Modeled and Observed Stratospheric Temperature Changes: Implications for Fingerprint Studies

Changes in the vertical structure of atmospheric temperature are an important “fingerprint” of human effects on global climate. These changes are mainly driven by human-caused increases in atmospheric levels of CO2 and other well-mixed greenhouse gases. Key features of this fingerprint are warming of the troposphere, the lowest layer of the atmosphere, and cooling of the stratosphere, the layer above the troposphere. Cooling in the lower stratosphere (from roughly 15–20 km above Earth's surface) also arises from human-caused depletion of stratospheric ozone. While lower stratospheric cooling diminished in the 21st century, largely due to the emerging “healing” of stratospheric ozone levels after the Montreal Protocol, strong cooling of the mid- to upper stratosphere continued unabated. Satellite observations of this distinctive fingerprint are in accord with current state-of-the-art climate model estimates of human-caused temperature changes. The claim to the contrary made in the recent US Department of Energy review of climate science is factually incorrect.