareness of public administration about the importance of developing actions to mitigate the effects of greenhouse gas emissions,” states sociologist Pedro Roberto Jacobi, professor of the Institute of Energy and the Environment of the University of São Paulo (IEE-USP).

“We have seen that municipalities themselves can even develop actions of decarbonization on a local scale, such as controlling erosion with changes to legislation about soil use, or improvements in public policies about solid waste. However, global measures are also necessary, which depend on agreements between countries, in order to mitigate climate change.”[/restricted]

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