IPCC report: Important science on methane and GWP*

// Climate Change

Buried in a landmark IPCC report this week is a detailed and important section on the metrics for short-lived gases. We summarise the key findings and what these mean for our sector. 


The latest Intergovernmental Panel on Climate Change (IPCC) report reinforces that climate change is real, it’s already happening and it is contributing to the extreme weather events such as floods, storms and droughts that we are experiencing.

There’s no question that all New Zealanders, including farmers, have to contribute to reducing emissions, if we are to keep global warming in check. 

We’re working through the detail in the report, including the latest developments in the science around methane.

Here’s an overview.

About the IPCC report

The Intergovernmental Panel on Climate Change (IPCC) is the world’s leading authority on climate science. The IPCC’s Sixth Assessment Report (AR6) summarises the latest climate change science from around the world from thousands of scientists and reviewers, including New Zealanders. 

The headlines from the report include: 

  • Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. 
  • Global surface temperature will continue to increase until at least the mid-century under all emissions scenarios considered. 
  • Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in carbon dioxide (CO2) and other greenhouse gas emissions occur in the coming decades.
  • That level of continued global warming is projected to further intensify the global water cycle, including its variability, global monsoon precipitation and the severity of wet and dry events.

What the report says about methane

There’s some significant information in Chapter 7 of the report with respect to measuring the contribution of methane to climate change. 

In brief, this makes it clear that the impact of methane has been overstated when emissions are not increasing (as is the case in New Zealand). This means New Zealand’s current targets for reducing methane emissions (24-47 percent by 2050) do not “let farmers off the hook” but may actually be asking more of methane producers than fossil fuel emitters. 

We still have to tackle methane emissions, but this report should help set targets that are fair and appropriate.

The report recommends countries treat short-lived gases such as biogenic methane differently from long lived gases such as CO2. This is effectively an endorsement of New Zealand’s split gas approach, which B+LNZ advocated for, in the Climate Change Response (Zero Carbon) Bill.

B+LNZ’s main ‘take-outs’ from Chapter 7 are:

  • The report clearly states that a 0.3 percent reduction per year in methane is equivalent to net zero for CO2 – that is, there would be no additional warming at this level. 
  • The report also clearly states that the current accounting method, known as GWP100 (which compares the global warming potential of emissions over a 100-year period) overstates the effect of constant methane emissions on global surface temperature by a factor of 3-4 over a 20-year horizon, while understating the effect of new (or increasing) methane emissions by a factor of 4-5 over a 20-year horizon.  
  • It notes that an alternative accounting method, known as GWP*, scales emissions over time and better accounts for the different warming behaviours of short-lived gases.  
  • The report recommends careful choice of metrics and consideration of the different impact of short-lived and long-lived gases when building pricing systems for emissions and when undertaking life-cycle analysis, for example comparing the carbon footprint of foods. 
  • This report is very important for the ongoing conversation about the target in the Zero Carbon Bill of 24-47 percent reduction in methane by 2050. The science laid out in the IPCCC report makes it clear those targets mean methane producers would be going beyond reductions required to prevent additional warming and would be reversing previous warming, while fossil fuel emitters only need to get to “no additional warming” by 2050.  
  • B+LNZ has been frustrated for some time by claims agriculture was being “let off the hook” by the 24-47 percent reduction targets and the IPCC report makes it clear this is not the case.  
  • It also makes it clear that if methane is stable or reducing (as it has been in New Zealand since 2001) then using GWP100 to report on methane’s contribution each year to climate change is inaccurate. Methane in New Zealand may be around 40 percent of annual emissions, but it has not been 40 percent of warming each year for quite some time. 
  • This report reinforces our call for the Government to start to report on both emissions and warming each year so that the true contribution of each sector’s emissions to warming can be seen and understood.  

What this means for sheepmeat and beef farmers 

  • Our sector is committed to playing its part in addressing climate change and this report is important for continuing to build understanding of agriculture’s contribution to global warming and what the appropriate actions and frameworks need to be. 
  • Our sector has already made a significant contribution and has a good story to tell. Greenhouse gas emissions from sheep and beef farming have decreased by 30 percent in absolute terms since 1990, while production levels have remained stable. We are also offsetting a significant proportion of our remaining emissions through the native and exotic trees on our farms.  
  • Through the He Waka Eke Noa programme, we are putting in place a practical programme that holds management and mitigation of greenhouse gas emissions in farmers’ hands.
  • The most important step for farmers to take right now is to know your emissions numbers and have a plan. You can use the B+LNZ GHG Calculator as it reports on the different emissions, and our Farm Planning programme to support you. 
  • By the end of next year (2022) we have to show that all farms know their greenhouse gas emissions numbers, and by the end of 2025 all farms have to have a written plan to measure and manage their emissions. This will involve measuring emissions and offsets, and a farm-level pricing system will be developed (by 2025) that will incentivise changes and recognise action taken.  

What’s next

  • We’ll continue to work through the IPCC report and use this latest science and information to inform our advocacy on your behalf.
  • The Government is currently working on an Emissions Reduction Plan, drawing on the advice of the New Zealand Climate Change Commission’s advice.
  • We’ll be advocating for a fair approach that ensures all sectors of our society and economy are contributing, and that recognises the work you are already doing to shift to more sustainable food production.
  • We’ll also continue to provide advice, support and research to help you mitigate emissions and adapt to a changing climate.