Accelerated Recent Warming and Temperature Variability Over the Past Eight Centuries in the Central Asian Altai From Blue Intensity in Tree Rings

Warming in Central Asia has been accelerating over the past three decades and is expected to intensify through the end of this century. Here, we develop a summer temperature reconstruction for western Mongolia spanning eight centuries (1269-2004 C.E.) using delta blue intensity measurements from annual rings of Siberian larch. A significant cooling response is observed in the year following major volcanic events and up to five years post-eruption. Observed summer temperatures since the 1990s are the warmest over the past eight centuries, an observation that is also well captured in Coupled Model Intercomparison Project (CMIP5) climate model simulations. Projections for summer temperature relative to observations suggest further warming of between similar to 3 degrees C and 6 degrees C by the end of the century (2075-2099 cf. 1950-2004) under the representative concentration pathways 4.5 and 8.5 (RCP4.5 and RCP8.5) emission scenarios. We conclude that projected future warming lies beyond the range of natural climate variability for the past millennium as estimated by our reconstruction.