Douglass' interests have been in the general area of Experimental Condensed Matter Physics. His work has involved experiments in the areas of liquid helium and superconductivity (both low temperature and high temperature). Significant contributions have also been made in the field of gravitational wave detectors. \Douglass has also worked on chaos and frequency drifts of spectral lines of extended sources. His interests for the last several years have been on climate change.
A 2005 study by Douglass and fellow University of Rochester physicist Robert S. Knox argued that global climate models underestimated the climate response to the 1991 eruption of Mount Pinatubo. The study also contended that global temperature returned to normal much faster after the eruption than the models had predicted.
A 2007 paper by Douglass and coworkers questioned the reliability of 22 of the most commonly used global climate models analyzed by Benjamin D. Santer and used by the IPCC to predict accelerated warming in the troposphere. The study had originally been submitted to Geophysical Research Letters the previous year, but was rejected in September 2006 on Santer's recommendation. Santer and 17 co-authors later rebutted Douglass' paper.
^Douglass, David H.; Christy, John R.; Pearson, Benjamin D.; Singer, S. Fred (15 November 2008). "A comparison of tropical temperature trends with model predictions". International Journal of Climatology. 28 (13): 1693–1701. Bibcode:2008IJCli..28.1693D. doi:10.1002/joc.1651.