Mean summer (June, July, August) temperatures from the D1 Meteorological Station (3739 m.a.s.l.) on Niwot Ridge, CO, USA, showing a strong warming trend in the time between the orthophotos (1972, 2008). The linear regression line (red, p < 0.001, R2 = 0.31) as well as a loess function (blue), with 95% confidence intervals (shaded) are shown.