Air Carrier Captain reported GPS jamming from 50 NM west until 250 NM west of TVL. The Captain states the aircraft eventually left the jamming area. In addition the Captain reported requesting a change to the QRH procedures in order to help overcome the unwanted situation. The request was sent to the Flight Operations Department.

Narrative

Flying Aircraft X TLV-ZZZ. During climbout we got ADS-B L EICAS warning. I ran the Non-Normal checklist which had us switch the Transponder to R. Immediately got ADS-B R EICAS. Followed by GPS EICAS. I selected the GPS Interference Supplementary Procedure. Reading through the procedure; it is divided into phase of flight. First DESCENT; then PREFLIGHT; and finally CLIMB. Since I was in the CLIMB phase of flight; I went straight to that section of the procedure. Climbing through FL250 it directs us to select GPS NAV - ON then RAD NAV INHIBIT - ON. This is actually the exact opposite of what we want to do while climbing with GPS Jamming. I had to improvise the procedure by using the DESCENT section (despite climbing) which directs us to correctly select GPS NAV - OFF and RAD NAV INHIBIT - ON.This Supplementary procedure should be assessed by the Fleet and rewritten so that it is usable when needed.The GPS was jammed by the Country X until we were approximately 250 miles west of TLV. At that time; GPS worked normally and the flight proceeded uneventfully.