UK Contribution to Plio-MIP (Pliocene Modelling Intercomaprison Project)

Advanced numerical models of climate, often referred to as General Circulation Models, are being extensively used to predict the impacts of human induced climate change on global and regional scales. Although advanced such models remain imperfect tools with which to simulate climate change, and thus the robustness of climate models must be tested so that confidence in their predictions can be increased. There is no way climate model predictions for the future can directly test, but scientists can evaluate the capability of state of the art climate models to reproduce climate states that existed in the past and that were radically different from those of today. Since the mid 1990's an international programme called PMIP (Palaeoclimate Modelling Intercomparison Project) has championed the systematic study of several climate models and assessed their ability to simulate large changes of climate that occurred in the past. However, PMIP has not studied a period in Earth history that was globally warmer than present-day, and which had higher than pre-industrial levels of carbon dioxide (a greenhouse gas) in the atmosphere. In other words PMIP has not examined the ability of, and determined the differences between, climate models when simulating a period in Earth's history that provides a close analogue to climate as it is predicted to be in the future, as a result of human modification. The project will help fill this gap and enable a leading UK contribution to a new project set up to systematically study climate model outputs for a warm period in Earth history (the mid-Pliocene warm period ca 3 to 3.3 million years before present) which has a number of parallels to climate predictions for the end of this century. The recent Intergovernmental Panel on Climate Change (IPCC) 4th assessment report states that 'the mid-Pliocene is the most recent interval of geological time when mean global temperatures were ~2 to 3 degrees Celsius above pre-industrial temperatures for a sustained period. Therefore, the mid-Pliocene represents an accessible example of a world that is similar in many respects to what models estimate could be the Earth of the late 21st century'. In June 2008 representatives from 10 climate modelling groups worldwide met in New York to discuss and agree the details of new climate model simulations that will be carried out for the mid-Pliocene. This proposal outlines the programme of work and resources necessary to allow the UK to take part in this exciting new international initiative. It is expected that outcomes from this new project will be included in the next Intergovernmental Panel on Climate Change report, thereby helping to inform scientists and politicians worldwide about the ability and differences between climate models in simulating the last great period of sustained global warmth in our planets long history.