Posted 13 December 2015
Below is a link to the text of the final agreement at COP21 UN conference in Paris. Of interest is this opt-out clause: "Article 28 1. At any time after three years from the date on which this Agreement has entered into force for a Party, that Party may withdraw from this Agreement by giving written notification to the Depositary. 2. Any such withdrawal shall take effect upon expiry of one year from the date of receipt by the Depositary of the notification of withdrawal, or on such later date as may be specified in the notification of withdrawal. 3. Any Party that withdraws from the Convention shall be considered as also having withdrawn from this Agreement."
Read pdf file here
But GWPF says agreement "non-binding & toothless" here