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(Image: Andrzej Krauze)

CRUCIAL climate talks in Paris are fast approaching, hailed as the last chance for a deal to avert dangerous warming. The good news is that the talks are already a success, in the sense that national pledges on emission reductions would change our current worst-case trajectory 鈥� we鈥檇 go from expecting a 4 掳C increase by 2100 to .

The bad news is that the pledges won鈥檛 avoid 2 掳C of warming, the point where dangerous climate shifts loom large. Existing greenhouse gas concentrations , and the size of the changes needed to decarbonise the global economy makes it look inevitable that we will breach 2 掳C this century.

And yet I remain hopeful. Why? Because we aren鈥檛 factoring in what I call third-way technologies. These can reinforce Earth鈥檚 natural system of self-regulation by drawing greenhouse gases out of the atmosphere on a grand scale. They are distinct from emissions cuts 鈥� the first way of tackling climate change. And they should not be confused with second-way geoengineering 鈥� ideas such as pumping sulphur into the stratosphere to cool Earth, but which risk side effects like harming the ozone layer.

The third way encompasses biological and chemical routes to sequestering carbon. Biological paths involve photosynthesis, and include biochar creation, altered regimes of agricultural and , and . One indicates that if 9 per cent of the oceans were used for seaweed farms, the equivalent of all annual human carbon emissions could be captured, and the protein would be sufficient to feed the world.

Chemical pathways are diverse, including , the use of 鈥� which absorb CO₂ as they weather 鈥� manufacture of and from CO₂ and the use of clean energy to convert CO₂ to hydrocarbons. Combined with a fresh look at carbon capture and storage, which involves locking the gas away long term, the third way offers a potent tool in efforts to stabilise the climate.

Today, all such technologies are immature or at the concept stage. For example, only 1000 tonnes of biochar are produced a year. Some of these methods sound like science fiction.

But 2050 is as distant from now as 1915 was from nuclear 1950. At a conservative estimate, by 2050 the third way could be drawing away the equivalent of 40 per cent of current emissions, close to what would by 1 part per million a year. If this is to happen, we need to start large scale R&D now.

And while there may be a moral hazard in potentially diverting attention from the urgent task of reducing emissions, there is also one in neglecting the third way.

This article appeared in print under the headline 鈥淗ere comes Plan C鈥�