Improved knowledge of climate cycles to aid croppers

The Australian cropping industry has long wanted more lead time in identifying potential climate drivers that could influence weather through the growing season.

At present, the period around winter crop sowing, in mid-autumn, is a time of low skill for forecasting events such as El Niño (ENSO)

However, Matias Heino, a doctoral candidate at Aalto University, in Finland, which has conducted research into large scale weather cycles and their influence on cropping systems globally, said a  newly proposed method, based on network analysis, has increased the potential forecasting range of El Niño to up to 12 months.

However, the improvements will not extend to other important climate drivers such as the Indian Ocean Dipole (IOD) or the North Atlantic Oscillation (NAO), where the forecasting skill is not as high.

Mr Heino said the development of better climate driver forecasting would aid agriculture worldwide.

“There is great potential to increase the resilience of the global food production system by coupling this increased forecasting skill with knowledge about the impacts of these oscillations,” he said.

The Aalto University research has highlighted the massive impact climate cycles have on crop production across the globe.

Mr Heino said ENSO’s effect on grain production in Australia and North and South America was well documented, with El Niño phases drier than average in general in Australia and wetter than average in the Americas and vice versa for La Niña.

ENSO has the largest impact on crop production globally, however, other climate drivers less well known in Australia, such as the NAO, significantly affect crop production, not only in parts of Europe, which directly border the North Atlantic, but in many parts of Mediterranean Europe, North Africa and the Middle East.

The NAO is similar to ENSO in that it mainly impacts the flow of moist air onto land masses.

When the air pressure in Iceland is significantly lower than in the Azores, stronger winds increase the transport of warm, moist air from the Atlantic to Europe.

When the Atlantic air pressure difference has been high, the productivity of crops in Europe have reduced by 2 per cent compared to the average.

The effect has been particularly strong in places like Spain and the Balkans, where the decrease in productivity has been as much as 10pc.

During the other phase of NAO, when the air pressure difference is weaker, the same areas have shown positive changes, in crop productivity.

The IOD has a similarly profound impact on cropping in Australia.

Crop productivity may, depending IOD’s phase, be up to 8pc smaller or 6pc larger than average.

Drilling down, he said various phases had subsets that could impact weather patterns differently.

For instance, in Australia he said there was a difference in the impact on rainfall between an eastern Pacific and central Pacific El Niño.

“The eastern Pacific El Niño events are characterized by strong sea surface temperature (SST) anomalies in the eastern Pacific, while during a central Pacific El Niño event strongest SST anomalies are observed close to the dateline,” Mr Heino said.

“Australia seems to be impacted especially by central Pacific El Niños, which is related to decreased rainfall over its eastern parts.”

Mr Heino said the impact of weather phases varied from region to region, not only according to the intensity of the event, but also by prevailing conditions.

For instance, in Australia’s case, where most cropping systems are generally limited in moisture he said any decrease in rainfall would have a stronger impact compared to an area where crop growth is not limited by water availability.

Into the future, Mr Heino said researchers were unsure what impact climate change would have on weather phases.

“Climate change can have a significant effect on the fluctuation of these oscillations, however, understanding these effects is still on the science agenda.

“For example, it is not certain whether the eastern tropical Pacific (source of El Niño Southern Oscillation) will warm permanently or whether the nature of the fluctuations between El Niño and La Niña will change.

“Regarding Indian Ocean Dipole and the North Atlantic Oscillations it seems that climate change might lead to an increase in the frequency of their positive events, which also suggest increasing occurrence of the climate and weather events related to their positive phase.”

This would be bad news for Aussie farmers, as IOD positive events are correlated with drier than average conditions here.

The Aalto University study has been conducted in collaboration with researchers from Columbia University, Vrije Universiteit Amsterdam, Potsdam Institute for Climate Impact Research (PIK), and University of Bonn.