A sweeping stocktake out today has described the early indicators of a warming New Zealand, now being transformed by a shifting climate, rising sea levels and changing oceans.

The Ministry for the Environment and Stats NZ's latest report, focused on our climate, found our country was experiencing the impacts of excess greenhouse gas emissions in our atmosphere and oceans.

The 60-page report pulled together a mass of data on climate, oceans, soils, emissions, carbon, sea level and UV light.

"We have enough data on measures like annual average temperature to confidently say New Zealand's climate is warming," Government Statistician Liz MacPherson said.

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That had been marked, she said, by the quarter of volume that New Zealand's glaciers had lost since 1977.

"National and international data collections on the atmosphere and climate are increasingly comprehensive but there are still some things we don't know at this time, in particular the full impact of climate change on our biodiversity, cultural values and the economy."

Secretary for the Environment Vicky Robertson said the most concerning change was the unprecedented high levels of carbon dioxide, which were leading to increasing global temperatures and changes to our oceans, including rising sea levels and increasing ocean acidity.

"The future impacts of climate change on our lives all depend on how fast global emissions are reduced and the extent to which our communities can adapt to change."

Herald science reporter Jamie Morton looked at five defining figures in the assessment.

1C

Since 1909, our annual average temperature has climbed by 1C - a figure in line with global average temperature increases, which are almost certainly the result of high levels of atmospheric greenhouse gases emitted from human activities.

Although seemingly small, this warming represented a rapid increase over a century, and was already affecting the natural systems on which we depend.

2016 was New Zealand's warmest year since at least 1909, and the five warmest years on record have occurred in the last 20 years.

Globally, 19 of the 20 warmest years occurred within the last 20 years.

Over the 45 years between 1972 and 2016, the number of frost days decreased at 10 of 30 measured sites and increased at one site, while no trend was apparent at the others.

Since 1909, our annual average temperature has climbed by 1C. Photo / File
Since 1909, our annual average temperature has climbed by 1C. Photo / File

The number of warm days - over 25C - increased at eight and decreased at one, with no trend at the others.

For most of New Zealand, there was no clear evidence that intense rainfall events had changed between 1960 and 2016.

But there were localised trends at some places: the proportion of annual rainfall occurring in intense events decreased in Auckland, New Plymouth, Rotorua, and Taupo, but increased at Napier and Timaru.

Sunshine hours have also increased across New Zealand, largely because of reduced cloud cover, and some locations also experienced changes in seasonal rainfall and extreme wind.

Yet, because New Zealand's climate varied naturally, it was ultimately hard to pick out patterns from short-term observations.

While longer-term data was needed to confirm whether humans were contributing to these sorts of trends, it was clear that further warming in the long term was expected.

How much, exactly?

That depended on the amount of greenhouse has emissions we pumped into the atmosphere over coming years and decades.

Under the Paris Agreement, which aims to rein in future global temperature rise by no more than another 2C, New Zealand has pledged to slash its greenhouse gas emissions by 30 per cent from 2005 levels and 11 per cent from 1990 levels by 2030.

24%

Along with natural variability, the global climate is shifting as a result of increased greenhouse gases and aerosols in the atmosphere from human activities.

While the burning fossil fuels are mainly to blame, changing land use and emissions from other activities, like transport and agriculture, have also been big contributors.

The figures showed how, between 1990 and 2015, New Zealand's gross greenhouse gas emissions rose by 24 per cent, with most of the increase having occurred by 2005.

The bulk of that could be put down to road transport and agricultural production - largely from nitrogen fertiliser use, grazing animal excrement on managed soils, and ruminant cattle belching methane.

Agriculture emissions, mainly methane and nitrous oxide, made up almost half our greenhouse gas emissions in 2015. Photo / File
Agriculture emissions, mainly methane and nitrous oxide, made up almost half our greenhouse gas emissions in 2015. Photo / File

Agriculture emissions, mainly methane and nitrous oxide, made up almost half our greenhouse gas emissions in 2015.

But road transport also drove one of the largest increases in emissions - with a 78 per cent increase since 1990.

Over the same time, our net greenhouse gas emissions rose 64 percent, as a result of increasing gross emissions and higher logging rates in production forests.

Net emissions acknowledge the role of carbon sinks, such as growing forests, in removing atmospheric greenhouse gases but also adding them when forests are harvested and land use is changed.

Road transport emissions have increased 78 per cent increase since 1990. Photo / File
Road transport emissions have increased 78 per cent increase since 1990. Photo / File

Globally, gross greenhouse gas emissions levels rose by 51 per cent from 1990 to 2013, mainly due to people burning more fossil fuels for electricity generation, heat, transport, manufacturing, and construction.

Carbon dioxide levels in New Zealand's atmosphere have meanwhile increased by nearly a quarter since 1972.

Last year, global concentrations of atmospheric carbon dioxide passed the symbolic level of 400 parts per million - the highest level of carbon dioxide in our atmosphere in at least the last 800,000 years.

The data made it clear that New Zealand was experiencing the effects of past global emissions.

Even if these emissions stopped today, many aspects of climate change would continue for centuries.

The full extent of future global warming depended on the emissions added from this point onward.

22cm

Sea levels around our country had risen by up to 22cm depending on location, over the last century.

The data showed that, since 1916, sea level had climbed by between 14 and 22cm at our four main New Zealand ports.

Over this period, sea level rose an average of 1.8mm a year across monitoring sites.

This was in line with the global record from tide gauges of about 1.7mm a year between 1901 and 2010.

Sea level has been rising around the globe as a result of the world's oceans expanding as they warm and because ice previously stored in glaciers and in parts of the polar ice sheets has been melting.

With rising seas, we can expect tides, waves, and storm surges to reach further inland more regularly, resulting in more frequent and serious flooding. Photo / File
With rising seas, we can expect tides, waves, and storm surges to reach further inland more regularly, resulting in more frequent and serious flooding. Photo / File

Globally, sea level rose 19cm between 1901 and 2010.

Rising sea levels and more intense heavy rainfall events associated with climate change are projected to increase coastal flooding and erosion, which may in turn cause damage to coastal ecosystems, housing, and critical infrastructure, such as roading, sewage, and power supply.

The planet's sea level is projected to rise by about 20 to 40 centimetres by 2060.

While New Zealand's sea level rise has aligned with the global average so far, at least one study projected that our sea level may rise a little faster than the global average in the future.

Moreover, with rising seas, we can expect tides, waves, and storm surges to reach further inland more regularly, resulting in more frequent and serious flooding.

There was also a recorded 0.7C increase in sea surface temperature recorded between 1909 and 2009, and acidity of the subantarctic ocean off the Otago coast had increased since 1998.

However, recent satellite data, only available since 1993, showed no trend in sea-surface temperature change in the Tasman Sea and New Zealand's oceanic, subtropical, and subantarctic waters.

This result wasn't not surprising given the short time these data have been available and the year-to-year temperature variations.

Ocean acidification and warming may cause widespread harm to marine ecosystems, for example, by reducing the survival and growth rates of marine species, extending or reducing the range of species, and modifying habitats.

The impacts could occur across New Zealand's entire ocean area, with implications for biodiversity, marine-based industries such as commercial fishing and aquaculture, and Maori customary practice.

25%

There have been more pronounced effects on our natural environment - perhaps none more dramatic than our shrinking glaciers.

New Zealand's mountains are home to 3144 large glaciers, most of them located along the Southern Alps of the South Island, and 18 on the flanks of Mt Ruapehu.

Glacier ice volume is strongly influenced by temperature and precipitation.

From 1977 to 2016, it was estimated our glaciers lost almost 25 percent, or 13.3 cu km, of their ice volume - a trend in step with shrinking glaciers elsewhere in the world.

The shrinking Franz Josef Glacier in the South Island, pictured in 2015. Photo / File
The shrinking Franz Josef Glacier in the South Island, pictured in 2015. Photo / File

Since the 1972/73 measurement season, soils at one fifth of sites around New Zealand have been getting drier.

The frequency and intensity of drought in drought-prone regions were expected to increase with climate change, with important implications for our primary industries.

Rising temperatures had also resulted in a greater number of "growing degree days" across the country, which can be used to predict plant, and subsequently, animal growth.
Plant and animal cycles are interdependent across the food chain.

Small changes in the timing of insect reproduction could mean that species further up the food chain miss out on a crucial food source.

The greater the change in timings, the more pressure species further up the food chain experience.

We didn't yet have a detailed understanding of how the changing climate will add to the pressures faced by already vulnerable native flora and fauna.

Drought will become a more common occurrence under climate change. Photo / File
Drought will become a more common occurrence under climate change. Photo / File

Our species have evolved in near isolation, forming our country into a biodiversity hotspot home to many species found nowhere else on Earth.

Despite humans only arriving in this country comparatively recently, our biodiversity has declined rapidly because of the cumulative effects of land disturbance, overexploitation of resources, and introduced pest plants and animals.

A changing climate has the potential to exacerbate these existing pressures - and some emerging evidence has already pointed to early effects.

For example, the sex ratios of North Brother Island tuatara were changing - there were now more male offspring in response to warmer nest temperatures.

Numbers of invasive wasps had also increased around the Nelson area because of increasing spring temperatures. Photo / File
Numbers of invasive wasps had also increased around the Nelson area because of increasing spring temperatures. Photo / File

Numbers of invasive wasps had also increased around the Nelson area because of increasing spring temperatures.

98%

The one piece of good news out of the report was that global production of ozone-depleting substances has dropped 98 per cent from 1986 to 2015.

Ozone is a greenhouse gas that exists throughout our atmosphere.

Four billion years ago, before life on Earth, the planet's atmosphere contained much lower levels of ozone, and much higher levels of UV sunlight reached the planet's surface than today.

It took the development of the ozone layer in the atmosphere for life to be able to withstand the damaging effects of intense UV sunlight.

In the troposphere, the layer of the atmosphere closest to Earth, ozone was typically present only in low concentrations.

Its concentrations were greatest in the second layer of Earth's atmosphere, the stratosphere, and peak at around 25km altitude.

At this level of the atmosphere, ozone is beneficial because it absorbs damaging UV sunlight, reducing the levels experienced at Earth's surface.

For years, the ozone had been depleted by substances - mostly used as refrigerants in air conditioners and refrigerators, and as propellants in aerosol cans - containing synthetic gases, creating a hole.

Exposure to ultraviolet (UV) sunlight has positive and negative effects on human health, but importantly for New Zealand, contributes to our high rates of the skin cancer melanoma. Photo / File
Exposure to ultraviolet (UV) sunlight has positive and negative effects on human health, but importantly for New Zealand, contributes to our high rates of the skin cancer melanoma. Photo / File

In the 1980s, scientists were concerned that stratospheric ozone was at risk, with associated increases in UV sunlight reaching Earth's surface.

Increases in UV sunlight due to depleted ozone were observed globally during the 1980s and 1990s, particularly at high latitudes.

Since the 1987 Montreal Protocol was en-acted under the Vienna Convention, the global production of ozone-depleting substances decreased by 98 percent - and the ozone hole has started to shrink in response.

In 2016, the mean maximum size of the ozone hole was 20.9 million square kilometres, a 21 percent decrease from its largest mean maximum size in 2006.

It was possible that the ozone hole would cease to form by the middle of this century, and ozone levels would return to their normal levels, more than 60 years since the world took action to reduce emissions of the harmful substances.

Exposure to ultraviolet (UV) sunlight has positive and negative effects on human health, but importantly for New Zealand, contributes to our high rates of the skin cancer melanoma.

Our high summer UV levels are partly caused by the naturally thinner ozone layer over New Zealand at this time, our clear air, and Earth's orbit, which brings the Southern Hemisphere closer to the sun during summer.

Graphic / NZ Herald
Graphic / NZ Herald

"Although ozone appears to be on a path towards recovery, we need to remain vigilant," said Emeritus Researcher Dr Richard McKenzie, who served on the technical advisory group for the report.

"The situation is delicate at present, and we remain at risk from possible effects from future volcanic eruptions, or non-compliance to the terms of the Montreal Protocol.

"And some of the atmospheric processes are not yet fully understood.

As far as UV radiation is concerned, we need to be especially vigilant.

"New Zealand is the melanoma capital of the world, and any change in UV expected from future recovery in ozone will not change that.

"Changes to personal behaviour are needed."

Climate action 'desperately important'

Environment groups have responded to the report by calling for greater action to curb emissions.

"Most concerning is that net emissions have risen 64 per cent, a function of a decline in planting of new forests," said Gary Taylor, chairman of the Environmental Defence Society.

"That is a wake-up call for all of us and we clearly need to do more offsetting while at the same time substantially increasing our mitigation efforts.

"This will require robust policy changes by Government."

Taylor argued the report confirmed what was already known: New Zealand needed to be better organised do more to meet its 2030 Paris Agreement target.

"The best way to ramp up our efforts is to legislate to set up an independent Climate Commission to plan, recommend, monitor and report on the transition we need to make over the next several decades.

"We need to develop a proper carbon budget, like other countries, to work out the least cost pathway to net zero emissions by mid-century."

Forest and Bird climate advocate Adelia Hallett said it was "desperately important" that our Government and industry leaders acted with urgency.

"We still have a window to keep climate change in check," Hallett said.

"Scientists recently confirmed that it is possible to keep warming under 1.5C, if we make urgent emissions cuts now."

Greenpeace New Zealand executive director Dr Russel Norman noted the report's findings that our country had the second-highest level of emissions per gross domestic product unit of the 35 OECD countries, and the fifth highest emissions per capita.

"This report is an opportunity for us to have a national conversation about how we're going to start reversing these statistics so we can pass on a safe climate to our kids."

He called for an urgent moratorium on new oil exploration.

WWF-New Zealand meanwhile wanted to see a new climate law for New Zealand.

"It's 100 per cent possible for New Zealand to be a world leader in renewable energy," the group's chief executive, Livia Esterhazy, said.

"But we need all political parties, whoever is in government, to support this crucial transition.

"The newly elected Parliament has an opportunity to pass a new climate law like the Zero Carbon Act - to create an expert, non-partisan Climate Commission, to set a science-based target of net zero emissions by 2050, and to give Aotearoa a plan to get there."

Their call for action was echoed by prominent climate scientist Dr Jim Salinger.

"This confirms global warming is alive and well, and that the next Parliament must accelerate action on climate change."

Associate Professor Simon Hales, an environmental epidemiologist at the University of Otago, argued that the report's main message was New Zealand was not living up to its international obligations on climate change.

"We need to reduce net greenhouse gas emissions, not increase them."

Well designed policies to reduce emissions could have important short-term health benefits, by reducing health risks and by promoting healthy lifestyles, Hales said.

"Mitigating climate change will have long-term health benefits in New Zealand and globally, by reducing extreme climate events, sea level rise, food and water insecurity and the spread of communicable diseases.

"This is especially important for vulnerable Pacific island nations that expect and require New Zealand to support their own efforts to address climate change.

"We require a much better, more quantitative understanding of the likely adverse impacts of climate change on human health than the brief, vague statements in the MfE report."