What you should - and shouldn't - believe about climate targets, via Mark Twain

"Believe none of what you hear, and only half of what you see." – Benjamin Franklin

• Read more 2nd Degree

In the near future, the Abbott government is expected to announce the pledge that it will take to the Paris climate change summit in December. Almost certainly, it will be confusing.

This may not be the government's intention, though it is reasonable to assume it won't mind.

For reasons not immediately clear, the diplomats who dreamed up the language of climate negotiations made the solution to this great global problem impenetrable to anyone beyond the trainspotter. Every word is argued over and carries meaning, but the resulting documents - a blur of acronyms, square brackets and bureaucratese  – can glaze eyes at Olympic standard.

The process is becoming ever-more confusing ahead of the Paris conference, as countries set emissions targets that can't be compared without a university level knowledge of statistics. Some are targets for 2025; some for 2030. Some pledge to cut emissions below what they were in 1990; some 2000; some 2005. Some developing countries are promising to reduce not emissions, but "emissions intensity"; others to cut emissions compared with "business as usual".

Australia is one of few major countries, and the only major industrialised country, yet to make its announcement.

Already, Australia has changed how it expresses its target: the goal of a 5 per cent cut by 2020 is now routinely described as a 13 per cent cut. Why? It has shifted the year against which the cut is measured from 2000 to 2005, when emissions were significantly higher. While there is an arguable justification - the US uses 2005 - Benjamin Disraeli would no doubt approve.

How, then, to measure Australia's target when it lands?

The aforementioned trainspotters offer a valuable guide.

Australian think-tank the Climate Institute says there are two key things to consider. The first relates to population – how much will Australia be emitting per person under the new target? The second relates to the economy – how much will it be polluting for every dollar of gross domestic product earned?

Australia, you may not be shocked to learn, is a world-leader in both categories.

The institute says there are 24 countries with emissions comparable to Australia, each releasing between 0.5 and 1.5 per cent of the global total. Together, they pump out 21 per cent of greenhouse pollution – equivalent to that from China. Climate change can't be properly addressed if this group doesn't act.

Among the 24, Australia has easily the highest per person emissions and ranks fifth in pollution per GDP, or emissions intensity. This is largely due to its overwhelming reliance on coal.

Given the goal is to get emissions to what scientists advise is a safe level, the institute says it suggests Australia needs to not just match what similar countries – particularly the US – are doing, but make even deeper cuts to play its part.

Consider, if only as a guide, the targets that Australia was reportedly considering a couple of weeks ago – a 24-28 per cent cut by 2030 compared with 2005 levels.

In per capita terms, this would be a smaller cut than the average across the developed world, or than that proposed by any of the US, European Union or Japan.

The Climate Change Authority – set up under Labor, and still operating because the Senate wouldn't let the government abolish it – undertook a similar analysis. Compared to 2005 levels, it found to play its part and set up its economy for life in a low-emissions world Australia should cut emissions by:

• 36 per cent by 2025.
• Between 45 and 63 per cent by 2030.

This, it says, is necessary to bring it roughly into line with the US and take it past Canada, which authority chairman Bernie Fraser described as a laggard.

You can see here how the authority's proposed target would change Australia's per capita emissions, compared with what other countries are doing:

And you can see here what it would do to emissions per unit of GDP: 

Meeting this goal would require a significant overhaul in policy, probably including buying carbon credits that pay for some cuts in developing countries.

Overseas, the Climate Action Tracker – a scientific analysis undertaken jointly by four research organisations – is working its way through each country's responsibility if global warming is to be limited to two degrees.

Based on current policies, Australia is considered "inadequate" – a label it shares with Canada, Japan, Russia and New Zealand. Its position will be updated once the new target is out.

China, the US and the EU are rated "medium" – their pledges are better, but barely OK measured against the science, and likely not enough to stop a second degree of warming. Only the tiny Himalayan country of Bhutan – which has a goal of staying carbon neutral – is rated a "role model".

Speaking of China, Australian National University economist Frank Jotzo recently offered a nice shorthand explanation of why experts argue it is taking significant strides on climate change, despite its total emissions having increased dramatically this century.

He found for about a decade it had been cutting its emissions per unit of GDP by about 4 per cent a year, and was now promising to continue this to 2030.

This pace of improvement is unprecedented in a country with a growing economy. It is matched only by Russia and other former Soviet states – and they did it only after the Cold War, when their industry shut down, and their economies and emissions went into freefall.

The main game with China, of course, is when it will start making cuts in actual emissions. Beijing promises by 2030, though some analysts predict it will be earlier. Jotzo says early data suggests they stayed flat from 2013 to 2014.

A footnote on Russia: its target for Paris is expressed as a cut below 1990 levels, but given the staggering crash shortly after that year it actually appears to add up (depending how you cut it - it is not clearly expressed) to a 40 per cent increase above where its emissions are today.

As in so many things, Russia is considered a rogue at the negotiations, and not representative of what other countries are doing. But it is an illustration of how climate targets can beguile - and the importance of a clear translation.

What happened while you were out

▪ The Abbott government gave conditional approval to a 35-square kilometre coal mine proposed by China's Shenhua Group for the Liverpool Plains in north-west NSW. If it goes ahead, it will produce up to 268 million tonnes of coal to be burned over the next 30 years. Agriculture Minister Barnaby Joyce hit out at his government's approval of a mine on prime farming land, saying it was evidence the "world has gone mad".

▪ Respected journal Science published a study that found sea levels could rise at least six metres over coming centuries, swamping coastlines across the globe, even if the world limits global warming to 2 degrees. It found historical evidence tracts of ice in Greenland and Antarctica had melted when temperatures were about, or slightly higher than, those today.

▪ Broadcaster Alan Jones was found to have breached commercial radio codes by incorrectly saying the United Nations' Intergovernmental Panel on Climate Change had got the rate of global warming wrong "by almost 100 per cent". It hadn't.

What you may not have missed

It's cold this weekend. Here's why.

Follow Adam on Twitter. Or email him: amorton@fairfaxmedia.com.au