By Jinliang Liu, Hong Liu and Joyce Arabian
Climate change is an ongoing discussion in the scientific community, with efforts from scientists, policy makers and other players to accurately project future climate variables.
Models are continuously being updated in attempts to better fit historical data as well as to better represent regional climate patterns. The Intergovernmental Panel on Climate Change (IPCC) combines international scientific information to collaboratively improve climate change reporting. Its main activity is to prepare assessment reports about climate change.
Updated reports are typically published every five to seven years (IPCC, 2013). The Fourth Assessment Report (AR4) was released in 2007. The latest, the Fifth Assessment Report (AR5) was released in late 2014.
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Following the advances in physical science, the new climate model simulations, carried out under the framework of the Coupled Model Intercomparison Project Phase 5 (CMIP5) of the world climate research program, have used new emission scenarios. These are Representative Concentration Pathways (RCP), which are explicitly expressed in radiative forcing in Watt/m2, i.e., a net change in the energy balance of the earth system in response to greenhouse gas (GHG) emissions, instead of the four story lines (A1, A2, B1 and B2) used in IPCC’s previous reports.
Does the modelled data from AR5 differ from that of AR4? Which one provides projections more in line with historical climate data across Ontario?
The goal of the IPCC’s reports are to provide updated research on the socio-economic aspects of climate change, as well as more detailed regional information. The reports are based on modelled data projecting changes in climate variables, including temperature and precipitation. AR5 is based on these newly improved models, with inputs from countries all over the world.
Three key research questions are addressed in this study for the province of Ontario. Does the modelled data from AR5 differ from that of AR4? Which one provides projections more in line with historical climate data across Ontario? If there are differences, are they significant enough to re-evaluate previous studies conducted for Ontario with AR4 model results?
This investigation was carried out with a focus on two climate variables in Ontario: annual mean temperature and total precipitation. Additionally, to assess climate change impacts on municipal infrastructure, future Intensity-Duration-Frequency (IDF) curves up to the 2050s at one gauge station in southern Ontario have been constructed to facilitate a hypothetical design experiment on storm sewer pipe. The rational method is used to calculate peak design flow and Manning’s equation is deployed to estimate pipe sizing.
Data used in this study include the World Climate Research Programme’s (WCRP) Coupled Model Intercomparison Project 3 (CMIP3) multi-model dataset and the CMIP5 multi-model ensemble data set (downloaded from the website of Downscaled CMIP3 and CMIP5 Climate and Hydrology Projection).