Most pines are actually adapted to drier climates.

Also what do you mean 'tiny' - what are you comparing with? Pine needles are (in the great majority of species) larger than spruce or fir needles, despite the latter occurring in moister climates.

Resin

vmlb, I do not know how to do the math but I expect that total effective surface area (units x surface area) can be considerably more for needles than for regular leaves.
Then there is the question of shading out; 'broadleaves' shade out each other in a mature canopy more than needles do. My guess is that needles evolved from the need to conserve moisture (the leaf rolls up in times of moisture stress) and to maximise the light-trapping surface at the same time. Now, to parlay that into a PhD...

I thought the opposite was true: that surface area of pine needles would be more reduced compared to broadleaved plants and trees thus conserving moisture. Aren't needles basically a leaf's adaptation to drier environments and periodic droughts (which in cacti is reduced to spines)? Not sure regarding the length of pine needles (it does seem to be true that the subtropical conifer forests of the Southeast US is known for its long-leaf pine needles). I would guess that the smaller the leaf, the smaller the surface area (perhaps more important in colder or more arid regions). Interesting thread!

I was thinking of the needle as a cylinder and the lamina as a plane surface. The surface area of the former would be the length of the needle x pi x diameter. The area of the lamina is easier (depending on its shape). In each case one obtains an approximate result. My (gut)feeling is that if all the needles were 'unrolled', their surface area would be greater than the total area of the laminae on a broad-leaved tree. A reputable arborist once convinced us that only about one third of all the leaves on a broad-leaved tree receives enough light to photo-synthesize at any one time. This, and my observation of pine trees led to the conclusion that needles may be a more efficient model for photo-synthesis.
The flaw in my argument is that the laminate leaf may have "evolved" from the needle! I do not know.
Ah well, "one of the tragedies of life is the murder of a beautiful theory by a gang of brutal facts".

The link below is an abstract to a paper from Science Magazine about conifers vs. deciduous trees in the Pacific Northwest (United States), which I believe qualifies as a wet and cloudy climate.

In essence, the conifers have an advantage over deciduous trees in such a climate because they can photosynthesize year-round whereas deciduous trees cannot photosynthesize during the winter.

As far as the tiny size of your pine needles (compared to larger-sized pine needles elsewhere, I assume), I wonder whether the size helps prevent moisture accumulation in a place where moisture is really abundant. Here in the tropics, many deciduous plants have "drip tips" on their leaves to help drain off excess water. Just a thought.

And, by the way, I believe that indeed the fossil record for conifers predates that for deciduous trees.

Here is a link that might be useful: Science Magazine (1979)

Wouldn't the answer to the question be the fact of the existence of the "tiny" leaved conifer in the area versus those conifers that do not have "tiny" leaves?
But also the species present is indicative of condition that tend to favor their presence as opposed to other species.
The notion that the smaller size of leaf coupled with a larger plant that is evergreen could suggest that the need for photosynthesis is coupled to dessication where the smaller leaves with stomates on the underside of the leaf that is heavily cutinized and somewhat enfolded (curled on the edges) help retain water in the upperstory of the tree which is needed in the photosynthesis process. The wet cloudy areas are not 24/7 so but are commonly home to winds and other dessicating factors, summer heat, rapidly draining soil, etc. A closer look at the habitat where the "tiny" leaved trees are found can provide some correlation to why such trees are successful in such regions. My suspicion is that such trees are localized to exacting habitats that would prove more formdiable to trees without such adaptive traits.

Here is a link that might be useful: book on ecology of pines