"In the tropics at heights more than 10 miles above the surface, the prevailing winds alternate between strong easterlies and strong westerlies roughly every other year. This slow heartbeat in the tropical upper atmosphere, referred to as the quasibiennial oscillation (QBO), impacts the winds and chemical composition of the global atmosphere and even the climate at Earth's surface."
"The pulse of the QBO has weakened substantially at some altitudes over the last six decades, according to a new study by scientists at the International Pacific Research Center, University of Hawaii at Manoa, and the Japan Agency for Marine-Earth Science and Technology.
The decline in the strength of the QBO is consistent with computer model projections of how the upper atmosphere responds to global warming induced by increased greenhouse gas concentrations. The study appears in the May 23, 2013, online issue of Nature."