Climate Change Making Nighttime Warmer, Study Finds

(Conrad Earnest via AP)

(CN) — After a long, hot day the nighttime becomes an escape from the sun and heat, an event that has been occurring since time immemorial.

Sidewalks have the chance to cool and the air grows crisp. But a study from the University of Exeter says nights are losing their advantage against climate change and more parts of the globe are heating up — even at night.

According to a study published this week in the journal Global Change Biology, most of the studied land mass experienced this phenomenon.

From 1983 to 2017, days have warmed up quicker in some parts of the world and then there were other parts where the night was warmer. That’s not remarkable, but the nighttime area is more than twice as large as the daytime areas that are warming up.

Blame global warming and cloud coverage, according to the study authors. More cloud coverage during the day means a cooler surface in the day, which in turn retains heat at night.

“Species that are only active at night or during the day will be particularly affected,” said lead author Daniel Cox with the Environment and Sustainability Institute at the University of Exeter in a statement. “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.”

The study also shows that more warming during the day equals drier conditions, which is coupled with greater vulnerability to heat stress and dehydration. Animals that are only active during the day or night will be thrown for a loop.

The scientists analyzed cloud coverage, humidity, rainfall and hourly records to map out their results, which shows different rates of temperatures during the day and night cycles. That ranged from a low, medium and high range. 

The study then analyzed the impact to plant growth and rainfall over the same time periods, which illustrates that plant life did depend on rainfall, but an increase in nighttime warming equaled less vegetation growth where it rained more.

The relationship between cloud coverage and rainfall points to a pattern that is doubly negative for plants, because in areas where there was too much cloud coverage, plants suffered at night when they did not get enough rain. Warmer days led to less growth because of a lack of rainfall.

Overall, more than half of the land surface that was studied saw an increase in warming asymmetry of a quarter of a degree and the researchers write, “this is driven primarily by changing levels of cloud cover and is associated with a wetting (increased night‐time warming) and drying (increased daytime warming) of the climate.”

The scientists go on to say that the 24-hour “asymmetry in how the climate is changing is likely to have major implications for temperature and water‐dependent ecological processes, impacting species through thermoregulatory and water budgets.”

The bigger problem will be for animals like ectotherms, which depend on external sources of heat, like reptiles and endotherms, which regulate their body heat through internal body functions. That’s a broad range of animals that will be tasked with adapting to a whole new world due to climate change.

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