Session: Last Millennium & Past2K
Author: camilo melo aguilar / firstname.lastname@example.org / universidad complutense de madrid
Co-author: jesús fidel gonzález rouco, universidad complutense de madrid;
elena garcía bustamante, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas;
jorge navarro montesinos, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas;
Past climate variations are known both from reconstruction methods that use proxy data as predictors and from simulations with climate models. Among them, borehole reconstruction is a well established method to reconstruct past surface air temperature (SAT) based on the assumption that SAT changes are coupled to ground surface temperature (GST) changes and transferred to the subsurface by thermal conduction. However, some physical processes can impact this hypothesis since they decouple SAT and GST. Climate model simulations from the Community Earth System Model Last Millennium Ensemble (CESM-LME) were considered for assessing the main processes that corrupt the SAT-GST coupling at local, regional and large to global scales. In addition, its implications for borehole temperature reconstruction are evaluated.
The analysis of SAT-GST coupling focuses here on the covariance structure during the last millennium (850-1850 CE) and specifically on the trend changes during industrial times (1850-2005 CE). During this period the influence of different anthropogenic external forcings such as greeenhouse gases (GHG), land use land cover (LULC) and ozone/aerosols is considered .
The results indicate that global long-term coupling is not significantly affected by local and regional decoupling processes although they are significant at smaller spatial scales. LULC changes play an important role in decoupling SAT-GST at local and regional scales with some implications for borehole temperature reconstructions therefore this must be considered in such type of reconstructions.