In this SPM, IPCC AR5's 'carbon-budgeting' has 3 results each with 3 'probability-levels' for keeping within the '2 degrees Celsius' limit agreed at COP-15 in Copenhagen in 2009

The: -

First result effectively says, ‘halve the UKCA’.

Second result says, ‘reduce UKCA by up to a third.’

Third result [50% odds] effectively says, 'the UKCA is just fine.'

Using CBAT it is straightforward relating these results to the UKMO's UK Climate Act

Set on-screen UKCA [UK Climate Act] toggle-switch to 'ON' and use slider - also see below.
The emissions-budget [path-integral] of 395 Gt C 2010 - 2100 [in yellow] is the carbon-budget in the UKCA.

Despite these omissions,
the UKMO will perhaps see this as a vindication of the UK Climate Act. On the other hand it could be seen as vindicating the position of those like Jim Hansen who told the UK Environmental Audit Committee Enquiry into the UKCA recently that it is "too weak".

When Domain Two is fully operational, it will look like this: -

. . . where both the: -

Vertical Slider ['y' axis] for Domain One and the

Horzontal Slider ['x' axis] for Domain Two and the

Table of values for Domain Two shown in the image above

. . . will be adjusting to read any Domain One/Domain Two combination chosen by the user.
That means that for any relevant rate of Contraction with any rate of Convergence arising . . .

. . . . CBAT will calculate instantly and show from any of the: -

Three Carbon Budgets, [three buttons LOW, MEDIUM, HIGH, top right] multiplied by

80 positions each [from +40 to -40 - VERTICAL SLIDER] multiplied by

Any convergence start-date [2010-2110 - HORIZONTAL SLIDER] multiplied by

Any convergence end-date [2010-2110 or 100 years] [HORIZONTAL SLIDER]

. . . giving 2.4 million 'C&C' Carbon-Budget options, where 'Contraction' and 'Convergence' totals 'commute' [are the same].

This means in turn that the 'Budget-Total-Clock' on Vertical Slider and the 'Budget-Table-Total' will always show the same quantity of tonnes of carbon in the same path-integrals [shape and weight of budgets in Gt C], no matter which user-positions the SLIDERS are pushed to.

Basically this establishes that the 'numeraire' [unit of measurement] is the tonne of carbon, before it embraces the derivative dollars-per-tonne ['carbon-pricing'] arising in Domains Three and Four.