Sir David King speaks with gravitas.
"Let me emphasise the magnitude of the transition we're talking about. Today we're emitting globally 36 billion tonnes of carbon dioxide," says the former chief scientific adviser to the British Government.
"In order to manage this problem the scientific community is speaking with a single voice - by mid-century that needs to get down to 18 billion tons of carbon dioxide per annum." Halved, in other words.
King may be overstating the "single voice" - some scientists say a lower target is needed. But he is correct about what needs to happen over the next 40 years to avoid the catastrophic effects of climate change - a progressive "de-carbonising" of world economies.
It's the sort of principle he hopes the 192 countries of the United Nations Framework Convention on Climate Change (UNFCCC) will agree upon when they descend on Copenhagen in December to try to thrash out a new global climate deal - a potential successor to the 1997 Kyoto Protocol.
Emissions aren't the only thing growing. By mid-century the world will have a population of nine billion people. Divide 18 billion by this figure and you get two tonnes of carbon dioxide per person per annum - "our allowance on the planet by mid-century".
It's worth pointing out the carbon dioxide King is talking about here is actually carbon dioxide "equivalents", which include a contribution from other greenhouse gases, mainly methane and nitrous oxide. Greenhouse gases trap the sun's energy in the atmosphere, which in turn contributes to global warming, climate change and rising sea levels.
There is a long way to go to achieve King's goal of two tonnes per person per annum.
Just 47 per cent of New Zealand's 17.6 tonnes total of carbon dioxide-equivalent emissions is, in fact, carbon dioxide. The bulk of the rest comes from agricultural emissions (48 per cent) comprising methane and nitrous oxide. But whatever way you at look it, there is no escaping the fact that, per capita, we are one of the highest emitters of greenhouse gases in the world - a fact that sooner or later is going tarnish our clean, green image.
It also means we have a long way to go, if we're to ever meet King's target of two tonnes per person.
New Zealand is due to put forward its emission reduction targets on Monday at an international meeting in Bonn - a precursor meeting to Copenhagen. It's expected to ask the world to give us a break, because half of what we emit comes from farming and most of the food we produce is exported.
The figure the New Zealand Government is talking about is a 15 per cent cut from 1990 levels by 2020. While it sounds pathetic - especially when many developed countries are talking about at least 40 per cent cuts - it's quite a big ask because our emissions have been growing steadily since 1990 and are 22 per cent above those levels.
In the context of dealing with the overall problem of climate change, New Zealand is really making no headway at all. In 1990 when our population was smaller our per capita greenhouse gas emission was 18.1 tonnes per person. The Green Party believes New Zealand can do much better and has put forward a detailed proposal for a 40 per cent cut in emissions by 2020.
New Zealand is also hoping it can offset its high emissions through increases in the area of plantation forests - mostly pine trees. Forests are carbon "sinks" which take carbon dioxide out of the atmosphere. But many think this is a bit of a cheat that is not sustainable in the long term - especially because much of our pine plantations are due for harvest around 2020. So the only way to make such a scheme work would be to plant new forests every year.
Meanwhile policymakers around the world are still trying to figure out the best way forward. The European Union has adopted a goal of keeping global mean temperatures below 2C above pre-industrial levels. Some are arguing for a stabilisation of atmospheric greenhouse gases at concentrations equivalent to 350 parts per million (ppm) of carbon dioxide while others reckon 450ppm is a more realistic option.
A New Zealand cabinet paper in March indicates our Government supports "the lowest feasible global goal of long-term stabilisation of all greenhouse gases in the atmosphere at no higher than 450ppm CO2-equivalent."
But quite how it intends to do that remains to be seen.
Since pre-industrial times, the concentration of carbon dioxide in the air has risen by a little over one-third, from 270ppm to 380ppm. A level of 45ppm would be reached by around 2040 if emissions continue at today's rates. But that's not counting all greenhouse gases and the biggest problem of all - that as developing countries industrialise, global emissions are going to increase. Last year, China's emissions grew by 8 per cent, or around 450 million tonnes and emissions of other large developing countries like India, Brazil and Mexico are increasing at a similar pace.
As the International Energy Agency warned in 2008, 97 per cent of projected growth in emissions of carbon dioxide from energy use through 2030 will come in developing countries.
Which makes for a huge problem at the Copenhagen negotiation table.
New York Times' Dot Earth columnist Andrew Revkin paraphrases the developing countries view: "You rich folks out there who have spent 150 years building your economies and your wealth around fossil fuel-burning, you're going to have to help. You're going to have to pay."
How much? In June British Prime Minister Gordon Brown gave a speech on climate in which he proposed that the rich nations ante up some US$100 billion ($149 billion) a year in such assistance by 2020.
There's a big hurdle in America, too. Though President Obama has proposed reducing emissions by 80 per cent by the year 2050, he is yet to turn the idea into reality. "Every president in this climate energy arena has this huge iron shackle attacked to one leg and a wall," says Revkin. "The wall is the Senate. The way American law is structured you need two-thirds consent." Already, he says, American politicians are working hard to lower expectations.
How bad could it get if no action is taken? "We're talking about business-as-usual taking us to temperatures as high as five degrees above current levels," says Grantham Research Institute director of public policy Bob Ward. "That's something we've not seen on Earth for more than 30 million years. The idea that humans, who have only been around for 100,000 years, can adapt to a world that hasn't been seen on Earth for 30 million years is somewhat far-fetched."
Ward works with Lord Nicholas Stern, author of 2006's landmark Stern Review on the effects of climate change on the world economy. He has an alarming outlook on just how fast climate change is approaching.
"When you take into account all the other greenhouse gases, the current level of carbon-dioxide-equivalent concentrations is 435ppm. Most scientists will tell you 450ppm is the highest we can afford to be. The concentration is increasing by 2.5ppm per year. That means we've got six years at the current rate before we get to a level beyond which most scientists think it is unsafe to be."
Six years. In reality, Ward says many scientists expect the world to overshoot 450ppm, but hope we can stay below 500ppm and eventually reduce to a stable level of 450 ppm or lower.
Little wonder that King, currently director of the Smith School of Enterprise and the Environment at the University of Oxford, has described climate change is the most severe problem we are facing today - "more serious even than the threat of terrorism".
His message is clear. Unless emissions begin to decline very soon, we can expect severe disruption to the climate system - warmer temperatures, more extreme weather events and sea level rises - will which will be very expensive to clean up. And that it's cheaper in the long run to avoid making the mess in the first place.
"There is no room for complacency here. We need an appetite for change in the shortest possible time."
PLENTY OF GAS
Greenhouse gases, in tonnes, emitted annually per capita. The amount includes carbon dioxide, methane and nitrous oxide.
Britain and Europe
British scientist Sir David King's target
Sir David King speaks with gravitas.