I have been thinking about carbon budgets on and off since the Paris Agreement at COP21 last December.
By 'carbon budget' I mean "a finite amount of carbon that can be burnt before it becomes unlikely we can avoid more than two degrees of global warming". And I have been asking myself "where is New Zealand's carbon budget that is consistent with no more than two degrees Celsius of average global warming"?
There is a Canadian "2C"-consistent carbon budget. I read that Canadians Simon Donner and Kirsten Zickfield asked themselves similar questions in two blog posts Canadas contribution to meeting the Paris temperature targets and Can Canada live up to the promise of the Paris Agreement? The chart on the left shows three Canadian 'temperature' budgets/emission pathways under a share of emissions approach.
In short, Donner and Zickfield calculated several "2C"-consistent carbon budgets, based on a range of temperature goals, a range of probabilities of success, and a range of sharing principles used for allocating part of the global carbon budget to Canada. They wrapped that up in a short 3-page paper "Canada’s Contribution to meeting the temperature limits in the Paris Climate Agreement".
Simon Donner also wrote a more policy-oriented summary What do the temperature targets mean for Canada?
This is their summary table of budgets by temperature targets and probabilities.
Simon Donner's conclusion from Can Canada live up to the promise of the Paris Agreement is:
The analysis in our report suggests that the current Canadian target of a 30% reduction below 2005 levels by 2030 could be consistent with maintaining a likely chance (66%) of limiting warming to less than 2°C globally, but only if Canada is given a generous allocation of the world’s “remaining” future carbon budget (based on the present fraction of the world’s emissions). A target consistent with a likely (66%) chance of avoiding 1.5°C of warming globally is extremely limited regardless of the method of allocation. Even under a generous allocation to Canada, national net CO2 emissions would need to decline 90-99% below 2005 levels by 2030.
Simon Donner also notes that "The 1.5°C limit is at best unrealistic, at worst politically impossible.”
Simon Donner is also highly aware that 'sharing-on-current-emissions' unfairly favours developed highly carbon-intensive OECD countries like Canada (or New Zealand) over the developing countries with much lower greenhouse gas emissions per capita.
Allocating the remaining carbon budget based on present-day emissions places an unfair burden on developing and rapidly industrializing countries that historically have had low per-capita emissions. Despite being far less responsible for climate change to date, and currently having low per-capita emissions, countries like India would essentially be asked to bear an equal part of future mitigation efforts.
Good work Canada! But where the bloody hell is New Zealand's 2C consistent carbon budget?