Floods, droughts worsen with warming

Earth’s water storage measured

The intensity of extreme drought and rainfall has “sharply” increased over the past 20 years, according to a study published Monday in the journal Nature Water. These aren’t merely tough weather events, they are leading to extremes such as crop failure, infrastructure damage, even humanitarian crises and conflict.

The big picture on water comes from data from a pair of satellites known as GRACE, or Gravity Recovery and Climate Experiment, that were used to measure changes in Earth’s water storage — the sum of all the water on and in the land, including groundwater, surface water, ice, and snow.

The researchers say the data confirms that both frequency and intensity of rainfall and droughts are increasing due to burning fossil fuels and other human activity that releases greenhouse gases.

“I was surprised to see how well correlated the global intensity was with global mean temperatures,” said Matthew Rodell, study author and deputy director of Earth sciences for hydrosphere, biosphere, and geophysics at NASA Goddard Space Flight Center.

The strong link between these climate extremes and rising global average temperatures means continued global warming will mean more drought and rainstorms that are worse by many measures — more frequent, more severe, longer and larger. Researchers looked at 1,056 events from 2002-2021 using a novel algorithm that identifies where the land is much wetter or drier than normal. Drought events outnumbered heavy rain events by 10 per cent.

A warmer atmosphere increases the rate at which water evaporates during dry periods. It also holds more water vapour, which fuels heavy rainfall events.