Abstract
Despite uncertainties as to the real causes, there is a large amount of evidence of climatic change on Earth. With the objective of investigating changes in extreme air temperatures, as well as the local effects of these changes, eight data sets, collected throughout the State of Ceará in Brazil, were analyzed. Four series of data were obtained from the semi-arid region, three from the coastal zone, and one from a mountainous region. To quantify the changes that occurred during the study period, variations in maximum and minimum temperatures were calculated in relation to the mean of each data series. The annual rates of temperature increase were estimated from the angular coefficients of the best-fit lines. The results showed that although there are differences in trends between stations, there was a systematic increase in the maximum and minimum temperature in the nineties, which was especially evident in the following decade. The highest rates of increase were recorded for the minimum temperatures (from 9.0 to 8.3 °C per century) for the stations at Guaramiranga and Crateús respectively. These data provide evidence for a greater retention of energy in the form of sensible heat during the night, possibly due to a more difficult energy exchange between the surface and the atmosphere.
Highlights
Since the start of the second half of the 20th century, meteorological observations have been registering systematic increases in the air temperatures, both at the global and regional scales (SILVA, 2004)
Research studies conducted in different parts of the world (LEBASSI et al, 2009; LINKOSALO et al, 2009; WALTERS et al, 2007) have identified that the increases in the minimum air temperatures are more significant than increases in the maximum air temperatures
This study focused on the investigation of the tendency of extreme air temperature changes in three different climate areas of Ceará State, Brazil
Summary
Since the start of the second half of the 20th century, meteorological observations have been registering systematic increases in the air temperatures, both at the global and regional scales (SILVA, 2004). The increases of air temperature occur in an asymmetric form, representing the effects of different global and regional agents (PITMAN; PERKINS, 2009) on the air temperature changes. The asymmetries of these changes have had significant impacts in many regions of the globe, while in other places no significant changes have been observed (BONSAL et al, 2001; PRIETO et al, 2004). Many uncertainties still exist regarding the real cause responsible for generating these climatic changes that have been registered in the last two decades (SPENCER, 2010)
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