Maybe because the heat is evaporating water from your body and therefore the proportion of alcohol is higher in your blood.. This is pure guesswork but it sound logical.
yeah sounds quite plausable. I thought that perhaps the sun might cause you body to accelerate the processing of fluids, and as a result speed up absorbtion of alcohol. But again this is pure conjecture.
The rate of alcohol absoprtion is constant and not affected by heat (which is why scientists can predict how long you have to wait per unit of alcohol, before it's safe to drive a car again, to a precise time), I would imagine the "getting drunk quicker" sensation is caused by a) body warmth (feel-good factor?) b) increased evaporation of water from the body (sweating)
sorry, i meant not affected by heat in this sense - i guess if you warmed up your body internally (around the alimentary canal) it would increase absoprtion, but the sun will not do this - the outer skin will be warmed up (hence the sweating to counter-act this) but your body temperature remains constant (a change of only a few degrees in body temperature can be fatal)