Yesterday, in the Herald ($), I challenged Climate Change Minister James Shaw to explain how his Emissions Reduction Plan lowers emissions.

In this post, I want to head off what he is going to say. His lines are, frankly, not right. So let’s get that on the table and go through the argument before he says it.
Shaw’s plan is vast. It covers every sector of the economy. The government could regulator, tax or subsidise anything or everything in the name of reducing emissions.
But Shaw’s plan is not going to reduce emissions.* The government has already placed a quantity cap, a sinking lid, on emissions with the ETS. Legislation passed in 2020. It is widely accepted that cap-and-trade schemes neutralise other emissions policies. If the cap determines total emissions, policies under the cap do not.
This neutralising effect of an emissions cap is called “the waterbed effect”.
Here is how a cap-and-trade scheme will neutralise an EV subsidy, for example:
Imagine an economy normally produces 100 tonnes of emissions. This year, the government decides to cap emissions at 80 tonnes. It issues 80 emissions permits and demands the surrender of one permit per tonne of CO2. Emissions fall to 80 tonnes.
Next year, the government issues another 80 permits and introduces a new EV subsidy. The subsidy successfully reduces transport emissions by five tonnes.
Total emissions remain at 80 tonnes. Why? Because there are still 80 emissions permits available. The five permits which transport no longer needs due to the subsidy will be used elsewhere. They will raise emissions (or postpone reductions) by exactly five tonnes somewhere else in the economy.
So, the EV subsidy reduces emissions from one sector. But overall emissions do not change. This is the waterbed effect.
Now, before I go any further, let me say that “The ETS Is Not Enough”™ is not an answer. That line is a mantra in Wellington. It is useless except for the fact it has fooled everybody who hears it.
Somehow, nobody has noticed “The ETS Is Not Enough”™ does not make any case for doing other policies if those policies are going to be neutralised by the cap.
Even if the ETS leaves you short of your emissions target (because it is Not Enough™), the waterbed effect is still in play.
So even if the “The ETS Is Not Enough,”™ complementary emissions policies don’t help. If they are neutralised by the cap, then those policies are going to leave you exactly as far short of your target as if you had not done them.
Every day, this advanced logic escapes hundreds of public servants who do nothing except think about climate change policy at your expense. You pay their salaries but I assure you they are not working for you.
Anyway, if Shaw’s Emissions Reduction Plan is to reduce emissions, it has to find a way around the waterbed effect.
Shaw has previously spoken about how to avoid the waterbed effect. His solution seems obvious: lower the cap as policies bring down emissions.
Here is Shaw speaking to Carbon News earlier this year:
[W]hat they’re talking about is something called the ‘waterbed effect’. If you cut emissions in one area and that takes things below the cap then it allows others to pollute more in the meantime.
But if you’re successfully lowering the cap every time then you minimise that effect because you’re saying, ‘Yes we’re taking emissions out here with the feebate and also with the ETS and then next time we set an emissions budget it will take account of the fact that emissions are lower.’
The way it works is you’ve got your 2050 target which is sort of long term. Then you’ve got your three five yearly budgets and each one is smaller than the one before. Every five years, at the start of each budget period, if circumstances dramatically change since you set the budget five years earlier, you can adjust at that time and say, ‘hey look things have moved far quicker or in unexpected ways we can adjust the budget to take account of that emissions budget.’
Shaw’s logic, as I understand it, is this: Ministers set the cap; Ministers can link the cap to complementary policies (EV subsidies, for example); complementary policies therefore lower emissions.
In the earlier example, emissions stayed at 80 tonnes after the EV subsidy had cut transport emissions. That is because there were still 80 emissions units in circulation. The intuitively obvious solution is to lower the emissions cap to 75 tonnes. Total emissions come down in line with the emissions benefits of the EV subsidy. Problem solved.
No. Problem not solved. That logic is not right.
Linking the cap to the policy does not make the policy lower emissions. It is the cap, not the policy, which lowers emissions. The policy is actually redundant. We explain why in our submission earlier this week on Shaw’s plan:
[Linking] the cap with complementary policies may imply the policies lowered emissions. However, this is an illusion. To see why consider this from the earlier example:
# If the government reduced the cap to 75 tonnes without the complementary policy, emissions would fall to 75 tonnes.
# If the government did the complementary policy but left the cap at 80 tonnes, emissions would remain at 80 tonnes.
The cap is doing all the work.
Accordingly, it is wrong to say that linking the cap to complementary policies means complementary policies reduce emissions. The connection is arbitrary. Ministers could link the cap to, say, cumulative rainfall, but nobody would suggest last week’s storm had lowered emissions. It is the cap, not the complementary policies, which lowers emissions. Complementary policies are still neutralised by the emissions cap. The waterbed effect is not avoided.
The cap is doing all the work. So long as the government has the option to reduce emissions simply by tightening the cap, other policies cannot cause emissions to come down (provided they are subject to the cap). The other policies are redundant.
The next obvious question is: what happens when the government does not have the option to simply tighten the cap? What if carbon prices rise to the point that voters or Parliament will not countenance any further tightening? Can complementary policies help further reduce emissions then?
This does open the door to complementary policies reducing emissions, but only by the smallest amount. Our submission walks through the weird permutations which are needed to get complementary policies to to cut emissions under an emissions cap. Short answer: we see no real way for complementary policies to cut more than a little extra emissions, at best.
If anything, complementary policies are more likely to raise emissions because of their lower economic efficiency and likely political inefficiency. The high cost of top-down emissions policies probably translates to a higher burn rate of political capital per tonne of emissions. That may seem like a fairly esoteric metric, but it matters in principle when the limiting factor on further reducing emissions is political feasibility.
Think about it this way: if the reason the ETS becomes politically constrained is because voters don’t like its cost of living effect, then how can policies which spend far more per tonne of abated emissions be any solution?
Complementary policies only have the opportunity to make any difference to emissions, up or down, if the ETS first becomes politically constrained.
It is hard to see any way the ETS is going to become politically constrained before 2050. New Zealand is already comfortably on track to achieve net zero emission in 2050 with existing policies. We include a list of reasons why in our submission. Nearly all of the evidence shows existing policies get us there.
I need to be clear about what “politically constrained” means. I mean it in the sense that a future government has no politically feasible way to net zero emissions.
Sure, the government could force the ETS price all the way to $500 if it stamps hard enough on trees and other removals technologies and rules out offshore mitigation entirely. That is what this government wants to do. And voters could well object to paying $500 per tonne of carbon.
But the ETS is not politically constrained if the government has the option to just stamp a bit less hard on trees or open the door slightly to offshore mitigation. Politically constrained is when the government cannot tighten the ETS any further, it cannot plant more trees, it cannot commission other removals technologies, and it cannot go offshore, and it is still short of net zero emissions.
Not going to happen. See the submission for why.
So, there is no question at all that right now we have legitimate, affordable, genuine pathways to net zero emissions, and we have options. We can plant a less trees and still get to net zero. We could plant no more trees and get to net zero. None.
Which means the government will always have the option to tighten the cap.
Which makes complementary policies under the cap redundant, including existing emissions policies.
Which means James Shaw’s vast plan is not going to reduce emissions. Not by one tonne.*
* For policies covered by the ETS cap, which is nearly everything except agriculture.