I would start by reapplying the thermal paste. The paste that Apple issues is subpar and is applied very poorly at the factory. Try Artic Silver 5 thermal paste. My mac runs a 5C cooler since reapplying thermal paste. I would also check the processes your machine is running. Your machine should not reach 70C with just Safari open. Are you reporting these temps as Celsius or Fahrenheit? If its Fahrenheit then they are fine, if Celsius, then you have problems. I also recommend you download SMC Fan Control, and keep the fans running at higher RPM than Apple's default RPM's as they are actually too low for these machines. Apple does this for quieter operation, but the machines tend to run a little hotter.