B. D. Santer, M. F. Wehner, T. M. L. Wigley, R. Sausen, G. A. Meehl, K. E. Taylor, C. Ammann, J. Arblaster, W. M. Washington, J. S. Boyle, W. Brüggemann


Published date July 25, 2003

Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes

  • Observations indicate that the height of the tropopause—the boundary between the stratosphere and troposphere—has increased by several hundred meters since 1979
  • Comparable increases are evident in climate model experiments, which show that human-induced changes in ozone and well-mixed greenhouse gases account for ∼80% of the simulated rise in tropopause height over 1979–1999
  • Their primary contributions are through cooling of the stratosphere (caused by ozone) and warming of the troposphere (caused by well-mixed greenhouse gases)
  • Finds that a model-predicted fingerprint of tropopause height changes is statistically detectable in two different observational (“reanalysis”) data sets
  • Concludes that this positive detection result allows us to attribute overall tropopause height changes to a combination of anthropogenic and natural external forcings, with the anthropogenic component predominating