Halliday & Matthiessen (2014: 465-6):
Clauses with which whose domain is either the whole of the primary clause or some part of it that is more than a nominal group (the paratactic and cohesive agnates being extended text references with it or this); e.g.
||| He talks down to people, || which automatically puts people’s backs up. |||
meaning ‘talking down to people automatically puts people’s backs up’, and so on. Here the sequence is always α ^ =β. The elaborating β-clause is often an ‘attributive relational’ one, with an Attribute such as no good, a serious loss, odd that provides an evaluation of the primary clause (this thus being one grammatical strategy for ‘appraising’ a proposition).