Guest Post by Willis Eschenbach
The abstract of a new study from Science Magazine entitled “The Unusual Nature of Recent Snowpack Declines in the North American Cordillera”, Gregory Pederson et al., 9 June 2011 (paywalled, all data available here, figures here, overview here) opens by saying:
In western North America snowpack has declined in recent decades, and further losses are projected through the 21st century.
The abstract goes on to describe their findings:
Over the past millennium, late-20th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains, and in their north-south synchrony across the cordillera.
Figure 1. The future of skiing in the North American Rocky Mountains? Eric Lon, rock skiing
And the culprit, the Grinch stealing the white Christmas? Why, us fools who ate the fossil-fuel-fertilized apple and got ourselves thrown out of climate Eden, of course. Or in their words,
Both the snowpack declines and their synchrony result from unparalleled springtime warming due to positive reinforcement of the anthropogenic warming by decadal variability.
First, kudos to the authors for archiving their data and meta-data at the time of the publication of their work. This is an excellent example of providing the necessary information so that others can investigate their results.
Now, about those results …
I’ve mentioned that the first thing that I want to look at is the actual data. While they didn’t exactly provide that, they did provide the standardized data for the two regions that they studied, the “Northern Cordillera” and the “Southern Cordillera”. (To “standardize” data, it is adjusted so that the average is zero and the standard deviation is 1. This allows the comparison of dissimilar datasets.)
In this case, the data that they used was the April snow water equivalent, or SWE. The SWE is how many inches of water you get when you melt a column of snow. Use of the SWE avoids the problem that different kinds of snow have different thicknesses, as some are fluffy and light and others are wet and heavy. Figures 2 and 3 show their standardized SWE results.
Figure 2. Pederson 2011 individual and average April snow water equivalent (SWE) for the northern part of the Rocky Mountains. Data Source (Excel, worksheet “HUC6 Observed SWE”)
Figure 3. Pederson 2011 individual and average April snow water equivalent (SWE) for the southern part of the Rocky Mountains. Data Source (Excel, worksheet “HUC6 Observed SWE”)
Well … I looked at that and I thought “western North American snowpack has declined in recent decades”? Really? I thought “unprecedented reductions”?!?
I thought, well, maybe we’re not talking about the same thing. Maybe the actual snowpack records show something different, something unprecedented, some big decline in recent decades. So I went to the NRCS SNOTEL records and got the data for Colorado. I averaged it by year and month, and calculated the average April Colorado SWE data to compare with the Pederson 2011 Southern Cordillera data (where Colorado is located.) Figure 4 shows how well they match the Pederson data.
Figure 4. Comparison of the SWE records for Colorado (SNOTEL figures) and the Southern Cordillera (Pedersen 2011 figures).
So we are definitely talking about the same thing …
OK, I thought, that’s it. I’m blowing the whistle. According to both their figures and the SNOTEL figures, there’s no “late twentieth century decline” in snowfall in either the Northern or the Southern Cordillera. That’s hype, and their own data says so. This is particularly true when the more recent data is included (blue line). For unspecified reasons their data ends in 2006. Since then, the snowfalls have generally increased.
Once again, the AGW proponents haven’t even begun to show that anything out of the usual is occurring. Instead they’ve jumped directly to explaining the cause of something that they haven’t yet shown to exist.
In other words, another day, another alarmist exaggeration. Don’t you love how well peer review is working at Science Magazine for climate articles? Oh, well, I suppose the good news is that it results in a target-rich environment, makes my job easy … but the bad news is that we all lose when this kind of alarmism is published as though it were science.
PS – There’s other issues in this. They say that they can reconstruct historical snowpack from tree rings … hmmmm, where have I heard something like that before? And if they can do such reconstructions, their results don’t show an unprecedented decline in the late 20th century. Instead, they show a decline starting about 1880 or so, and only in the more northern regions.
But that’s all raw meat for someone else to chew on … I’ve seen enough of this study.