Big Science: Will 'feedback loops' worsen climate change?
El Nino climate events have caused devastating droughts in the past. Photo / File As part of five-part series on major new Kiwi research projects, science reporter Jamie Morton speaks with the University of Auckland mathematician Professor Bernd Krauskopf about an effort to unravel the complex causes of El Nino. They're called delayed feedback loops and in our fast-warming planet, they're expected to play an increasingly influential role in the climate system. Yet what drives them and more importantly, how we might understand their consequences remain some of the most notoriously difficult challenges facing climate modelers today. Now, Bernd Krauskopf, a professor of applied mathematics at the University of Auckland, is about to unravel these complex effects by focusing on a climate phenomenon known to mess with our weather around this time of year: El Nino. What makes climate systems tough to study is their many sub-systems the atmosphere, and oceans, land and ice below that all influence each other. Making this tangle of drivers yet harder to comprehend is the fact that the planet's climate doesn't just influence each sub-system it is itself also influenced by them in turn, but only after some delay. Krauskopf described such delays as "crucial ingredients" in the dynamics of climate systems. Delays generally came as a result of either the time it took to shift mass or energy across the globe and through the atmosphere, or for the sub-systems themselves to react to changing conditions. This wasn't just important in natural climate variability, but in global climate change in the future, packing the potential to ramp warming up higher than some models predict, with a cascade of possible knock-on effects. In a new study, supported with a $689,000 Marsden Fund grant, Krauskopf will try to better understand feedback loops and the role of their delays by deconstructing the process that creates El Nino systems. "El Nino events have major consequences world-wide, yet they remain notoriously hard to predict even with sophisticated global climate models," he said. In New Zealand, farmers know these to bring too much rain to western, wetter parts of the country - and not enough of it to drier, eastern regions. El Nino events have been devastating in the past the last severe one in 1997 and 1998 caused a major drought that cost the country hundreds of millions of dollars. They form from big increases in sea surface temperature in the eastern equatorial Pacific Ocean, and occur around once every three to seven years, invariably around Christmas time. As part of their formation, positive and negative delayed feedback loops arose from the "coupling" of ocean and atmosphere out in the central equatorial Pacific Ocean, usually taking several months. With Professor Henk Dijkstra from Utrecht University in the Netherlands, Associate Professor Tony Humphries of Canada's McGill University, and Associate Professor Jan Sieber of the UK's University of Exeter, Krauskopf aims to create and analyse representative mathematical models that explain how these El Nino feedback loops behave. Specifically, they plan to shed new light on the properties of feedback loops in those tricky cases where the delays in the system weren't "fixed" and instead depended on the state of the system itself to shape them. "In other words, it does not always take the same amount of time for the interaction between atmosphere and ocean to take effect and lead or not lead to an El Nino event." His ultimate hope was that his team's findings could improve global climate models, and their projections for the future. "While natural mechanisms are associated with variable delays of feedback loops, research into their effects has been hindered by a lack of mathematical theory and numerical tools," he said. "In this way, our results at the conceptual level will help constrain parameters in more complex models, including those used by the climate modelling community for sensitivity analysis and prediction. "The dynamics of climate systems, and El Nino in particular, are subjects of great interest in the scientific community and the wider public, and a large number of colleagues internationally are working on climate models of widely differing complexity. "The proposed research will make a contribution of a fundamental nature to the topical question of how feedback loops shape observed behaviour." New programme for preschool children about to be trialled in New Zealand.