Temperatures on our planet are rising.

This much is blatantly apparent, with 2024 the hottest on record, and an average of almost two degrees Celsius temperature rise since the pre-Industrial era.

Scientists have long warned that any further temperature rises could be catastrophic to our planet, with the already significant rise contributing to crop failures, droughts and wildfires demonstrating the seriousness of their message. Should the situation be allowed to worsen, food scarcity, large-scale climate migration, extreme weather events, and monumental health impacts are all on the horizon.

And that is just on land. The effects to our oceans will be equally extreme, with ocean acidification and rising sea levels among the effects on the waters that cover 70% of our planet, triggering one of the several tipping points that signal irreversible damage to our planet’s delicate climate.

Ocean temperatures are already rising, causing vulnerabilities among the vital ecosystems beneath the surface that actually support our atmosphere and terrestrial life too. Phytoplankton, for example, are tiny and an often overlooked part of the marine environment.

But the role they play in the marine food chain and the huge amounts of oxygen that they release into our atmosphere (whilst removing carbon dioxide too) is vital – without their presence, ocean and land based ecosystems would collapse.

And any changes in ocean temperature, currents, nutrients, or pH levels threaten these important species, rendering our protection of our oceans ever-more important.

So what is happening in our oceans, as sea temperatures continue to rise?

Staggeringly, new research from the Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences suggests that – even though sea temperatures are rising – the evaporation levels of our oceans have hit a new low. Their study was published in the journal Geophysical Research Letters.

This factor is more concerning than it sounds.

Aside from the threats that higher sea levels (in part caused by glacial melt as a result of higher global temperatures) presents to our life on land, through flooding, coastal degradation, and the ever-present threat of tsunamis, evaporation from our seas is important, as the research team explain in a statement:

“Ocean evaporation plays a central role in Earth’s hydrological cycle, contributing more than 85% of atmospheric water vapor. Historically, higher sea surface temperatures were expected to increase evaporation rates. However, observations since the early 2000s have revealed a puzzling slowdown in the growth of global water vapor.”

Atmospheric water vapor is important, since it helps to regulate temperatures on our planet, with its important role in our weather ensuring that rain and snow continue to feed into our water cycles.

Scientists’ assumptions that higher temperatures would mean more ocean evaporation seem logical: after all, we all know that water evaporates more quickly at higher temperatures.

However, as the study’s lead author Dr Ma Ning goes on to explain, their findings – based on satellite data gathered over decades – shows that since the late 2000s our planet’s levels of ocean evaporation have reduced:

“Since then, two-thirds of the world’s oceans have experienced a reduction in evaporation, resulting in a slight decline in global evaporation rates between 2008 and 2017. This contradicts what we would typically expect in a warming climate.”

And there is one key factor at play here.

According to meteorological data, the winds that breeze around our planet have changed, with an unexpected average decline in wind speed. Known as ‘wind stilling’, this phenomenon has had subtle but detrimental effects on atmospheric circulation.

Consequently, this has affected the way that our weather cycle – and, by association, our water cycle – operates, feeding into continually rising water levels.

The message from our swelling oceans is clear: if we want to protect our climate, we need to act decisively, and fast.

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