At the start of the project in 2010 initially, three target regions where chosen and are now available for download: the Western US, Southern Africa and Europe. These were chosen because the majority of climateprediction.net participants (to date) live in Europe and the US, and because Southern Africa is a region thought to be particularly vulnerable to climate change. All regional experiments will ultimately be managed from our partners within the region, but the development of the models (to date) takes place in Oxford.
The ultimate aim is to have model simulations for all CORDEX regions in the world – CORDEX, the Coordinated Regional Climate Downscaling Experiment, is a World Climate Research Programme (WCRP) framework to evaluate regional climate model performance through a set of experiments aiming at producing regional climate projections.
Results from our regional modelling experiments are freely available to anyone investigating the impacts of weather and climate changes across the available regions. Scientists interested in using this data should contact the weather@home scientific coordinator, Friederike Otto.
This is our own home region and thus also our experimental region with currently the largest data sets available. For the European region we have a standard ensemble of simulations with 50 km resolution from 1960 to 2010 forced with HadISST monthly observed SSTs. Additionally we have a perturbed physics ensemble (PPE) for the same period where we disturbed not only the initial conditions but also a set of the model parameters to investigate physical plausible parameters.
Additionally we submit work for a “counterfactual” ensemble simulating a climate that might have been without anthropogenic climate change. We plan to have several counterfactual, or “natural” ensembles based on SSTs from different GCMs of the CMIP5 project where all major modelling centres in the world provided counterfactual model simulations for the upcoming IPCC report AR5.
The Western US region, labelled PNW for Pacific North West, is an unusual region as it is smaller than our other regions and has a resolution of 25 km. The model region encompasses the Eastern Pacific Ocean and the Western US, extending inland as far as the Rocky Mountains. North to south it stretches from Canada down to the Gulf of California, and includes the Coast Range of mountains. It is currently the only region where simulations of the future are already available (2020 to 2040).
The Western US region is coordinated from our Partner Phil Mote at Oregon State University.
There are three experiments planned for Southern Africa:
- The first experiment will help document and increase our understanding of the Southern African climate. Unlike other regions of the world, there are few observational measurements. By simulating what the weather could have been over the 1960 to 2010 period, we can work out how relevant the observed data is to the areas where no data are available. We may also be able to use the data from the model simulations to find methods of “filling in the gaps” between measuring stations. Comparing trends in the observations with model simulations will allow us to get a better idea of whether extreme weather events are becoming more or less frequent.
- To make simulations manageable on today’s computers, climate models have to take “shortcuts” in representing some of the more complex processes in the climate system. The second experiment tests the shortcuts against results of the first experiment.
- What might the weather have been like without human intervention? The third experiment reflects what conditions would have been like if we had not emitted greenhouse gases, amongst other things which affect the climate. The difference between these simulations and those from the first experiment indicate the human contribution to recent weather trends.
Researchers at the University of Cape Town coordinate the Southern African part of Weather@home.
Australia & New Zealand
Our newest completely ready-to-go region is the largest region so far, including the whole of Australia and New Zealand at 50 km resolution. A standard ensemble for the historic period 1960 to the present is to be submitted in due course. Further experiments are planned, including counterfactual simulations of a world that might have been without climate change and simulations of future weather over the region.
Results of this experiment will go to our partner David Karoly at the University of Melbourne and analysis will also be undertaken by Sue Rosier at NIWA (The National Institute of Water and Atmospheric Research), Wellington, New Zealand.
South West Asia
The most recently developed region is the CORDEX region West Asia which stretches from the Horn of Africa and the Arabian Peninsula in the West to Vietnam and Cambodia in the East. In North-South direction it includes the Himalaya as well as Lake Victoria, India and the surrounding Ocean is in the centre of the region. For this region initially two sets of ensembles are planned, 1960 to the present forced with monthly observed SSTs and 1985 to the present forced with daily observed SSTs. Additionally counterfactual ensembles will be designed aiming to investigate the impacts of anthropogenic climate change on the Indian monsoon.
The data of this project will be analysed by our partners at the Indian Institute for Tropical Meteorology in Pune.
Our newest project is to develop regional climate model over the whole African continent, with a range of experiments planned to explore various aspects of anthropogenic influence on weather events over Africa.
This project in particular aims to quantify the link between a range of external climate drivers and observed high-impact weather in Africa and assess the implications for climate impacts. A particular focus will be the role of short-lived climate forcings (SLCFs), including sulphate, mineral and black carbon aerosols and tropospheric ozone. Studies linking climate change and extreme weather have so far focused on mid-latitude phenomena and the impact of rising greenhouse gases. Yet in many tropical regions, SLCFs and regional changes in land-surface properties may have played a larger role in changing patterns of weather risk to date.
Attribution is inextricably linked with understanding the response to natural climate drivers, including ENSO and SST variability in surrounding ocean basins. Radiative processes involving mineral aerosols play an important role in the development of the West African Monsoon. Many of these responses involve uncertain interactions between multiple climate system components, so rather than attempting to represent them internally, which increases model complexity and makes results more model-dependent, we will exploit our capability of running very large ensembles to explore sensitivities to different drivers, imposing a range of SST and aerosol optical depth (AOD) patterns. This will allow us to place the, often subtle, role of human influence into the context of, often large, uncertainties in natural forcings and response. The most extreme weather events, by definition, are relatively rare, so their occurrence is dominated by chance. Attribution hence depends on simulation models, whose reliability can be tested and if necessary recalibrated.