Statistically Downscaled Projected Changes in Seasonal Mean Temperature and Rainfall in Cagayan Valley, Philippines

Rice is an important commodity in the Philippines. In the Cagayan Valley (CV), rice production provides employment to more than half of the region's population and any climate variability and change can cause negative impacts on crop production and people's livelihoods. This paper attempts to understand projected climate changes in seasonal rainfall and mean temperature (2011-2040) to inform climate change adaptation planning in CV. The climate change projections were provided to crop and water resource modeling, agricultural market modeling, food insecurity vulnerability analysis, community-based climate change adaptation planning, and policy simulation. The results are presented for the Provinces of Cagayan, Isabela, Nueva Vizcaya, and Quirino based on the statistical downscaling of three global climate models (BCM2, CNCM3, and MPEH5) and two emission scenarios (A1B and A2). A spatial interpolation technique was utilized in interpolating downscaled climate projections at weather stations to grids, and subsequently aggregated to administrative provinces. Results obtained in the downscaling showed anticipated significant climate changes from 2011 to 2040 in terms of rainfall and temperatures relative to 1971-2000. Consistent signals of climate change were found in many seasons and variables, whereas conflicting signs of changes were found in a few cases. A larger warming effect is projected for a daily minimum temperature than that for the maximum temperature, thus reducing diurnal temperature range. Precipitation is projected to increase in general in the Valley. Regarding seasonality, dry months (March-April-May) will continue to remain dry but during the rainy season, July and November are likely to become more notable wet months. There are also indications of an increasing frequency of heavy rainfall events, prolonged dry spell events and extreme daytime temperatures (especially in Aparri).