A long-term context (931-2005 C.E.) for rapid warming over central Asia

Abstract:

Our understanding of long-term temperature variability and its causes is extremely limited in remote Central Asia, due to short and sparse meteorological data, as well as a paucity of long-term, high-resolution, temperature-sensitive proxy records. Instrumental records, typically only reaching back to the 1940s or later, show that temperatures in central Asia have been increasing rapidly, particularly since the mid 1990’s, and are currently warmer then at any other time in recorded history. We develop a millennium length (931-2005 C.E.) tree-ring width chronology from larch trees (Larix sibirica) growing at elevational treeline (2400 meters) sites in Mongolia, where the dominant limiting factor for growth is temperature. The chronology and reconstruction, from a site named Ondor Zuun Nuruu (OZN; meaning 'High East Ridge'), has a large sample depth (> 200 samples) and can be calibrated and validated using regionalized meteorological data from Mongolia and Russia. The reconstruction allows us to evaluate temperature variability and extremes over the past millennium in Central Asia, a region that is warming faster then many places on Earth. It also places recent warming trends into a long-term context, contributes to our understanding of spatial patterns of the Medieval Climate Anomaly and the Little Ice Age across Asia, and provides evidence of significant volcanic influence on Central Asia temperature. We also present preliminary results from novel Blue Light Intensity methods that demonstrate that blue intensity reflectance significantly improves the climate signal of temperature sensitive tree-ring width chronologies from Central Asia and will lead to additional millennial length reconstructions from several sites that were not previously possible using ring-width alone.