Climate change under a scenario near 1.5 C of global warming: monsoon intensification, ocean warming and steric sea level rise

摘要: We present climatic consequences of the Representative Concentration Pathways (RCPs) using the coupled climate model CLIMBER-3α, which contains a statisticaldynamical atmosphere and a three-dimensional ocean model. We compare those with emulations of 19 state-of-the-art atmosphere-ocean general circulation models 5 (AOGCM) using MAGICC6. The RCPs are designed as standard scenarios for the forthcoming IPCC Fifth Assessment Report to span the full range of possible future greenhouse gas (GHG) concentrations pathways. The lowest of the RCP scenarios, RCP3-PD, is projected in CLIMBER-3α to imply a maximal warming by the middle of the 21st century slightly above 1.5◦ C and a slow decline of temperatures thereafter, 10 approaching today’s level by 2500. We identify two mechanisms that slow down global cooling after GHG concentrations peak: The known inertia induced by mixing-related oceanic heat uptake; and a change in oceanic convection that enhances ocean heat loss in high latitudes, reducing the surface cooling rate by almost 50%. Steric sea level rise under the RCP3-PD scenario continues for 200 years after the peak in sur-15 face air temperatures, stabilizing around 2250 at 30cm. This contrasts with around 2 m of steric sea level rise by 2500 under the highest scenario, RCP8. 5. Maximum oceanic warming at intermediate depth (300–800 m) is found to exceed that of the sea surface by the second half of the 21st century under RCP3-PD. This intermediatedepth warming persists for centuries even after surface temperatures have returned 20 to present-day values, with potential consequences for marine …