COMMENT

The Government is calling for a target of Net Zero Greenhouse Gas Emissions by 2050 through the proposed Zero Carbon Act.

Or more correctly, we will refer to it as the Zero Anthropogenic Carbon Emissions Act (ZACE Act) as we are dealing with the extra greenhouse gases produced because of human activities.

This is very likely the most significant piece of legislation affecting the environment and economy, as well as human welfare for years to come.

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In its discussion document, the Ministry for the Environment is requesting public feedback on 16 questions.

Most of these are straightforward, but question number two is quite complex with three options presented that could replace our current target of 50 per cent reduction below 1990 levels by 2050.

"They are: firstly reducing net carbon dioxide (CO2) and nitrous oxide (N2O) emissions to zero but ignoring mainly short term agricultural gases such as methane (CH4), secondly, reducing net carbon dioxide emissions to zero while stabilising short term agricultural emissions, and thirdly achieving net zero emissions of all greenhouse gases - both short and long-term - by 2050.

The Wise Response Society believes that the target here must be the third option: reducing net emissions of all greenhouse gases to zero by 2050.

The society represents a broad coalition of academics, engineers, lawyers, artists, sports people and others who are calling on New Zealand's Parliament to comprehensively assess imminent risks to New Zealand – and climate change is one of the most important of these.

The ZACE Bill is New Zealand's response to the Paris Agreement which states: "relative to pre-industrial times, the increase in global average temperature should be kept to well below 2C and efforts should be made to limit the temperature increase to 1.5C."

These are ambitious targets indeed.

Our reasons for supporting net zero emissions across all greenhouse gases are numerous.

The climate does not distinguish between the different greenhouse gases – any gas addition, whether it is CO2 from gas guzzling and emitting cars, CH4 from belching cattle and sheep, or N2O from fertilizer and manure, they all, indirectly, warm the planet.

Thus, it is important to cover all the greenhouse gases: both CO2 and the non-CO2 ones.

Not only the short-lived ones like CH4, but also N2O and other long-lived greenhouse gases such as CFCs.

Net zero anthropogenic emissions means the summation of all the warming effects on climate by the greenhouse gases emitted from our various activities, is zero.

This could allow, for example, cutting CO2 emissions from transport and generation of electricity to zero, stabilising methane CH4 at much lower levels, cutting N2O to zero, and then using carbon capture in forests, other vegetation plantings, and soils, to offset the balance.

Clearly, net zero anthropogenic CH4 emissions from ruminant livestock is an impossibility, and there is a limit in the capacity to capture and hold carbon, so net zero emissions across most New Zealand greenhouse gas emissions is a compromise target.

The Wise Response Society is particularly concerned that we might fail to heed the obvious signs and that it's time to get serious - that is, more extreme temperatures and increasing rates of sea ice and glacier melt, large volumes of CH4 emitted from the thawing of permafrost across the Arctic, heat waves in Europe, Asia and North America, hurricanes and wild fires affecting tropical and temperate parts of the globe - which are widely interpreted as growing risk of crossing an irreversible climate tipping point.

The Fifth Intergovernmental Panel on Climate Change Report in 2014 illustrates the difference between the risks of 1.5C and a 2C temperature increase above show that pre-industrial levels shift from "moderate" to "high" and the 2C upper temperature goal of the Paris agreement may not represent a "safe" climate zone.

In this context it is hard to see the wisdom of adopting a "middle way" to reducing emissions.

Any thought for recommendations on how to achieve such targets is complex.

For example, in a paper just published by Joseph Poore and Thomas Nemecek in Science on reducing food production's environmental impacts, the analysis concludes that avoiding meat and dairy products is the single biggest way to reduce our environmental impact on the planet.

The new research shows that without meat and dairy consumption, global farmland use could be reduced by more than 75 per cent – an area equivalent to the US, China, European Union and Australia combined – and still feed the world.

The new analysis shows that while meat and dairy provide just 18 per cent of calories and 37 per cent of protein, it uses the vast majority – 83 per cent – of farmland and produces 60 per cent of agriculture's greenhouse gas emissions.

Most strikingly, impacts of the lowest impact animal products typically exceed those of vegetable substitutes.

US biotech company Perfect Day claims its synthetic protein reduces greenhouse gases by 84 per cent, land use by 91 per cent, energy by 65 per cent and water consumption by 95 per cent.

With mounting pressures on the environment and space for land globally, such resource economies would represent major incentives for world agriculture to undergo a paradigm shift in the food system, irrespective of the climate issue.

Given such complexity with aspects of the global warming and associated climate disruption, we of Wise Response consider the detail of how to arrive at the Net Zero Emissions target should be a task for the proposed Climate Change Commission with its expert analysis, once the bill is enacted.

The Climate Change Commission can then put the choices before Parliament, who can determine how it is to be done.

The general public can provide direction and encouragement on the discussion document by making a submission by July 19.

• Jim Salinger is a Visiting Professor at the University of Haifa, Israel, and a member of the Wise Response Society. Sir Alan Mark is chair of the society and an Emeritus Professor of the University of Otago.