Climate change is already redefining coastlines and the weather here in New Zealand and around the world. How will it affect us and what can we do about it? Two of New Zealand's leading climate change experts, Professors Tim Nash and James Re wick of Victoria University, are heading out on the road this month on a nationwide speaking tour. They shared 10 facts people might not know about climate change.
1Wellington has the longest continuous carbon dioxide record in the Southern Hemisphere.
The measurement station at Baring Head at the mouth of Wellington Harbour (now run by Nita), and its predecessor at Maker on the coast west of the city, have been measuring carbon isotopes since the 1950s and carbon dioxide since the early 1970s.
The only longer-running site is the famous Mauna Loa record in Hawaii, started by Charles Keeling in the late 1950s.
2The last time we had a record cold year was 1909.
Temperatures vary up and down from year to year, because of El Nino and La Nina events, or in association with other natural influences.
But the background trend has been upwards for all of the last century and beyond.
The warmest year in the observational record going back to the 1880s was 2015, and the previous record warm year was 2014.
Meanwhile, 2016 looks set to be the new record warm year.
The coldest year on record since 1880 is 1909, 107 years ago.
Temperatures today are so much higher than they were then that even a huge volcanic eruption blocking out sunlight for months would not cool the planet back to early 20th century values.
3 Almost 100 per cent of scientists are certain that global warming is human-induced.
In the game of attributing global warming to humankind's use of fossil fuels, scientists are almost 100 per cent certain.
The reason that the UN's Intergovernmental Panel on Climate Change (IPCC) report says "the human influence on the climate system is clear" with 99 per cent certainty is due to a technical rule -- they have agreed that "cause and effect statements" must allow for a slight uncertainty.
The facts are that the present levels of carbon dioxide in the atmosphere have not been seen for three million years on planet Earth.
At that time the world was on average two to three degrees warmer, and global sea levels were at least 10m higher.
The carbon we have been adding to the atmosphere has a chemical signature of fossil wood - coal, oil and gas. It is not from volcanic eruptions.
Oxygen levels in the atmosphere have been declining as carbon dioxide levels have increased, due to the combustion of oxygen by burning fossil fuels. And finally the radiative effects of carbon dioxide and methane as powerful greenhouse gases has been known for more than a century.
The physics is beyond question.
Skeptics would do well to stop wasting their energy, and distracting the public and scientists by trying to deconstruct this scientific truth, and join the rest of humanity in helping figure out what to do about climate change.
4 The tropics are expanding.
The tropics hold most of the heat in the climate system, and as things warm, the tropical belt is expanding slightly.
And, the atmosphere is getting deeper.
The region of warmest tropical waters, north of Australia, where sea temperatures are above 28C, has got 20 per cent bigger in the past 60 years.
Some of that warm water runs down the east coast of Australia and then across the Tasman to New Zealand.
Sea temperatures have risen really fast off the southeast of Australia and near Tasmania, as the East Australian Current has strengthened.
Some of that warm water may be heading our way.
5 Ninety-three per cent of the heat and 24 per cent of the carbon dioxide from humankind's use of fossil fuels has gone into the ocean.
While the ocean is slowing the pace of warming, putting gas and heat in the ocean has other unintended consequences.
The ocean is warming, especially the Southern Ocean which is melting the edges of the Antarctic ice sheet, contributing to sea-level rise.
As the ocean warms it also expands and this has caused half of the sea-level rise observed during the 20th and 21st centuries.
Once the heat is in the ocean it will take centuries to remove it.
This commits us to long term sea-level rise.
6 The polar regions warm twice as much as the rest of the planet.
This phenomenon, known as polar amplification, is a concern because 70 per cent of the world's fresh water is locked up in the polar ice sheets, and if it all melted it would lead to the equivalent of 60m sea level rise from Antarctic and 7m from Greenland.
Powerful climate feedbacks, associated with sea-ice, are already expressing themselves in the Arctic, with Arctic ocean summer sea-ice expected to be all gone by as soon as 2050.
The replacement of white ice with dark ocean absorbing even more heat is a powerful amplifier of regional atmospheric warming.
The Antarctic Peninsula has warmed 0.5C per decade for the last 50 years -- the fastest-warming place on the planet -- and ice shelves are collapsing catastrophically.
7 Global sea-level predictions might be on the low side.
The latest science suggests that the contribution from Antarctic ice sheets may be underestimated in predictions of future sea-level rise to the end of the century and beyond made in the recent IPCC report.
The new ice sheet melting models add as much as 80cm of additional sea-level rise to the upper bound projection of at least 1m by the year 2100 made by the IPCC.
Of even more concern is that with 30cm of sea-level rise expected by 2050, the 100-year coastal flooding event will be happening every year in some parts of New Zealand, such as Dunedin city.
8 The Paris Agreement is a huge ask.
The Paris climate agreement was a major diplomatic success with the world's nations agreeing to limit global warming to no more than 2C above pre-industrial levels.
However, achieving the ambition of Paris is an enormous challenge.
If each national pledge to reduce green house gas emissions is acted on this will limit global warming to about 2.7C.
So even more action is required, and low-lying island countries and African nations have requested 1.5C be achieved as 2C is too much for them.
More disturbing is that current policy settings, including New Zealand's, have us on target for 3.5C global warming.
To achieve the 2C target, emissions must peak very soon and all emissions of carbon dioxide must be reduced to zero before the end of the century. Business as usual will have us at 2C by 2035.
9 New Zealand's per capita emissions are well above the global average.
We often hear that New Zealand's emissions are so small that we can't make any difference in the world.
But every group of 4.5 million people in the world could say that.
Per head of population, our emissions are in the top 10 globally.
Although agricultural emissions are a big part of the story, the biggest growth in emissions in recent decades has been in transport and energy production/industry, so there are plenty of avenues for reduction.
10 New Zealand is well placed to make significant greenhouse gas reductions by transferring to a low-carbon economy.
Zero emissions of carbon dioxide by the end of the century can be achieved for all sectors of society and the economy except agriculture.
Agriculture accounts for 50 per cent of New Zealand's greenhouse gas emissions and, while efficiencies are being made, these are being offset by increased production.
Significant reductions require major economic trade-offs with livestock productivity, and given the dependence of our economy on the primary production sector, this is unlikely in the short term.
A goal of 90 to 100 per cent renewable electricity generation by 2025 is achievable through more wind, solar and hydro, and a national smart grid where distributed electricity generation can be fed in, as well as improving efficiency of existing generation.
Arguably the biggest opportunity for reductions is in the transport sector, where a transition to more efficient vehicles, including electric vehicles, use of public transport and coastal shipping and rail transport for freight would greatly reduce emissions.
New Zealand needs a functioning carbon pricing mechanism, whether that be a tax or emissions trading scheme that works to incentivise change.
New Zealand is well placed to lead the way internationally to a thriving low carbon economy with all the co-benefits of energy security and independence, more livable cities, leaders in new green-tech industries powering economic growth, and increased sustainability and resilience to climate change.
The recent report by the Royal Society lays out the opportunities for transitioning New Zealand to a low carbon society and economy.
Professor Tim Nash and James Re wick speaking tour
Napier: 6pm Wednesday, July 6, Century Theatre, MTG, 9 Herschell Street
Palmerston North: 7.30pm Thursday, July 7, Palmerston North Public Library, 4 The Square
Christchurch: 6.30pm Wednesday, August 3, C1 LT, Central Lecture Theatre Block, University of Canterbury, Arts Road
Dunedin: 5.30pm. Thursday August 4, Hutton Theatre, Otago Museum, 419 Great King Street
Wanaka: 6pm Friday, August 5, Presbyterian Church Hall, 91 Tenby Street
Auckland: 6pm Tuesday September 6, The Auditorium, Level 2 Auckland Museum, The Domain, Parnell
Wellington: 6pm Wednesday September 7, Aronui Lecture Theatre, Royal Society of New Zealand, 11 Turnbull Street, Thorndon
Nelson: 7.30pm Thursday, September 8, Elim Christian Centre, 625 Main Road, Stoke
• For more information, visit http://www.royalsociety.org.nz/events/ten-by-ten/ten-by-ten-climate-change