If a bricklayer builds a wall that falls over 12 years later, killing someone, the bricklayer can be sued and even jailed. If a doctor finds some old packets of thalidomide in their surgery and, in spite of the overwhelming scientific evidence of its horrific effects, dispenses it to pregnant women, they would go to jail. The example can be multiplied endlessly: the reality of our world is that we are responsible for our acts.

Unless, that is, you are an Australian politician.

A politician can destroy our future, a politician can ignore the best evidence and be responsible for decisions that lead to deaths of many and the suffering of all, and still be free until the end of their days to milk the legal corruption that is Australian public life, picking up highly paid sinecures as ambassadors, board directors and lobbyists for the corporations they were once meant to regulate in our interest.

Wentworth byelection: John Hewson urges Liberal 'drubbing' over climate change Read more

Last Monday there came the unbelievable news contained in the UN Intergovernmental Panel on Climate Change (IPCC) report. If large-scale action is not taken now we will face a global warming catastrophe.

The report was a nightmarish scream heard through a spithood of formal scientific language. Any rise above 1.5C is highly likely to be disastrous, with millions of people displaced by rising seas, the extinction of numerous species, and the loss of most coral reefs. At 2C the rate of crop loss doubles, as does the decline in sea fisheries. Almost all coral reefs will be dead. Diseases such as dengue and malaria will be far more widespread, extreme droughts and floods far more common, while security and economic growth will be imperilled.

One of the report’s lead authors, the geographer Adelle Thomas, said, “The scientific consensus is really strong. It’s not just a political slogan: ‘1.5 to stay alive.’ It’s true.”

The report was specific in how long we have to keep warming at 1.5C: until 2030.

Twelve years.

This Saturday the voters of Wentworth have the opportunity to turn their byelection into a referendum on climate change. If you are a Wentworth voter, consider the historic responsibility you have and how in the past you have used it to good effect. Last year it was Wentworth, after all, that voted 80.8% yes for marriage equality, the fourth-highest yes vote in the nation.

Marriage equality, as many have since noted, was not given to us by enlightened politicians. It was forced on a recalcitrant government by the countless acts of individual courage shown by those who stood up in their workplaces, families, in their kitchens, cafes, sporting clubs, for their dignity and freedom; it was made possible by organisation and a passion that transcended party loyalties, and could not finally be refused. Marriage equality was won by the people, in other words, not gifted by the politicians.

Our prime minister, a man with a wit that would make Kenny look like Oscar Wilde, once thought it funny to wave a lump of coal in parliament during the middle of one of eastern Australia’s worst heatwaves. Luckily he had Barnaby Joyce there to laugh. With a similar bro and brio he dismissed the IPCC report while speaking to Alan Jones, saying he wouldn’t be bound by its recommendations. His deputy, Michael McCormack, declared the government would not change policy “just because somebody might suggest that some sort of report is the way we need to follow”.

That “some sort of report” – the findings of 91 of the world’s most eminent climate change scientists surveying more than 6,000 studies of the most recent research – didn’t trouble McCormack because he hadn’t read the report. Neither had our environment minister, Melissa Price, who told ABC radio the IPCC report, whatever the shared judgment of its global expertise, was “drawing a long bow” by calling for an end to coal by 2050.

But then, of course, this is the same government that offers total political support for the Adani coalmine at a time when the IPCC says coal must be phased out. This is the same government that granted $440m to a foundation that never asked for the cash, to deal with water runoff and the crown-of-thorns starfish on the Great Barrier Reef when the science is clear that climate change is what will kill the reef.

We have shown that we are large, that we care, and that we think

And this is the same government that has no policies to meet Australia’s commitments to the Paris climate agreement. This is the same government that hides shameful greenhouse emissions reports showing our pollution increasing by releasing them in the days before Christmas, without publicity.

And its leader, our prime minister, is the man who says that “we’re doing well” when the government’s own figures show that our pollution is increasing.

The Liberal candidate Dave Sharma echoes the same smug complacency of the Liberal government he expects to join next Monday.

“I do think we are doing enough,” Sharma has said, “and I do think we have had a good record on climate change. Emissions are at their lowest levels in 28 years,” he said. The evidence is otherwise: absolute emissions continue to rise and are among the highest in the OECD.

Like our prime minister, who claims we will meet our Paris agreement targets “in a canter”, Sharma says: “We are on track to meet the Paris commitments and I believe we will address the Paris commitments and we will be addressing affordability and sustainable and coherent energy policy.”

Sharma’s diplomatic wording cloaks the truth: the Liberal government is the Aleppo of energy policy. It has none, only the shell-shocked ruins of a once great party. As for the Paris climate targets, according to consultants, NDEVR Environmental, Australia is on a trajectory that will see it fail to reach them.

In the face of such sustained stupidity by our leaders many Australians have felt an overwhelming sense of powerlessness.

But we should not.

If you are a Liberal voter, consider the voices of true conservatism and business

As the marriage equality vote showed, as the Sydney Opera House controversy revealed, if we choose to exercise our power we discover that we are not as we have so often been told, small and mean and self-serving, cast in the shrivelled image of our politicians. To the contrary, we have shown that we are large, that we care, and that we think – and that when we dare to exercise it, that the power is ours.

In evading their responsibilities on climate change, our politicians have been irresponsible to the point of what would be, in any other sphere of life, criminality.

If you are a Liberal voter, consider the voices of true conservatism and business.

Mark Carney, the governor of the Bank of England, recently warned “of the catastrophic impacts that climate change could have for the world financial system”.

“We accept the IPPC assessment of climate change and that human influence is clear and that the physical impacts are unavoidable,” Jac Nasser, the former chairman of BHP, the world’s biggest resource company, declared, while Eric Schmidt, the former chairman of Google, said: “The facts of climate change are not in question. People who oppose it are hurting our children and making the world a worse place. They’re just simply lying.” Listen to Fiona Simson, the president of the National Farmers’ Federation, who has stated “We’ve turned a corner on climate change … overwhelmingly, I think it’s got to a point where the science is very acceptable.”

These are hardly the lunatic voices of the far left. It is clear that the traditional constituencies of the Coalition, business and farmers, support major action on climate change – as do the majority of Australians according to all published research, as do the majority of people in Wentworth.

Yet the government, from the prime minister down, dismisses the issue. Indeed, both the government and Sharma, state that they are “doing enough” on climate change.

Don't despair: the climate fight is only over if you think it is | Rebecca Solnit Read more

The very phrase drips with the contempt of our political class for Australian citizens who they take for passive fools, easily manipulated. As with marriage equality we see a polity determined to do nothing.

Since 2013, the Coalition government in its various incarnations has lied, laughed and destroyed when it comes to this most fundamental matter: that of our future. Their record is one of deceit, obfuscation and craven capitulation to the fossil fuel industry. It is a party that has evaded its most fundamental responsibility to our land and our people, and the time for a reckoning has arrived.

This Saturday, voters of Wentworth can lead Australia as they did in the marriage equality survey. They can make the byelection a referendum on climate change by voting the candidate they believe has the best climate policy number 1, any who might have a reasonable policy from 2 to 15, and put Dave Sharma at 16.

“We have presented governments with pretty hard choices,” Prof Jim Skea, co-chairman of the IPCC panel has been quoted as saying. “We show it can be done within laws of physics and chemistry. Then the final tick box is political will.”

Wentworth byelection forum: the 'good-hearted people' and the missing Liberal Read more

The most important thing a voter can do on election day is demonstrate that this threat to our future must be our politicians’ number one priority, and give our politicians the political will to act now.

There is so much beauty in this world. Sometimes it is hard to believe this life that is given us. Sometimes it is hard to believe that it is possible to change it for the better, or save it from the worst. But from today we must, and we can.

If we take our compass from power we will know only despair. But if we take our compass from those around us and their actions we discover hope. It is time we rediscovered not partisan division but a common humanity ready to take on our gravest crisis. It is time we acted, and the Wentworth byelection is the first chance Australians have. Our tomorrows are running out. We have only today.

Play Video 3:48 Australia's climate wars: a decade of dithering – video

• Richard Flanagan is the Man Booker prize winning Australian author

• Businessman Geoff Cousins is a former Howard government adviser