If you've ever lived though the horrible pain of blood returning to your numb fingertips, or dropped an ice screw because your gloves were too bulky, then you understand the importance of having the right glove system for pursuing your outdoor fun.
All things being equal (fabrics, thickness, and insulation), mittens are warmer than gloves. Mitts trap body heat by keeping your fingers together and reducing evaporative heat loss. In frigid temperatures, a layered mitt system is the best choice for warmth. Layers dry faster than one heavily insulated piece, and let you swap out wet layers. However, gloves offer better grip and dexterity for fiddling with ice screws and ski bindings. Wearing a shell outer glove and a thin polypro or Windstopper® liner is a good compromise. Your hands will retain some warmth even when you have to remove your outer gloves or mitts.
Tip: In wet, cold conditions, carry a spare pair of gloves or mittens in the inside pocket of your jacket. This ensures you always have warm, dry handwear to put on when your fingers get really cold.
Synthetic materials can melt or burn if placed too close to a heat source, so keep wet gloves or mitts away from a hot stove or fire. If you’re tenting or burrowed in a snowcave, sticking gloves or mitts in your sleeping bag will help them dry.