If you read the progression of references below, it looks like the global average temperature goal is getting more definite around a lower temperature goal.
The Copenhagen Accord 2009:
To achieve the ultimate objective of the Convention to stabilize greenhouse gas concentration in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system, we shall, recognizing the scientific view that the increase in global temperature should be below 2 degrees Celsius, on the basis of equity and in the context of sustainable development, enhance our long-term cooperative action to combat climate change.
The IPCC Fourth Assessment Report:
with a view to reduce global emissions so as to hold the increase in global temperature below 2 degrees Celsius…
Cancun, COP16 in 2010:
to reduce global greenhouse gas (GHG) emissions to keep the global average temperature below 2°C above pre-industrial levels
Paris – negotiating text 25 Feb 2015:
hold the increase in global average temperature below 2 °C / 1.5 °C above pre-industrial levels
Paris – Co-chairs informal working paper 5 October 2015:
to hold the increase in the global average temperature [below 2 °C][below 2 or 1.5 °C] above pre-industrial levels, without prejudice to adjusting the global long-term temperature goal on the basis of the best available scientific knowledge.
Paris – negotiating text 5 December 2015:
To hold the increase in the global average temperature [below 1.5 °C] [or] [well below 2 °C] above preindustrial levels;