When I was writing my guidebook I did an extensive analysis of weather data for the Wind River Mountains. I found that the climate HAS changed if you use the last 10 years vs the last 30 years. In fact, there is significantly measureable melting of the glaciers. However the change is small with respect to the actual gear I would take. Honestly, a 5 degree change would not impact what I pack. The last 10 years has been warmer on the average with less early season snow. The greater impact is when the trailheads become snow-free and this DOES impact WHEN I plan my trips.

As for what I pack, I pay a lot more attention to the NWS short-term forecasts. There is so much variation in 50 years of weather records that I think you would really over-pack if you used the historical lows.

When I moved to California and started backpacking in the Sierra, at first I just took the same stuff I used in the Wind Rivers and that was too much, so over the years I have cut back to gear rated for more moderate temperatures. It was difficult to do this because I really had a "Rocky Mountain" mindset. My shoulder season Sierra gear is much like my mid-season northern Rocky Mountain Gear.