Climate changes in Brazil through 2100

By Elton Alisson*

More heat, less rain in the country’s north and northeast and more rain in the south and southeast are some of the projections of the National Assessment Report of the Brazilian Panel on Climate Change (photo: Eduardo Cesar/FAPESP)

Agência FAPESP – The climate in Brazil in the next few decades should be hotter, with a gradual increase in the average temperature in all regions of the country, varying between 1 °C and 6 °C by 2100 compared with the temperatures at the end of the 20th century.

In the same period, rainfall should also decrease significantly in the majority of the central regions and the north and northeast. In contrast, there will be an increase in precipitation in the south and southeast.

These are the conclusions of the first National Assessment Report (RAN1) of the Brazilian Panel on Climate Change (PBMC), the executive summary of which was released on September 8, 2013, during the 1st National Conference on Global Climate Change (Conclima). Organized by FAPESP and sponsored by the Brazilian Research Network on Global Climate Change (Rede Clima) and the National Institute of Science and Technology for Climate Change (INCT-MC), the event ran through September 13, 2013, at Espaço Apas in São Paulo.

According to the assessment, Brazil needs to consider regional differences when developing adaptation and mitigation actions and agricultural, energy generation and water supply policies for these different regions because climate change and the impacts on populations and economic sectors will not be identical throughout the country.

Split into three parts, Report 1, which is in the final stages of preparation, presents the regionalized projections on climate change that are predicted to occur in the six different biomes of Brazil through 2100 and indicates the estimated impacts and possible ways to mitigate these impacts.

The projections were based on revisions of studies conducted in from 2003 to 2013 by 345 researchers from several areas, members of the PBMC and the scientific results of global and regional climate modeling.

“The Report is being prepared similarly to reports published by the Intergovernmental Panel on Climate Change [IPCC], which does not conduct research but rather evaluates published studies,” commented José Marengo, researcher at the National Institute for Space Research (INPE) and coordinator of the event.

“After much work and interaction, we arrived at the main results of the three work groups [i.e., Scientific Basis of Climate Change; Impact, Vulnerability and Adaptation; Mitigation of Climate Change],” he stressed.

Main conclusions

One of the report’s conclusions is that extreme dry periods and prolonged droughts, particularly in the Amazonia, Cerrado and Caatinga biomes, are likely to increase, and these changes will likely be accentuated beginning in the second half and the end of the 21st century.

The temperature in the Amazon should increase progressively by 1 °C to 1.5 °C through 2040 (with a 25% to 30% reduction in the volume of rainfall), to between 3 °C and 3.5 °C in the 2041 to 2070 period (with a 40% to 45% reduction in the occurrence of rain), and to between 5 °C to 6 °C from 2071 to 2100.

Although modifications in the climate related to global changes could compromise the biome in the long term, according to the report’s authors, the current question of deforestation as a result of intensive land use represents a more immediate threat to the Amazon.

The researchers stressed that the observational and numerical modeling studies suggest that if deforestation reaches 40% of the region in the future, there will be drastic changes in the cyclical hydrological pattern, with a 40% decrease in rainfall from July through November, which would prolong the duration of the dry season and cause a superficial warming of the biome by up to 4 °C.

In this manner, the regional changes resulting from deforestation coupled with global changes would create the conditions necessary for the savannization of Amazonia – a problem that will tend to be more critical in the eastern region, stressed the researchers.

“The projections will allow for a better analysis of the problem of savannization in Amazonia, which, as some studies have indicted, we realize might occur in certain areas of the forest and not the biome as a whole,” underscored Tércio Ambrizzi, one of the authors and coordinators of the executive summary of the work group on the scientific basis for climate change.

The temperature in the Caatinga should also increase between 0.5 °C and 1 °C, and rainfall in the biome will decrease between 10% and 20% through 2040. From 2041 to 2070, the region’s climate will be between 1.5 °C to 2.5 °C hotter, and the standard rainfall will decrease by 25% to 35%. By the end of the century, the biome’s temperature will have increased progressively by 3.5°C and 4.5 °C, and the occurrence of rainfall will have diminished by 40% to 50%. These changes could trigger the desertification of the biome.

In the Cerrado, the temperature should increase by 5 °C to 5.5 °C, with rainfall declining between 35% and 45% in the biome by 2100. The Pantanal wetlands should experience temperature increases of 3.5 °C to 4.5 °C by the end of the century, with an accentuated decrease in rainfall of 35% to 45%.

Because the Atlantic Rainforest spans areas from the south to southeast and even the northeast, the projections indicate two distinct regimes of climate change.

The southeast portion should experience a relatively small temperature increase, of between 0.5 °C and 1 °C, and a drop in rainfall levels of approximately 10% through 2040. Between 2041 and 2070, the region should warm up by 2 °C to 3 °C, with a 20% to 25% decrease in the pluviometric index. Intense warming will occur by the end of the century (2071 – 2100), with a 3 °C to 4 °C increase in temperature and a 30% to 35% reduction in rainfall.

In the south and southeast regions of the Atlantic Rainforest, the projections indicate a relatively low temperature increase of between 0.5 °C to 1 °C through 2040, with a 5% to 10% rise in rainfall. From 2041 to 2070, a gradual increase of 1.5 °C to 2 °C in the temperature should continue, and rainfall should increase by 15% to 20%.

These trends should be more enhanced at the end of the century, when the climate will be between 2.5 °C and 3 °C hotter and 25% to 30% wetter.

Lastly, for the Pampa biome, the projections indicted that the climate in the region will be between 5% and 10% wetter and 1 °C hotter by 2040. From 2041 to 2070, the biome’s temperature will rise by 1 °C to 1.5 °C, and rainfall will be 15% to 20% heavier. The region’s climate projections for the 2071-2100 period are more severe, with the temperature climbing 2.5 °C to 3 °C and the occurrence of rainfall at 35% to 40% above normal.

“In general, the models predict a tendency toward an increase in temperature and a reduction in rainfall in the north and northeast regions of Brazil over this century,” sums up Ambrizzi.

“Conversely, this trend is inverted in the most southern regions: there is a trend toward increases in both temperature – albeit not intense – and precipitation,” he explained.

Impacts, adaptation and mitigation

The changes in rainfall standards in the different regions of the country caused by climate change should have direct impacts on agriculture and the generation and distribution of energy and hydric resources in these regions because water should become more scarce in the north and northeast and more abundant in the south and southeast, warned the researchers.

This is why the country will need to develop specific adaptation and mitigation actions and revisit investment decisions, such as the construction of hydroelectric plants in the eastern region of Amazonia, a region where the river flow may be reduced by up to 20%, stress the researchers.

Mercedes Bustamante, professor at Universidade de Brasília (UnB) and one of the coordinators of Work Group 3 on Mitigation of Climate Change, presented a synthesis of the studies and research on the topic, identifying gaps in the knowledge and the future directions under the scenario of global warming.

Bustamante noted that the reduction in deforestation rates during 2005 and 2010 – from the equivalent of 2.03 billion tons of CO2 to the equivalent of 1.25 billion tons of CO2 – has had positive effects on the greenhouse gas emissions due to land use.

“The emissions from energy generation and agriculture, however, have increased in absolute and relative terms, indicating a change in the profile of Brazilian emissions,” she added.

If the current policies remain in place, the forecast is for energy and transportation emissions to increase by 97% by the year 2030. Increases in energy efficiency, advances in technological innovations and more incentive-based policies are recommended to revert this scenario.

*Claudia Izique and Noêmia Lopes contributed to this article.

Fonte: Agência FAPESP