• For most of the world, nights are getting hotter more quickly than days are. Warmer night temperatures are also associated with cloudier, wetter weather.
  • Unequal temperature rises in a 24-hour period could have a skewed impact on the natural world. Species only active during the day or at night could be particularly affected.
  • The Tibetan Plateau, West and East Africa are among the regions to have the most unequal day and night warming.

Nights are getting hotter more quickly than days are, scientists say, potentially adding to the burden of climate change on the natural world.

In most of the world, the average nighttime temperature increase has outpaced daytime rises in the 35 years to 2017, according to a new study. Given that different animals and plants carry out different activities and processes depending on the time of day, unequal temperature rises may have a skewed impact, the researchers say.

Nineteen of the 20 warmest years have occurred since 2001.
Nineteen of the 20 warmest years have occurred since 2001.
Image: NASA

Warmer, cloudier nights

Global warming is affecting both day and night, but over the majority of land, the temperature at night has risen by at least 0.25°C more than during the day. The Tibetan Plateau and West and East Africa are among the regions to have marked asymmetry in day and night warming.

Cloud cover has a large role to play in this. Many of the places seeing greater night-time temperature rises also had more clouds, and in turn more rain. Daytime temperatures were limited by these clouds.

But in the parts of the world where daytime temperatures are climbing faster, there tends to be reduced cloud cover and increasingly dry climates.

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Another blow for the natural world

Ecosystems are finely balanced, and fluctuations in temperature and precipitation could have “profound consequences for the species inhabiting those regions and their ability to adapt in the face of the changing climate”, the study says.

Daniel Cox, a research fellow at the University of Exeter and leader of the study, said that species only active at night or during the day would be particularly affected.

“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,” he said.

Data from over 20,000 populations of more than 4,000 species shows an average 68% decline between 1970 and 2016.
Data from more than 4,000 species shows an average 68% decline.
Image: WWF/ZSL

This signals another potential blow for biodiversity, which has plummeted in recent years. A new study from the WWF and the Zoological Society of London shows the population sizes of mammals, birds, amphibians, reptiles and fish have fallen on average 68% between 1970 and 2016.

Climate change and biodiversity also have an impact on the outbreak of pandemics – and our ability to fight them. Deforestation, for example, brings humans and animals into greater contact and drives wildlife out of its natural habitat. This increases the chances of zoonotic diseases taking hold.

Hand-in-hand with this, cutting back such rich and diverse seams of nature hampers our chances of finding new solutions and treatments for these diseases.