Reconciling opposing Walker circulation trends in observations and model projections
Natural processes have intensified Pacific trade winds, according to a major reanalysis of climate models and observations.
The Pacific Walker circulation (PWC) is caused by warm air rising over land around the western Pacific and descending over oceans to the east. Climate models predict the PWC will weaken as the sea surface warms, but this goes against observations, which reveal the PWC has strengthened since the 1980s.
A team that included researchers from the Institute for Basic Science in Korea used surface observations, satellite data and multiple climate models to compare how human activities and natural processes affect the PWC. They found that natural decadal variability is behind the PWC strengthening, temporarily overshadowing a longer-term PWC weakening that could be associated with human activity.
Although natural processes currently dominate, the imprint of human activities may emerge within the next few decades.
- Nature Climate Change 9, 405–412 (2019). doi: 10.1038/s41558-019-0446-4