During the Black Summer bushfire crisis of 2019-20, a political moment came and went without much reflection.

"I think to suggest that at just 1.3 per cent of emissions, that Australia doing something more or less would change the fire outcome this season - I don't think that stands up to any credible scientific evidence at all," said Prime Minister Scott Morrison in December 2019, facing new pressure and scrutiny on climate.

It was an important moment to me.

Morrison was expressing a commonly held view: that it's OK to allow greenhouse gases to be released into the atmosphere, if it's just a little bit. This week, in response to a landmark report by the Intergovernmental Panel on Climate Change updating the physical science of climate change, Morrison said much of the same, trying to shift the blame to countries with larger emissions, like China.

The IPCC's report reinforces a core principle of the climate problem that neatly explains why Morrison's attitude is so dangerous.

"There is a near-linear relationship between cumulative anthropogenic CO2 emissions and the global warming they cause. Each 1000 [gigatonnes] of cumulative CO2 emissions is assessed to likely cause a 0.27-degree to 0.63-degree increase in global surface temperature, with a best estimate of 0.45 degrees," the report's summary states.

In the words of the executive director of the United Nations Environment Programme, Inger Andersen: "It's time to get serious because every tonne of CO2 emission adds to global warming."

Old forms of climate denial were easy to spot. Think wide-eyed obsessives and Abbott-era pleas about carbon dioxide being plant food. Today the real problem lies in delaying climate action, and refusing to accept that every single moment of complacency results in additional harm to life on Earth.

This has been known for some time, but the most recent science reduces uncertainty thanks to faster computers and more advanced modelling techniques. In a very real sense, Scott Morrison was directly contradicting the science when he said Australia's emissions are too small to count. We know for sure that everything counts, and that historical decisions made to worsen Australia's carbon footprint played some part in the circumstances that led to those catastrophic bushfires.

What we are seeing here is a mumbled acknowledgement of the macro problem, but an aggressive refusal to consider the micro components that comprise it. It is the core engine of climate inaction in Australia. Politically, you can see it everywhere.

Consider the prospect of Australia setting a net-zero target by 2050 (and briefly put aside the fact that it really ought to be much earlier). This too flew by with little remark, but Morrison actually outlined some detail on what the "pathway" to net zero looks like in April this year.

"The trajectory to any net-zero outcome is not linear, and anyone who thinks it is I think doesn't get it," he said, before tracing out the curve of technological growth over time with his hand. Implicitly, he's suggesting emissions reductions occur very late in the 30 years between now and 2050.

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This is known as "backending" - putting off climate action by as many decades as possible. Hence Australia's incredibly weak 2030 target of 26 per cent, and Morrison's steadfast refusal to update or strengthen that target. Acting late means that, between now and 2050, far more cumulative tonnes of greenhouse gases are emitted compared to if we decided to act fast and early. And it is the cumulative amount of greenhouse gases, not the end point, that causes the harm. Morrison wants to bend the curve in a way that causes more climate harm, but also prolongs fossil revenues.

The problem is widespread. AGL Energy, Australia's largest corporate emitter by a large margin thanks to its highly polluting coal plants, claims to be on track to reach carbon neutrality by 2050. But its last coal plant will still be running hot in 2048. The International Energy Agency's recent roadmap for the world's energy sector to limit warming to 1.5 degrees found that advanced economies like Australia need to shut coal down before 2030. Even AGL's own modelling found the "do nothing" approach breaches a 1.5-degree target.

Do decision-makers at AGL understand that every tonne of carbon dioxide is doing damage? Did they read the IPCC report?

What about the executive team at Whitehaven Coal, in the legal fight of their lives to ensure that their new coal mine gets built - which will unlock hundred of megatonnes of carbon dioxide, all eventually released into the atmosphere? That company faced a setback in May when the Federal Court found that the extraction of coal and its eventual burning causes direct personal injury to young people, including death and hospitalisation (Australia's Environment Minister, Sussan Ley, is appealing the ruling).

What about the West Australian government and Woodside Energy, also fighting to ensure a gas mining project that will unlock emissions equivalent to 15 coal plants goes ahead? Earlier this year, the Callide Power Station in Queensland suffered a serious accident, with a generator irreparably damaged. It should have been the perfect opportunity to replace a coal-powered generator with new, zero-emissions technology.

"The Queensland government has committed to rebuilding the unit," said Opposition Leader Anthony Albanese. Does he understand that every additional tonne does harm? Does he think locking in another few decades' worth of coal emissions is worth the pain and suffering that climate change causes?

Australia's Black Summer bushfires, the drumbeat of climate-intensified disasters we're seeing this year around the world, and the finding of the IPCC's latest report all point to the summarised consequences of a mountain of micro-scale decisions that have worsened our reliance on the burning of fossil fuels. Years of outright climate change denial, corruption and cronyism have led to well over 2300 gigatonnes of carbon dioxide being added into our habitat from the mid 1700s through to now. A million moments of "Surely this tonne doesn't matter" adding up to actual lives being lost today.

Over the next 10 years, those with access to power will face another 100,000 decision points. The IPCC's report tells us that, depending on those decisions, we'll either experience catastrophic, unimaginable levels of global heating, or only slightly more global heating than exists today.

Until the IPCC's core message - that every tonne of carbon dioxide hurts us badly - is understood widely across political and corporate culture, those decisions lean heavily in precisely the wrong direction.