Scientists claim to have provided a clearer answer to a 20-year climate puzzle, but the finding won't be welcome news for farmers, policymakers or the wider public.

The El Nino-Southern Oscillation, which operates over the Pacific and is viewed as an engine room for driving variability in the world's atmosphere, has long been studied to understand how it will be affected by global warming as humans emit more greenhouse gases.

New research: The El Nino is expected to "take greater toll" through the effects of climate change. Credit:Stefan Postles

New work by the Centre for Australian Weather and Climate Research, jointly run by the Bureau of Meteorology and CSIRO, shows the impact of El Nino years - marked by a relative warming of waters in the eastern Pacific and shifting rainfall patterns - will be exacerbated by climate change.

''There's an intensification of changes in rainfall that are driven by El Nino,'' said Scott Power, research leader and a senior climate scientist at the bureau.