While the verdict is still out, recent research has shown that volcanic eruptions can have a dramatic effect on rivers. According to a report from New Scientist, a recent study from researchers at the University of Edinburgh seeks to explain how the aerosols produced by volcanic eruptions can affect the overall level or major rivers across the world.

Researcher Carly Iles and Gabriele Hegerl discovered that in the two-year period following a major volcanic eruption, the flow of major rivers decreased in wed tropical climates, most notably in rivers like the Amazon, the Nile, and the Congo. The Amazon, for example, dried nearly 10 percent following a major volcanic blast.

Interestingly, this pattern didn’t quite hold up across the different climates on the planet. In dry, subtropical regions, the flow of water in major rivers actually increased following volcanic eruptions, by some calculations as much as 25 percent.

The discrepancy observed between changing river levels as a result of volcanism in different climates can largely be explained by the aerosols produced by a volcanic blast. Tiny particles are projected into the air, which coalesce and block out sunlight. This affects atmospheric circulation of heat and moisture, which determines how rain falls.

This phenomenon can lead to different precipitation results across different climates. Take the Hadley cell, for example. The term describes when air rises near equatorial regions but falls near cooler, subtropical areas. The equatorial air is moist, but as it rises towards the sun, this moisture is converted to liquid form and drops to the ground as rain. It is the primary driver of daily rains in the rainforests of the world.

When this flow of air and heat gets blocked off by aerosols, however, the rains become less prolific. As a result, rivers dry up and this moisture in the air is carried further to higher latitudes where subtropical rivers experience unusual rainfall.

The precipitation patterns of different regions around the world are extremely sensitive, and climate scientists are just learning about the factors that influence them. For example, El Niño causes a similar shift in distribution of rainfall, leading to unseasonably dry and wet seasons in places that aren’t used to them. Sudden changes in precipitation can have devastating results on agriculture in areas where high levels of water are necessary.

Volcanoes have long perplexed scientists trying to measure the amount of greenhouse gases in the atmosphere, as some are considerably large sources of carbon dioxide and methane. Learning how they can affect precipitation patterns, however, can lead to a much better understanding of the way forecast models are written and carried out. It can help researchers more accurately predict some of the secondary and tertiary effects of shifts in the climate as a whole.

Another interesting idea has evolved out of the recent volcanic research – geoengineering. Researchers have suggested that putting particles into the atmosphere that would mimic the effect of a volcanic eruption could actually block heat from entering the atmosphere, cooling the planet at a time of warming.

According to Anja Schmidt, a researcher of volcanic impacts and hazards at the University of Leeds, this idea is still in its infancy. Scientists want to place sulphate aerosols into the atmosphere, which would likely have negative effects on agriculture and food safety, especially in regions of the world that are already the most susceptible to climate change.

The recent study was published in the journal Nature Geoscience.