Professor Tim Palmer, one of the review authors of the Intergovernmental Panel on Climate Change’s Fifth Assessment, spoke to the Oxford Martin School’s communications officer Sally Stewart ahead of Friday's release of the first of three reports.
Human influence on the climate system is clear, the UN's Intergovernmental Panel on Climate
Change (IPCC) has stated, after approving the first of three reports making up its Fifth Assessment.
Professor Tim Palmer, Co-Director of the Oxford Martin Programme on Modelling and Predicting Climate and one of the report’s review authors, said climate scientists continued to be concerned about substantial future climate change.
“The threat of dangerous climate change for the future is still unequivocal in the sense that models show significant probability of changes that would be calamitous for humanity,” said Professor Palmer.
Climate modelling had improved considerably since the last assessment, in 2007, he said.
“Models have become more complex and precise; in the old days they were crude representations. Trying to represent the carbon cycle explicitly has improved. Instead of making single forecasts we now run an ensemble, varying the parameters, and produce probability distributions of outcomes. You can’t give a single number for global warming in 2100 because there are fundamentally a lot of uncertain processes that we can’t represent perfectly.”
There would always be uncertainty involved in scientific predictions of future events, he explained. “It is never based on perfect knowledge, and that is the same for all walks of life. But we can see those probability distributions reaching out into the type of climate that would be catastrophically bad for humanity, in terms of sea level rises and increases in droughts and floods, which would certainly lead to movement of populations.
“The question for policy makers is how big does the risk have to be of those sorts of things happening before we decide to take action on reducing greenhouse gas emissions.”
Professor Palmer said he and the report’s other authors took part from a “completely disinterested” perspective on climate change.
“We’re not environmental activists, I’m not doing it because I want to influence policy in one direction or another. I am trained as a mathematician and physicist to apply knowledge to a scientific problem. Scientists are doing the best job they can with the best tools available. They aren’t as perfect as we would like and we don’t try to hide the uncertainties. The question of what action to take is for the policy makers to decide.”
Thomas Stocker, co-chair of the IPCC's Working Group 1, said: “Global surface temperature change for the end of the 21st century is projected to be likely to exceed 1.5°C relative to 1850 to 1900 in all but the lowest scenario considered, and likely to exceed 2°C for the two high scenarios.
"Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions."