There is an article in the March 23 2010 issue of EOS
Zahn et al, 2010: Investigating the Global Impacts of the Agulhas Current. Eos, Vol. 91, No. 12, 23 March 2010. pages 109-110 [subscription required]
which illustrates yet again how regional climate effects can have global climate consequences.
The article starts with the text
“The Agulhas Current is the major western boundary current of the Southern Hemisphere [Lutjeharms, 2006] and a key component of the global ocean “conveyor” circulation controlling the return flow to the Atlantic Ocean [Gordon, 1986]. As such, it is increasingly recognized as a key player in ocean thermohaline circulation, with importance for the meridional overturning circulation (MOC) of the Atlantic Ocean.”
The article includes the statements
“New research is giving tantalizing suggestions that variations of the Agulhas leakage south of Africa are key players in global climate developments, and hence understanding their operation is important to climate projections.”
“The Agulhas Current influences climate in two ways. First, the warm tropical waters carried by the current stimulate convection of the overlying atmosphere with direct consequences for regional weather systems [Reason and Jagadheesha, 2005]. Second, the shedding of Agulhas rings south of Africa causes buoyancy anomalies in the South Atlantic that stimulate dynamical responses with potential consequences for the Atlantic MOC…”
On my weblog, I have frequently emphasized that the focus on the global average surface temperature trend is a grossly inadequate metric to monitor and describe climate change (e.g. see). This new paper further illustrates why a regional climate focus is essential.