May 25, 2024

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Snow gives way to rain in the mountains. And this has all kinds of unexpected consequences

Snow gives way to rain in the mountains.  And this has all kinds of unexpected consequences

It actually makes sense: the earth is getting warmer and so the snow turns into rain, too oddly enough, especially in the mountains. The fact that rain makes skiing less enjoyable is not the only consequence, it also leads to more severe flooding and long-term water shortages.

Scientists user Rain and snow measurements from the 1950s and computer simulations predicted future climate. It showed that for every degree Celsius the Earth warms, more rainfall in the mountains increases by 15 percent.

Snow as a store of water
Heavy rains in the mountains cause much more problems than heavy snowfall. Think floods, landslides, and erosion. Even worse: Snow is in principle a very efficient water storage system, which means that groundwater, streams, and rivers are replenished in the spring and summer. It rains instantly, which leads to a shortage of water. “It’s not a show that is far from your bed that will only become reality in the future. The data shows us that this is already happening. We see this in the data of the past decades,” said lead researcher Mohamed Ambadi.

It’s harsher in the mountains
In the 2015 Paris Climate Agreement, it was already agreed that the Earth may not warm by more than 1.5°C in order to counteract the worst consequences of global warming. This limit has now almost been reached. This has major consequences for the amount of precipitation. “Every degree of warming is important, because it leads to a significant increase in extreme precipitation in the mountains,” Ambadi says. This increase in mountains is twice what the rest of the world experiences because warm air holds more water.

The researchers only studied the highest annual precipitation over six decades in the northern hemisphere. They found that as the altitude increased, the amount of precipitation increased exponentially. The greatest increase in precipitation is observed at an altitude of about 3000 meters. This applies, for example, to the American West, where the impact was very strong, but also to parts of the Appalachian Mountains. Another hotspot in Asia was the Himalayas. Also in the European Alps there is more rain and less snow.

Billions of people are affected
Ambadi says about a quarter of the Earth’s population lives so close to mountains that heavy rains and floods affect them. He warns that there will be more floods like the one in Pakistan last year that killed more than 1,700 people and submerged a third of the country.

A fellow UCLA climate scientist responds to the study and speaks of “serious implications”. “Scientists expect more precipitation due to higher temperatures, but the effect of heavy snowfall on flooding is less as it takes time to melt, and it is easier to observe a pack of snow to see what is happening,” Park Williams said. “But if the percentage that falls in the mountains decreases with less snow, the risk of flooding will increase rapidly,” he predicts.

crops and livestock
Hydrologist Charulika Varadharajan explains that the consequences are particularly severe in the western part of the United States. “This kind of heavy rain makes flooding worse. And then you have to wonder where that water is going.” She points to the flooding problems the western US has already faced this year in the wake of a series of atmospheric rivers — streams of moist air — and melting snow.

Of course, floods can also harm food production. For example, California authorities estimated that heavy rains in 1997 cost nearly $90 million in crop and livestock losses.

Groundwater is under pressure
But the long-term consequences are worse: the water supply will be strained. Normally, snow that falls in winter melts slowly in spring and summer. This will replenish groundwater that will be needed later when it becomes dry.

“It reduces your water supply in the future,” Varadharajan says. In the short term, a lot of water flows away, creating floods. There is much less snow, which means that groundwater is not replenishing enough and groundwater is ultimately important to keep the water cycle going.”

“These mountain water systems provide most of the streams, rivers, and canals, so any reduction in water supply is very important when it comes to water management,” she explains.

severe dehydration
Large parts of the western United States have been battling a massive drought for more than 20 years. During these periods, authorities like to keep the water levels in the tanks high, which they can do with large amounts of snow because it melts so slowly. But this, as explained earlier, does not work with heavy rains.

With rising temperatures leading to more precipitation, the researchers said, countries must choose between sharply reducing water use due to groundwater shortages or building expensive new reservoirs.

Both options are not desirable. It is therefore important to prevent the Earth from warming further, so that we can limit the damage to some extent.