When I lived in the Caribbean my cat went missing for 3 weeks. Then I was walking my dog one day and heard a cat meowing. I was somewhat close to my house at the time so thought that it could be my cat.I started looking for the source of the meow. Finally I realize it's coming from the top of a palm tree 60 feet above my head. There was no way I could climb the tree so I headed down the road in search of a local who climbs trees for coconuts.

I find such a local at the bar and offer him 20EC to climb up and get my cat down. He agrees and we head back to the palm tree. He climbs the tree in about 10 seconds, unbelievable, then asks me when he's up there if the cat is going to scratch him. I proceed to tell him how to scruff a cat so he wont likely get scratched. He grabs my cat successfully but then decides that he might as well get some coconuts while he's up there. He starts roughly shaking the palm tree to get the coconuts which causes my cat to start spaz out...obviously. He then starts to slide down the tree but my cat is struggling and he is afraid to get scratched so drops my cat from about 15 feet from the ground. Of course now my cat just hits the ground and bolts as fast as he can away into some brush and out of site. I pay the man his 20ec even though he was too much of a puss to hold onto the cat.
What's ironic is the name of local that helped me. It was "Scratch"

So luckily my cat came home within another week, skin and bones, luckily no fatty liver syndrome. What's unfortunate is that 8 months later a roommate of mine would accidentally let my cat out of the house. He never came back that time. Some cats you just can't contain indoors I guess.

Oh and yes, cats if they know how can climb down trees. As P-dub said, they go down rear first since their claws are curved to do so. My cat was just too scared to try.