From instrumental records, we know that the Earth has warmed by 0.5°C (0.9°F) since 1860. Only through the study of the climate history over the past several centuries and millennia can we truly assess whether this warming should be expected in a naturally changing climate or if it is being caused by human activities. Paleoclimatology is the reconstruction of past climate changes. In order to accurately identify the causes and mechanisms of climatic change, it is necessary to develop high-resolution paleoclimate records which tell us about past climate changes on seasonal, annual, and decadal time scales. In addition to helping us understand the natural spatial and temporal patterns of climate variability, these high-resolution records provide an important means of testing the results of general circulation models, which are used to predict future climate changes that may result from anthropogenic carbon dioxide (CO₂) emissions.

As historical and instrumental climate records cover only the very recent past, it is necessary to use indirect (proxy) records for a longer-term perspective on climatic variability. Paleoclimate records may be derived from natural archives, which incorporate climate-dependent physical or chemical proxy variables in their structure. The most complete and robust paleoclimate proxy records to date are ice-core records, marine-sediment records, and the Chinese loess record. While these records have provided key information about the Earth's climate history, they often are limited by low temporal resolution, uncertain chronologies, and poor geographic coverage.