Leading climate change scientists Professor Michael Mann, Professor Will Steffen and Professor Daniel Nocera each has a ‘hockey stick’.

The ‘hockey stick’ is a term Mann, Distinguished Professor of Atmospheric Science at Pennsylvania State University in the United States and Director of its Earth System Science Center, helped introduce as lead author of the Intergovernmental Panel on Climate Change Third Scientific Assessment Report chapter where it first appeared in 2001.

The term describes the shape of timeline graphs that chart global warming and other climate change data across earth’s history ­– millions of years of relatively flat stability followed by a sudden steep spike in the second half of the 20th century as the figures escalate to their current heights and projections for 2100 if we don’t radically reduce carbon dioxide emissions.

The graphs do indeed look like a hockey stick: on its side, with the staff recording the past, the head the present and, if we carry on as we are, the future.

“We passed 400 parts per million of carbon dioxide in the atmosphere a few years ago for the first time in modern measurements that go back to 1958 and in fact we can use ice cores to go further back in time,” Mann told the second Pacific Climate Change Conference, hosted by Victoria University of Wellington and the Secretariat of the Pacific Regional Environment Programme.

“There’s evidence that the levels we’ve reached of over 400 parts per million of carbon dioxide in the atmosphere that we see today are higher than we’ve seen in millions of years.”

We are engaged, said Mann, in an “uncontrolled experiment with the one planet that we know that supports life”.

Given the “incontrovertible measurements of the dramatic and unprecedented rise in greenhouse gas concentrations, we wouldn’t be able to explain it if the earth were not warming up. And it’s warmed up thus far a little less than a degree Celsius”.

Mann went through the record-breaking years we have had: “2014 – the warmest year on record. Jump to 2015 – that globally was the warmest year on record. Into 2016 – which was the warmest year on record. But 2017 was not the warmest year on record – it was only the second warmest.”

Climate change sceptics are wrong to say climate varies naturally so maybe the warming is natural, said Mann.

“Once you set in motion the collapse of these ice sheets it is very difficult to stop it from happening. You cross a tipping point where you’re basically committed to the collapse of a large part of the Western Arctic ice sheets.”

“We actually published an article last year where we calculated the likelihood that we would have seen those three consecutive record-breaking years in the absence of human-caused climate change and we estimated it was somewhere in the range of one in 4000 – extremely small. Or as a journalist writing for Discover put it, a snowball’s chance in hell. It’s not natural. We can’t explain the warming we’ve seen from natural causes.”

In fact, said Mann, modelling suggests natural factors would put earth into a cooling trend.

“It’s only when we add the human effect of increasing greenhouse gas concentrations that we can reproduce the warmth that we’ve seen,” he said.

“Climate change critics seem to come around and concede that, ‘Oh yes, maybe humans have some role.’ Well, no we don’t just have some role. Humans are actually responsible for more than 100 percent of the warming that we’ve seen. What I mean there is that natural factors were actually pushing us in the opposite direction.”

For Pacific island nations, “the danger of climate change has arrived, it’s already here”, said Mann – with sea level rises, extreme weather events and ocean acidification.

The Paris climate agreement has a target of keeping global warming below 1.5 degrees Celsius.

Any more warming than that would be devastating, said Mann, with two degrees “the level many scientists would say really constitutes a dangerous and irreversible climate change”.

We can still stabilise warming, he said, but if we continue with “business as usual burning fossil fuels” there will be between four and five degrees Celsius warming by the end of the century.

That is “truly profound warming for the climate system” and “in many respects the impacts appear to be greater than we first estimated”.

Uncertainty, said Mann, “is not our friend. Uncertainty can work against us and historically it appears to be doing so”.

For example, sea ice in the Arctic has melted more than models predicted based on ‘business as usual’.

“The models say that by the end of this century you might see an ice-free Arctic. If you follow where the observations are taking us, many scientists have concluded that […] at the end of a decade or two we could see an ice-free Arctic at the end of the summer.

“Well, that’s just the Arctic. It turns out, as a colleague of mine says, what happens in the Arctic doesn’t stay in the Arctic. It influences climate over the rest of the planet.”

Mann warned of tipping points beyond which there is no turning back – for example, the Greenland ice sheets in the Western Arctic.

“We’re only here for a short amount of time to do what we’ve been put here to do, which is look after the country.”

“Once you set in motion the collapse of these ice sheets it is very difficult to stop it from happening. You cross a tipping point where you’re basically committed to the collapse of a large part of the Western Arctic ice sheets.”

Because of what is happening in the Arctic and also in the Antarctic, scientists’ worst-case scenario for sea level rise by the end of the century has now doubled to two metres.

Samoan Prime Minister Tuila’epa Dr Sa’ilele Malielegaoi told the conference of the calamitous effect six to eight feet (ie around two metres) of sea level rise would have on Pacific island nations.

“We didn’t think it was possible a few years ago,” said Mann. “What didn’t appear possible a few years ago now appears to be possible. And we have to start preparing for those potential eventualities.”

Hurricanes, cyclones, unprecedented rainfall, unprecedented heat, unprecedented drought – these we are already seeing, said Mann, and they will increase still further, with once-in-a-hundred-years events happening every few years.

“In Wellington, you have had the driest November in 90 years, but you’ve also had some of the most severe weather events on record just within the past few months. And by the way January was the hottest month ever recorded in New Zealand.”

Mann added that “everywhere I go when I give a lecture about climate change it’s too easy now to find examples of the profound impact climate is having on us where we live in our daily lives”.

He said the effects of climate change around the world will add to growing populations competing for food, water and land.

“Increased competition for resources leads to increased conflict and that’s a fundamental problem for all of us.”

Despite President Donald Trump’s withdrawal from the Paris climate agreement, Mann predicted the US will still meet its previous obligations under the agreement, because cities’ and states’ and even some companies’ “fierce pushback” against Trump’s approach means “nearly a third of the US population now lives in a state that does have policies for addressing the problem”.

However, he said, the Paris agreement commitments need to be substantially improved “if we are going to keep warming below two degrees Celsius, let alone 1.5 degrees Celsius”.

It is, he said, ultimately an issue of intergenerational ethics.

“It is our imperative to act now so we do not leave behind a degrading climate for our children and grandchildren.”

Earth system scientist Emeritus Professor Will Steffen from Australian National University told the conference not only about potential tipping points but also about potential tipping cascades — affecting interconnected parts of the earth’s eco-system.

As background to his own ‘hockey stick’ data timelines, Steffen highlighted that:

– Since 1970 the global average temperature has risen at a rate about 170 times the background rate of the previous 7000 years, and in the opposite direction

– In the past two decades atmospheric carbon dioxide has risen at about 100 times the maximum sustained rate during the last deglaciation, which ended more than 11,000 years ago.

– Ocean acidification has risen at a rate unparalleled for at least 300 million years.

The spikes upward on Steffen’s timelines start their ascent after World War II – it being more of a period of what he calls “great acceleration” than the industrial revolution of the 18th and 19th centuries.

The spikes reflect “a real step-change in human activity”, said Steffen.

The consequences of that activity “are now looking from a geological perspective like one of the extreme events that hit earth in the past – like the huge volcano or the meteorite strike typical of past rapid changes in the biosphere, for example the one 56 million years ago.”

The importance of respecting the interconnectedness of the earth’s system “is no surprise to indigenous cultures around the world”, said Steffen. “They are life-centric focused. But we are human-centric focused.”

He ended with a quote from an elder of the Noongar People of Australia — Aboriginals being stewards of the land for at least 65,000 years, he said: “We’re only here for a short amount of time to do what we’ve been put here to do, which is look after the country. We’re only a tool in the cycle of things … [We] go out into the world and help keep the balance of nature. It’s a big cycle of living with the land, and then eventually going back to it …”

The conference presentation by Daniel Nocera, Patterson Rockwood Professor of Energy at Harvard University, charted the development of the bionic leaf he has created to make biomass and liquid fuels through artificial photosynthesis 10 times more efficient than natural photosynthesis.

The initial artificial leaf for the technology was named Innovation of the Year by Time magazine in 2011 and the full fuel process was named Breakthrough Technology for 2017 by Scientific American and the World Economic Forum.

Nocera wanted a cheap and easy green energy solution that could be distributed individually without users being reliant on centralised grids, which are expensive to establish and operate and require a lot of capital investment, infrastructure and policy support.

He was looking for “a McDonald’s hamburger of energy we could just hand out to the poor” in countries such as Africa, rural China, Indonesia and India.

Climate change needs to be tackled systemically, he said, and “you can’t have a sustainable planet if you can’t take care of the poor of the world”.

“What do the poor have available to them?” asked Nocera. “Sunlight – so that’s why I’m a big solar fan, because it’s an indiscriminate energy source. Whether you’re poor in Africa or rich in Beverly Hills, California, you can look at and see the same energy source. The other thing the poor have is air. And the other thing is water.”

All three are fundamental to a leaf’s photosynthesis process and so to Nocera’s technology.

It is now being trialled in India.

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