Climate change evidence in Brazil from Köppen's climate annual types frequency

This article proposes to use the Köppen classification to evidence climate change in Brazil. To do so, the average monthly temperature and precipitation data were computed for a set of 208 stations, representative of the climatic diversity of Brazil for the period from 1964 to 2015. The originality of our approach is not only to look at the shift between the averages of two references periods but also to observe how each year can be classified using Köppen's classification; thus, we defined “annual climate types” (ACT) and established the frequency of ACTs for each station and each period of 26 years: 1964–1989 and 1990–2015. The statistical and cartographic treatment of this information makes it possible to define the limits of the climates of Brazil and look at its evolution showing the diversity of regional situations in Brazil. The results show that 35 stations (17%) changed from the average Köppen's type, with significant regression of wet tropical types (Af and Am) and temperate types (C). On the other hand, the tropical (Aw), arid and semi‐arid (B) types progress between the two periods showing significant modifications of the climatic limits in Brazil: extension of aridity in the northeast of Brazil and increasing extinction of tropical types upon temperate climates in the south of the country and upon rainy types in the south of the Amazon. These results are consistent with other studies and illustrate the potential for climate change and variability monitoring using a simple classification method. The Köppen's classification is very often used in climatology. However, almost all the works use it on average data over periods of 20 or 30 years, thus erasing the inter‐annual variability of climate. The originality of our study is to use this classification on an annual scale to calculate frequencies of “types of annual climate” for two periods and to compare them. The study focuses on Brazil, which presents two additional interests: such a frequency approach has never been realized there to study climate change; the diversity of climates and changes observed in this country makes it possible to test the robustness of the method on different climates (from equatorial to semi‐arid and temperate types). In the figure, frequency of TCA per station for the period 1990–2015.