The Green Party says it is extraordinary that the government is holding back information about how it actually intends to reduce carbon emissions when it is in the public interest to know.

Photo: RNZ / Alexander Robertson

The government has a target of reducing emissions by 11 percent from 1990 levels by 2030, which it will take to Paris for the major United Nations climate change convention in December.

Earlier this week Radio New Zealand reported that the country's first climate change ambassador had criticised officials over the unwillingness to disclose the data which was used to model the emission reduction target.

Official documents released to the Green Party on advice provided by the Ministry for Business, Employment and Innovation (MBIE) and the Ministry for the Environment have large sections redacted, related to how emissions would be reduced and the cost of it.

Green Party co-leader James Shaw said it was not transparent how the government came to the target it had set, nor what the plan is to get to the target.

He said it was extraordinary that so much information had been blocked.

"This is something that involves the whole country, it is the public's right to know what the costs of doing something are, what the costs of doing nothing are, what the possible return is, and I find it extraordinary that our government has been so untransparent about this given that many other countries in the western world have made this kind of information completely available."

He said the government kept saying that there were enormous costs involved in doing anything about climate change, but the public had not been told of the possible cost of doing nothing.

"Some of the Treasury papers that we've seen say that there may be up to $59 billion worth of liability over the course of the next 15 years if we have such a low target, or if we don't achieve anything."

One of the government's key tools for reducing emissions is the Emissions Trading Scheme.

A document released by the MBIE shows that the department looked at the possibilities around domestic mitigation of emissions.

However, the detail of what it actually considered has been removed.

View the documents as a PDF (PDF, 1.6MB)

MBIE manager of energy markets Jamie Kerr said it stood by the decisions it made in regard to the redaction to parts of the document.

"The reason for withholding the information that relates to domestic abatement opportunities is that the work is still underway and feeds into ongoing advice to ministers and discussions with other agencies that are broader than climate target setting."

Documents from the Ministry for the Environment have removed the costs for meeting certain emission reduction targets as well as information on using forestry to mitigate emissions.

It said the information was redacted because it included the impact of forestry rules on the cost of the target, and that as the international forestry rules may be subject to international negotiation, releasing this information could prejudice New Zealand's negotiating position.