5.11 How do the UK and Scottish Climate Change Acts compare with a 1000 GtCO₂ budget for 2000–2050?

The UK's Climate Change Act was passed in 2008. The Climate Change (Scotland) Act received Royal Assent in August 2009. Both are rooted in the analysis and recommendations of the UK CCC.

Broadly, they both require reductions of at least 80% of greenhouse gases by 2050 compared with 1990 levels, with an interim target of reductions by at least 34% or at least 42% in 2020. The increase in the 2020 target depends on success in international negotiations during 2009 and a consequent increase in the EU carbon reduction target from 20% to 30% in 2020.

The UK CCC notes the importance of cumulative emissions and estimates the global budgets associated with the recommended targets (now adopted) to be around 2500 GtCO₂-eq, of which they estimate about 780 GtCO₂-eq has already been used (since 1990). They further emphasise the importance of continued reductions out to 2100.

The overall budget for 2000–2050 recommended by the UK CCC, therefore, is around 2200 GtCO₂-eq (subtracting global emissions between 2000 and 2007 of about 300 GtCO₂-eq from the 780 GtCO₂-eq used since 1990 – assuming that emissions rose from around 40–48 GtCO₂-eq from 2000–2007, based on figures in the report). The 1000 GtCO₂ budget is equivalent to around 1500 GtCO₂-eq for a 75% chance of avoiding 2°C (a 2000 GtCO₂-eq budget gives a 50/50 chance of avoiding 2°C).

So, UK and Scottish targets would need to be higher and the emission reduction pathways would need to be steeper to maintain a better-than-evens chance of avoiding 2°C, consistent with the answer to ‘How do you work out a carbon budget?’ (Section 5.10).

• The report ‘Part I: the 2050 target’ from the UK CCC sets out the rationale for recommended UK emission reduction targets, including associated global budgets.