Climate Change at the Micro-Region Scale: The Case of Tamazula, State of Jalisco, Mexico.

In Mexico rainfed agriculture is carried out in a mosaic of micro-regions that undergoes several adverse events such as the great winter drought (GWD), the midsummer drought (MSD), frosts, floods and heat shocks. Studies on Global Climate Change give us a general idea of the phenomenon, but at the micro-region scale it is necessary to know the specific variations. From Figure 1 of the book Climate Change 2001 (IPCC, 2001), it follows that 1975 is a reference line of appreciable climate change. Therefore, we have compared historical climate data from 1975 and previous years (P1) against later years (P2). The present report refers to Tamazula, Jalisco State, Mexico (103.23ºW, 19.66ºN, 1127 m), located in a micro-region planted with sugarcane (Saccharum spp.). The studied variables were: minimum and maximum temperature (Tmin, Tmax) in each of three tens (T) by month (M), the sum of mm of rainfall of each ten (Ll). It was observed that Tmax was no greater in P2 than in P1, although it showed a greater variance in P2, increasing the probability of temperatures above the threshold for sugarcane. Tmin was 0.74ºC higher in P2 than in P1. The greatest Tmin in P2 was from July in one year to April in the following year. The frequency of years with MSD was 17 in P1 and 8 in P2. This effect could be related to the increase in frequency and intensity of hurricanes in the Pacific Slope. There is an effect of climate change on Tamazula, as detected through a 29 year sample data in P1 and P2. 1975 was a consistent reference line.