Split over which emissions to cut

Environment Minister offers more detail on Zero Carbon Bill but experts divided on best approach to curbs

Experts have hailed New Zealand’s ambitious new Zero Carbon Bill — but some question whether all types of greenhouse gas emissions should be slashed to nothing by 2050.

Climate Change Minister James Shaw this week shared more information about the proposed bill, which Kiwis are being urged to have their say on.

The three big options on the table are making the 2050 target apply only to carbon dioxide, ramping down CO but stabilising short-lived gases like methane or nitrous oxide, or requir- ing that all emissions are reduced to net zero by the middle of the century.

All of the options would have big implications for households, whose incomes would likely not grow as quickly, and for industries, which faced having to change and innovate to meet ambitious new requirements.

But Shaw said economic modelling showed New Zealand could cut emissions while growing the economy, jobs, and per-household incomes.

By 2050, the “per household national income” could still increase by 40 per cent, although lowerincome households could be disproportionately affected as they spent more on products and services that would become more expensive.

“We are mindful . . . there could be a disproportionate impact on lower income households, unless there are strong and effective policies in place to avoid these costs,” Shaw said.

The analysis also showed how acting on climate change would likely bring other benefits like better health, water quality, less traffic congestion and more innovative businesses.

“More innovation across our economy is a key part of the long-term fix, but planting the right mix of native and exotic trees is also one of the . . . quickest, and most cost-effective things we can do to help achieve our climate change goals,” Shaw said.

The director of Massey University’s Centre for Energy Research, Professor Ralph Sims, said planting more forests on to marginal pasture land would buy some time to phase out coal, oil and gas — but could only be a temporary option.

Sims believed nitrous oxide, arising mainly from nitrogen fertilisers and animal urine, was a long-lived gas and would have to be reduced, but could still be given a lower priority because of its comparably smaller contribution to global warming.

With methane, Sims said choosing to stabilise levels rather than reducing them to zero would take pressure off the farming sector, at a time when research to date had yielded only small opportunities to cut levels.

Otago University energy expert Associate Professor Ivan Diaz-Rainey said the right option likely lay somewhere between stabilising agricultural emissions them and cutting them to zero — which meant the big focus would be on CO .

But Massey University’s Distinguished Professor Robert McLachlan said there were good reasons for pursuing the boldest, all-gas option — a goal the Productivity Commission recently found could be achieved.

“Cutting methane emissions provide an immediate decrease in temperature; cutting [CO ] does not.”