James Shaw pushed for a more ambitious 2030 emissions reduction pledge, which would have cut net emissions by 54 per cent of their gross 2005 levels - although he considered a cut of as high as 70 per cent.
Shaw also proposed committing New Zealand to a net zero emissions target for all greenhouse gases by 2050, meaning the country would have to drastically reduce its biogenic methane emissions - mainly from agriculture.
Currently, the target is to reduce those emissions by between 24 and 47 per cent of 2017 levels.
But pressure from the Labour side of the Government forced the Government to compromise on a 50 per cent pledge, which was released on Sunday.
The pledge, officially known as a Nationally Determined Contribution, or NDC, is a promise to reduce emissions set out under the Paris Agreement. Every five years, countries are encouraged to check in on their Paris pledges to make them more ambitious - the new NDC is a result of that review.
The fact Shaw and Deputy Prime Minister and Finance Minister Grant Robertson were locked in difficult negotiations over the pledge is well known, and written about in the Herald. Both parties have subsequently confirmed their positions to the Newsroom website.
A draft paper obtained by Adam Currie, a climate justice activist, reveals Shaw's original pledge was more ambitious than what was finally proposed, but only slightly.
His written remarks say he "considered a range of options to update NCD1 and propose the Government updates New Zealand's NDC1 to commit to reducing net emissions 45 per cent below gross 2005 levels by 2030 based on a budget approach, equivalent to a reduction in emissions of 54 per cent in 2030 when expressed as a point-year target".
The target would have given New Zealand an emissions budget of 553 Mt of CO2 equivalent to be emitted between now and 2030. The budget that was actually agreed on was 571 Mt, and the original budget, set under the previous government was 623 Mt.
Shaw said the "updated target represents both the minimum credible contribution New Zealand can make towards limiting the average global temperature rise to 1.5 degrees Celsius as well as our highest possible ambition in light of our national circumstances".
Currie described the proposal as "gutting" and "unambitious".
"It's gutting to see James Shaw propose such an unambitious 2030 NDC of 553 Mt - barely more ambitious than the 571 Mt Cabinet agreed to.
"The Greens always tell us that the inaction is because the Climate Minister can't get his recommendations through Cabinet - but here we can see the weak ambition of his own proposals. A Green Minister should be pushing the overton window of what is possible - not proposing weak targets that then get even further watered down by Cabinet.
"James Shaw should be ashamed of himself," he said.
The paper said that international mitigation - that is, New Zealand paying money to other countries to reduce their emissions and counting those reductions as our own - will "make up around 70 per cent of New Zealand's NDC", which is equivalent to reductions of about "120 Mt between now and 2030".
The Climate Change Commission's proposed emissions budgets see New Zealand expected to reduce emissions by 47 Mt between now and 2030.
Treasury advice, included in the paper, said that while "New Zealand had a 'strong interest in encouraging an effective global response to climate change," it could not support the proposed reduction.
Treasury recommended a "smaller increase" in ambition".
"The Paris Agreement allows nations to take their national circumstances into account when setting NDC targets. In the Treasury's view, New Zealand's national circumstances, while referenced, are under weighted in this analysis," the advice said.
Treasury said the estimated cost of the international cooperation offsets required to meet Shaw's NDC would be $9.3 billion to $16.3b between now and 2030 - a significant increase on the cost of the previous NDC which was estimated to cost between $3.8b and $6.8b.
Both Treasury and MBIE registered concern about the lack of analysis, with MBIE saying "insufficient analysis has been undertaken to understand the fiscal and social impacts" of the new target.
Shaw was less enthused by the 50 per cent pledge that was eventually chosen.
The paper said this pledge "not reflect our highest possible ambition in light of our national circumstances".
One area where the paper was ambitious, was a proposal to cut methane emissions to net zero, bringing them under the same target as all other greenhouse gases.
The paper said the proposal to bring methane into the 2050 target would bring New Zealand into line with most similar countries, which did not use different targets for different gases.
"This would clearly signal our commitment to the global effort to reduce emissions beyond 2030 and puts us on an equal footing with countries that have committed to reducing all gases to net-zero by 2050.
"Fifty-six countries (including the UK, EU, and Canada) have either achieved or set in law or policy net-zero 2050 targets, with net-zero targets under discussion in a further 75 countries. New Zealand is, as far as we know, the only country of these 131 that has a split-gas 2050 target.
"We are seen as an outlier in this regard," the paper said.
Currie said the all-gases target was some solace for the unambitious NDC.
"It is a small solace, though, that James did at least propose an all-gases 2050 target - important given the prominence of NZ's high methane emissions," Currie said.
"A 2050 net-zero all-gases commitment would be much, much stronger than the C02-only one we have now. Generally speaking, net-zero CO2 comes around 20 years before net-zero all gases.
"It's unfortunate Cabinet didn't agree to announce this alongside the NDC - hypocritical as at the same time New Zealand signed the global methane pledge," he said.
Shaw has been approached for comment.