In July 2021, the Irish parliament (Oireachtas) enacted climate legislation [4] (hereafter 'the Act') which mandated the adoption of successive 5 year 'carbon budgets' (legally binding constraints on total domestic GHG emissions), structured into a rolling 15 year programme. Recommendations for the quantitative budget amounts in each period are first formulated by an independent statutory body, the Irish climate change advisory council (CCAC), and submitted for legal adoption (potentially with revision) by the full parliament. Once adopted, successive Governments are legally required to bring forward and implement policies and measures to ensure 'in so far as practicable' that total emissions over each period are held within the required budget limit. By default, any excess of emissions in a given period should be carried forward and subtracted from the budget for the immediately following period.

Most critically, the Act requires that the actors involved (CCAC, Government, Ministers) must discharge their prescribed functions '... in a manner ... that is consistent with ... the steps specified in Articles 2 and 4(1)' of the Paris Agreement [4] (s. 3(3)(a)(ii) as amended; emphasis added). This PA consistency requirement therefore encompasses the (rolling) process of adopting the quantitative budgets.

Accordingly, in formulating its recommendations for the first 15 year budget programme (covering 2021–2035, in three 5 year periods) the CCAC considered explicitly how to assess these for PA consistency. This is not specified in detail in the Act; so the CCAC itself formulated an explicit, quantitative Paris Test. The methodology of this Test, and the outcomes of applying it to their budget recommendations, were presented briefly in their published Technical Report on Carbon Budgets [5], and elaborated in a further advisory note [6]. A supporting spreadsheet was shared with the authors on request, and is publicly archived [7]. The outcome of the Test is shown in figure 1(a). The methodology is somewhat cumbersome, but will be summarised here as concisely as possible.