Climate change ‘causing nights to be disproportionately warmer than days’

The changing climate is causing nights to be “disproportionately” warmer than days in many parts of the world, according to scientists.

Researchers have found night-time warming to be more common than daytime warming in more than half (54%) of the land surfaces across the planet – a phenomenon they describe as “warming asymmetry”.

The study, published in the journal Global Change Biology, said higher night-time temperatures could have “potentially significant implications” for nocturnal species.

The team from the University of Exeter looked at warming records from 1983 to 2017.

They found that night-time temperatures were, on average, “disproportionately” warmer (by more than 0.25C) when compared to daytime temperatures.

The researchers believe warming asymmetry is being driven primarily by clouds.

Clouds cool the planet’s surface during the day but retain the warmth during the night, leading to greater night-time warming.

In contrast, a lack of clouds allow more warmth to reach the surface during the day, but that heat is lost at night.

Lead author Dr Daniel Cox, of the Environment and Sustainability Institute on Exeter’s Penryn Campus in Cornwall, said: “We demonstrate that greater night-time warming is associated with the climate becoming wetter, and this has been shown to have important consequences for plant growth and how species, such as insects and mammals, interact.

“Conversely, we also show that greater daytime warming is associated with drier conditions, combined with greater levels of overall warming, which increases species vulnerability to heat stress and dehydration.

“Species that are only active at night or during the day will be particularly affected.”

He added: “Warming asymmetry has potentially significant implications for the natural world.”