'Climate index' would boost mitigation efforts - NZ researcher

Climate Change Issues Minister Tim Groser Photo AP / Rob Griffith

Countries should introduce an adaptive approach to climate change mitigation to avoid procrastinating about long-term carbon reduction policies, a New Zealand researcher has suggested.

Professor David Frame, the director of Victoria University's Climate Change Research Institute, is the co-author of a newly-published paper which offers what the researchers argue is an effective way to tackle the issue.

Ahead of crucial UN climate negotiations in Paris in December, which aim to firm up post-2020 emission reductions commitments, New Zealand last month set a new target of reducing its greenhouse gas emissions by 30 per cent from 2005 levels by 2030.

Although Climate Change Issues Minister Tim Groser called this a "significant increase" on previous commitments - it was the equivalent of an 11 per cent reduction below a 1990 baseline, he said - the majority of submitters who took part in the Government's earlier consultation asked for much more ambitious targets.

In their paper, published in the journal Nature Climate Change, Professor Frame and his colleagues argue the "pledge and review" approach that will form the basis of commitments made at the December talks presents an opportunity to explicitly link mitigation goals to the evolving climate response.

The authors believed that mitigation strategies needed to be better able to succeed despite scientific, economic and political uncertainties, and suggest an adaptive strategy based on an index of warming attributable to human influence, drawn from observed temperatures.

At the end of 2014, the rise in global mean temperature that could be attributed to the impact of people was calculated to be 0.91C.

Such an index was not subject to high variability year to year, did not require complex modelling and could be updated annually, allowing governments to regularly review their pledges to reduce greenhouse gas emissions, they argued.

"Recognising that long-lived greenhouse gas emissions have to be net zero by the time temperatures reach a target stabilization level, such as 2C above pre-industrial levels, and anchoring commitments to an agreed index of attributable anthropogenic warming would provide a transparent approach to meeting such a temperature goal without prior consensus on the climate response," the authors said.

The paper concluded that using such an index allowed a transparent link between the policy instrument and the policy goal, and would be a simple way to ensure consistency between changes in climate, individual countries' pledges, and the overall goal of reducing CO2 emissions.

"The creation of an agreed index of global warming would be a useful tool to assist policymakers work out where we are in terms of achieving the main aims for climate policy," Professor Frame said.

"As we know from inflation-targeting and other aspects of health, social and environmental policy, indexing can help governments by reducing the opportunity for diversionary arguments based on the selective use of data."

Prrofessor Frame believed these adaptive policies were attractive because they avoided the "worst excesses" of over-preparing in response to worst-case scenarios, as well as the under-preparedness which often accompanied environmental planning based on cost-benefit approaches.

"At such a crucial time for climate negotiations, this proposed index offers a way to evaluate climate policies that tackles the uncertainty of climate response, which to date has stalled progress of mitigation strategies."

Meanwhile, the vice chair of the UN's International Panel on Climate Change, Professor Jean-Pascal van Ypersele, is scheduled to visit New Zealand next week.

While in Wellington, Professor van Ypersele will speak about the key messages of the IPCC's Fifth Assessment Report, released in 2013, and meeting New Zealand climate change officials and academics.

The Fifth Assessment Report, or AR5, found that it was "extremely likely" human activities caused more than half of the observed increase in global mean surface temperature since 1950 and that it was "virtually certain" that natural variability alone cannot account for the observed global warming since 1950.

Under the highest emission scenario, there was at least a 50 per cent chance that the global surface temperature increase by the end of this century would exceed 4C above pre-industrial times, while under the lowest scenario, global surface temperature increase was unlikely - with less than a 33 per cent chance - to exceed 2C.

Professor Frame said at the time that climate change was expected to continue in line with long-held scientific expectations, as it had over previous decades, and keeping warming to a 2C target would require limiting CO2 emissions to around half a trillion tonnes.

Last month, the Berlin-based Carbon Action Tracker initiative rated New Zealand's 11 per cent reduction proposal as "inadequate" and claimed it could be achieved without the country taking any action to contain a growing level of emissions over the next 15 years.

If most other countries were to follow New Zealand's approach, global warming would exceed 3 or 4C, a world that would see oceans acidifying, coral reefs dissolving, sea levels rising rapidly, and more than 40 per cent species extinction, it reported.