Clause 60.1 (or more specifically 60.1(1)) does not give you the right to instruct a change to the scope; it only states what happens when you do instruct such a change. Clause 14.3 gives you the right to change the scope, and that right is not limited in any way.
Therefore, you already had the right to change the scope to reduce the impact of the works on climate change if you or the client wishes. As with all other instructed changes to the scope, that will usually cause a compensation event to occur, see clause 60.1(1), and it will be dealt with in the same way as any other compensation event. In addition, if you want to know what the probable costs in terms of time and money will be for the change, you can utilise the provisions for proposed instructions contained in clause 65.
You are correct that clause X29.11 allows the contractor to propose a change in the scope to reduce the effect of the works on climate change. Note that the contract already allows the contractor to propose changes to the scope for other reasons, see clauses 16.1 and 16.2. Clause X29 is just a sensible extension of its ability to do so.