The families made the difficult decision on Saturday to call off the search after air sweeps of the mountain turned up no sign of the two, who took off to climb Ogre II on August 21.
Family and friends originally launched the search on August 28, when Dempster and Adamson didn’t return.
Global Rescue organized the air search, but CEO Dan Richards said bad weather stalled the efforts for days.
Richards said ground search crews were not able to ascend the mountain because of an extremely unstable snow pack.
Finally on Saturday, the skies cleared and a Pakistani government helicopter took off on two separate sorties, or missions.
"The first one was a comprehensive search of the route that we expected the climbers to be on, and we went up and down and traversed across the mountain, and we found unfortunately no signs of them" Richards explained. "Then, we launched a second sortie, and that sortie actually went as high as within about 200 meters of the peak of Ogre II."
He said the helicopter also flew around the circumference of the mountain, and in both sorties, experienced climbers joined the helicopter crew on board to help look from the air.
Richards said they found no trace, no equipment, nothing that would point to a sign of Dempster or Adamson. He said the crew spotted avalanche activity, though it was difficult to tell whether the avalanches occurred during Dempster and Adamson’s ascent up Ogre II.
"We think at this time, that the highest likelihood is that there might have been an avalanche. And if there was an avalanche, then they very easily could have been submerged under the snow," Richards said. "Then with the subsequent snowfall, because of the bad weather that ensued for several days afterwards, there would likely be really no trace."
After that, he said the family decided it was best to call off the helicopter search. Richards said at this point, the likelihood of finding either of them alive is extraordinarily low. From his understanding, Richards said the ground crew is also halting the search, and is set to leave base camp soon.
"The one solace, I think, that the family can take is that these guys were out there doing what it is that they loved, and they're at rest in a region where they were doing something that they loved," Richards said.
The climbing community has been expressing their sorrow on social media.
Sandy area company Liberty Mountain posted on Thursday it had received a post card in the mail from Dempster. It featured a picture of the Karakoram mountains, and the last sentence read, “Catch up with you in Sept.!”
Richards did say that crews planned to leave behind a tent, supplies and communication equipment at the base camp of Ogre II, in the outside chance that one or both of the climbers is somehow still alive, and will make it out.