6 8 4 ▁m ▁Ref uge ▁Cos mi ques , ▁ 3 6 1 3 ▁m ▁Ref uge ▁T ête ▁R ous se , ▁ 3 1 6 7 ▁m ▁Ref uge ▁Francesco ▁Gon ella , ▁ 3 0 7 1 ▁m ▁Ref uge ▁Gr ands ▁Mu lets , ▁ 3 0 5 0 ▁m ▁ ▁Imp act s ▁of ▁climate ▁change ▁ ▁Rec ent ▁temperature ▁r ises ▁and ▁heat w aves , ▁such ▁as ▁those ▁of ▁the ▁sum mers ▁of ▁ 2 0 1 5 ▁and ▁ 2 0 1 8 , ▁have ▁had ▁significant ▁impact s ▁on ▁many ▁clim bing ▁routes ▁across ▁the ▁Al ps , ▁including ▁those ▁on ▁Mont ▁Bl anc . ▁For ▁example , ▁in ▁ 2 0 1 5 , ▁the ▁Grand ▁Mu lets ▁route , ▁previously ▁popular ▁in ▁the ▁ 2 0 th ▁century , ▁was ▁blocked ▁by ▁virt ually ▁im pen et rable ▁cre vas se ▁fields , ▁and ▁the ▁G outer ▁H ut ▁was ▁closed ▁by ▁municipal ▁dec ree ▁for ▁some ▁days ▁because ▁of ▁very ▁high ▁rock fall ▁danger , ▁with ▁some ▁str and ed ▁clim bers ▁ev acu ated ▁by ▁hel ic opter . ▁ ▁In ▁ 2 0 1 6 ▁a ▁cre vas se ▁opened ▁at ▁high ▁alt itude , ▁also ▁indicating ▁previously ▁un ob ser ved ▁gla cial ▁movements . ▁ ▁The ▁new ▁cre vas se ▁forms ▁an ▁obst acle ▁to ▁be ▁scale d ▁by ▁clim bing ▁parties ▁on ▁the ▁final ▁part ▁of ▁the ▁it iner ary ▁to ▁the ▁top ▁shared ▁by