Thomson v Minister for Climate Change Issues: The expanding reach of judicial review?


Thomson v Minister for Climate Change Issues[1] is a recent judicial review, brought by law student Sarah Thomson, of two decisions made by the Minister for Climate Change Issues (the Minister) concerning targets for reducing greenhouse gas emissions.

The first “2050 target” was set under the Climate Change Response Act 2002 (the Act). The Minister had declined to review the 2050 target following a more recent Intergovernmental Panel on Climate Change (IPCC) report on climate change (the AR5 Report – the first decision).

The second “2030 target” was set pursuant to the international Paris Agreement.[2] The Minister faced allegations that the decision to set the 2030 target (the second decision) was based on irrelevant considerations, and was irrational and unreasonable because of a lack of evidence to support it, and a scientific consensus against it.

Mallon J found that both decisions were amenable to judicial review:

  • The first decision regarding the 2050 target involved the exercise of a statutory discretion, and was plainly reviewable. The Court held that under the Act, the Minister (at that time, Hon. Tim Groser) was required to base his decision on up-to-date evidence in line with our international obligations – here, the latest IPCC report – and turn his mind to whether there was any change between the reports relevant to the target set under the Act.[3]
  • For the second decision regarding the 2030 target, the issue of justiciability was central: the Minister was acting pursuant to an international agreement not domestic legislation, and the target setting process involved what the Government regarded as a matter of socio-economic and financial policy requiring the balancing of many factors.

It is the justiciability of the Minister’s second decision that is of interest for present purposes.[4] Traditionally, Courts shy away from considering matters of policy – and for good reason. Policy judgements are not something the Courts could or should interfere with as such balancing and judgements are not generally regarded as susceptible to determination by any legal yardstick.

Reasons why the second decision is amenable to review

The Paris Agreement requires each country to put forward their own Nationally Determined Contribution (NDC). NDCs represent the post-2020 climate actions that a country intends to take and are to be updated every five years to be the country’s “highest possible ambition, reflecting its common but differentiated responsibilities and respective capabilities, in light of different national circumstances”. New Zealand set its NDC in 2015 to reduce greenhouse gas emissions by 30% from 2005 to 2030.

Mallon J held that the Court’s jurisdiction to review the NDC decision to set the 2030 target arose from the common law, whereby any exercise of a public power by the executive that has an important public consequence is potentially amenable to review by the courts.

Following review of the justiciability of government action on climate change in other jurisdictions, the Court found a consensus that it is sometimes appropriate for domestic courts to play a role in Government decision making about climate change policy. In a number of jurisdictions, including the United states, Canada, United Kingdom and the Netherlands, the courts have not considered the subject matter a “no go” area just because the obligations arise from international law, or because the decisions involve weighing of different policy considerations, or because the problem is a global one.

Courts internationally have recognised the significance of the issue of climate change for the planet and its inhabitants and that those within the courts’ jurisdiction are necessarily amongst all who are affected by inadequate efforts to respond to climate change.

The various domestic courts have held they have a proper role to play in Government decision making on this topic, while emphasising that there are constitutional limits in how far that role may extend.

Mallon J held that “The importance of the matter for us all warrants some scrutiny of public power in addition to accountability through parliament and the general elections”.

On the facts, the Court held that none of the pleaded grounds of review had been established

On the facts, however, Mallon J was not persuaded that the Court could intervene in the Minister’s decision to set the 2030 target:

  • The Paris Agreement did not stipulate any specific criteria about how a country is to set its targets. When assessing its targets the Minister obtained economic modelling alongside other inputs. Mallon J was critical of the economic model due to its limited parameters. However, the targets set by the Minister were not outside of the proper bounds of the Minister’s power to set targets.
  • Ms Thomson as plaintiff had submitted that the Minister was required to consider the circumstances of Tokelau and developing countries in general when developing the NDC. Mallon J held that the impact on Tokelauans is a mandatory relevant consideration when New Zealand is considering its responses to climate change, given Tokelau’s dependence on New Zealand and its status in international law. However, Mallon J was not convinced that this meant that New Zealand’s NDC needed to be consistent with a 1.5°c target, or that the NDC would be different if the circumstances of Tokelauans had been considered when making the NDC decision.
  • Ms Thomson had also submitted that the scientific consensus showed that countries’ combined NDCs fell short of the reductions needed to stabilise greenhouse gas emissions in the atmosphere at a level that would prevent dangerous interference with the climate system. However, Mallon J held that this was not a mandatory relevant decision under the Paris Agreement. There was no requirement for countries to adopt a new target if combined targets were insufficient to keep warming below 2°
  • Finally, Ms Thomson submitted that the NDC decision was irrational or unreasonable as there was no rational evidential foundation for the belief that the NDC will strengthen the global response to the threat of climate change, and the global scientific consensus shows the NDC falls short of reductions needed. Mallon J disagreed and held that the 2030 target is not inconsistent with the global temperature goal under the Paris Agreement such that the NDC does not meet New Zealand’s international obligations. The decision was not unreasonable or outside of the Minister’s powers.


This decision of the High Court serves as an important reminder to all those exercising or advising on the exercise of public powers that Courts have broad powers of review that may extend beyond decisions made pursuant to the exercise of domestic statutory powers.

The Court may intervene in any case where there is an exercise of public power and/or important public consequence from the decisions being made, such as the impact of climate change. This is the case even where this causes the Court to stray into the policy arena. The Court may intervene to ensure appropriate action is taken while leaving the policy choices about the content of that action to the appropriate public decision maker.

[1] [2017] NZHC 733 (2 November 2017)

[2] The Paris Agreement builds on the United National Framework Convention on Climate Change (UNFCCC), and aims among other things to strengthen the global response to the threat of climate change by keeping a global temperature rise this century below 2oC above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5oC.

[3] The recent change in Government lead the Court to decide not to assess whether there were any material changes, as the cause of action was essentially overtaken by the Labour Party’s newly announced 2050 targets.

[4] In terms of the first decision, Mallon J held that in order to give effect to the Act and what New Zealand has accepted, recognised and committed to under international instruments, and in light of the threat that climate change presents to human kind and the environment, the publishing of a new IPCC report required the Minister to consider whether a target set under section 224 should be reviewed. Mallon J noted that the IPCC report provides the most up to date scientific consensus on climate change. Thus, following the release of the AR5 report in 2014, the Minister was required under the Act 2002 to turn his mind to whether there had been any material change between the 2007 AR4 report and the AR5 report that was relevant to the target. The Minister did not carry out this assessment.