The carbon tax starts on July 1 this year, so there’s some tidying up to do around the edges — appointments, financing, regulations — and then a big tick next to the climate policy box on the cabinet whiteboard. Minister Greg Combet has already taken on the additional portfolios of industry and innovation.

If only. A barely reported new study on Earth’s energy imbalance from NASA climate chief James Hansen and his research team contends that, far from answering the climate challenge, we have constructed “a Faustian bargain”.

The new NASA study (and science brief) reaffirms that increased levels of greenhouse gases caused by human activity — and not changes in solar activity — are the primary force driving global warming. With new calculations of the Earth’s energy imbalance, the study finds the planet’s surface continued to absorb more energy than it returned to space, despite unusually low solar activity between 2005 and 2010.

The study uses improved measurements from free-floating instruments to calculate the amount of heat that has been absorbed by the world’s oceans, and thus refines understanding of how heat and energy imbalances are distributed in the climate system. And that’s where news becomes more sobering.

One conclusion of the study is that “the overall cooling effect from aerosols could be about twice as strong as current climate models suggest”.

So what’s the big deal? Human activity modifies the impact of the greenhouse effect by the release of airborne particulate pollutants known as  aerosols. These include black-carbon soot, organic carbon, sulphates, nitrates, as well as dust from smoke, manufacturing, wind storms, and other sources. Aerosols have a net cooling effect because they reduce the amount of sunlight that reaches the ground and they increase cloud cover. This is popularly known as “global dimming”, because the overall aerosol impact is to mask some of the warming effect of greenhouse gases.

Hansen’s new study estimates this aerosol “dimming” at 1.2 degrees (plus or minus 0.2°), much higher than previously figured. Aerosols are washed out of the atmosphere by rain on average every 10 days, so their cooling effect is only maintained because of continuing human pollution, the principal source of which is the burning of fossil fuels, which also cause a rise in carbon dioxide levels and global warming that lasts for many centuries.

So on the one hand, we desperately need to reduce the burning of fossil fuels to zero, and quickly. Emissions need to fall off a cliff. Hansen has shown that to keep warming in the long run to a safe level of under one degree, fossil fuel emissions would need to be cut by 6%  a year beginning in 2012, plus 100 billion tonnes of carbon reforestation drawdown this century. Other work finds that if global emissions do not peak until 2020, then to limit warming to the (unsafe) two-degree range, the rate of emissions reduction needs to hit 9-10% a year, and requires total de-carbonisation by 2035-45. Needless to say, those figures are not on the cabinet whiteboard, and would be greeted with incredulity by most climate policymakers.

On the other hand, rapid and deep reductions in fossil fuel emissions (and emissions from burning cleared vegetation from rainforest destruction) will cut the aerosols and their temporary cooling. If all aerosols were removed from the system, about half the 1.2° of lost cooling would appear very quickly as a pulse of warming, with the other half following over a few decades.

And that is the Faustian bargain. If we keep burning fossil fuels the way we are, the planet will head towards four degrees of warming by century’s end, and a carrying capacity of less than a billion people. And if we cut emissions rapidly, we lose aerosol cooling and get a pulse of warming that creates very dangerous conditions.

There are two conclusions that help us find a way out of this maze. The first is that part of the answer is to develop and deploy, at very large scale, methods that draw down carbon from the atmosphere (whether by reforestation, biochar or other means) to reduce the energy imbalance and the warming to come.  The second is that some form of geo-engineering, that provides temporary cooling while carbon emissions and aerosols are run down and carbon drawdown is scaled up, is probably the least-worst option.

Decarbonising the economy quickly is absolutely necessary. It will build new industries and jobs, but also require stranding of capital embedded in obsolete, fossil-dependent technologies, and reshaping how and where we live, travel and maintain food and water security. There is, as yet, no political model of how these changes could be achieved in the developed nations. The plethora of rapid transition plans that have appeared in the past few years are strong on the technology and the financing, but weak on the politics.

The choice is between some significant disruption now while we make the transition quickly, or a state of permanent and escalating disruption as the planet’s climate heads into territory where most people and most species will not survive. Our task now is to chart the “least-worst” outcome. Delayed action over the past three decades has created a Faustian bargain, or bureaucratic terms, a “super wicked problem“.