Net zero means net negative?

Will look forward to reading the Climate Commission's latest report. This bit, from Jim Rose over at Carbon News, is a bit concerning:

The world is not on track to meet the Paris Agreement’s 1.5 degrees target, the commission says, and New Zealand is likely to continue contributing to global warming after 2050.

That’s because the country’s current target doesn’t require biogenic methane to reach net zero by 2050 and has no requirement for long-lived greenhouse gases to be reduced beyond net zero.

“This means that it is possible to achieve the 2050 target and still have net positive emissions of 700–1,000 KtCH4 – and the associated contribution to global warming – in 2051 and every year after,” the commission says.

The commission says that when New Zealand’s net zero target was set in 2019 it was seen as ambitious but that’s no longer the case.

I had always understood Net Zero 2050 to mean that the unbacked NZU issued before 2050 would represent the sum total of net emissions from the covered sector from now until forever. An NZU might be redeemed after 2050; it's the quantum of unbacked units issued through 2050 that determines the amount of net emissions overall. 

If the Commission is shifting to a view that Net Zero implies undoing the emissions that have obtained from an indeterminate start point through to 2050, that's of course a much bigger job, and one that Parliament certainly didn't authorise.  

A clean ETS is certainly capable of driving beyond net zero. The government or others just need to buy credits through the system and retire the credits, unused. And if tech follows some potential paths, doing so may well be cost-effective in undoing some accumulated emissions. But probably a good idea to wait and see what the cost paths wind up looking like before committing on that one.