A field study was carried out to determine the impact of climate change on growth, nitrogen use efficiency and achene yield in sunflower production under arid, semi arid and sub humid conditions of Punjab, Pakistan. The experimental data needed to run the model was obtained from two years (2008 and 2009) field experiments conducted at three locations, including the Central Cotton Research Institute (CCRI) Multan, Agronomic Research Area, University of Agriculture Faisalabad, and the Adaptive Research Farm, Gujranwala. The achene yield among various treatments was associated with the growth and development of crop or to their photosynthetic activity. At all the experimental locations, the nitrogen level 180 kg ha - 1 gave maximum yield as compared to standard (120 kg N ha -1 ) N dose. Similarly, Hysun-38 performed well, in terms of achene yield and achene oil yield at different agro-climatic conditions than other sunflower hybrids (Hysun-33 and Pioneer-64A93). Sub humid (Gujranwala) environmental conditions are much better as compared to semi arid (Faisalabad) and arid (Multan) climate for sunflower productivity. The OILCROP-SUN model testing and application in this study established that this specific model could be satisfactorily used as a research tool in different agro-environmental conditions of Punjab-Pakistan. The OILCROP- SUN model was calibrated and evaluated under local conditions and it predicted phenology, growth and yield of sunflower to a reasonable accuracy among different sunflower hybrids and nitrogen application. The findings propose that the model can be used to direct the alternate path for improving sunflower production in Pakistan. The climate change analysis describes the strong effect of temperature increment on sunflower production. The achene yield will be considerably reduced with increasing temperatures up to 2 o C in the area. If we look at present scenario than it can be estimated that there will be reduction in yield up to 25 % beyond 2050 for sunflower crop. Future studies for possible effects of climate change on field crop production should therefore includes, more number of weather stations to better reflect the heterogeneity in different cropping areas, standardization of field crop production technology through crop growth models should be initiated, development of site specific mitigation strategies to enhance agricultural productivity under changing climate scenarios. At the end, following suggestions must be under take to meet the challenges of changed climate on sunflower productivity, I) the development or breeding of new sunflower hybrids must be initiative that might be tolerant to higher temperature and adverse climatic conditions, II) The water storage capacity should be enhanced and proficiently managed to increase water use efficiency under changed climatic conditions for different field crops to get maximum benefit and ultimately to meet the challenge of food security. III) All the agronomic management practices (hybrid selection, sowing method and time, application of irrigation & fertilizer, insect pest and disease management) may need to meet the needs of food security under threatens of climate change, IV) More number of weather stations to better reflect the heterogeneity in different cropping areas must be initiated so that site specific production technology might be developed.