His research group uses a combination of observational and computational techniques to study the characteristics, dynamics, and forecasting of certain weather phenomena.

He writes a popular online column on climate science for the Houston Chronicle.

He wrote, On December 22, 2009, Nielsen-Gammon wrote a detailed analysis of the erroneous projected date of melting of Himalayan glaciers in the Working Group II section of the IPCC Fourth Assessment Report which said that "the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate."

This had already been controversial in India, and the error had been found by J. Graham Cogley, a glaciologist in the Department of Geography at Trent University, Ontario.

The story had been covered by BBC News but had not at that time gained wider publicity.