The business of prediction

Irish scientists are helping to create a new model to predict climate change, writes CLAIRE O'CONNELL

DEVASTATING FLOODS at home and high-level talks in Copenhagen are keeping extreme weather and climate change in the headlines.

However forecasting climate change is fraught with challenges. Not only does it need enormous computing power to calculate the effects of processes over decades or even centuries, but uncertainty is an integral issue in climate modelling.

So the European “EC Earth” initiative, in which Ireland is a partner country, is developing a new climate model that will add to global knowledge and hopefully improve the outlook for long-term predictions.

Around a dozen good global climate models already exist, but there’s room for more, according to Ray McGrath, who heads the research and applications division at Met Éireann. “When you are forecasting the future climate there is always uncertainty and the models are getting better and better but there is still a gap,” he says. “A climate model itself is only an approximation of what is really going on and the climate system is incredibly complex with so many interlocked processes running at different speeds and affecting different aspects, that it is extremely difficult to model them all.”

Even the perfect model would still have to contend with the chaotic nature of the atmosphere, he adds. “There will always be uncertainty there in your projections. But by having better models and more models you can map out this uncertainty by running several simulations.”

What the EC Earth consortium of 19 institutions across 10 European countries aims to add is a new model that looks at how the atmosphere, the oceans and the biosphere interact. At present the EC Earth system is basing its atmospheric component on the “gold standard” model from the European Centre for Medium-Range Weather Forecasts and coupling it with an ocean model.

“Heat from the atmosphere is being transferred into the ocean and there’s also a feedback from the ocean to the atmosphere,” says McGrath. “So at the moment these two models are running together and in 2010 it will be extended further – atmospheric chemistry would be coming into it and eventually in about two years you would have the full carbon cycle added in.”

As partner countries each run various different simulations through the model, a dataset can be built up, he explains. “By starting at slightly different points we try to tease out the uncertainty, and by putting the simulations together at the end we can see what information we are getting out.”

The model needs to be settled, and then calibrated against known observations from history. “You run the model for hundreds of years to allow the system to adjust. Then you start running from the pre-industrial period up to the current period, and you can examine how well the climate model has captured the recent climate,” explains McGrath.

Then come the all-important simulations of future climate. “Once we are convinced it’s doing a good job of looking at climate over past years, we continue to let it run into the future and then we will produce simulations for the rest of the century. And we will try to focus on what is going to happen over the next decade.”

Ireland is contributing to the European initiative through Met Éireann, University College Dublin and the Irish Centre for High-End Computing (Ichec), and the super-computing resources are particularly key, according to McGrath. “If we didn’t have Ichec we couldn’t do these big simulations,” he says, noting that Ireland is the only partner country to run global simulations through the new model.

Ultimately EC Earth’s results will feed into global impact assessment reports, but the project will also downscale raw data relating to Ireland to get higher-resolution information over the region about rainfall and extreme events.

While a climate model can’t predict individual events, McGrath hopes the EC Earth system and particularly its downscaled regional version for Ireland will help improve our understanding of local climate.

As for the floods of 2009, it’s too soon to tell yet whether something is changing in the climate, says McGrath. “Climate models can tell you nothing about what’s happening for a specific year or particular events, it’s always relative to a period – usually of decades,” he explains. “Yes it looks like extreme weather events are going to increase in frequency in Ireland in the future but it’s not possible to put more flesh on that statement.”