Jul 25, 2003

Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes

by
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
,
Science
  • 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