From the tables for a Boeing 767-300 with GE CF-80 turbofans
CLB 2 (reduced thrust climb power)
weight 160 tonnes
climbing for Fl 370
ISA +10 and cooler 24 mins, 151 nm
ISA + 15 27 mins, 177 nm
ISA + 20 32 mins, 218 nm
at ISA +10 and cooler, it can make FL 390, at ISA +15 it can only make FL 370.
As previously stated, temperature reduces climb performance.
