We compared output from 3 dynamic process-based models (DMs: ECOSSE, MILLENNIA
and the Durham Carbon Model) and 9 bioclimatic envelope models (BCEMs; including BBOG
ensemble and PEATSTASH) ranging from simple threshold to semi-process-based models. Model
simulations were run at 4 British peatland sites using historical climate data and climate projections
under a medium (A1B) emissions scenario from the 11-RCM (regional climate model) ensemble underpinning
UKCP09. The models showed that blanket peatlands are vulnerable to projected climate
change; however, predictions varied between models as well as between sites. All BCEMs predicted a
shift from presence to absence of a climate associated with blanket peat, where the sites with the
lowest total annual precipitation were closest to the presence/absence threshold. DMs showed a more
variable response. ECOSSE predicted a decline in net C sink and shift to net C source by the end of
this century. The Durham Carbon Model predicted a smaller decline in the net C sink strength, but no
shift to net C source. MILLENNIA predicted a slight overall increase in the net C sink. In contrast to
the BCEM projections, the DMs predicted that the sites with coolest temperatures and greatest total
annual precipitation showed the largest change in carbon sinks. In this model inter-comparison, the
greatest variation in model output in response to climate change projections was not between the
BCEMs and DMs but between the DMs themselves, because of different approaches to modelling soil
organic matter pools and decomposition amongst other processes. The difference in the sign of the
response has major implications for future climate feedbacks, climate policy and peatland management.
Enhanced data collection, in particular monitoring peatland response to current change, would
significantly improve model development and projections of future change.