The IPCC has revised its assessment of the impact on temperature of ruminant methane downward by a factor of three to four times.
The IPCC has revised its assessment of the impact on temperature of ruminant methane downward by a factor of three to four times.
Opinion by Owen Jennings
OPINION
It would not be difficult to imagine the huge outcry if, when elected, the Green Party decided to value your assets four times higher than their true value for the purposes of their Asset Tax concept.
Outrage would follow.
It is hard to think it could happen, even amongthose desperate to hike taxes.
Yet, in its latest report, the Intergovernmental Panel on Climate Change (IPCC) revised its assessment of the impact on the temperature of ruminant methane downward by a factor of three to four times.
In the face of recent and evolving science, the formula had to be updated. Had the earlier numbers been used to tax farmers, our Government would have over-taxed farmers by a massive and crippling 300-400 per cent.
The IPCC AR6 report, page 1016 of Chapter 7, said: “…expressing methane emissions as CO2 equivalent of 28, overstates the effect on global surface temperature by a factor of 3-4″.
Farmers were hugely relieved but remained querulous and concerned about why there was no generous applause from the wider community, no expressions of relief headlined across all media, and not even a whiff of relief from the Government or any political party. Are we not delighted that a potentially huge monkey on farmers’ backs has been replaced with a much smaller monkey?
The IPCC has been held up as the definitive authority on greenhouse gas issues, yet the Government and its departments continue to state that agriculture is responsible for “up to half New Zealand’s greenhouse gas emissions” by using outdated figures calculating ruminant methane emissions erroneously at three to four times their ability to impact the climate.
Even the Leader of the Opposition recently used the “nearly half” claim in respect of farmers’ methane emissions.
The science behind the lower number goes back to 2011 when a Scottish researcher, Dr Wilson Flood, a member of the Royal Society of Chemistry, wrote: “A doubling of the amount of methane in the atmosphere with its present composition would produce a warming equal to only about one-thirtieth of the warming produced by a doubling of carbon dioxide. At present rates of increase, it would take about 360 years for atmospheric methane levels to double. Molecule for molecule, methane is 7 times more effective at being a greenhouse gas than carbon dioxide. Present changes in atmospheric methane levels pose no environmental risk whatsoever.”
Then in 2018, Professor Myles Allen and a team at Oxford University published a solution to the misrepresentations of CO2-equivalent emissions of short-lived climate pollutants under ambitious mitigation that agreed with Flood that methane is seven times (not 28 times) more effective at being a greenhouse gas than carbon dioxide.
This group was also IPCC lead authors, and the AR6 document from the IPCC put beyond any doubt that the GWP100 formula, which had always been used in New Zealand, was now off the table, once and for all. Or should be.
So, farmers want to know why they are still being pursued for the higher number. Do we only follow the IPCC science when it is more extreme?
Owen Jennings.
Science does evolve. It is at the very core of the scientific process. New findings shift the debate, refine, challenge, add information so the community can respond accordingly.
Just as the IPCC adopted new scientific findings on methane’s warming ability so it has modified the use of what was an extreme scenario for the future called RCP8.5. This option has been quietly dropped.
There are now even more recent findings released that raise serious questions about whether any methane can impact temperature in a measurable way.
Research by Wijngaarden and Happer, supported by Sheahen, Coe, Alison, McLean and others shows we have been giving methane too much credit as a greenhouse gas for pushing temperatures up.
These findings have not been refuted or shown to be false. They were done in real air – a first for greenhouse gas research - improving their credibility.
Farmers wait with keen interest to see whether the IPCC will continue to adapt as new findings emerge. They wait with even keener interest to see whether our policy makers will adapt to what the IPCC has already proposed. It is of great moment to farmers.
- Owen Jennings is a former national president of Federated Farmers.
