Since 1998, he is a fellow of the
American Geophysical Union. His research is on the nature of climate variability, specifically focusing on the timescales of years to centuries. He uses natural recorded records such as
tree rings. Hughes has studied geographical areas including Europe, Asia, and the Sierra Nevada. In addition to tree rings, Hughes uses
ice cores,
laminated sediments, and the
historical temperature record to help understand past climates. In 1998, he was a co-author with
Michael E. Mann and
Raymond S. Bradley on a paper which produced the first
eigenvector-based climate field reconstruction (CFR) incorporating multiple climate proxy data sets of different types and lengths into a high-resolution reconstruction of northern hemisphere temperatures. In 1999 the same team extended the method to cover 1,000 years, producing what was dubbed the
hockey stick graph. ==References==