May we discuss 'net zero' 2050?

Since 1900, the global population has jumped fivefold. World greenhouse gas (GHG) emissions are 15-20 times higher. Real Gross World Product has soared even more.

Earth and seas used to reabsorb "natural" or background emissions. They can't handle the "anthropogenic" load.

So atmospheric CO2 and land-ocean temperatures keep rising . Much of that rise comes in recent decades.

In Australia, setting aside fluctuating estimates of "land use" (LULUCF) emissions, emissions have risen from 400s of megatonnes (Mt) in 1990 to the 500s today.

Before any "offsets", our latest projection for 2030 is 511 Mt. Slashed from 563.

From 1990, our population has grown 40 per cent. So growth looks "decoupled" from emissions. Similarly, with global growth. Problem, the constant-sized earth reads aggregate and not per capita emissions. Hence, still-rising CO2.

Claims the European Climate Foundation, this inexorable 20th century trend can be overturned. World emissions neutralised.

To limit global warming, the Paris Agreement urges global Net Zero "as soon as possible" after 2050. "Developed economies" should get there no later than 2050.

Such might happen, via two avenues.

First, "emissions reductions". Humans could get a much better handle on decarbonising electricity, plus electrifying (or otherwise transforming) industry and transport. These fossil-fuel intensive sectors account for most emissions today.

Second, "negative emissions". Earth, rather than just producing its own (LULUCF) emissions, could be groomed intensively to "capture" excess human emissions.

"Net Zero" happens, when these two balance out. Residual emissions are offset by CO2 (or GHG) removals.