SSP-Based Land Use Change Scenarios: A Critical Uncertainty in Future
Regional Climate Change Projections
Abstract
We assess the combined effects of greenhouse-gas (GHG)-forced climate
change and land-use changes (LUC) on regional climate projections. To do
so, we produced regional climate model (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),
allowing us to assess the influence of the LUCs on RCM projections
through the SSP+RCP scenarios framework. 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
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 into previous forest, projected annual mean temperature
increases are diminished by around 0.5-1.0℃. Where urbanization is high,
projected temperature increases are magnified, particularly in summer
where 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 the warm-season,
increasing storm intensity, event length, and the overall amount over
urbanized areas, and decreasing precipitation in surrounding areas.