I have read that in the past, the British Isles had a warm tropical climate, but I can't find more detailed information. I would like to know how the high latitude would have affected yearly cycles. Currently in the tropics seasons are more related to changes in rainfall, because day-lenght doesn't change much over a year, but in temperate zones seasons are related to day length and temperature.

How would a tropical climate be affected by changing day length? Would the winters have been colder than the summers? Would there be a massive amount of plant growth during the summer, and next to nothing in the limited daylight of winter? Could you point me towards resources which could give me more details?

There were several periods of warmer climate, the last one is about 1000 yrs ago and called the 'medieval warm period'.

Another period is in the middle Pliocene (ca. 3 Million Years Ago) when it was generally warmer than present, particularly at middle to high latitudes. It has been suggested that this period may represent an analogue for future climate change. Mechanisms that have been proposed to account for this warming are enhanced thermohaline circulation and/or greater concentrations of CO2 in the atmosphere. In the European and Mediterranean region the climate might have been warmer by 5 °C, wetter (by 400-1000 mm/yr), and less seasonal than present.

Some remarlable plant fossils were found along the British cliffs e.g. in the Bournemouth cliffs (which are notable for sands and clays of Eocene age). The fossil leaves seem to indicate that in Eocene times there was here an unusually warm environment even thought the palaeolatitude would normally suggest temperate rather tropical conditions .

Probably the best link about the different periods is this one here: http://www.awi-bremerhaven.de/Modelling … riods.html

The question concerning the latitude is a quite different. What is now the British Isles moved due to plate tectonics over the globe. Therefore it was once closer to the equator and the climate was therefore comparable to the tropics today.

For the determing factors of tropical climate this site here gives some good background: http://www.ace.mmu.ac.uk/eae/Climate/Ol … imate.html