If combating climate change is left up to the governments of the world's wealthy nations, much of humanity is likely done for.
That's not the message that was meant to emerge from the July summit meeting in Italy of leaders of the G8 group of countries — Britain, Canada, France, Germany, Italy, Japan, Russia and the US. But apply a little climate science to the meeting's outcome, and that is the unmistakeable conclusion.
At the summit, the G8 leaders agreed to aim to keep global warming to less than 2ºC above pre-industrial levels. To achieve this, they set the goal of reducing world greenhouse gas emissions by 50% before 2050.
As leaders of industrialised nations, the G8 chiefs further accepted that their countries should bear a heavier burden than the underdeveloped world. Developed countries were urged to cut emissions by 80% by 2050.
True, Russia bluntly rejected the target and the Canadian government insisted that 80% merely be an "aspirational" goal. But the soothing assurances were spun out: the rich world would act firmly and make real sacrifices.
Blame for the climate danger was implicitly shifted from the world's wealthy nations — responsible for the great bulk of excess carbon dioxide in the atmosphere — to poorer countries.
Would China and India, the world was encouraged to ask, now agree to make substantial emissions cuts?
The wealthy global North, however, cannot dodge its responsibility for the climate peril. Emissions in developing countries have boomed, but the biggest polluters in these countries often include foreign-owned firms producing consumer goods for export to rich-country markets.
And if China is the world's largest greenhouse gas polluter in absolute terms, in 2005 Chinese emissions per capita were still less than 20% that of the US.
It is blatantly misleading for the G8 countries and other wealthy nations to pretend to be grasping the nettle on climate change. Carbon dioxide lasts for hundreds of years in the atmosphere. A crucial need is to cut emissions quickly to stop levels building up.
But when underdeveloped-world observers at the G8 summit called on the participants to commit themselves to cutting their 2020 emissions by 40%, the main response was embarrassed silence.
But what about the 2050 target of a 50% reduction overall, with 80% in developed countries? If met, would this keep global warming to bearable levels?
At present, human activity results in the release of more than 7 billion tonnes of carbon (not CO2) into the atmosphere each year. British writer George Monbiot said in his 2006 book Heat, the present capacity of the earth's biosphere to absorb carbon is about 4 billion tonnes a year.
If global emissions in 2050 were half those of the present, this suggests atmospheric carbon levels would be stabilised, perhaps even dipping.
But would they? Unfortunately, every tonne of emissions is doing the biosphere damage.
Monbiot said the capacity of the earth's carbon "sinks" — mainly oceans and forests — is expected to decline from 4 billion tonnes a year to 2.7 billion by as soon as 2030.
By 2050, with emissions continuing at above-stabilisation levels, the carbon sinks will likely be degraded still further.
The G8's overall 2050 goal, which would put global emissions that year at about 3.5 billion tonnes, is probably at least a billion tonnes too high. Greenhouse gas levels in the atmosphere would still be rising steadily.
What about the 80%-by-2050 target for developed countries? Would this represent a fair sharing of the burden?
Monbiot does not provide figures for 2050, but his calculations for 2030 are indicative.
Assuming a global population in 2030 of 8.2 billion, Monbiot worked out that if atmospheric carbon is to be stabilised by that year, world-wide emissions per capita must not exceed 0.33 tonnes. In Australia at present, the figure is about 5.6 tonnes.
For the burden of emissions reduction to be shared equitably, Monbiot concludes, emissions in Britain in 2030 will need to have fallen by 87% compared to present levels; in Germany by 88%; and in the US, Canada and Australia by 94%.
By 2050, the world's population is projected to be higher than in 2030, and the capacity of carbon sinks will almost certainly be lower. This suggests that humanity's per capita ration of carbon emissions will be well below 0.33 tonnes.
For rich countries in 2050 to bear their fair share of the costs of carbon stabilisation, they will need to have cut their emissions not by the G8's 80%compared to present levels, but by almost 100%.
If the G8 leaders were bank directors, and did their accounting as they have in this case, they'd be locked up as crooks.
Even if the G8's targets could do it, would keeping the average temperature rises to 2ºC over pre-industrial levels be safe, as the G8 leaders imply?
Warming of 2ºC (it is now about 0.8ºC) would almost certainly see at least one important climate "tipping point" passed with the disappearance of summer ice in the Arctic Ocean.
The G8's goals are not a pledge for serious action, but a dangerous deception that loads the burden of emissions cuts unfairly onto the world's poor.
Confronted with the truths of climate change, the leaders of world capital