After the feast of words in Durban, comes the reckoning: the deal ensures beyond doubt that our children will be worse off than we have been.
Unlike the economic debt currently transfixing the attention of world's leaders, it appears possible to them that we can put our climate debt on the never-never.
The loans in euros, dollars and pounds will be called in within days, weeks, and months. But the environmental debt – run up by many decades of dumping carbon dioxide waste in the atmosphere – won't be due for full repayment before 2020, according to the plan from Durban. If this roadmap to agree a global deal to tackle climate change by 2015, which would take force by 2020, is a triumph, it is a pitiful one. It aspires to achieve in four year's time what was deemed essential by the world's governments in 2007, but crashed at the Copenhagen summit in 2009.
That eight-year failure is why the ecological debt will inevitably transform into a new economic debt dwarfing our current woes. Like a loan-shark's debt, the cost of halting global warming - and coping with the impacts already certain - spirals higher and higher the longer you leave repayment. At the moment, as record rises in carbon emissions show, we are paying back nothing.
Cleaning up the energy system that underpins the global economy is inevitable, sooner or later. If not, true economic Armageddon awaits, driven by peak oil, climate chaos and civil unrest.
Moving to fuel-free renewable power is the only sustainable path, and the sooner we move the cheaper it is. Even better, a international deal showing genuine urgency would unleash the trillions of dollars of private savings currently stuffed under the beds of investors. They are too nervous to put money into the old economy, yet too uncertain of the low-carbon commitment of politicians to put their money into the new economy.
Some action to tackle global warming is being taken, but far too little, far too slowly. A catastrophic 4C of warming remains our final destination, without a heroic change of course.
The failure to truly act in South Africa shows politicians are only galvanized by crises that crash and burn between elections. Dealing with longer, more difficult crises gets set aside, with only rhetoric to salve them.
Yet climate change is here and now, if they only looked. Scientists now know global warming tripled the chance of the infernal heatwave that struck Russia in 2010, killing 55,000 people, destroying 25% of the nations crops and costing the economy $15bn. Across the world, and particularly in its poorest parts, droughts, floods, storms and more are destroying livelihoods with only the certainty of worse to come. Record leaps in greenhouse gas emissions and forecasts of carbon lock-in by 2016 guarantee that.
For all the current talk in Europe of austerity - "having no comforts or luxuries" as the dictionary defines it - the environmental austerity we face as a result of yet more procrastination is far more daunting. Ecology and the economy are both rooted in the Greek word for 'home' and the less we do now to tame climate change, the more it will cost us later to keep our homes safe from global disaster.
Getting 194 nations to agree on anything with legal force, as happened in Durban, is an achievement, as is the rejection of the alluring calls to abandon the UN as the place to solve this global problem.
But the brutal truth is that our leaders lack the political will to do what is necessary. The delay in Durban means politicians have deepened our titanic environmental overdraft. That debt will fall to the next generation to pay, but as Lehman Brothers and Greece showed us, debts are not always honored.
In the economy, banks can create new money and recessions can double dip. In the real world, thanks to climate tipping points which turn modest temperature rises into searing ones, we cannot afford to dip at all. One deep climate "recession" will destroy the lives and livelihoods of many for ever.
History will judge us. And which will be seen as the greatest sin: the failure to calm the Eurozone crisis or the failure to calm our seething climate?