More than 50 years ago, Bill Barr began measuring snowfall outside his remote home in the Rockies of Colorado. Twice every winter’s day he has been measuring the snow depth and weighing it to calculate its water content, then logging the information. He does this work purely for his own interest, without pay and until fairly recently he remained unrecognised.
Now 73, his records reveal how the snow is arriving later, disappearing earlier and the snowpack is becoming less substantial. That snowpack acts a solid reservoir of water, and as it dwindles so the melting of the snow over spring and summer is leading to shortages of water for millions of people in drought-stricken lands in the southwestern United States.
Barr’s measurements have proved priceless because automated snow measurements are unreliable and satellite measurements are simply estimates that need to be calibrated with ground measurements. Barr’s measurements give a “ground truth” to gauge the accuracy of satellite measurements, and when news of his work reached scientists they used his data in their research, especially studies of the changing mountain climate and its impact on water supply.
Barr is one example of “citizen scientists” who have contributed decades of observations crucial to studying how the climate is changing. In the Scottish Highlands, Adam Watson was a biologist who studied wildlife in the mountains, but became fascinated with snow patches that survived all summer, sheltered in mountain hollows. Out of curiosity he detailed these patches on Ben Macdui every June from 1938 to 2011. His surveys, and research on historical documents going back centuries, revealed a marked decline in snow cover from 1986 onwards.
Watson died in 2019, but his work on the snow patches has been carried on by the amateur scientist Iain Cameron, who reports on the snow patches in the science journal Weather. His work has revealed even more dramatic declines in snow over recent years, with the longest surviving snow patch melting five times since 2017. What was once considered near permanent snow cover in the Highlands has been reduced to scraps of snow that often disappear over the summer.
