I help lead collaborative projects that assemble proxy climate records to study the climate changes of the past. These studies give insights into externally-forced and intrinsic climate variability over regional to global scales, and can be used to place recent trends in a long-term context. Comparisons between the proxy records and the output of general circulation models (GCMs) provide validation opportunities for GCMs, including their response to climate forcings on time scales that are not adequately represented by the instrumental record.

- The Artic Holocene Transitions (AHT) Project is a PAGES-endorsed effort to investigate centennial-scale variability in the Arctic climate system during the Holocene, and to understand the feedbacks that lead to pronounced changes. The AHT project has generated a major database of Arctic Holocene proxy climate records

- The PAGES / USGS Powell Center, North American 2k (NAm2k) Project is compiling proxy records from a variety of natural archives toto produce multiple-archive climate reconstructions for North America over the past two millennia.

And I have led collaborative projects that have resulted in syntheses of paleoclimate and paleoenvironmental information, including:

- PAGES 2k continental-scale temperature reconstructions over the past two millennia

- 2000 years of Arctic temperature variability - recent warming reverses long-term cooling

- Holocene thermal maximum in the western Arctic

- Holocene paleoenvironmental recrods from Arctic lake sediment

- Late Holocene climate and environmental change inferred from Arctic lake sediment

- Alaska Paleo Glacier atlas

- Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment