Climate Change Models & Data
There are two climate model types generally used by the Climate Risk Engines: 1. General Circulation Models (GCMs) and 2. Regional Climate Models (RCMs). GCMs simulate past, current and future climate worldwide, and RCMs focus on smaller regions. The Climate Risk Engines select by default the most appropriate climate modelling to use based on information that may include (i) the models available in the region (ii) the ‘skill’ of the model in capturing typical weather behaviour in a certain region (iii) the range of parameters included or reported (iv) the spatial resolution and (v) how the results of the model fit within the ensemble of other models for the region (vi) the age / generation of the model.
General Circulation Models (GCMs)
The Coupled Model Intercomparison Project (CMIP) provides GCM data from research groups around the world. Phase 5 (CMIP5) was completed in 2014 and formed the basis of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Being longstanding, a substantial amount of RCM downscaling has been completed for CMIP5 models. The latest generation of GCMs have been developed under the CMIP6 program. There are many more modelling groups and future scenarios (shared Socioeconomic Pathways, SSPs) being examined. The CMIP6 models show a wider range of equilibrium climate sensitivity – i.e. the amount of warming for a doubling of carbon dioxide concentrations. The Climate Risk Engines can use both CMIP5 and CMIP6 model data.
Regional Circulation Models (RCMs)
The Climate Risk Engines use data from the Coordinated Regional Climate Downscaling Experiment (CORDEX). Regional Climate Models (RCMs) can be employed to increase resolution even further. RCMs represent all the atmospheric physics of GCMs but are run only over a smaller area and can therefore can have higher resolution (from 60 km down to below 10 km).
Warming Scenarios
Climate models employ IPCC emissions scenarios. These scenarios, also known as Representative Concentration Pathways (RCPs), represent different levels of greenhouse gas and aerosols in the atmosphere, their associated effect on the additional energy stored within the Earth system and the consequent changes to global mean temperatures. For example, RCP8.5 represents greenhouse gas and aerosol concentrations that would cause an increase in radiative forcing of 8.5 W/m2 by 2100, which is the scenario typically considered as ‘business as usual’, where no policy action is taken to mitigate climate change (Figure 3). The IPCC's sixth assessment report introduces a new type of illustrative scenario, the Shared Socioeconomic Pathway (SSP), labelled SSPx-y where the 'x' refers to the socioeconomic trends underlying the pathway and the 'y' refers to the approximate amount of radiative forcing resulting from that scenario by 2100, the same as RCPs. There are five illustrative scenarios considered in the Sixth IPCC assessment report, covering high and very high greenhouse gas emissions (SSP3-7.0 and SSP3-8.5 is the commonly considered scenario in AR6), intermediate emissions (SSP2-4.5), low and very low emissions (SSP1-2.6 and SSP1-1.9). These consider similar pathways of radiative forcing levels as the fifth assessment report which used the RCPs. However, emissions between scenarios vary depending on socioeconomic assumptions, the level of climate change mitigation, and air pollution controls. Downscaled CMIP6 and CMIP5 data availability is variable. Figure 3: Development of emissions following the shared socioeconomic pathways (SSPs) and representative concentration pathways (RCPs).
Model Selection
The Climate Risk Engines run an assessment of changes to a particular parameter for each domain and by default select the model that results in the strongest driver of change for the parameter on average over the whole domain. Figure 4 shows the current coverage of hazard projections in the Climate Risk Engines. Each climate model has its own biases. If there is historical data in the local area of interest, the Climate Risk Engines use the historical data distribution to adjust the climate model data and reduce the model bias. Figure 4: Geographical coverage in the Climate Risk Engines, 2020, where the coloured areas are covered, and the white areas are not.
Available Domains
A “domain” is a region for which the regional downscaling is taking place The table below lists the available global and custom domains within the Climate Risk Engines. Full list available to clients.
Available Models
Models available in the Climate Risk Engines are a combination of GCMs and RCMs. Models available include: • Drought • Freeze-Thaw • Flood • Fire • Heat • Wind; synoptic and convective • Sea Surface temperature • Landslip • Sea level rise Full list available to clients.
Climate parameters associated with each hazard
The Climate Risk Engines use a range of climate parameters as inputs to the various hazards. This includes: • Sea Level Rise • Max Near Surface Wind Speed • Forest Fire Danger Index (FFDI) / Hot Dry Windy (HDW) • Minimum Daily Temperature (TMIN) • Maximum Daily Temperature (TMAX) • Annual Total Precipitation • Annual Maximum 24-Hour Total Precipitation • 7-day accumulated precipitation • Annual max monthly mean Sea Surface Temperature • Convective available potential energy (CAPE)
