The southwestern U.S. is one of many regions susceptible to the effects of our changing climate system. Numerous climate phenomena, such as the North American Monsoon and Madden- Julian Oscillation, are known to correlate with precipitation and temperature variations in the Southwest. These processes can be linked to sea surface temperatures (SST) in the tropical Pacific Ocean which also influence global climate. This study explored the relationship between ocean temperatures in the Pacific and temperature and precipitation changes in the southwestern U.S. by comparing observational data in an Intensive Observation Period (IOP) of the Southern Great Plains to the Community Atmosphere Model (CAM 4.0) and the Community Climate System Model (CCSM 4.0). This comparison was used to verify that these model data accurately depicted the present climate and could be used to capture a reasonable prediction for our future climate. Our analysis showed a correlation between tropical Pacific SST and variations in temperature and precipitation in the southwestern U.S. that creates a persistent El Niņo effect in part because of an increase in greenhouse gases. Our statistical analysis yielded large values for this correlation, confirming our hypothesis that our changing climate system is affecting weather patterns in the southwestern U.S. through increased tropical Pacific sea surface temperatures.