EXETER, England — The earth is getting warmer — but night temperatures are rising at a faster rate than daytime temperatures. That’s the conclusion of a new study by scientists at the University of Exeter. Researchers find greater nighttime warming is much more common in most areas of the world than greater daytime warming.
The study’s authors examined global temperatures between 1983 and 2017. That process helped them discover a 0.25°C mean annual temperature difference between daytime and nighttime warming across over half of the land on Earth.
Some regions did see daytime temperatures rise more than night temperatures, but the overall area of “disproportionately greater night-time warming” was over two times as big, researchers say.
‘Greater nighttime warming associated with climate becoming wetter’
As far as why this is happening, the research team point to gradual changes in cloud cover. More clouds means cooler surfaces during the day and increased warmth during the night. Conversely, less cloud cover leads to hotter days and cooler evenings.
“Warming asymmetry has potentially significant implications for the natural world,” says lead study author Dr. Daniel Cox, of the Environment and Sustainability Institute on Exeter’s Penryn Campus in Cornwall, in a release. “We demonstrate that greater nighttime 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,” he adds. “Species that are only active at night or during the day will be particularly affected.”
The study is published in Global Change Biology.