Half of world’s annual rain falls in 12 days

Half of the measured global precipitation in a year falls in just 12 days, an analysis of data collected at weather stations across the globe.

By century’s end, climate models project that this lopsided distribution of rain and snow is likely to become even more skewed, with half of annual precipitation falling in 11 days.

Previous studies have shown we can expect both an increase in extreme weather events and a smaller rise in average annual precipitation in the future as the climate warms, but experts are still exploring the relationship between the two trends.

“This study shows how those two pieces fit together. What we found is that the expected increases happen when it’s already the wettest the rainiest days get rainier,” said Angeline Pendergrass, a scientist at the National Center for Atmospheric Research (NCAR), the US.

The findings, published in the journal Geophysical Research Letters, suggests flood and the damage associated with it could also increase.

The results are also a concern for agriculture, which is more productive when rainfall is spread more evenly over the growing season.

Scientists who study extreme precipitation — and how such events may change in the future—have used a variety of metrics to define what qualifies as “extreme”.

Pendergrass noticed in some cases the definitions were so broad extreme precipitation events actually included the bulk of all precipitation. In those instances, “extreme precipitation” and “average precipitation” became essentially the same thing, making it difficult for scientists to understand from existing studies how the two would change independently as the climate warms.