Prof Allen says New Zealand's decisions later this year on a Zero Carbon Act could help frame the global climate agenda for decades to come.
Passing this legislation could make us one of the first advanced economies in the world to commit itself to nett zero emissions, and the first with such a large agricultural sector.
But, like any pioneer entering uncharted waters, there are challenges to be overcome as well as first-mover opportunities.
We should be clear about our priorities.
"The big picture could not be simpler," he says. "Carbon dioxide emissions accumulate in the climate system, like lead in the bloodstream. Stopping global warming requires nett carbon dioxide emissions to be reduced to zero, permanently.
"Decisions about other warming gases, like methane, could make a few tenths of a degree difference to the peak warming level reached, but they don't change that all-important fact. And a permanent nett zero world cannot rely indefinitely on forestry to offset continued use of fossil fuels in sectors like aviation."
The methane burped by our livestock is short-lived in the atmosphere, whereas the impacts of carbon dioxide carry on for hundreds of years. Analysis by scientists such as Prof Allen, and Victoria University of Wellington's Dr Dave Frame, show that while methane isn't a gas we can just ignore, so long as emissions are only 99.7 per cent of what they were the previous year then they will not contribute to any additional warming effect. So this would equate to needing something like a 10 per cent reduction in methane by 2050, a target New Zealand farmers can commit to.
Prof Allen contends that farmers who are not contributing to ongoing global warming should not be penalised as if they are. Perhaps more controversially, in view of the debate in Taranaki, he says recipients of off-shore oil exploration permits would need to explain what will happen to the carbon dioxide that their oil will generate.
It will be worth listening to what he says in Auckland and Whangarei.
