Given a sentence and two mentions from the text (arguments), indicate a phrase (a verb or noun phrase) that describes the relationship between the provided arguments.

Sentence: 'The only significant reduction in carbon emissions since Canada signed the Kyoto Protocol has come since the Pickering nuclear plant brought a number of its units back on-line .', Argument/Subject 1: 'canada', Argument/Subject 2: 'kyoto protocol'
sign