Sickly looking Gleditsia tree

Hello,

I moved into my current house just over 2 years ago, which has a lovely landscaped garden including a lot of mature trees and shrubs. Perhaps the best tree in there is the Gleditsia. I don't know for certain which type it is, but the leaves look similar to the sunburst honey locust (quite bright yellowy green in colour). It's approximately 10m in height.

The first year of living here, the Gleditsia looked lovely, but last year and this year the leaves have started growing in small clumps, but have stopped so that the tree is very sparse with sporadic tufts of leaves on the limbs of the tree. It's not that easy to describe, but I would say that the clumps of leaves are a maximum of 10cm in length and nowhere near fully grown.

I'm not really sure what to do with the tree...some of the branches have no leaves at all, but would it make any difference if I was to have these removed? The weather has been a bit unusual - very hot and dry last summer, very wet and warm this winter and again hot and dry recently - could this be the problem? Basically, I am worried that the tree is dying and I will need to remove it. Any ideas would be welcome. I'm fairly new to gardening and have no experience whatsoever with trees. I'm in Hampshire.

Thanks,

Nicola