Dr Andy Reisinger is deputy director of the New Zealand Agricultural Greenhouse Gas Research Centre wrote a column in the NZ Herald stating that he strongly rebuts the article I wrote in the NZ Herald.
The key points I made in my article were these.
Motu in a report co-authored by Dr Reisinger stated that “There is a strong relationship between cumulative emissions of CO2 and global warming; ultimately, net CO2 emissions have to decline to zero for the climate to stabilize. By contrast emissions of CH4 and other short lived climate forcers do not have to decline to zero for the climate to stabilize; they only have to stop increasing”. (Direct quote)
There were two points I concluded from this statement.
The first point is that constant emissions of methane are not responsible for a non-stabilized climate. In other words they are not causing global warming.
Dr Reisinger was upset by this conclusion. I don’t see how any other conclusion can be reached from Motu’s report and Dr Reisinger did not explain what was wrong with the conclusion I made.
Dr Reisinger’s response only said that the Motu report states quite clearly that methane contributes to global warming and he is right, but only in so far as it relates to methane emissions not in constant flow. On emissions that are in constant flow the Motu report is very clear, they are not responsible for a non-stable climate. They were the emissions I was referring to in the article and Dr Reisinger could not have misinterpreted that. He accuses me of making a wrong conclusion about emissions in constant flow, but attempts to back up his claim using an example relevant only to emissions that are not in constant flow.
Dr Reisinger makes the point that reducing CH4 emissions will help reduce warming because reducing these emissions provides some sort of offset against the CO2 emissions that are the real problem. That may well be right but it does not counter my argument. If it is true that reducing emissions helps reduce the impact of the CO2 emissions that does not equate to saying that maintaining CH4 emissions is causing global warming.
You could equally apply his argument to trees. Trees offset CO2 emissions, so not planting trees will continue to keep the world warmer than it would be otherwise. It is not fair to say though that people who don’t plant trees are causing global warming. Also Dr Reisinger does not appear to understand that global warming under UNFCC definitions can only be caused by activities which alter the composition of the atmosphere. An activity which maintains the status quo in the atmosphere does not even fit within the UNFCC definition of an anthropogenic activity.
On the point Dr Reisinger makes about the benefits of reducing CH4 emissions, the Motu report he co-authored states that there is no consensus amongst NZ scientists as to how much emphasis should be put on mitigation of agricultural non CO2 gases beyond continuing to improve intensity. He obviously believes there should be emphasis placed on reducing CH4 emissions but his views are contrary to the scientific consensus as outlined by Motu. The consensus is there is no consensus.
My second point is that Motu’s report states quite clearly that, in order to stabilize the atmosphere, carbon emissions sourced from CO2 need to decline to zero, whilst carbon emissions sourced from CH4 only need to stop increasing. The only conclusion possible is that these different carbon emissions have quite different impacts on the atmosphere. My point is that carbon is supposed to be an equivalence unit but it fails because the atmospheric impact of a carbon emission sourced from methane is different to a carbon emission sourced from CO2. (Dr Reisinger does not dispute this and in fact acknowledges this) The environmental impact of a carbon emission therefore cannot be known unless one knows the source. This was the central element of my article entitled ‘Carbon unit unfair to farmers’. Dr Reisinger did not challenge this argument at ll. He therefore did not strongly rebut the key point in my article and has maligned me by saying that he was.
Dr Reisinger has not rebutted either of my points. He is quite at liberty to make his case for reducing methane emissions but he cannot say that the conclusions I have drawn are misleading. He has also stated that there is no scientific basis for my assertion that New Zealand’s emissions are mostly harmless and he is wrong because they are. And the scientific basis is what led Motu to state in the report he co –authored that emissions of CH4 and other short lived climate forcers do not have to decline to zero for the climate to stabilize; they only have to stop increasing.
To read Dr Reisinger’s article click http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11909465