If you are at latitude 30*N, then by boat go to latitude 45*S, warmer or cooler region?" Why? Science?

In general it would be cooler, if only because the higher the latitude, the colder it tends to be since you are further during most of the year from the heating influence of the sun's direct rays. There are many other influences possible, but considering you're on the ocean, altitude can't be one of them in this case. Given no other information, mine is the correct answer.

You will be in a colder region, assuming that you are on an equinox day (sun is distributed evenly north/south). The reason you are in a colder region is because you are closer to the South Pole at 45 S, than you are close to the North pole at 30 N. Lower latitudes mean you are closer to the Equator, which is considered the hottest region of the world due to receiving the most sun. Higher latitudes mean you are closer to one of the Poles, which are the coldest parts of the world due to receiving the least sun.

30 n is tropical water region and so is 45s.

summers in north of equator are winters in the south, so these days 30n is cool while 45s would be warm.

also the position with respect to the meridian (e or west of 0degrees vertical) also governs if 30n or 45s would be cold or warm.

ps more ice masses in the south nearrer to 45s so generally 45s would be cooler

Cooler because the sun ray incidence Angle will be less than that of 30*N

http://en.wikipedia.org/wiki/List_of_cities_by_lat...