Senator Heinrich of New Mexico mentioned the declining snowpack in his home state during the senate’s recent all-night session about man-made climate change.
He was criticized in a comment at WUWT by Bill Parsons, who claimed that “Snow water Equivalent is up in 2014 between 20 – 30 % above the mean in nearly every NM drainage.” He even gave a link to some data to support his claim.
One of the lessons to be learned from Judith Curry is that when deniers give references to published papers or to actual data, claiming it supports their position, you damn well better look for yourself. Curry referred to half a dozen peer-reviewed papers to support her claim that Arctic temperatures in the 1930s may have been as high as they have been recently, but it turns out that none of the cited papers supported her claim. None. Bill Parsons linked to the update report on New Mexico snowpack to support his claim that NM snowpack is up in 2014, but it turns out that the update report says exactly the opposite. Opposite.
Even so, we’re far less interested in short-term events like the disturbingly low snowpack in New Mexico right now. We’re more interested in the trend, as a better indicator of whether or not changes are truly meaningful, and whether or not they may be a harbinger of worse to come. So, let’s look at trends in snowpack in New Mexico.
Daily data on SWE (snow water equivalent) in the snowpack can be obtained from SNOTEL. There are 26 SNOTEL stations in New Mexico, but only 13 of them have data since 1990 or earlier. Even that is not a very long time span, so any trend will have to be very strong in order to be detected. Let’s look anyway.
Here’s an example, the SWE at the Quemazon site:
It peaks each winter, then melts away each spring. But visually, it looks as though the peak amount has been declining. We can test that idea by noting the maximum value during each snow season, then testing whether or not there’s a significant trend. It turns out there is:
Annual maximum SWE has been declining at about 0.2 in. per year; over the 30+ years of record, the mean value has decreased by over 6 inches. In other words, it’s now only about half what it was in 1980. And that’s not just this year’s fluctuation — that’s the trend.
Lest anyone think you have to cherry-pick the Quemazon site to get such a result, you don’t. Of the 13 SNOTEL stations in New Mexico with data since 1990 or earlier, 10 show a statistically significant decline in snowpack while none show a statistically significant increase.
The snow is also melting out earlier in the year. I fit a smooth curve to the SWE data and determined, for each year, the time at which it was declining fastest — we can call this the “max melt day.” This too shows statistically significant decline at Quemazon, receding by 0.76 days/yr:
All told, maximum snowmelt at Quemazon is happening about 24 days earlier now than it was in 1980. Again, this is not just happening at Quemazon, it’s typical of the state of affairs in New Mexico.
Water is essential for all life. Changing the amount of water available, and shifting the timing at which water is available, is bound to have serious consequences for all living things, not just in New Mexico, but everywhere that man-made climate change is altering the hydrological cycle. In fact, changes to the hydrological cycle might just be the single most dangerous aspect of global warming.
One of the life forms most threatened by climate change, is the life form which has caused it to happen: humankind. We are also the only life form which can make the choice actually to do something about it. I say, let’s make that choice.