A new NASA study indicates that it will be rainier in the future than previously thought. This will occur as the climate continually warms up.
The study, which is titled Tightening of Tropical Ascent and High Clouds Key To Precipitation Change in A Warmer Climate, was published in the journal Nature Communications.
Globally, rainfall is not related just to the clouds that are available to make rain but also to Earth’s “energy budget” – incoming energy from the Sun compared to outgoing heat energy. High-altitude tropical clouds trap heat in the atmosphere. If there are fewer of these clouds in the future, the tropical atmosphere will cool.
Judging from observed changes in clouds over recent decades, it appears that the atmosphere would create fewer high clouds in response to surface warming.It would also increase tropical rainfall, which would warm the air to balance the cooling from the high cloud shrinkage. Rainfall warming the air also sounds counterintuitive -people are used to rain cooling the air around them, not warming it. Several miles up in the atmosphere, however, a different process prevails.
Climate modellers use retrospective simulations like these to check how well their numerical models are able to reproduce observations.For data, the team used observations of outgoing thermal radiation from NASA’s spaceborne Clouds and the Earth’s Radiant Energy System (CERES) and other satellite instruments, as well as ground-level observations.They found that most of the climate models underestimated the rate of increase in precipitation for each degree of surface warming that has occurred in recent decades.
The models that came closest to matching observations of clouds in the present-day climate showed a greater precipitation increase for the future than the other models. “This study provides a pathway for improving predictions of future precipitation change,” scientist Hui Su of NASA’s Jet Propulsion Laboratory in Pasadena, California said.