Scientists have yet to fully explain the recent slowdown in air-temperature increases. Although cool surface waters in the eastern Pacific Ocean have been identified as a key component of this feature, it has so far been unclear how this occurs. An Article published online in Nature Climate Change this week investigates how strengthened Pacific trade winds can account for 0.1-0.2 °C cooling - much of the temperature slowdown - through increased subsurface ocean heat uptake.
Matthew England and co-workers use observations and climate models to investigate the impact of increased trade winds on climate. They show that when the model is forced by the irregularly strong winds, the sea surface response matches observed trends. The shallow ocean circulation loops are sped up by the intensified winds, causing increased equatorial upwelling of cool waters and the subduction of warm water, or heat drawdown, to the subsurface layer. They find that around 80% of the surface temperature cooling occurred after 2000, indicating that wind acceleration is a key contributor to the slowdown in warming.
These findings suggest that if the stronger trade winds continue, the slowdown in warming will persist, but if they lessen there will be a return to rapid warming.