The Guardian reports that “Pledges … are likely to lead to less than 3C of global warming over the century, analysis of the data by the United Nations suggests.” This is simply wrong. The UN report linked to that sentence, does not mention 3C and states that no temperature evidence is possible in paragraph 40:
However, temperature levels by the end of the century strongly depend on assumptions on socioeconomic drivers, technology development and action undertaken by Parties beyond the time frames stated in their INDCs (e.g. beyond 2025 and 2030). Making such assumptions is beyond the scope of this report.
The real point here is that predicting 70 years of INDC effect (2030 – 2100) for INDCs that have not even been contemplated, is impossible, and arbitrary assumptions would be necessary. Wisely, the UN’s annalists do not engage in such baseless speculation.
Since the UN report does not speculate about temperature, where does the 3C number come from in the Guardian’s story? The answer is in the UN’s own press release, which does it’s best to put a positive spin on the report.