First, a generic wind stress definition is in order.
Ocean surface roughness (i.e., turbulence) as measured by satellite technology, is referred to as 'wind stress' in climate models. In plain-speak, it is sea surface turbulence, obviously driven by wind speed and direction, in addition to being impacted by atmospheric density/pressures, sea surface temperatures, sea buoyancy and currents. Wind stress affects the air-sea heat exchange, as well as the mixing of carbon/heat stored in the deeper parts of oceans. Wind stress also has impacts on cloud cover, ocean current circulations and sea ice movement/volumes.
In essence, wind stress is a powerful and critical elemental influence on the world's climate. Thus, to forecast future climate conditions with any sort of accuracy, it is absolutely necessary to be able to accurately simulate wind stress.
As this latest peer reviewed scientific research reveals, all climate "experts" and the IPCC's climate models remain unable to accurately simulate wind stress on their massively expensive, sophisticated, complex computer models.
(Hmmm...did we mention climate models can't predict squat yet?)
Note: Above wind stress map enlargement