From Hansard:
Lord Donoughue: To ask Her Majesty’s Government by how many degrees they forecast global temperatures will be reduced, compared with a baseline case of what would happen without intervention, as a direct result of the emissions reductions mandated by the Climate Change Act 2008 by (1) 2050, and (2) 2100.
Baroness Verma: The United Kingdom's 80% emissions reduction target for 2050 is derived from estimates of the UK's share of the global effort needed in order to keep the increase in global average temperature to below 2 Degrees Celsius above pre-industrial levels. The UK does not have emissions reduction target set for 2100. The UK's emissions reductions alone would result in a small but crucial proportion of total global emissions reductions, as all countries need to contribute to achieving the 2 degree goal. It is vital that we show leadership and demonstrate that the shift to a low carbon model is achievable in order to influence other major emitters to take action.
The beauty of asking a question to which the answer is a number is that this kind of evasion is patently obvious. No doubt the question will be put again in due course.