Cullen was previously the Chief Scientist for the non-profit science communication organization Climate Central, where she was part of the team that incubated and launched the World Weather Attribution initiative.

Interested in paleoclimatology and human history, Cullen collaborated with Harvey Weiss at Yale University to understand if climate was a factor in the collapse of the Akkadian Empire.

Cullen departed The Weather Channel in October 2008 to help launch Climate Central, a non-profit science communication organization based in Princeton, New Jersey.

In addition to her responsibilities at Climate Central, she lectured at nearby Princeton University and served as a senior research fellow at the Penn's Wharton Risk Management and Decision Processes Center.

She is part of the SOCCOM project and GO-BGC initiative to deploy autonomous biogeochemical-sensing floats and is a champion for building an ocean health and carbon observatory.