Another study by Mann and Park raised a minor technical issue with a climate model about human influence on climate change: this was published in 1996. In the context of the controversy over the IPCC Second Assessment Report the paper was praised by those opposed to action on climate change, and the conservative organization Accuracy in Media claimed that it had not been publicized due to media bias. Mann defended his PhD thesis on "A study of ocean-atmosphere interaction and low-frequency variability of the climate system" in the spring of 1996, and was awarded the Phillip M. Orville Prize for outstanding dissertation in the earth sciences in the following year. He was granted his PhD in geology and geophysics in 1998.