Jun 20, 2013

Climate-change impact on the 20th-century relationship between the Southern Annular Mode and global mean temperature

Guojian Wang, Wenju Cai
Scientific Reports
  • Highlights that the interannual relationship between the global mean temperature (GMT) and the Southern Annular Mode (SAM) undergoes significant multidecadal fluctuations over the 20th century through their common forcing by El Niño-Southern Oscillation (ENSO) variability
  • States an El Niño increases GMT but also forces a negative SAM, leading to a GMT-SAM negative correlation
  • Finds that, since the late 1970s, the negative correlation collapses despite the strong ENSO-SAM relationship associated with the strong ENSO over the period
  • Shows that this collapse is triggered by a global warming-induced trend in GMT and the SAM: an increasing GMT trend is associated with an upward SAM trend
  • Results highlight a rare situation in which climate change signals emerge against an opposing property of interannual variability, underscoring the robustness of the recent climate change