Biogeophysical Impact of Land-Use Scenarios on Holocene Surface Temperatures

Reconstructions and simulations disagree on whether the Holocene exhibited a long-term cooling or warming signal. Anthropogenic land-use could be an important forcing regionally, but available population-based estimates differ widely. We examine transient Holocene climate model simulations forced with three population-based disturbed-land reconstructions and compare this with a fourth scenario derived entirely from fossil pollen records. The direct biophysical temperature effects are broadly similar across the scenarios but the pollen-based product suggests an earlier onset of disturbance, particularly in China and accounting for its limited spatial coverage, falls closer to the upper limit of the existing uncertainty range. Impacts in many areas begin during the mid-Holocene but emergence of a signal varies spatially with earliest impacts over Europe, China and the North Atlantic. Significant uncertainties remain, and these could be tackled by improving the representation of land-use effects in climate models or by merging different information sources related to Holocene land-use.