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The average global temperature has risen by about one degree Celsius
since the start of the Industrial Revolution in the 1800s.
And it’s still going up.
The ten warmest years on record have happened since 2005,
leading to everything from more extreme weather to wildfires.
But one of the nuances of the climate crisis is that
the planet isn’t warming at the same rate all over.
Like, some parts of the world are warming up faster at night than during the day.
It’s part of a phenomenon called warming asymmetry.
And the reason it happens has to do with… clouds.
One study on this came from the University of Exeter,
and was published in 2020 in Global Change Biology.
In it, the team looked at climate change data from 1983 to 2017.
They found that both days and nights got hotter on average,
but for more than half the Earth’s land area, nights got hotter faster.
In these places, nighttime temperatures went up by more than an extra quarter
of a degree Celsius over the 34-year period, compared to daytime temperatures.
The team also found a trend: In places where nighttime temperatures went up
half a degree compared to daytime temps,
there was also more cloud cover, humidity, and precipitation.
For example, in the Tibetan Plateau, nighttime temperature lows
increased an average of 1.2 degrees Celsius more than daytime highs.
And sure enough, the Plateau now sees more than your average
amount of cloud coverage during the day and night.
Meanwhile, areas with less cloud coverage tended to
see higher temperature increases during the daytime.
Like, in East Africa, daytime highs increased by an average of
about 0.4 degrees Celsius more than nighttime lows.
As for why clouds are such a big deal… Well, during the day, white, fluffy clouds
can act as an umbrella, reflecting the Sun’s warming rays away from the planet.
But when the Sun goes down, clouds can have the opposite effect.
They turn from an umbrella into a blanket.
At night, all the heat that the ground absorbs
during the day radiates out from Earth’s surface.
If there’s a lot of cloud coverage, that heat gets trapped,
which then causes the air temperature near the surface to rise.
This is likely why cloudy areas are seeing those bigger increases in
nighttime temperature: That radiative heat just doesn’t have anywhere to go.
Meanwhile, this also explains why places without clouds are warming more
during the day: At night, radiative heat can escape into space,
but during the day, these places are getting blasted with sunlight.
On its own, this isn’t necessarily bad.
But when you add the climate crisis to the mix,
it can create a vicious warming cycle.
Like nighttime clouds, greenhouse gases also
prevent heat from escaping into space.
They absorb heat coming from Earth’s surface and radiate it
back into the atmosphere, which turns up the temperature even more.
And since a warmer atmosphere also holds more moisture, humidity tends to rise.
This can create more cloud coverage,
which then traps more radiant heat at night, and so on.
And this cycle doesn’t just lead to muggier sleeping conditions:
It could significantly impact plants and animals.
Like, the Exeter study suggests that since nighttime warming typically leads to
the environment getting wetter, it could make it harder for
nocturnal animals to get food, mate, and communicate.
In areas where it rained more, plant growth was limited, potentially because more
clouds during the day kept the plants from getting the sunlight they needed.
So herbivores in those areas ended up with less available food.
Shifts in temperature patterns like this can also change when and how
plants bloom, and could allow invasive species to expand to new areas,
all of which could further affect how much food is available for animals.
Meanwhile, in regions that see more warmth during the day
and have less cloud coverage, more animals could suffer from heat shock.
When outside temperatures get so hot that animals can’t regulate their body heat,
their immune systems become compromised,
and they have trouble metabolizing food.
That said, there is some nuance here.
Even these trends aren’t exactly the same all around the world.
Like, the effects of nighttime warming on plants can
vary widely with the season and region.
This warming can even have opposite effects on different types of plants,
which could be both helpful and hurtful for food supplies.
For example, a study from Nanjing Agricultural University in China found that
yields from the wheat crops they looked at
actually went up by about 18% with extra nighttime warming.
Meanwhile, rice yields shrank by about 4.5%.
Still, the overall theme is that neither more nighttime nor daytime
warming is great for animals and plants.
Even what seem like minor changes can make it harder for life to grow and survive.
And we’re already seeing some of these effects.
Right now, drought conditions are growing more intense in places that
experience extra daytime heating, like East Africa, which is causing
crops and livestock to die and leading to food insecurity for millions.
And as the climate crisis triggers more warming asymmetry,
events like this will become more severe,
and disproportionately affect poorer or lower-resource nations.
Still, something to remember is that there’s time to change things.
If governments, big businesses, and communities come together to limit
greenhouse gas emissions, we can still bring about meaningful and just change.
You can also lend support to local, grassroots efforts working to
help agricultural communities adapt to their changing landscapes.
So, this cycle of increased clouds and increased warming is
one more effect of the climate crisis we can observe.
And knowledge is power, but it’ll take action, too.
One way to connect with like-minded people to take action against
the climate crisis might be through online forums.
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