(credit: USGS)

Droughts in the coming decades could be longer than projected by current climate models, a new study published Wednesday in Nature warns.

The international team of scientists examined potential biases that could skew climate models used to make drought projections under Intergovernmental Panel on Climate Change midrange and high emissions scenarios. The researchers corrected for the bias by calibrating those models with observations of the longest annual dry spells between 1998 and 2018.

By the end of this century, they found that the average longest periods of drought could be 10 days longer than previously projected. Trouble spots included North America, Southern Africa, and Madagascar, where the newly calibrated models showed that the increase in the longest annual dry spell could be about twice what the older models predicted.

Enlarge (credit: Roman Studio)

Because most things about Earth change so slowly, it's difficult to imagine them being any different in the past. But Earth's rotation has been slowing due to tidal interactions with the Moon, meaning that days were considerably shorter in the past. It's easy to think that a 22-hour day wouldn't be all that different, but that turns out not to be entirely true.

For example, some modeling has indicated that certain day lengths will be in resonance with other effects caused by the planet's rotation, which can potentially offset the drag caused by the tides. Now, a new paper looks at how these resonances could affect the climate. The results suggest that it would shift rain to occurring in the morning and evening while leaving midday skies largely cloud-free. The resulting Earth would be considerably warmer.

On the Lamb

We're all pretty familiar with the fact that the daytime Sun warms up the air. And those of us who remember high school chemistry will recall that a gas that is warmed will expand. So, it shouldn't be a surprise to hear that the Earth's atmosphere expands due to warming on its day side and contracts back again as it cools (these lag the daytime peak in sunlight). These differences provide something a bit like a handle that the gravitational pulls of the Sun and Moon can grab onto, exerting additional forces on the atmosphere. This complicated network of forces churns our atmosphere, helping shape the planet's weather.