Here’s our chance to become climate leaders

New research could transform climate policy in New Zealand and provide farmers with a fairer target for managing their methane emissions.

The paper, published in the journal Nature Climate and Atmospheric Science, was a collaboration between researchers from Victoria University of Wellington, the University of Oxford and University of Reading in the United Kingdom and the Center for International Climate and Environmental Research in Norway, and shows how carbon budgets can better address the effects of short-lived greenhouse gases like methane compared with long-lived greenhouse gases like carbon dioxide.

Long-lived, or stock, pollutants remain in the atmosphere over centuries, increasing in concentration all the time and causing more and more warming; short-lived, or flow, pollutants disappear a lot quicker, so as long as emissions remain constant their concentration and warming effect remains constant as well.

Scientists have debated for many years about how to compare stock and flow pollutants. The international climate negotiations community grasped the first option discussed by the Intergovernmental Panel on Climate Change, way back in 1990, and has hung on to it resolutely ever since.

One of the beauties of the Paris Agreement, however, is countries are free to innovate in how they approach climate policy.

Our paper provides an opportunity to instigate a new approach that we demonstrate outperforms old ones in a range of emission scenarios, providing a much more accurate indication of how stock and flow pollutants affect global temperatures.

The issue matters most for countries with high shares of methane emissions compared with carbon dioxide. As well as New Zealand, this includes Ireland within the wealthy countries and much of Latin America and Africa within developing countries.

While it is unfair to give farmers a pass on their emissions when we expect others to pay for theirs, fairness also demands we charge them only in line with the effects of their pollution.

Because the effects of stock pollutants get worse over time, every tonne emitted increases damages, and this implies rising social costs, something an Emissions Trading Scheme (ETS) should reflect.

But this is not the case for flow pollutants. Here, constant emissions imply a fixed, not permanently worsening, level of warming. Increasing emissions of flow pollutants comes at a very high social cost; reducing them brings an equally large benefit; but leaving them constant is, as far as global temperatures are concerned, actually equivalent to zero ongoing carbon dioxide emissions.

Under current policies, stock and flow pollutants are treated the same. Implementing a policy to address methane and other flow pollutants directly would give farmers a more reasonable way to control their emissions and reduce their impact on the environment.

An ideal approach would be a policy that aimed for zero emissions of stock pollutants such as carbon dioxide and low but stable emissions of flow pollutants such as methane.

Achieving both goals would be enough to stop New Zealand’s contribution to global warming.

Climate Change Minister Minister James Shaw has said he wants to make New Zealand a leader in climate policy—here is the Government’s chance. There are fairer ways to compare agricultural methane with carbon dioxide than those used at the moment: fairer on farmers today, and fairer on future generations.

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