SSP-Based Land Use Change Scenarios: A Critical Uncertainty in Future
Regional Climate Change Projections
Abstract
To better understand the role projected land-use changes (LUC) may play
in future regional climate projections, we assess the combined effects
of greenhouse-gas (GHG)-forced climate change and LUCs in regional
climate model (RCM) simulations. To do so, we produced RCM simulations
that are complementary to the North-American Coordinated Regional
Downscaling Experiment (NA-CORDEX) simulations, but with future LUCs
that are consistent with particular Shared Socioeconomic Pathways (SSPs)
and related to a specific Representative Concentration Pathway (RCP). We
examine the state of the climate at the end of the 21st Century with and
without two urban and agricultural LUC scenarios that follow SSP3 and
SSP5 using the Weather Research and Forecasting model (WRF) forced by
one global climate model, the MPI-ESM, under the RCP8.5 scenario. We
find that LUCs following different societal trends under the SSPs can
significantly affect climate projections in different ways. In regions
of significant cropland expansion over previously forested area,
projected annual mean temperature increases are diminished by around
0.5-1.0℃. Across all seasons, where urbanization is high, projected
temperature increases are magnified. In particular, summer mean
temperature projections are up to 4-5℃ greater and minimum and maximum
temperature projections are increased by 2.5-6℃, amounts that are on par
with the warming due to GHG-forced climate change. Warming is also
enhanced in the urban surroundings. Future urbanization also has a large
influence on precipitation projections during summer, increasing storm
intensity, event length, and the overall amount over urbanized areas,
and decreasing precipitation in surrounding areas.