Its 70 pages boil down to four propositions we'd rather not think about. First, there is no doubt the climate is changing. The evidence is overwhelming and clear. The atmosphere is warming, the ocean is warming, ice is being lost from glaciers and ice caps and sea levels are rising. Global surface temperature is rising fast; the last decade was the hottest on record. Second, we are already seeing the social, economic and environmental effects of a changing climate. In the past 50 years the number of record hot days in Australia has more than doubled. This has increased the risk of heatwaves and associated deaths, as well as extreme bushfire weather. The sea level has risen by 20 centimetres since the late 1800s, affecting many coastal communities. Another 20-centimetre increase by 2050 is likely, on present projections, which would more than double the risk of coastal flooding. Third, these changes are triggered by human activities - particularly the burning of fossil fuels and deforestation - which are increasing greenhouse gases, with carbon dioxide the most important of these gases.

Fourth, this is the critical decade. Decisions we make from now to 2020 will determine the severity of climate change our children and grandchildren experience. Without strong and rapid action there is a risk climate change will undermine society's prosperity, health, stability and way of life. That scientists still need to repeat these long-established truths is a measure of how much we've allowed short-sighted and selfish concerns to distract us from the need to respond urgently to a clear and present danger. In this we haven't been well served by our leaders. The Labor government's decline dates from Kevin Rudd's loss of nerve after the defeat of his carbon pollution reduction scheme in the Senate in late 2009, following the success of the Coalition's climate-change deniers in overthrowing Malcolm Turnbull and replacing him with a man whose record showed him willing to take whatever position on climate change he thought would advance his career. Had Rudd the courage of his professed convictions, he would have taken the question to a double-dissolution election, fighting in defence of his ''great big new tax on everything''. Instead he dithered, eventually yielding to pressure from those in his party - including Julia Gillard and Wayne Swan - wanting to put the government's survival ahead of its duty. Oppositions play a vital role in a parliamentary democracy and opposition leaders are given considerable licence. They're not expected to speak the unvarnished truth. Dishonest scare campaigns have long been used by both sides.

I don't like using the L-word, but Tony Abbott is setting new lows in the lightness with which he plays with the truth. He blatantly works both sides of the street, nodding happily in the company of climate-change deniers, but in more intellectually respectable company professing belief in human-caused global warming, his commitment to reducing carbon emissions by 5 per cent by 2020 and the efficacy of his no-offence policies. He grossly exaggerates the costs involved in a carbon tax, telling business audiences they'll have to pay the lot and be destroyed by it, while telling the punters business will pass all the costs on to them. He forgets to mention that most of the proceeds from the tax will be returned as compensation to businesses and households. He repeats the half-truth that nothing Australians could do by themselves would reduce global emissions, while failing to correct the punters' ignorant belief that Australia is the only country contemplating action. Last week's news that Britain's Conservative coalition government has pledged to cut emissions by half within 15 years is ignored. Economists call this mentality ''free-riding''; the old Australian word for it is ''bludging''. But it's far too easy to blame our failure to face up to climate change just on our hopeless politicians. Our increasingly partisan media have failed to hold Abbott to account over his duplicity. Many have sought to increase circulation or ratings by joining in the fear-mongering and denial. The media's love of controversy has led them to give doubters of the science of climate change a credibility they don't deserve against the weight of scientific opinion. Australians are proud of their inbuilt bulldust detectors, but on this issue they seemed to have turned them off, happily believing whatever self-serving nonsense is served up to them. The one thing humans are meant to care about above all is the survival of their young. Yet people with the highest standard of living in history are whingeing that they couldn't possibly afford to pay a bit more for their electricity.

Ross Gittins is the economics editor.