Here are some highlights:
1. Research has shown that a focus on just carbon dioxide and a few other greenhouse gases as the dominant human influence on climate is too narrow, and misses other important human influences.
2. The phrases “global warming” and “climate change” are not the same. Global warming is a subset of climate change.
3. The prediction (or projection) of regional weather, including extremes, decades into the future is far more difficult than commonly assumed. As well, the attribution of extreme events to a particular subset of climate forcings is scientifically incomplete, if the research ignores other relevant human and natural causes of extreme weather events.
4. The climate science assessments of the IPCC and CCSP, as well as the various statements issued by the AGU, AMS and NRC, are completed by a small subset of climate scientists who are often the same individuals in each case.
Indeed, the production of multi-decadal climate predictions of regional impacts, whose skill cannot be verified until decades from now, is not a robust scientific approach. Models themselves are hypotheses.
A summary of his testimony is at his web site here.