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Fresh water cycles through the oceans, from air to clouds to rivers to oceans to oceans to oceans to oceans to oceans to oceans to oceans to oceans to rivers to oceans back to oceans. This constant shuttling can give the illusion of certainty. The tap will always have fresh water. Won’t it?
Unfortunately, that’s not guaranteed. Climate change is changing the places where the water cycle deposits its water on land. Wetter areas are becoming more wetter, while drier areas are becoming drier.
Our research Published today in NatureBased on the changes in oceans, it has been shown that the water cycle is changing much faster than we thought.
This alarming finding highlights the urgent need to stop the emission of gases that are warming the atmosphere.
If you find this sound serious, it is. Modern society is possible because of our ability to harness freshwater.
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Already, the water cycle has changed
As the Earth warms up, the water cycle has begun to intensify in a “wet-gets-wetter-dry-gets-drier” pattern.
This means that more freshwater is being taken from dry areas of the planet to be used in wet areas.
Continue reading:
The water cycle is intensifying as the climate warms, IPCC report warns – that means more intense storms and flooding
What could this look like Weather intensified. More frequent severe droughts are more common in areas that are relatively dry. Flooding and severe storms are more common in areas that are relatively dry.
Think of the Megadrought: America’s west, of the unprecedented floods Germany, or the increase in severe rain seen in cities like Mumbai.
This shift is already taking place. In its landmark 2021 report, the UN’s Intergovernmental Panel on Climate Change (IPCC) drew on this growing body of research to conclude climate change was already causing Long-term water cycle changes.
The changes we’re seeing are just the start. This water cycle intensification could make obtaining reliable water supplies across large areas of the globe much more difficult over the next few decades.
Troublingly, while we know the water cycle is intensifying, we don’t fully know how much and how fast. That’s where the ocean comes into play.
How to use an ocean as a rain gauge
The main reason it’s hard to directly measure changes to the water cycle is that we don’t have enough measurements of rainfall and evaporation over our planet.
On a practical level, it’s very hard to set up permanent rain gauges or evaporation pans on the 70% of our planet’s surface covered in water. We also need measurements from decades past to assess long-term change.
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Scientists have discovered that the ocean is the best solution. The ocean can vary in its saltiness depending on where it is located. The Atlantic is on average saltier than the Pacific.
Why? Rain. Rain. The salt is removed from the water surface when it evaporates. This increases the salinity. This means we can use the better-recorded changes in the ocean’s salinity as a kind of rain gauge to detect water cycle changes.
Earlier research used this method to track changes to the salinity at the ocean’s surface. This research suggests that the water cycle is Increasingly dramatic.
The ocean is not able to stay still like a rain gauge. Currents, waves and circular eddy currents keep the ocean’s waters in constant motion. This uncertainty has led to questions about how accurate the link between salt and water cycle change is.
Continue reading:
Predicting droughts or floods: Why we are studying 19th-century ocean records
In response, we have developed new methods enabling us to precisely link changes in the ocean’s salinity to changes in the part of the water cycle moving fresh water from warmer to colder regions. Our estimates reveal how the wider water cycle is changing in the air, on land, and through our oceans.
What did we discover in our new study? Since 1970, Sydney Harbour’s fresh water equivalent has shifted from the tropics towards the cooler regions. That’s an estimated 46,000 to 77,000 cubic kilometres of water.
This is consistent in an increase of the water cycle by up to 7%. This could mean that there is up to 7% more rain in areas where it is more humid and 7% less rain (or greater evaporation) when it is in dry areas.
This is the upper end of several estimates. previous studiesThe results suggested that there was an increase of around 2-4%.
These findings indicate that potentially catastrophic changes to the water cycle could be coming faster than thought.
What would the future look like if there was a modified water cycle?
If the water cycle is becoming more intense at a faster pace, it will lead to more frequent extreme droughts or rainfall events.
Even if the world’s governments meet their target and keep global warming to a ceiling of 2℃, the IPCC predicts we would still endure extreme events An average of 14% moreComparative to a baseline period between 1850-1900
As the IPCC report last years made clear, some people and ecosystems will be more affected than others. The Mediterranean countries, south-west and South-east Australia, as well as central America, will all become dryer, while the monsoon areas and the poles will become more wetter (or even snowier).
If desalination is not implemented in dry areas affected by these water cycle changes we can expect to see serious threats to the viability cities.
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What should we do next? You already know the answer.
Many decades of scientific research have demonstrated the clear connection between greenhouse gas emissions (and rising global temperatures) and water cycle intensification.
This is yet another reason to work as quickly as possible towards net-zero emission in order to reduce the climate change damage.
The changes we observed in the water cycle were largely due older emissions, mainly from the mid-20th century and earlier. Since then, we have seen a dramatic increase in our emissions.
It is up to us to decide what the next step will be.
