Ten things you need to know about climate change

"You warm things up and that can increase the frequency of drought, of floods, of storms, and forest fires." -  Victoria ...
Don Landwehrle

"You warm things up and that can increase the frequency of drought, of floods, of storms, and forest fires." - Victoria University professor James Renwick on the realities of global warming.

"The longer we leave it, the harder it gets" – that's the inconvenient truth about global warming from climate change experts.

Victoria University professors Tim Naish and James Renwick are travelling the country as part of the Royal Society of New Zealand Ten by Ten talk series: 'Ten things you didn't know about climate change'.

They visited Palmerston North recently and offered a glimpse into the future.

1. The last record hottest year was 2015; the last record cold year was 1909.

Records for a coldest year were becoming a thing of the past, Renwick said. Meanwhile, 2015 was the first year to get above pre-industrial temperatures by 1 degree Celsius.

"Is 1 degree a big deal? Well, it is when you're looking at the global average – the way we feel these changes of climate is from extremes, not just the average – it's not just a little bit warmer every day.

"You warm things up and that can increase the frequency of drought, of floods, of storms, and forest fires."

2. The Paris agreement is a big ask.

Last year countries agreed to keep the global average temperature to well below 2C above pre-industrial levels. However, Naish said it would be a "huge challenge".

The pledges made only reached 2.7C, and current levels would end up at a 3.5C increase.

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​3.93 per cent of the heat from human kind's global warming and 24 per cent of carbon dioxide has gone into the sea.

"It takes a bit to heat an ocean, but it takes a lot to take heat out of an ocean," Naish said. 

"Even if we stop global warming tomorrow, the heat already in the ocean will commit us to quite a bit of melting of the Antarctic ice sheets for decades, even centuries to come."

4. The north and south poles are warming twice as fast as the rest of the globe.

Naish said the Arctic was responding faster because it was in a shallow ocean and surrounded by land.

Antarctic heating was being subdued because it was a deeper ocean. However, large ice shelves were collapsing.

That meant the glaciers that fed the shelves would be flowing into the sea much faster, contributing to sea level rise.

5. Future sea level rise estimates may be on the low side.

Naish said sea level rise had been static for the past 5000 years, but since the Industrial Revolution had increased by 20 centimetres.

The Paris agreement will still result in a rise of half a metre.

However, that was based on 2013 science and had not included Antarctica because it was too dynamic. Since then, expectations were to add another 40cm.

6. Scientists are almost certain that global warming is human induced.

"You can never be 100 per cent certain about anything in science, but this is about as close as it gets," Renwick said.

"It has been clear for a long time; in the climate science community there is no debate about what is going on here."

7. The tropics are expanding towards NZ.

The globe could be becoming more tropical.

"It sounds nice, right?" Renwick said.

With the tropical belt moving closer to New Zealand, it pushes out drier regions on the edge of it.

The top of the North Island could feel that, becoming a climate more like that of Victoria, Australia, he said.

8. Per capita, New Zealand emissions are way above the global average.

Renwick said NZ was in the top 10 for highest emitters on a per capita basis.

"We pride ourselves as clean and green and 100 per cent pure but that's probably just because there aren't too many of us."

Nearly half of emissions came from agriculture, but those were relatively static. Growth had occurred in transport, industrial and energy production.

"These are areas where we can make inroads."

9. New Zealand is well placed to transition to a thriving low-carbon economy.

Making significant cuts in agriculture would take some major economic tradeoffs and something would need to take its place, Naish said.

"It's a tough one."

The country could use more renewable energy, and look for cuts in transport, which contributed 20 per cent of emissions.

Emissions could also be offset by 25 per cent by planting trees.

"It doesn't seem like much but if everyone is doing them, they make a big difference."

10. New Zealand has the longest carbon dioxide observational record in the southern hemisphere.

Based at a lighthouse on the eastern entrance of Wellington Harbour, the record started in the early 1970s and tracked the rise in carbon dioxide, taking observations from air blowing from the Antarctic Coast.

 - Stuff

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