By Robert McLachlan

As the Glasgow climate summits gets underway, New Zealand’s government has announced a revised pledge, with a headline figure of a 50% reduction on gross 2005 emissions by the end of this decade.

This looks good on the surface, but the substance of this new commitment, known as a Nationally Determined Contribution (NDC), is best assessed in emissions across decades.

New Zealand’s actual emissions in the 2010s were 701 million tonnes (Mt) of carbon dioxide equivalent. The carbon budget for the 2020s is 675Mt. The old pledge for the 2020s was 623Mt.

The Climate Change Commission’s advice was for “much less than” 593Mt, and the new NDC is 571Mt. So yes, the new pledge meets the commission’s advice and is a step up on the old, but it does not meet our fair share under the Paris Agreement.

It is also a stretch to call the new NDC consistent with the goal of keeping global temperature rise under 1.5℃.

True 1.5℃ compliance would require halving fossil fuel burning over the next decade, while the current plan is for cuts of a quarter.

Emissions need to halve this decade

Countries’ climate pledges are at the heart of the Paris Agreement. The initial round of pledges in 2016 added up to global warming of 3.5℃, but it was always intended they would be ratcheted up over time. In the run-up to COP26, a flurry of new announcements brought that figure down to 2.7℃ — better, but still a significant miss on 1.5℃.

As this graph from the UN’s Emissions Gap Report 2021 shows, the world will need to halve emissions this decade to keep on track for 1.5℃.

New Zealand’s first NDC, for net 2030 emissions to be 30% below gross 2005 emissions, was widely seen as inadequate. An update, reflecting the ambition of the 2019 Zero Carbon Act to keep warming below 1.5℃, has been awaited eagerly.

But several factors have combined to make a truly ambitious NDC particularly difficult.

First, New Zealand’s old climate strategy was based on tree planting and the purchase of offshore carbon credits. The tree planting came to and end in the early 2010s and is only now resuming, while the Emissions Trading Scheme was closed to international markets in 2015. The Paris Agreement was intended to allow a restart of international carbon trading, but this has not yet been possible.

Second, New Zealand has a terrible record in cutting emissions so far. Burning of fossil fuels actually increased by 9% from 2016 to 2019. It’s a challenge to turn around our high-emissions economy.

Third, our new climate strategy, involving carbon budgets and pathways under advice from the Climate Change Commission, is only just kicking in. The government has made an in-principle agreement on carbon budgets out to 2030, and has begun consultation on how to meet them. The full emissions-reduction plan will not be ready until May 2022.

Regarding a revised NDC, the government passed the buck and asked the commission for advice. The commission declined to give specific recommendations, but advised:

We recommend that to make the NDC more likely to be compatible with contributing to global efforts under the Paris Agreement to limit warming to 1.5℃ above pre-industrial levels, the contribution Aotearoa makes over the NDC period should reflect a reduction to net emissions of much more than 36% below 2005 gross levels by 2030, with the likelihood of compatibility increasing as the NDC is strengthened further.

The government then received advice on what would be a fair target for New Zealand. However, any consideration of historic or economic responsibility points to vastly increased cuts, essentially leading to net-zero emissions by 2030.

Announcing the new NDC, Climate Change Minister James Shaw admitted it wasn’t enough, saying:

I think we should be doing a whole lot more. But, the alternative is committing to something that we can’t deliver on.

What proper climate action could look like

Only about a third of New Zealand’s pledged emissions cuts will come from within the country. The rest will have to be purchased as carbon credits from offshore mitigation.

That’s the same amount (100Mt) that Japan, with an economy 25 times larger than New Zealand’s, is planning to include in its NDC. There is no system for doing this yet, or for ensuring these cuts are genuine. And there’s a price tag, possibly running into many billions of dollars.

New Zealand has an impressive climate framework in place. Unfortunately, just as its institutions are beginning to bite, they are starting to falter against the scale of the challenge.

The commission’s advice to the minister was disappointing. It’s being challenged in court by Lawyers For Climate Action New Zealand, whose judicial review in relation to both the NDC and the domestic emissions budgets will be heard in February 2022.

With only two months to go until 2022 and the official start of the carbon budgets, there is no plan how to meet them. The suggestions in the consultation document add up to only half the cuts needed for the first budget period.

Thinking in the transport area is the furthest advanced, with a solid approach to fuel efficiency already approved, and an acknowledgement total driving must decrease, active and public transport must increase, and new roads may not be compatible with climate targets.

But industry needs to step up massively. The proposed 2037 end date for coal burning is far too late, while the milk cooperative Fonterra — poised to announce a record payout to farmers — intends to begin phasing out natural gas for milk drying only after that date.

The potentially most far-reaching suggestion is to set a renewable energy target. A clear path to 100% renewable energy would provide a significant counterweight to the endless debates about trees and agricultural emissions, but it is still barely on the radar.

Perhaps one outcome of the new NDC will be that, faced with the prospect of a NZ$5 billion bill for offshore mitigation, we might decide to spend the money on emissions cuts in Aotearoa instead.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Kāpiti Coast Airport has hardly any flights and is living on borrowed time, but it just won’t die. Now a new report concludes that it “cannot remain operationally viable”.

By Paul Callister

In Glasgow, world leaders will be making big global decisions. These will have a major impact on whether we can avoid the worst of global warming. But it is also local decisions that will increasingly determine whether towns, cities and countries can reduce their emissions.

Throughout the world, aviation continues to get support from governments and local councils. It is also one of the sectors most difficult to decarbonise, especially as growth is still being promoted.

In New Zealand, regional air travel is subsidised in various ways. Sometimes it is through local authorities owning uneconomic airports. Or it can be through direct subsidies of airlines. This tends to spread the cost of air travel across the whole community, with the benefits mostly going to the better off members who also tend to have the highest emission profiles. Kāpiti Coast District Council provides direct support to Air Chathams. It now also wants to find ways to support the local airport.

Kāpiti airport needs to close. It is uneconomic and it is in the wrong place. It would be better suited to housing, which would help reduce local transport emissions. It will not get better. A report on the future of the airport undertaken in September 2021 by aviation consultancy group Lockie Airport Management highlights multiple problems.

Despite this, the future of Kāpiti’s “ghost” airport continues to be contested. In a report back to submitters on Kāpiti’s Long-term Plan, the council states that ‘the future of the privately owned Kāpiti Coast Airport is uncertain’. If the council had undertaken a number of measures, including taking advice from airport experts, undertaking a full cost benefit analysis of airport operations, and had looked at small airport ownership around the world, or considered the airport’s alternative uses, they would have realised the future is absolutely certain. The uneconomic, and potentially unsafe, airport will eventually close. Medium to high density houses and apartments will be built on the site helping solve the housing crisis. These houses will be close to the centre of Paraparaumu and public transport, with already-established walkways and cycleways. This is the intensification the government is trying to promote. It is something a council, which has declared a climate emergency and which expresses concern about housing, should support.

Instead, based simply on a popularity contest, the council has indicated that it will explore ways to have a role in the airport’s future. They say this will include operating the airport under a lease or owning it in partnership. Exploring these options will further waste ratepayer money and delay the construction of desperately needed housing.

A key problem is runway length. The runway is physically 1450m in length, but technical constraints caused by roads, houses and terrain mean that there is only 1042m available for landing from the North, or 1187m for landing from the South. Practically, this limits the size of passenger aircraft the airport can accept. The largest was the Bombardier Q300s operated by Air NZ. These have 58 seats. However, they were not able to use all of them when flying from Kāpiti due to the available runway length. Air New Zealand are phasing these aircraft out in favour of the ATR72, which cannot realistically land with a full load of passengers at the airport. Air Chathams SAAB 340s are currently the largest aircraft using the airport at 36 seats. Other than Air Chathams and Air NZ, no other airline currently has a 30 seat plus aircraft capable of using the airport. This seriously limits opportunities for growth. Mayor Gurunathan has been reported saying that he does not want Air New Zealand back anyway.

Then there is Runway End Surface Area (RESA). The report says that the airport has the minimum allowable RESA length of 90m when the preferred length is 240m. The 90m RESA was re-approved in 2019. However, the report states a RESA below the recommended specification of 240m will not be approved again. The report says that other airports which have applied for reduced RESA’s since Kāpiti’s was approved have been unsuccessful. Extending the RESA is not practicable due to fixed flight path obstructions, a road, a number of private houses and a retirement village.

But it does not end there. There is an Obstacle Limitation Surface issue (OLS). The OLS is the required clear flight path on approach and departure to maintain suitable margins in poor weather and emergencies. There are around 900 noted objects to monitor spread over several hundred neighbouring properties. The objects are mostly trees but also chimneys, antennas, street lights and buildings, which add to the practical limitations on extending the runways and RESA.

A key lobby group for keeping the airport open is the aero club. Under the banner “Kāpiti Air Urban”, the club and a group of other airport supporters make some startling claims that are not supported by international evidence. An example is that by 2030 40% of aviation fuel will be from sustainable sources. In a paper on sustainable aviation fuels, Air New Zealand suggests a ‘drop’ in rate of 2.5% by 2025, reaching 25% by 2040. But, more problematically, the clubs’ activities do not provide the income needed to sustain an airport. There are plenty of good options for relocating the aero club, including the Foxpine airstrip, or even Palmerston North.

Kāpiti Air Urban clearly see innovation, including electric flight, solving the airport’s problems. This will be an argument we increasingly see. Why invest in regional passenger rail when electric planes are just around the corner?

Unfortunately for Kāpiti, electric planes also will not solve the economic viability or safety issues. Even if they eventually fill a niche in short hop air travel, they will not be common in our skies any time soon. Those under the flight paths will not welcome experimental planes flying over them. Far better that they fly out of Palmerston North or Wellington airports with flight paths away from major housing. These airports will also be able to fund the expensive charging infrastructure.

KCDC is now consulting on a growth strategy. It wants to house an extra 32,000 people by 2051. There will be some intensification, but the draft also suggests some greenfield development. The latter will inevitably lead to further sprawl and increase the region’s transport emissions just when we need to be reducing them.

The current airport owners, the Templeton Group, are housing developers. Instead of wasting money on impractical schemes to keep the airport open to support a high emissions industry, the council should be working with these developers to build the houses the district so badly needs.

By Paul Callister and Robert McLachlan

Electric aircraft have arrived, but a lot has to happen to make commercial flights a reality. Can they live up to the hype, and can they reduce aviation emissions? We run the numbers.

It’s not easy to keep up with the rapidly-changing world of electric aircraft. It can look like a blizzard of breathless media coverage, corporate press releases, animations, venture capital deals and public offerings.

But as the launch dates creep closer, companies have been releasing more details, which makes it possible to see if the numbers add up.

Leaving aside Jetsons-like flying cars, three high-profile electric aircraft are Eviation’s Alice and Lilium’s Lilium Jet, both targetting commercial operations in 2024, and Heart Aerospace’s ES-19, targetting 2026. They are all startups, all with clean-sheet designs, all with substantial funding and order books.

While a lot of new technologies have to come together to make these planes fly, the most crucial part is the battery system. In this article we’ll use what we know so far about these three aircraft to see if they will deliver as promised.

The range equation

The range equation for battery electric aircraft is:

Here

R is the range in kilometres;

e_b is the specific energy of the battery in Wh/kg;

w_b is the fraction of the total mass of the aircraft occupied by the battery system;

g = 9.81 m/s  is the acceleration due to gravity;

L/D  is the lift/drag ratio;

𝜂  is the efficiency of the battery-motor-propeller system; and

f  is the available fraction of the battery capacity.

Aircraft design is always a matter of compromises. Limitations associated with takeoff, cruise, landing, and range all point in different directions, while the economics depends on payload, speed, and fixed and operating costs for starters.

The Eviation Alice

Eviation announced a major redesign of the 9-passenger Alice in July. Crucially, they released some details of its battery: it stores 820 kWh and weighs 3720 kg, implying a specific energy of 220 Wh/kg. That’s for the whole battery pack and system, including temperature management.

For reference, the Tesla Model 3 has the highest specific energy battery pack now in widespread commercial use, at 160 Wh/kg. However, Tesla’s forthcoming 4680 cell, due in 2022-23, is aiming to achieve 380 Wh/kg at the cell level, which could mean that (allowing for framing, wiring, and cooling) 240 Wh/kg at the pack level is achievable.

On the other hand, the safety and cooling requirements are likely to be more stringent for planes than for cars. A lot of engineering has to happen between now and commercial flight to achieve the required weight and performance, to say nothing of reassuring the regulators about the risks of thermal runaway in the batteries.

Let’s use 220 Wh/kg for all three planes.

A high propulsion efficiency  is also crucial for range. Here we take , which requires each of the electrical and the propeller systems to be well over 90% efficient. This is optimistic but we can be sure that the engineers are aiming for something like this.

This gives the 9-passenger Alice, with a whopping 58.6% of its mass taken up by batteries, a range of 658 km. That’s an upper limit, since we haven’t taken into account any energy used by the other on-board systems, or the fact that climbing uses extra energy that is not all recouped on the descent. It’s less than the claimed range of 820 km, but still very impressive.

But not all that range is available for scheduled flights. Most regulators (e.g. in the US), require a 30 minute safety margin for daylight flights – about 165  km. (Night flights need 45 minutes reserves, and flights under Instrument Flight Rules need to be able to fly to an alternate airport plus an extra 45 minutes.) In addition, the battery capacity will degrade over time and the batteries will likely be replaced every 1500 flights or so, or at 80% state-of-health. With 30 minutes reserve and 80% state-of-health, the available range of the Alice is reduced to 360 km.

Eviation do have a bit of weight free. They could add more batteries while staying under the 8618 kg weight limit for this class of plane. However, diminishing returns set in, because unlike in a car, the extra batteries have to be carried aloft, which costs energy. Adding 50% more batteries would only increase the range by 16%.

Another critical task is to reduce the empty weight as much as possible. Eviation are claiming an empty weight of 1530 kg, to be achieved through the use of composites. There is only one small jet currently flying using composites, the 6-passenger Hondajet. It has a composite fuselage, aluminum wings, and an empty weight of 3379 kg. Eviation is aiming for less than half that weight.

Heart Aerospace’s ES-19

Heart Aerospace have said that the battery of the 19-passenger ES-19 weighs 3000 kg. This puts the battery at 35% of the maximum take-off weight of 8618 kg.  This is also consistent with an 220 Wh/kg battery and a range chart released by the company. Together these give a range of 393 km, matching the company’s claim of 400 km. However, the reserve requirement now really eats into the possible routes, leaving only 150 km of range if a 30 minute reserve is needed.

The ES-19 is to be made of aluminum, which is cheaper, simpler, and heavier than composites. Heart Aerospace are aiming for an empty weight of about 3600 kg. The aluminum-framed Beech 1900, a popular 19-seat regional turboprop built from 1982 to 2002, has an empty weight of 4732 kg. A group of aircraft engineers at Linkoping University in Sweden have recently carried out a conceptual study of a 19-passenger electric aircraft very similar to the ES-19. It comes in at an empty weight of 3623 kg, achieved with extensive composites and no cost restrictions. Their more detailed model predicts a range of 284 km when 220 Wh/kg.

The Lilium Jet

The Lilium Jet is something different. By far the highest-profile project of the three, Lilium recently went public, raising $585 million to add to the $375 million already on hand. It has 600 employees. The Lilium Jet uses an array of pivoting ducted fans rather than conventional propellers, allowing a vertical takeoff which quickly pivots to conventional flight. It doesn’t need a runway, but it has a lower weight limit (used for helicopters) of 3175 kg. The data they have released, taking into account that the batteries cannot deliver the power needed for landing when the battery charge is below 10%, give a range of 160 km, much lower than their aim of 250 km. (This is less than what is given by the battery range equation, because the ducted fans are less efficient than propellers and the hovering phase is extremely energy-intensive, while the fan design is a compromise between the cruise and hover phases.)

Lilium gets a range of 250 km by incorporating a battery with 320 Wh/kg at the cell level and discounting the weight of the packaging and thermal management, remarking that “the structural modules of the battery cells will be part of the empty aircraft structure.” That’s a pretty big task, since they are already aiming for an empty weight less than half that of the Hondajet.

So is it all hype?

Not quite. Batteries now starting production do deliver a useable range, if not quite what the companies are hoping. They will be aiming to get a foot in the door and to upgrade to better batteries as they become available. There are engineering hurdles to overcome, including minimizing weight and ensuring the reliability of the battery cooling system. There are political hurdles to overcome in certification. Existing modern aircraft are extremely safe, with only one fatal crash per ten million flights. Any battery issues during test flights will make regulators extremely wary. In addition, developers will also be asking for flexibility on fuel reserve requirements.

Or is it greenwash?

The media are certainly greenwashing like crazy, talking about “Decarbonizing air travel”. Electric aircraft will not be contributing meaningfully to decarbonizing air travel for decades, if ever – decades in which aviation emissions have to reduce steadily to achieve climate targets. Flights of up to 200 km contribute less than 1% of aviation emissions, and flights of up to 500 km, 5%.

The companies themselves have slightly different goals. They are hoping to revive short-range commercial aviation, which has been in decline due to its unprofitability and limited time savings. The idea is to offer a cheaper, more comfortable, and more convenient service than existing regional jets. Cheaper because electric, more comfortable because quieter and new, more convenient because they will use more and smaller airports. If this comes about, and especially if the routes lead to major airports connecting to long-range flights, electric aircraft would lead to increased emissions overall. If successful, they would also undermine lower-emission ground transport, such as trains.

Put it all together and it spells… New Zealand?

With all this in mind, it makes sense that New Zealand’s Sounds Air has been chosen as the Australasian launch customer for the ES-19. Sounds Air currently has six 9-seater and four 12-seater aircraft, flying to mostly smaller destinations such as Blenheim (population 28,000). A key launch route would be Blenheim–Wellington, just 75 km across Cook Strait, a famously rough stretch of water that channels the Roaring Forties. The flight would avoid a 3 hour 40 minute ferry ride. Such a route – head winds permitting – is ideal, and could lead to services at many similar island hops around the world.

Sounds Air might also find the regulators easier to deal with. New Zealand has been keen to welcome urban air mobility companies, who applaud its “flexibility” and have said they can do things in New Zealand they wouldn’t be able to do in the US.

Electric aircraft are at an exciting stage and may well find a niche. But they also risk turning into one more means of hypermobility for the rich, at a time when all forms of transport need to reduce in emissions, energy, and resources.

This article was first published at CleanTechnica. Read the original article.

By Robert McLachlan

How are fossil fuels formed, why do they release carbon dioxide and how much of the world’s energy do they provide? And what are the renewable energy sources that could replace fossil fuels?

Fossil fuels were formed over millions of years from the remains of plants and animals trapped in sediments and then transformed by heat and pressure.

Most coal was formed in the Carboniferous Period (360–300 million years ago), an age of amphibians and vast swampy forests. Fossilisation of trees moved enormous amounts of carbon from the air to underground, leading to a decline in atmospheric carbon dioxide (CO₂) levels — enough to bring the Earth close to a completely frozen state.

This change in the climate, combined with the evolution of fungi that could digest dead wood and release its carbon back into the air, brought the coal-forming period to an end.

Oil and natural gas (methane, CH₄) were formed similarly, not from trees but from ocean plankton, and over a longer period. New Zealand’s Maui oil field is relatively young, dating from the Eocene, some 50 million years ago.

Burning buried sunshine

When fossil fuels are burnt, their carbon reacts with oxygen to form carbon dioxide. The energy originally provided by the Sun, stored in chemical bonds for millions of years, is released and the carbon returns to the air. A simple example is the burning of natural gas: one molecule of methane and two of oxygen combine to produce carbon dioxide and water.

CH₄ + 2 O₂ → CO₂ + 2 H₂O

Burning a kilogram of natural gas releases 15kWh of energy in the form of infrared radiation (radiant heat). This is a sizeable amount.

To stop continuously worsening climate change, we need to stop burning fossil fuels for energy. That’s a tall order, because fossil fuels provide 84% of all the energy used by human civilisation. (New Zealand is less reliant on fossil fuels, at 65%.)

There are many possible sources of renewable or low-carbon energy: nuclear, hydropower, wind, solar, geothermal, biomass (burning plants for energy) and biofuel (making liquid or gaseous fuels out of plants). A handful of tidal power stations are in operation, and experiments are under way with wave and ocean current generation.

But, among these, the only two with the capacity to scale up to the staggering amount of energy we use are wind and solar. Despite impressive growth (doubling in less than five years), wind provides only 2.2% of all energy, and solar 1.1%.

The renewables transition

One saving grace, which suggests a complete transformation to renewable energy may be possible, is that a lot of the energy from fossil fuels is wasted.

First, extraction, refining and transport of fossil fuels accounts for 12% of all energy use. Second, fossil fuels are often burnt in very inefficient ways, for example in internal combustion engines in cars. A world based on renewable energy would need half as much energy in the first place.

The potential solar and wind resource is enormous, and costs have fallen rapidly. Some have argued we could transition to fully renewable energy, including transmission lines and energy storage as well as fully synthetic liquid fuels, by 2050.

One scenario sees New Zealand building 20GW of solar and 9GW of wind power. That’s not unreasonable — Australia has built that much in five years. We should hurry. Renewable power plants take time to build and industries take time to scale up.

Other factors to consider

Switching to renewable energy solves the problems of fuel and climate change, but not those of escalating resource use. Building a whole new energy system takes a lot of material, some of it rare and difficult to extract. Unlike burnt fuel, metal can be recycled, but that won’t help while building a new system for the first time.

Research concluded that although some metals are scarce (particularly cobalt, cadmium, nickel, gold and silver), “a fully renewable energy system is unlikely to deplete metal reserves and resources up to 2050”. There are also opportunities to substitute more common materials, at some loss of efficiency.

But many metals are highly localised. Half the world’s cobalt reserves are in the Democratic Republic of Congo, half the lithium is in Chile, and 70% of rare earths, used in wind turbines and electric motors, are in China.

Wasteful consumption is another issue. New technologies (robots, drones, internet) and economic growth lead to increased use of energy and resources. Rich people use a disproportionate amount of energy and model excessive consumption and waste others aspire to, including the emerging rich in developing countries.

Research analysing household-level emissions across European countries found the top 1% of the population with the highest carbon footprints produced 55 tonnes of CO₂-equivalent emissions each, compared to a European median of 10 tonnes.

Scientists have warned about consumption by the affluent and there is vigorous debate about how to reduce it while preserving a stable society.

One way of turning these questions around is to start from the bottom and ask: what is the minimum energy required for basic human needs?

One study considered “decent living” to include comfortable housing, enough food and water, 10,000km of travel a year, education, healthcare and telecommunications for everyone on Earth — clearly not something we have managed to achieve so far. It found this would need about 4,000kWh of energy per person per year, less than a tenth of what New Zealanders currently use, and an amount easily supplied by renewable energy.

All that carbon under the ground was energy ripe for the picking. We picked it. But now it is time to stop.

This article is republished from The Conversation under a Creative Commons license. Read the original article. Climate explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change. If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz.

By Robert McLachlan

Climate solutions are often judged not just by whether they work – that is, by whether they reduce emissions – but also by whether they support a “just transition”. As Sam Huggard of the New Zealand Council of Trade Unions writes, “the costs of the necessary changes that deliver all of us a more stable climate must be spread evenly and not fall heavily and disproportionately on workers, particularly those in carbon-exposed industries.” New Zealand has joined international declarations to that effect, and set up a “Just Transitions” unit in the civil service, to ensure that the process is “fair, equitable and inclusive [and] that the Government works in partnership with iwi, communities, regions and sectors to manage the impacts and maximise the opportunities of the changes brought about by the transition to a low emissions economy.“

All well and good. But what is “fair”? It’s easier to detect things that are unfair, like a large and sudden petrol tax. People whose only available choice is to commute long distances in cheap gas guzzlers would bear the brunt, while wealthy inner-city dwellers could continue to clog up the roads in their Teslas. Most would agree that we don’t want anything as unfair as that and that it’s worth looking for another way.

I want to turn things around and look, not at the impacts on poor people, who generally have low personal emissions and less ability to change them, but at the rich high-emitters.

The Paris Agreement, after all, is founded on the principle of equity, and the “common but differentiated responsibilities and respective capabilities” of the nations. Just what those are is open to debate, but this clause is generally held to mean that countries with high historical emissions – the ones that caused this problem – and rich countries, that have more scope and power to reduce emissions, should move faster than others.

How about within countries? Should rich people, and/or high-emitting people, pay proportionately more towards a country’s transition, and reduce emissions more than others?

How are carbon emissions distributed?

To begin to get a handle on this thorny question we first need to know the distribution of emissions within individual countries. A 2020 paper by Diana Ivanova and Richard Wood (“The unequal distribution of household carbon footprints in Europe and its link to sustainability“) looks at this for 26 EU countries. (The data comes from a survey of the expenditure of 275,000 households carried out in 2010, mapped into greenhouse gas emissions for each type of spending.)

Household emissions measure the emissions related to final consumption, wherever the actual greenhouse gases were emitted. The EU as a whole produces impressively low greenhouse gas emissions of 8 tCO2e per person, a lot lower than New Zealand’s 16.5 tCO2e. But many EU countries effectively import emissions by buying things from other countries, such as China. Imports take the UK’s 6.8 tCO2e per person up to 9.6 tonnes, and Germany’s 9.6 tonnes up to 11. New Zealand, a net exporter of greenhouse gases, consumes 12.5 tonnes per person. Of these 12.5 tonnes, 8.9 tonnes are assigned to households.

Here are Ivanova and Wood’s overall results:

The lowest-emitting half of EU households emit an average of 5 tonnes per person; the middle 40%, 10 tonnes; the top 10%, 23 tonnes; and the top 1%, a whopping 55 tonnes CO2e per person.

Air travel is strikingly unevenly distributed. 90% of EU households have air travel emissions averaging 0.1 tonnes per person; 9% average 0.8 tonnes; and the last 1% average 22.6 tonnes. That’s enough to fly around the world five times (or once in business class). This is confirmed in the breakdown by household expenditure:

Emissions from essential items (food and housing) increase more slowly that total spending: there’s a limit to how much food you need. Emissions from goods, services, and land transport increase in tandem with total spending, while emissions from air travel increases very little in the lower quintiles but very rapidly in the top two. The authors write that this “confirms air travel as a highly carbon-intensive luxury” and describe transport as “one of the most unequally distributed and the strongest drivers of the carbon footprints of the rich“.

They also report the distribution of household emissions across countries. For most countries these track very closely to the distribution of income:

55 tonnes per person may seem like a lot, but it is confirmed by other studies. A 2015 paper by Lucas Chancel and Thomas Piketty (“Carbon and inequality: From Kyoto to Paris“) found that the top 1% of Americans emit 318 tonnes CO2e each per year. They put the emissions of the top 1% globally at 56 tonnes a year. (They get slightly higher figures than Ivanova and Wood, because they include all emissions and all income, not just those tagged to household consumption.)

The extremely skewed distribution of air travel is also reported by Stefan Gössling and Andreas Humpe, in “The global scale, distribution and growth of aviation: Implications for climate change” (2020). They find that in any given year 1% of the world’s population are extremely frequent flyers, emitting 10 tonnes CO2 each on average and causing half of all aviation emissions; another 10% fly less and emit 1 tonne CO2; and the remaining 89% do not fly at all. People with access to one of the world’s 22,000 private jets could be associated with emissions of 7500 tonnes each. Even in rich countries like the US and Germany, and rich islands like Taiwan, less than half the population flies in any particular year.

One final report, by Oxfam in 2020, “Confronting carbon inequality: Putting climate justice at the heart of the Covid-19 recovery“, reaches a similar conclusion. Oxfam find that the richest 1% globally have emissions of 74 tonnes of CO2 per person on average, adding up to 15% of all emissions.

Where does New Zealand fit into all this?

Statistics New Zealand have calculated consumption emissions by household for 2017. They only report the average, not the distribution, so I will try to relate the New Zealand figures to the EU study.

The median take-home income in New Zealand is $41,500 per person. Adjusted for purchasing power that comes to €19,300, above the EU median of €17,300, and similar to countries that we think of as ‘rich’, like Ireland and Finland, and above the UK.

I’ll compare New Zealand’s average household emissions to those of a median EU household.

	New Zealand 2017	EU 2010
Food	2.5	1.5
Housing	1.4	2.1
Clothing	0.24	0.4
Services	0.5	0.6
Manufactured products	0.95	0.8
Land travel	2.3	2.4
Air travel	1.0	0.17
Total	8.9	9.4

We have higher food emissions – I’m not sure why, although the 2.5 tCO2/person figure does agree with another study by Drew. We have lower housing emissions, which makes sense because our electricity is cleaner and we don’t heat our homes with gas (some would say we hardly heat them at all.) Consumption of “stuff” as about the same, as is (surprisingly), land travel. We fly six times as much.

One way to measure income distribution is by the ratio of the total income of the richest 20% to the total income of the poorest 20%. For New Zealand, this ratio is 5.6. For the UK is is 6.1, for Germany 4.4, and for the EU as a whole it is 5.0 – all in the same ballpark.

Therefore, my first estimate is that the emissions of New Zealand households are distributed very unequally. Given our high air travel emissions, and the high elasticity of air travel amongst rich people, it’s likely that our top 1% and top 10% of households have very high emissions indeed. The distribution may look similar to that of Great Britain, shown above.

A second line of attack views New Zealand in light of Piketty’s global income distribution. A take-home income of $75,000 per person puts you globally in the top 1%, which, as we have seen, have sky-high emissions of 56 tonnes per person. In New Zealand, 12.3% of households reach that income level. (Technically, this is net income per ‘equivalent adult’, in which children under 14 count as 0.3 and children 14-17 count as 0.5 adults.) New Zealand’s top 5% ($100K) have similar purchasing power to the top 5% in the richer European countries (~€50K). This also points to distributions similar to those found in the EU.

What then?

The authors of the four studies quoted above have some suggestions.

Oxfam call for

special taxes or bans for high carbon luxury goods and services; wider carbon prices with pro-poor revenue recycling; broader income and wealth redistribution; or challenging stereotypes that promote growth and individual consumerism as normal, desirable, ‘powerful’ and ‘masculine’… such measures may lead to a broader ‘social tipping point’ that makes reductions by other relatively high emitters more acceptable, challenges the political influence of high emitters, and sparks wider shifts in social, gendered and racial norms about endless consumption.

Gössling, on aviation, writes:

Emissions Trading Schemes are inappropriate for a sector in which the distribution of air transport demand and associated emissions is more highly skewed than in other areas of consumption. From a market-based viewpoint, a modest increase in the cost of air travel will not affect business travelers, who are causing disproportionally high emissions… [we] need to develop more complex transition policies for aviation.

Ivanova and Wood:

The contributions of land and air transport are disproportionally large among the top emitters. As land transport and, even more so, air transport are both highly carbon intensive and highly elastic, we would argue that significantly more needs to be done in these domains. Action here is likely to affect those with the highest footprints, incomes and expenditures most, but impacts on low-income groups are also key, as they have significant expenditure shares on land transport.

Overconsumption and materialistic practices are not only damaging for the environment, but may also reduce psychological well-being. In order to reduce trade-offs between social and environmental goals, policies should target changes in higher-order need satisfiers, such as social structures and practices, and reimagine forms of need satisfaction within environmental constraints.

Chancel and Piketty suggest a global progressive carbon tax for above-average emitters, to fund climate initiatives globally, or, failing that (for they acknowledge this is unlikely), progressive income taxes, or a global tax on air tickets of about €20 per 1000 km.

Whichever way you slice it, aviation is a problem. It’s a luxury good that has managed to sell itself as essential, and to be above reining in. International air travel escapes all GST, fuel taxes, and emissions trading schemes, even in places that otherwise have them. Its use is highly skewed towards the rich, even within rich countries, and it has shown very high growth rates over long periods.

The problem is not just that the high emitters have to pay more towards the transition, even more as a proportion of their income: that’s not that controversial, it’s already embedded in progressive income taxes to some extent. The harder problem is that they actually have to reduce their emissions, which means way fewer luxury cars and much less air travel. Ivanova and Wood regard a target of 2.5 tonnes per person by 2030 as consistent with the Paris agreement. (Oxfam say 2.1 tonnes). That means average emissions falling by 70%. But the bottom half of emitters can’t reduce by very much at all, which means the top half have to do more.

Which brings me right back where I started: Should rich people, and/or high-emitting people, pay proportionately more towards a country’s transition, and reduce emissions more than others? And if so, how?

By Robert McLachlan

New Zealand’s Climate Change Commission is facing its first legal hurdle, as a group of 300 climate-concerned lawyers seek judicial review of the processes it used to calculate carbon budgets in its recently released advice to government.

Carbon budgets are a cornerstone of New Zealand’s climate change response under the Zero Carbon Act and lie at the heart of the commission’s advice package. They specify the allowed emissions over successive five-year periods, initially up to 2035. The advice calls for net emissions of all greenhouse gases to fall 27% between 2019 and 2030.

The Lawyers 4 Climate Action group claims the commission has misinterpreted pathways in Intergovernmental Panel on Climate Change (IPCC) reports in its calculations, making its advice inconsistent with the act, especially regarding the goal to limit global temperature rise to 1.5℃.

Pending the outcome of the legal challenge, the government is likely to adopt the recommended budgets, which would then flow into the settings of the Emissions Trading Scheme and all other aspects of climate policy.

The commission has engaged extensively with the more than 15,000 submissions it received on its draft advice. So it was surprising that in its final advice, the budgets were increased, allowing higher emissions.

The commission’s immediate reason for the increase was the significant blow-out of emissions in 2019, up by three million tonnes of CO₂-equivalent emissions. It judged this was not a one-off, and has allowed another two million tonnes in each year to 2030.

The commission also had to balance a long list of requirements, including that the budgets be ambitious, achievable and fair to both present and future generations, while supporting the global effort to limit warming to 1.5℃. The commissioners write:

A transition that is fair, inclusive and equitable for people is crucial so that it is acceptable to New Zealanders. Putting the values of manaakitanga, tikanga, whanaungatanga and kotahitanga at the forefront means having a deep ethic of care for people and the land. Having support and buy-in from New Zealanders is vital for meeting and sustaining emissions reduction targets.

But consider Ireland. Like New Zealand, Ireland has high agricultural emissions and a poor climate track record to date. Yet Ireland recently adopted a new climate law that requires net zero emissions of all greenhouse gases by 2050 and cuts of at least 51% between 2018 and 2030. This is unquestionably much stronger than New Zealand’s act.

Many goals, but no easy options

New Zealand is indeed in a tight spot. Decades of delay and spurious manoeuvring have seen emissions rise steadily, with few transition plans in place.

The main emitting sectors are often also key export industries, which should not face unfair competition, while consumption sectors (like private cars) lie broadly across the whole society.

Some key approaches from the past — international carbon trading, and extensive forest planting — have fallen out of favour. Following a collapse in credibility, international carbon trading will need new rules to allow it to restart, while afforestation, though still playing a part, pushes the transition out to future generations.

The scope of the transition is challenging, and the commission argues its budgets are the best combination of ambitious and achievable.

A path towards lower emissions

A major part of the report describes in detail how the budgets could be met. For example, a relatively easy first step is to phase out coal burning for electricity generation.

Coal and gas use in the food industry, mostly for the production of milk powder, has to rapidly decrease. So far, one plant, at Te Awamutu, has been converted from gas to biomass, saving 83,000 tonnes of CO₂-equivalent emissions per year. But by 2030, the industry needs to cut more than 20 times as much.

Fossil fuel use in buildings, like coal boilers in schools, gets a lot of attention, but only adds up to a small part of the cuts needed. All other industries (including steel, aluminium, methanol, cement, mining, hydrogen, and ammonia) need to cut fossil fuel use substantially, preferably without all having to close.

The table below shows the proposed emissions reductions for different sectors, under the commission’s demonstration path.

The transport sector has finally seen government action, with the introduction of an extensive system of fuel efficiency standards and fees and discounts for newly imported vehicles. The commission argued for all of these and more, with a substantial shift away from private cars to active and public transport on a scale beyond New Zealand’s experience.

This transformation is sure to be contentious, from local battles over car parking and cycleways to the entire operation of the public transport system.

New Zealand’s Paris commitments

Another significant piece of advice the commission was asked to give was whether New Zealand’s Nationally Determined Contribution (NDC) is adequate. Climate change minister James Shaw had punted this question to the commission, which has passed it right back like in a game of hot potato.

There are two difficulties. First, the commission has already identified the biggest domestic emission cuts; anything further must come from overseas. That will be expensive, and there are no rules yet on how these “internationally transferred mitigation outcomes” will be conducted. This will be on the agenda at the 26th UN Climate Change Conference of the Parties (COP26) in Glasgow later this year.

Second, the entire basis for the NDC stems from the requirements to balance equity, responsibility and need. For New Zealand, that points towards much higher ambition than at present.

The commission did advise the NDC should involve an international mitigation effort of “much more than” 10% of current gross emissions, at a cost of many billions of dollars per decade. But it argued this required political, social and ethical considerations only the government could determine.

All of these matters will now fall under the scrutiny of the High Court.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

On 27 June, the New Zealand Government announced the phase-out of some hard-to-recycle and some single-use plastics. Robert McLachlan talks to Massey University’s Trisia Farrelly, a tireless campaigner against plastic waste.

Trisia: I’m an anthropologist at Massey University, I wear quite a few hats around New Zealand and internationally on plastic pollution, which I’ve been researching since 2016.

Robert:  And here I thought it was a lifetime passion! You’re an anthropologist… so are you trying to save the world, or just study how it works?

Trisia: Save it! One piece of plastic at a time. 

Robert:  The talk you gave recently described everything from your plastic-free year all the way up to the UN.

Trisia: Yes, multiscale! My personal journey started with a film, I watched the Clean Bin Project. The directors were in New Zealand and I invited them to Massey. That was the turning point. Film can be powerful! The revelations hit home and made me become quite concerned about plastics. A moment of realisation, a wake-up call. After that, things happened. 

My UN work came out of one presentation I gave in Switzerland. In fact I angsted over whether I should go for a long time, but a number of New Zealand organisations urged me to go and speak for them. 

I gave a very impassioned, political talk on why we should stop putting so much attention on the individual, on “ecological citizenship”, and start focussing head on on state–industry relationships and start talking about limiting production. I gave it my best shot. Then I was invited to join the UNEA Ad Hoc Open Ended Expert Group on marine litter and micro plastics.

I also met Pete Myers, author of Our Stolen Future. He later came to New Zealand and talked to the Ministry for the Environment, he talked to Kim Hill. That inspired my work to try and regulate toxic chemicals in plastics.

Robert:  This “state–industry relationship”, is that as simple as industry lobbying government to do what they want, or is there more to it than that?

Trisia: There’s a whole playbook that industry has on how to influence government and redirect responsibility for plastic pollution onto consumers. It’s an exciting area to study. Since the 1950s they’ve been playing the recycling card, diverting attention from one thing to another, complicating by confusion.  Very much the ‘merchants of doubt’ situation.

Robert:  So New Zealand has now announced that we are going to ban some single-use plastics by 2025. And apart from the supermarket shopping bags, it’s the first time that something has actually been banned, is that right?

Trisia: They also banned some types of microbeads. This is all covered under the Waste Minimization Act: since 2008 there’s been a facility provision to prioritise some products for product stewardship schemes. It’s exciting that this is finally being used. It sets a precedent for a number of problematic products.

Robert:  Is the hope that this will get people used to the idea of banning things?

Trisia: Yes, but it doesn’t have to be bans. There are other tools, like incentives. But for the worst products, banning is suitable. And unfortunately, 2025 feels like a long way away!

Robert:  Apparently New Zealanders generate 58 kg of plastic waste each per year. Are these the most urgent products to be looking at?

Trisia: I think so. They partly made these determinations based on what is found in the beach cleanups/audits, a very powerful citizen science initiative. For example, expanded polystyrene (EPS) is very toxic, and it’s difficult to recycle, and also to transport because it’s so light and bulky. It’s nasty stuff. With  an EPS meat tray, you’ve got a high fat food item which potentially increases the potential for toxic leaching from the plastic packaging into the food. They are also starting to find increasing volumes of disgusting plastic ties from meat works on some beaches, and a lot of plastic preproduction pellets. These are not on the list. But they have caught some of the high-volume items, and they’re starting with the low-hanging fruit. That’s not a bad way to go. It will ease industry and consumers into this new way of thinking about regulating problematic items.

A lot of people missed the very last line of the press release, which is the bit that got me really excited: New Zealand has now declared that we will support a global treaty on plastic pollution. I’ve been working on this for years and we couldn’t get even an informal statement of support. Now we could be seeing support for an international negotiating committee in the September ministerial meeting, before the UN environmental assembly meeting next February. We are the 131st country to support the treaty! 

Robert:  With the New Zealand phase-out by 2025 – why is it so long?

Trisia: It’s about getting everyone on board. For me it’s too long, but I keep reminding myself to celebrate the small stuff. And I can see it setting a precedent for more problematic items. There’s so much more I’d like to see in there, that a lot of people submitted on: cigarette butts, wet wipes that clog waste water plants, agri-plastics.

It’s good to see that the oxo-degradable and photo-degradable plastic are included. They break down into microplastics but are not truly biodegradable. That came about because of the Prime Minister’s Chief Science Advisor’s report, which had some really good scientists on it. 

Robert:  There were 8000 public submissions on the proposal.

Trisia: It was so huge! It was the biggest public engagement on plastics we’ve ever seen. There are a lot of people really wanting this to happen.

Robert:  Thanks Trisia! We look forward to our plastic-free future.

Trisia: We do indeed.

By Robert McLachlan

What’s that? You wanted action, not just words, on climate change? And you wanted it now, not next year or the year after? How about something big, really big, maybe also diving right into the heart of an emotional, touchstone issue – say, the private car? 

Welcome to the EV subsidy.  

The New Zealand government has surprised and delighted electric vehicle advocates by announcing significant direct subsidies for electric vehicles – both all-electric and plug-in hybrid, whether new or used but newly imported) of up to $8625. These take effect in just a few weeks time, on 1 July 2021. 

From 2022 they will be replaced by a revenue-neutral ‘feebate’, in which higher-emitting vehicles pay a fee, and lower emitting vehicles (including some petrol cars) receive a rebate. That year fuel efficiency standards also come into effect, with fines for noncompliance applying to vehicle importers from 2023. Taken together, these three steps bring New Zealand firmly and finally into line with most other developed countries, where fees, subsidies, and efficiency standards are the norm. 

Ināia tonu nei: The time is now 

Now we’ll find out if EV sales will start to increase significantly from their currently puny levels. We’ll find out if the charge that the taxpayer is subsidizing rich suburbanites’ consumption will stick. We’ll find out if more EVs means less power for the fossil fuel industry. In the meantime, winning the support of the car industry and of drivers’ advocates (the AA called the plan “well-balanced and positive” with a “good mix of carrot and stick”) is no small feat. 

Carbon price: necessary, but not sufficient 

The Climate Change Commission, in their advice to Government released on 10 June, were very clear that existing tools to address emissions are far from adequate. In particular, the market-based Emissions Trading Scheme (ETS), even with a rising price on carbon and a falling but flexible cap on emissions, cannot do the job on its own. Their landmark report discusses a whole smorgasbord of market failures (such as split incentives, bounded rationality, and infrastructure lock-in), all of which of have arguably been preventing climate action so far, and all of which are addressed by the new vehicle package. 

Think collectively 

For example, the benefits of an EV subsidy don’t fall mainly on the car buyer. The benefits arise collectively from starting the decarbonisation of the entire transport system, from building networks of suppliers and supporters, and from beginning the delegitimisation of burning petrol. 

Yes, it would be more environmentally sound to rapidly ramp up the cost of all unsustainable consumption, especially of cars and petrol; to stop all new road construction; and to divert the lion’s share of transport funding towards walking, cycling, and public transport. It would also have massive side effects and be politically completely impossible from our current starting point.  

While the ETS retains a central role – the Commission advises raising the carbon price from its present $20-$50 range to $30-$70 immediately, and to $50-$150 by 2030) – its actual operation under the Zero Carbon Act remains to be tested. While the international evidence is that a mixed approach of carbon pricing and regulation has worked so far, for the far more sweeping changes needed in the years ahead we are in uncharted waters. 

To sketch just one possible outcome of an “ETS only” approach, a sharp rise in the carbon price could result in excessive tree planting and damage to industry, while still not having any noticeable effect on suburban drivers. (Even $100/tonne would only add an extra 12c/litre to the price of petrol.) 

The Climate Change Commission is just the kind of institution we need more of to safeguard the future 

The Climate Change Commission, through its establishment in 2019 under the Zero Carbon Act in 2019, its formation, its draft report, its extensive community engagement resulting in more than 15,000 submissions, and now its first package of official advice (engaging in detail with the public’s arguments and evidence), is amply fulfilling early hopes of depoliticising climate and fixing the areas of debate.  

That’s not to say that carrying out the advice will be easy. A common thread running through the 400 page report is the almost complete lack of planning up to this point. The Commission recommends that the government develop national strategies to decarbonise the energy system; for the bioeconomy; for a circular economy; for an equitable transition; for industry transition; for low-emission freight, for hard-to-abate industries; for waste; for buildings and urban form; and for an equitable transition for Iwi/Māori and the Māori economy.  

This “planning” is not central planning. Communities, Iwi/Māori, and industry are all expected to take part. But a failure to plan at all can lead to trouble, one current example being electricity shortages that have led to price spikes and an increase in coal burning. This could have easily been avoided if we had had even slightly more direction on climate change just five years ago.   

An example of what long-term strategies might look like is found in Hīkina te Kohupara – Kia mauri ora ai te iwi: Transport Emissions: Pathways to Net Zero by 2050, a May 2021 green paper from the Ministry of Transport, now out for consultation. One pathway, the only one that achieves a 47% cut in transport emissions by 2035, as suggested by the Climate Change Commission, involves significant shifts throughout the transport system. Driving by cars and light trucks falls 39%; public and active transport increases massively (five times as many buses as now, and all of them electric), while total demand for travel decreases. The main tool that reduces driving is “distance pricing”.  

Let’s hop on that pathway, sure, but let’s bring everyone else on board too. And if you know a better way, tell me. 

We now know the first three carbon budgets (probably) 

The Commission’s carbon budgets have been the focus of attention, for the government is very likely to adopt them. Gross CO2 emissions, mostly from fossil fuels, are to fall from 37.5 Mt a year in 2019 to 27.5 Mt by 2030. In addition, tree planting – which largely stopped fifteen years ago – starts expanding again, so that net emissions of long-lived gases fall 38% over 2019–2030. The scope of the changes suggested in the detailed plan give some idea of how challenging this will be. The Commission argue that this, in fact, the most that is practical and achievable. 

Are we meeting the Paris Agreement? 

The question of the country’s Nationally Determined Contribution (NDC), which the Minister of Climate Change James Shaw punted to the Commission, has been passed right back again like a game of hot potato. There are two difficulties. One is that the Commission has already found the biggest domestic emission cuts it thinks it can; anything on top must come from overseas. That will be expensive, and there are no rules yet or how these “internationally transferred mitigation outcomes” will be conducted. It was on the agenda at COP25 in Madrid, it will be on the agenda at COP26 in Glasgow. It’s a famously difficult issue. Most developed countries aren’t using them, but many developing nations would love it.  

Secondly, the entire basis for the NDC stems from the requirements to balance equality, responsibility, and need. For New Zealand, that points towards much higher ambition that at present. The Commission found that the precise level of the NDC involves political, social, and ethical considerations that could only be determined by the government. Still, they did advise that the NDC should involve “much more than” 8 Mt CO2e a year of international mitigation (10% of current gross emissions), at a cost of many billions of dollars per decade. Over to you, Minister. 

And to any ute drivers out there worried about price rises: I’m reliably informed that modern utes are built to last forever. If a ute really is the best vehicle for the job, just keep driving it a while longer. 

By Robert McLachlan

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change. If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

I’ve heard the gravity changes when Antarctica melts will lower the seas around New Zealand. Will that save us from sea level rise?

The gravitational changes when Antarctica melts do indeed affect sea levels all over the world — but not enough to save New Zealand from rising seas.

The ice ages and their effects on sea level, geology, flora and fauna were topics of intense scientific and public interest all through the 19th century. Here’s how James Croll explained the “gravity effect” of melting ice in his 1875 book Climate and Time in their Geologic Relations:

Let us now consider the effect that this condition of things would have upon the level of the sea. It would evidently tend to produce an elevation of the sea-level on the northern hemisphere in two ways. First, the addition to the sea occasioned by the melting of the ice from off the Antarctic land would tend to raise the general level of the sea. Secondly, the removal of the ice would also tend to shift the earth’s centre of gravity to the north of its present position – and as the sea must shift along with the centre, a rise of the sea on the northern hemisphere would necessarily take place.

His back-of-the-envelope calculation suggested the effect on sea level from ice melting in Antarctica would be about a third bigger than average in the northern hemisphere and a third smaller in the south.

A more detailed mathematical study by Robert Woodward in 1888 has falling sea level as far as 2000km from Antarctica, but still rising by a third more than average in the north.

Sea-level fingerprints

Woodward’s method is the basis of determining what is now called the “sea-level fingerprint” of melting ice. Two other factors also come into play.

1. The elasticity of the earth’s surface means the land will bounce up when it has less ice weighing it down. This pushes water away.
2. If the ice is not at the pole, its melting shifts the south pole (the axis of rotation), redistributing water.

Combining these effects gives the sea-level fingerprints of one metre of sea-level rise from either the West Antarctic Ice Sheet (WAIS) and Greenland (GIS), as shown here:

Woodward’s method from 1888 holds up pretty well – some locations in the northern hemisphere can get a third more than the average sea level rise. New Zealand gets a little bit below the average effect from Antarctica, and a little more than average from Greenland. Overall, New Zealand can expect slightly higher than average sea level rise.

Combining the sea-level fingerprints of all known sources of melting ice, together with other known changes of local land level such as subsidence and uplift, gives a good fit to the observed pattern of sea level rise around the world. For example, sea level has been falling near West Antarctica, due to the gravity effect.

Sea-level rise is accelerating, but the future rate is uncertain

The global average rise in sea level is 110mm for 1900-1993 and 100mm for 1993–2020. The recent acceleration is mostly due to increased thermal expansion of the top two kilometres of the oceans (warm water is less dense and expands) and increased melting of Greenland.

But the Gravity Recovery and Climate Experiment satellite has revealed the melting of Antarctica has accelerated by a factor of five in recent decades. Future changes in Antarctica represent a major source of uncertainty when trying to forecast sea levels.

Much of West Antarctica lies below sea level and is potentially subject to an instability in which warming ocean water melts the ice front from below. This would cause the ice sheet to peel off the ocean floor, accelerating the flow of the glacier towards the sea.

In fact, this has been directly observed, both in the location of glacial “grounding lines”, some of which have retreated by tens of kilometres in recent decades, and most recently by the Icefin submersible robot which visited the grounding line of the Thwaites Glacier, 2000km east of Scott Base, and found the water temperature to be 2℃ above the local freezing point.

The big question is whether this instability has been irreversibly set into motion. Some glaciologists say it has, but the balance of opinion, summarised by the IPCC’s report on the cryosphere, is that

Observed grounding line retreat … is not definitive proof that Marine Ice Sheet Instability is underway. Whether unstable West Antarctic Ice Sheet retreat has begun or is imminent remains a critical uncertainty.

The IPCC special report on 1.5℃ concluded that “these instabilities could be triggered at around 1.5℃ to 2℃ of global warming”.

What’s in store for New Zealand

Predictions for New Zealand range from a further 0.46 metres of sea-level rise by 2100 (under a low-emission scenario, with warming kept under 2℃) to 1.05 metres (under a high-emission scenario).

A continued rise in sea levels over future centuries may be inevitable — there are 66m of sea level rise locked up in ice at present — but the rate will depend on how fast we can reduce emissions.

A five-year, NZ$7m research project, NZ SeaRise, is now underway, seeking to improve predictions of sea-level rise out to 2100 and beyond and their implications for local planning.

This article originally appeared on The Conversation. Read the original article.