An EU-funded team of scientists has developed a new model that can determine the levels of carbon dioxide (CO2) emissions reductions needed in order to decelerate, and potentially put an end to, global warming. Their objective was to simulate future changes in the climate and CO2 emissions in a single scenario in which the CO2 equivalent concentrations in the atmosphere are stabilised in the long term at 450 parts per million (ppm). This would limit global warming to a maximum of 2°C above the pre-industrial level. The model was presented in the journal Climate Change. Their work is an outcome of the ENSEMBLES ('Ensemble-based predictions of climate changes and their impacts') project, which received EUR 15 million under the 'Sustainable development, global change and ecosystems') Thematic area of the EU's Sixth Framework Programme (FP6) to develop a common ensemble forecast system for use across a range of timescales (e.g. seasonal, decadal) and spatial scales (e.g. global, regional). According to the scientists, the concentration of CO2 in the atmosphere, boosted by the combustion of fossil fuels, has swelled by around 35% since the start of the Industrial Revolution. Failure to curb both CO2 emissions and atmospheric CO2 concentrations could lead to a major rise in global temperatures by the end of 2100. 'What's new about this research is that we have integrated the carbon cycle into our model to obtain the emissions data,' explained lead author Erich Roeckner of the Max Planck Institute for Meteorology in Hamburg, Germany. The model predicts that CO2 emissions will climb by 3 billion tonnes of carbon to around 10 billion tonnes in 2015. If we are to ensure the long-term stabilisation of the atmospheric CO2 concentration, emissions must be cut by 56% within the next 40 years and approach zero in the latter half of this century. Although the calculations show that global warming would remain under the two-degree threshold between now and 2100, further warming may result in the long term, the scientists said. 'It will take centuries for the global climate system to stabilise,' Dr Roeckner pointed out. The team from Germany and the US used a novel method to reconstruct historical emission pathways on the basis of existing CO2 concentration calculations. Dr Roeckner and his colleagues adopted the methodology proposed by the International Panel on Climate Change (IPCC), a scientific intergovernmental body that evaluates the risk of climate change caused by human activity, for simulations performed for the future Fifth IPCC Assessment Report. The scientists used earth system models incorporating the carbon cycle and estimated the anthropogenic CO2 emissions that are compatible with a prescribed concentration pathway. According to the team, the emissions are contingent on the proportion of the anthropogenic carbon in the model that is absorbed by the land surface and oceans. They also succeeded in distinguishing between anthropogenic climate change and internal climate variability. The model used in this study is based on a low-resolution spatial grid with a 400-kilometre grid spacing. Information about land surface, ocean, and the marine and terrestrial carbon cycle is included. Climate centres across Europe are now evaluating the study's data. 'As soon as all of the results are available, we can evaluate the spread between the models. The more significant the data we have, the more accurate our forecast will be,' Dr Roeckner concluded.
Germany, United States