Ramifications of dwindling snowpack

Paris – The amount of snow that stays on the ground is rapidly dwindling due to human-caused climate change, threatening the water supply of hundreds of millions of people, researchers warned on Wednesday.

Global warming – which hits high mountain areas especially hard – has already reduced snowpack affecting up to 80% of the northern hemisphere’s population, a trend that is set to continue, scientists reported in the journal, Nature.

Accumulated snow is a naturally stored resource that becomes a vital reserve of fresh water as it melts in spring.

But the impact of a warming world on snowpack is deceptively hard to measure due to natural year-to-year variability, and the complex interplay of temperature and precipitation.

That is why even as temperatures rise, some regions are seeing more snow while others are seeing less.

Researchers warn some populations reliant on melting snowpack for water supply should prepare for a future without snow.

In the new study, Dartmouth University researchers sifted through four decades of precipitation and snowpack data across the northern hemisphere in March, when spring thaw begins to turn snow into water.

Building on the observational data, the team used climate models to measure the impact of changes in snowpack, with and without human influence.

Some 80% of snowpack, they found, is in regions cold enough to be resilient to rising temperatures, which has seen earth’s surface warm on average 1.2oC since the 19th century.

But the other 20% occurs in regions reaching a temperature threshold scientists called the “snow-loss cliff”, where each additional degree of warming above -8oC depletes a larger percentage of winter snow.

The southwestern and northeastern US, along with central and eastern Europe have seen snowpack declines between 10% and 20% per decade since the 1980s.

Four of five people in the northern hemisphere live in these regions of “tremendous snow vulnerability”, Justin Mankin, associate professor of geography and study author, said.

River basins, for example, along the upper Mississippi in the US and the Danube in Europe – home to 84 and 92 million people respectively – have seen a 30% and 40% decline in spring water due to snowpack loss.

Repercussions of snow loss extend to winter-dependent economies, impacting sectors such as tourism and skiing.

Mankin suggested a transition from snow to rain could also harm ecosystem health, encourage the spread of pests and render forests more susceptible to drought-induced wildfires. –