Countries around the world are bracing for a torrid few months as the El Niño weather phenomenon looks set to wreak havoc on shorelines, farmland and ocean ecosystems. Already, India is grappling with the impacts of one of the driest monsoon seasons on record. Meanwhile, in Indonesia, schools have closed and authorities have advised residents to stay indoors to avoid the toxic smoke from huge wildfires supercharged by El Niño.
But what if we could take the sting out of the tail of El Niño – or even stop it from happening altogether? That’s the hope of physicists, chemists and engineers working on ideas ranging from the outrageously radical to the just-might-work. One of the most ambitious ideas for halting El Niño is to repurpose a technique called artificial upwelling that was initially conceived to boost the uptake of carbon by the oceans.
This form of geoengineering involves pumping cold, nutrient-rich water from the deep ocean up to the surface to encourage the growth of plankton, which would then absorb and store carbon from the atmosphere. Katharine Ricke at the University of California, San Diego, says artificial upwelling could be used to cool sea-surface temperatures in the tropical Pacific, potentially preventing an El Niño from forming. But – and it is a big but – the technical feasibility of deploying artificial upwelling on this scale would be a “major, major undertaking”, she says.
Ricke has previously investigated whether the approach could be used to cool sea-surface temperatures in the Indian Ocean and found it would require approximately 5.8 million kilometres of pipe, nearly double the total length of all pipelines in the world. There is also the problem that nobody knows what putting that amount of pipework into the ocean would do to other marine life. Another equally ambitious, but perhaps more promising, approach for preventing El Niño could be to use another geoengineering technique called marine cloud brightening.
The El Niño climate phase occurs when easterly winds weaken, allowing warm water built up in the western Pacific to slosh back across the central and eastern parts of the ocean. Spraying droplets of seawater into the air below low-lying stratocumulus clouds in the Pacific would increase their brightness, reflecting more sunlight back to space. This would then bring down sea-surface temperatures, strengthening trade winds to blow warm water back into the western Pacific and reverse the El Niño pattern.
A study published in July, co-authored by Ricke, concluded that deploying marine cloud brightening in this way would dramatically reduce the strength of an El Niño and push the system back into a neutral state much earlier than normal. This won’t come in time to prevent the current El Niño, says Jessica Wan at the University of Chicago, a co-author of the research. The technology needed to brighten clouds on this scale doesn’t exist, plus there is no international framework for countries to agree this kind of geoengineering intervention.
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