Modelling the future

Uni Research

Scientists at the Bjerknes Centre for Climate Research in Norway are creating a new generation climate model. Incorporating a dynamic carbon cycle, the so-called ‘Earth system model’ will provide improved scenarios for the next Intergovernmental Panel on Climate Change (IPCC) report due in 2013.

The Bjerknes Centre for Climate Research is located in Bergen, Norway. The director, Eystein Jansen, is concerned with how the rising sea level can affect Bryggen, the old Hanseatic wharf in Bergen. Bryggen is on the UNESCO World Heritage List (Photo: Tor Erik Mathiesen, Trygg Vesta)

In recent decades, climate models have evolved from being based on simpler atmospheric physics to incorporating components such as oceans, sea ice and land surface. The new generation also integrates interactive models of land and ocean carbon cycles and atmospheric chemistry, earning them the name ‘Earth system models’. One such model is currently being developed in Norway, a project involving several national partners led by the Bjerknes Centre for Climate Research in the city of Bergen.

“Our model will provide new climate scenarios for the next IPCC report. We expect them to be more precise than previous scenarios, as the model takes into account how natural sources and sinks of carbon are likely to change as a result of global warming, and how, potentially, this will result in a larger fraction of CO₂ emissions remaining in the atmosphere. This knowledge will be essential in relation to future emission targets and mitigation strategies,” says Professor Eystein Jansen, director of the Bjerknes Centre and one of the lead authors of the 2007 IPCC report.

The Norwegian Earth system model, called NorESM, extends conventional climate models to incorporate marine and terrestrial cycling of carbon. For the Bjerknes Centre, this capacity complements its internationally-leading role in observing and quantifying ocean uptake of CO₂, which is necessary in order to evaluate the extent to which emission regulations are effective and prevent harmful climate change.

The first simulations using a preliminary version of the model run on one of the world’s most powerful computers have already confirmed scientists’ concerns that reduced uptake of CO₂ will intensify the human-induced greenhouse gas forcing.

Recent decades have seen significant improvements in the models scientists use to produce climate scenarios. The newest generation takes both dynamic carbon cycles and atmospheric chemistry into account and will produce improved and more accurate scenarios for the next IPCC report due in 2013

Worst case scenarios

“Model runs based on IPCC’s business-as-usual emission scenario show that atmospheric CO₂ concentration by the end of 21st century will be up to 25% higher than previous estimates,” says Eystein Jansen. Combined with the fact that current emissions already exceed the IPCC’s worst case scenario, this means the ongoing negotiations for a new climate agreement build on data that are too conservative. The director says, “in order to limit the global average temperature rise to 2° C above preindustrial levels we need to stabilise the atmospheric concentration of CO₂ at a lower level than considered so far. This is yet another reason why the Copenhagen conference is of such importance.”

Looking at the wording in previous IPCC reports, the authors speak of scenarios and projections. One significant development in climate research since the 2007 report is that scientists are now trying to forecast climate change in much the same way that meteorologists forecast the weather. While the process of estimating the climate in 20-30 years’ time is much more complicated than predicting whether or not tomorrow will be rainy, new knowledge and technologies are slowly making such estimates more feasible.

And, just as the Norwegian physicist Vilhelm Bjerknes founded modern weather forecasting, the centre that is named after him has now entered into the field of regional climate modelling in order to provide data relevant to planning ahead on a local level, both in Norway and in developing nations.

“Extreme weather and changes in precipitation are poorly presented in large scale models that have a predominantly global focus, but this knowledge is essential as societies demand more regional models for planning and adapting to climate change. By feeding the large-scale models with local data and thus correcting systematic errors, we can calibrate the scenarios to local scale,” says Eystein Jansen, stressing that the field of local climate forecasting is still in its infancy.

To overcome this major scientific challenge, the Bjerknes Centre has strengthened its partnerships with institutes such as the University of Washington, Massachusetts Institute of Technology and the Nansen-Zhu Centre in Beijing. New partnerships in South Africa and India are also being established.

“With our qualifications in climate modelling, paleoclimatology and ocean observations, the Bjerknes Centre is uniquely positioned to deliver key results. But it is through partnerships that our qualifications will improve and become more relevant to the global challenges we face. We realise that we have expertise of global significance as well as a global responsibility,” says Mr. Jansen.

The Bjerknes Centre for Climate Research
W: www.bjerknes.uib.no

Media contact: Jill Johannessen
Uni Research Website: www.uni.no