A method for operating a gas turbine below the nominal power includes: determining a lower power threshold value of the gas turbine which causes the gas turbine to leave a CO-emission-compliant partial load range of the gas turbine; providing a specified threshold value for output gas turbine power, wherein the specified threshold value is less than the nominal power of the gas turbine; and operating the gas turbine at an output gas turbine power above the specified threshold value at a constant exhaust gas temperature, wherein the inlet guide blades of a compressor of the gas turbine are closed further in order to reduce the output gas turbine power. A sufficiently large valve is selected for the specified threshold value so that increases of the primary zone temperature, combustion temperature, and exhaust temperature extend over a CO-emission-compliant partial load range of the gas turbine that is as large as possible.