May we discuss 'net zero' 2050?

Australian Government isn't buying, not yet. The Opposition is, provided we retain coal exports. Our states are on board. The big champion for Australian Net Zero is economist Ross Garnaut, in the book Superpower.

Says Garnaut, two-thirds of the emissions savings to Net Zero would come from relinquishing fossil fuels. Land use "transformation" would deliver the rest.

His "intermittent renewables" would meet electricity needs as early as the 2030s, with emissions savings also flowing to increasingly electrified industry and transport sectors.

But there's scientific to and fro, as to whether you can approach 100 per cent renewables, via "pure" wind, water and solar. Even if you sort your energy mix, there are barriers, in terms of networks, transmission, storage and grid fluctuations .

Garnaut glosses the physical and logistical problems of nullifying power/industry/transport emissions. He does indicate the increasing affordability and desirability of Australian transition towards renewables. Also, that the technical "intermittency" of renewable power could be managed better.

It's the remaining LULUCF sector where things get interesting. In effect, Garnaut offers the attractions of indefinite economic expansion, plus a Rolls Royce environment that handily reabsorbs the emissions of such expansion.

Here's mainstream economics, which likes to "externalise" the environment, co-opting it as a get-out-of-jail card. Who said this was a dismal science?

Let's step back. No question, lands and seas "sink" CO2 and other GHG. As above, they more or less neutralise "background" emissions.

Some landscape types absorb, better than others. But landscapes also emit GHG, naturally. Or, dramatically. Our 2019-20 forest fires unlocked maybe two-thirds of "official" annual emissions.

Earth, exuding CO2 during fires or droughts, inhales in wetter spells. Over two decades, CSIRO estimated Australia reabsorbed just one-third of the CO2 emitted via its own fossil-fuel use.

World findings are not dissimilar. Lands and oceans, each might mop up roughly a quarter, of the human-related emissions.

Couldn't we just "plant more trees", or otherwise engineer the environment, to increase the rate of CO2 absorption? It's problematic.