Apple has issued a SMC Firmware update for the MacBook (13″).
Apple says the SMC Firmware Update adjusts fan behavior in the MacBook. After this update has completed successfully, your SMC Version will be: 1.4f10.
The updater application will be installed in the /Applications/Utilities folder. Please follow the instructions in the updater application to complete the update process.
MacBook (13″) SMC Firmware update is available as a 420 KB standalone download.