The scientists sought to address the uncertainty surrounding the impact of climate change on ENSO strength and frequency with a view to helping predict how the ENSO phenomenon will respond as the Earth warms over the coming years. Dr Tudhope cautions that the team's data do not prove or disprove the theory that ENSO has already become stronger as a consequence of human activity. However the data do indicate that ENSO has been sensitive to global climate change in the more distant past. This observation may ultimately lead to more accurate ENSO predictions by research groups who run sophisticated computer climate models, and Dr Tudhope has begun collaborating with two groups who run such programs. The data produced by this research will help fill the gaps that have limited the precision of climate models in the past.
Coral is an ideal material to study as it forms yearly bands, much like the banding seen in trees.
Examining this coral record has shown that ENSO has indeed operated over the past 130,000 years, even during the very cold glacial times, although its intensity has varied. The team found that during the twentieth century ENSO was strong compared with previous cool glacial times. Part of the continuing uncertainty is not knowing what the comparison would be with times that are as warm as global climate change forecasts would suggest are on the way. The Earth is heading towards temperatures warmer than experienced for millions of years, so there is no way of examining what ENSO has done in the past under these conditions. It is predicted that global temperatures will rise on average by between 1 and 3 degrees as the greenhouse effect takes effect.