Taking stock of climate change

People living in low-lying Kiribati (pictured), Tuvalu and the Marshall Islands are among the...
People living in low-lying Kiribati (pictured), Tuvalu and the Marshall Islands are among the most threatened.PHOTO: ODT FILES
Heatwaves, deluges, rising seas: climate change isn't a future scenario but one we're living in now.

How bad it will get all depends on what happens over the next few decades, or even the next one.

Best-case scenario

The best-case scenario is that the world succeeds in ramping down man-made emissions of carbon dioxide, within this century, to net zero.

Mean global warming would likely flatten off a little under 2degC above pre-industrial temperatures - the target number of the Paris Agreement that New Zealand and about 200 other nations are signed up to.

But even under this optimistic trajectory, our world would still be transformed and face a big change in extreme events like floods and droughts.

The world's rainfall levels could rise or drop by 10%, and the number of heatwaves and the risk of forest fires would soar.

The worst-case scenario

A high-carbon future - as the world is on track to experience if it continued to pump out carbon dioxide at its current rate - would be much bleaker.

"By just another human lifetime away, people could be living in a climate outside anything that any of us have ever experienced,'' Victoria University climate scientist Prof James Renwick said.

"The potential for mayhem is astronomical and it really could be catastrophic.''

The Arctic could lose all of its summer time sea ice and oceans could be 1.5m higher, with another 10m locked in over coming centuries.

In New Zealand, only another metre of sea level rise would add 116,000 people to the 72,000 - and $12.5billion worth of buildings - already exposed to extreme coastal flooding.

Temperatures might be 3degC or 4degC higher than today, and warm summer days in Canterbury and Hawke's Bay could reach the high 40s, he said.

Most of New Zealand could be in a subtropical climate, at least, with heavy rainfall events possibly double the current amounts.

Drier, eastern parts of the country would have long, very severe droughts, and forest fire risks would rise by a factor of five.

By the end of the century, many parts of the country would record more than 80 days a year above 25degC.

Most places typically experienced those temperatures for only between 20 and 40 days now, but, already, about 14 elderly people in Auckland and Christchurch have died when temperatures exceeded 20degC.

With about one in four New Zealanders projected to be 65 and over by 2043, the problem would be amplified.

In the Pacific, where about half the population live within 1.5km of the ocean, even a further 2degC of warming could result in small island countries being inundated by sea-level rise.

What needs to happen now

If warming continues at the current rate, the Paris Agreement's aspirational threshold of 1.5degC - and that of New Zealand's Zero Carbon Bill - will be crossed at some point between 2030 and 2052.

If the 1.5degC threshold can be held, the world could escape an extra 10cm of sea level rise, above what's already been locked in for this century.

If the world cannot hold the line, then the 2degC threshold - the ultimate limit the Paris Agreement was built around - could be over-shot only about a decade later.

"I can guarantee that climate models do not lie.

"If we don't take action, it's going to be a very difficult future,'' Prof Renwick said.

• This story originally appeared in The New Zealand Herald. It is republished here, in edited form, as part of the Otago Daily Times' partnership with Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.

 - By Jamie Morton

Comments

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There seems to be an organised attack on the people. They are using climate change this time. This is funny:

https://youtu.be/NjlC02NsIt0

The elderly are dying, which elderly do, but before their time, due to changes in air temperature.

The future belongs to the young. Let's at least make an effort, and leave something for them to work with.

We cannot be that selfish as to leave desolation.

"I can guarantee that climate models do not lie." – this is the sort of nonsense that makes many people sceptical about the whole climate change movement. Models are, by definition, approximations of reality. They can only predict what might happen, not what will happen. They are often wrong, and they are always imperfect.

Claiming they "do not lie" is the behaviour of a lobbyist, not a scientist.

"I can guarantee that climate models do not lie.
"If we don't take action, it's going to be a very difficult future,'' Prof Renwick said.
RUBBISH !!!
It’s a computer model. One wrong or omitted variable and it’s wrong. The longer the projection, the bigger the error.
The climate is a complex system and anyone that says we completely understand it is talking rubbish.
Will we get off fossil fuels about the end of the century?
Yes. Most likely !
Do we need to destroy our economy to get there ? NO !
If we do that, we will be unable to adapt and mitigate issues that WILL arise in the future regardless of what we do.
Is the science settled ? NO !
There are many scientists that don’t agree with the doomsday scenario of activists.

Deniers need to stop shouting. You don't get anywhere exercised and emotional.

Why has there been no mention of the vast tracts of land in Canada, Alaska and Siberia which will become more liveable and productive if the rising temperatures continue. Sure we all need to live more sustainably where possible especially as the global population continues to rise, but why are we getting a never ending supply of futuristic horror stories.

Let's have some balance.

Total crap. What we are living in now is weather. Climate is the average of weather factors over a minimum period of 30 years. Before the El Nino that peaked in December 2016 there had been a 18 year period of no warming. In fact the world cooled by half a degree since then and is still cooling.
All of the claims are pure speculation based on the IPCC's worst case senario and on the output of their climate models.
The problem with these is they use parameters which are no more than guesses.
For example; they factor in an effect from clouds, but the IPCC AR5 science report summary says that they know neither the SIGN nor the MAGNITUDE of the low cloud response to warming.
NASA says https://notrickszone.com/2019/08/29/nasa-we-cant-model-clouds-so-climate...
So how accurate are the models when the effect of a major factor like clouds is unknown.

The weather data that has been collected for over a 100 years tells us that there has been no increase in any form of extreme weather. The IPCC AR5 WG1 (science) repeats many times in various parts that no increase in extreme weather has been observed and none is expected.

The lack of logic is beyond belief. 6000 to 9000 years ago the world was many degrees warmer than now. The evidence for this is overwhelming, not just proxy temperature records but physical evidence such as tree stumps dating 1000 years (medieval warm period) and 4000 years old appearing from under retreating glaciers. 5000 year old stumps in what is now arctic tundra, showing it was forested.
Did any of these claimed apocalyptic events happen, of course not.
We need to remember that people like Renwick gain a lot of funding, kudos, advisory position, trips to IPCC conferences etc, they have a lot to lose, including credibility if they were to admit that CO2 has little effect.
Then there is the fact that Earth, by having polar ice caps, is still in an ice age, albeit a warmer phase. For 75% of the last 600 million years Earth did not have polar ice caps, it was considerable warmer, yes sea levels were higher, so what. Biodiversity, during the last of these periods, the Eocene, increased at one of the highest observed rates. Must have been good times for life.
Oh, and CO2 has been over 400 ppm for 84% of the last 600 million years and over 1000 ppm for 70% of that time.

Some people observe climate change, others write opaque tracts spinning statistics.

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