With the UN climate talks now underway in Paris, the Herald's science reporter Jamie Morton is talking to a range of experts on climate-related issues. Here he talks to Massey University’s Professor Ralph Sims - a former lead report author with the UN’s Intergovernmental Panel on Climate Change (IPCC) and a former senior analyst with the International Energy Agency (IEA) - about how New Zealand might slash emissions in its energy and transport sectors.

Q. What ways - through technology and policy mechanisms - might we achieve further reduction in transport emissions. And do you expect this will be much more difficult than achieving those gains we've made already?

We could simply impose fuel efficiency standards on all new and imported vehicles, as is done in many other places, to drive down average emissions per vehicle over time.

We could also transfer freight from road to rail and coastal shipping, and encourage non-motorised transport, such as walking, cycling, for the 30 per cent of all journeys that are less than three kilometres long.

This would mean building more infrastructure and spending less on major roads and more on local cycleways.

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Many young people are driving less, if at all, and there is the future power of IT to gain mobility without car ownership, as we are seeing with Uber taxis.

We could encourage urban planning toward more compact, liveable cities with local "village communities".

Electric vehicles - including two-wheelers and plug-in hybrids - will grow.

Given 80 per cent of New Zealand's electricity now comes from renewable energy, this reduces grams of CO2 emitted for every kilometre travelled from around 200 grams per kilometre with today's fleet to around 30 grams per kilometre, although this varies with vehicle size.

We've not made many gains to date in transport.

All of this is basic, well understood elsewhere and working successfully in many European cities in particular.

Q. What do you see as the biggest hurdles or challenges in stripping significant amounts of carbon out of our transport system?

A lack of government support, New Zealanders' love of the car, cheap fuels and a lack of impact of the Emissions Trading Scheme.

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Buy $1000 worth of gasoline or diesel and the ETS contribution equates to a cup of coffee - hardly a disincentive.

And most people have no idea they are paying it anyway.

Call it a "climate levy" and show it on the receipt along with GST paid.

Q. Besides agriculture, our second biggest source of emissions remains energy (22 per cent). What are the principle emissions contributors from the energy sector and what patterns or trends have we seen here over more recent times?

Electricity has declined as renewable shares have increased to about 80 per cent.
Heat emissions increases as demand grows and is met largely by coal and gas combustion.

That Fonterra is intending to use even more coal for the milk drying process is deplorable.

So overall, emissions from the stationary energy sector has been static.

But we can certainly reduce heat emissions by improved energy efficiency - improving boiler designs or reducing waste heat, for example - and substituting coal and gas with solar or thermal for water heating, geothermal heat, and bioenergy.

All of these are used in New Zealand but much more extensively in countries such as Sweden, Denmark and Finland, which have large district heating plants and combined heat and power plants fuelled by local biomass sources.

Q. New Zealand has a target of having 90 per cent of our electricity generated from renewable energy by 2025. If this can be achieved, what dent might this put in energy emissions?

It is likely to be achieved - and without any government intervention - as Huntly coal ages.

In power plants planned or already consented, there is around 4700MW of renewable energy.

Wind, solar, bioenergy, geothermal and small hydro have become more cost competitive.
The demand for solar photovoltaic system on rooftops will continue to increase.

Since we are already at a rate of 80 per cent renewable electricity, going to 90 per cent would only reduce our total greenhouse gas emissions by two to three per cent.

But it's still worth doing and we should be aiming for 100 per cent.

The system will have to become more flexible to accommodate higher shares of wind and solar - and maybe wave in the long term - that are variable, but this is technically possible.

The main challenge for smart-grid designers is to establish a market that will be effective in a dry year where hydro - currently around 60 per cent of total generation - gives lower generation.

This may need gas power stations used as standby back-up, as well as peaking plants perhaps - but who would pay for their maintenance?

It's technically possible to manage, but in a free market system it will be more of a challenge with uncertain returns on investment - so it would need government intervention.

Q. Given about 80 per cent of our electricity comes from renewable energy already, does New Zealand face a much harder task than other nations in cutting meaningful amounts of carbon from its energy supply?

That's the line that [Climate Change Issues Minister] Tim Groser uses.

But our total rate of renewable energy is only at 39 per cent, so we can still displace the 20 per cent of thermal coal and gas plants by renewables and we can use renewables for heat, such as in greenhouse crop production.

Transport can also be improved with renewable electricity - including more rail, and electric vehicles - or with sustainably produced liquid and gaseous biofuels that could displace diesel and gasoline.

Q. There has been much discussion around biofuel as an alternative to fossil fuels. Despite $42 million being invested in this space and ongoing research, is it realistic to expect this could be a credible option and are we really doing enough to realise this?

I started my energy career at Massey University making biodiesel from animal fats - back in 1974.

We know how to do it and some is being produced, along with ethanol from whey.

There are good biofuels and bad biofuels - the latter compete with food for land and produce relatively high greenhouse gases, such as corn ethanol in the United States.

Good biofuels can utilise crop residues otherwise left to decompose, but the technology is only just reaching maturity in the US and Europe, where millions have been spent in subsidies.

Scion, previously the Forest Research Institute, was researching wood to ethanol when I was making biodiesel and it has become apparent that Pinus radiata is not an ideal resource for that process.

However, there are other routes currently being explored.

The current cheap oil price - around US$45 per barrel today - is a disincentive to invest.
When I was based at the International Energy Agency, from 2007 to 2010, I did an analysis that showed oil needs to be around $100 per barrel for wood to ethanol to be viable.

Processing costs have declined but there remain the logistics of collecting and storing the biomass.

Nevertheless, in theory New Zealand could convert land from producing milk for export to earn money to pay for our oil imports - around NZ$7 billion per year - to produce biofuels and hence become more energy secure.

However, Z energy and Norske Hydro's "Stump to Pump" project has been put on hold because, in spite of the major investment, it didn't stack up.

Q. Can we expect increasing pressure from other countries to de-carbonise our transport and energy sectors and how might these pressures be applied?

It's hard to know as it partly depends what will come out of the Paris talks.

It could be by trade embargoes - but we can still argue, at least for milk products, apples and other exports, that if produced efficiently in New Zealand and transported across the world by ship, that the carbon footprint per kilogram of product is still less than if produced in US or European Union.

The key is to preserve the New Zealand clean, green brand that is fast slipping away once the reality of dirty waterways, growing greenhouse gas emissions and lack of greenhouse gas reduction policies are investigated.

Q. Do you hold any concerns that we may be overly relying on future technological advances to cut carbon, and is this a dangerous excuse for inaction today?

We can not guarantee technologies will develop fast enough.

According to the Ministry of Transport, we could have 350,000 electric vehicles (EVs) in New Zealand by 2025 - so that is a good example of disruptive technologies reducing emissions in New Zealand with zero per cent renewable electricity.

In countries like Australia, with high coal-fired generation shares, EVs can actually increase greenhouse gas emissions, as more are produced during the electricity generation than from the avoided gasoline or diesel combustion.

But behavioural change is also needed, and that is hard to predict - and the hardest to change in terms of use of public transport, smaller vehicles, opting for walking and cycling, and avoiding journeys altogether.

Modal choice for a journey by a person comes down to a combination of cost, comfort, convenience, speed and safety - so the challenge is to make it harder for cars and easier for other options.

If people realised the true cost of owning and operating a modern family car is around $1 per kilometre - according to the Automobile Association - there may be an incentive to change - but most people just count the cost of the gasoline.

Q. Finally, what does de-carbonising our economy mean for New Zealand as a brand?

This is the key challenge.

I'm chairing a Royal Society of New Zealand panel on climate change that will show we can achieve a low-carbon economy.

Local governments have a major role to play and are progressing well.

Sadly, the current National Government has little incentive to push mitigation - and hence our efforts as outlined in the recent Intended National Determined Contribution [post-2020 climate target] have been deemed "inadequate" by international analysts.
It's not a good image.

Jamie Morton will be travelling to Paris with the support of the NZ Science Media Centre and the Morgan Foundation.