Temperature Trends over South America: 1979–2017

In this work the objective is to evaluate the temperature trends over South America (ASSEA; 90^oW a 20^oW e 60^oS a 10^oN; Fig. 1). The analysis included the tropical/Northern (TSA; 90^oW-20^oW and 20^oS to 10^oN) and subtropical/southern of the ASSEA area (SSA; 90^oW to 20^oW and 60^oS to 20^oS). To compare the climate change over ASSEA with global changes, the temperature tendency over the entire planet is shown too. The subperiods 1979 to 2005 and 2006 to 2017 are also analyzed. The air temperature 2 meters above the surface provided by the NCEP/Department of Energy (DOE) reanalysis was used (https://www.esrl.noaa.gov/psd/data/gridded/reanalysis/). The resolution of the NCEP/DOE reanalysis is T62L28, with nearly 2.5^o latitude × 2.5^olongitude and the simulations were initiated in 1979, which is also when environmental satellite data began to be produced on a large scale (Kanamitsu et al. 2002, Bull AMS). The average of the monthly values was considered to determine the annual temperature. Trend signs are examined by the Mann–Kendall test and trend signs and magnitudes for Sen’s slope estimator (Sen, 1968, J. Amer. Stat. Assoc.). The normally or not of the datasets not was tested, once again that Mann–Kendall and Sen´s tests can be used for any distribution. The Mann–Kendall and Sen tests indicate same trend in all regions and period. The temperature trend between 1979-2017 for the GLOBE, ASSEA, TSA and SSA were: 0.19^***, 0.01^-, 0.08^*, -0.06^{* o}C/decade; between 1979-2005: 0.16***, -0.08⁺, 0.04^-, -0.12^***oC/decade and between 2006-2017: 0.25⁺, 0.24⁺, 0.21⁺, 0.18^{+ o}C/decade, respectively. It was observed that the trends of increasing temperature were higher in recent years, however with lower statistical significance in most regions. The trend of temperature increase in recent years was more pronounced in South America and its sub-regions, mainly on the SSA region, which over the globe. The difference between the average temperature of the two subperiods is 0.37^oC, 0.09^oC, 0.21^oC and -0.04^oC for the globe, ASSEA, TSA and SSA, respectively. For the globe and the TSA region this mean difference is statistically significant (99% confidence).

^***0.001 level of significance; ^** 0.01 level of significance; ^* 0.05 level of significance; ⁺ 0.1 level of significance; - > 0.1 level of significance