It's a hard jump, but there's not just the one.
Have you heard the puzzle about the bacteria colony that doubles its area in the agar tray every night? On day 10, it occupies half the area. How long before it occupies the whole tray? One more day. You can add another agar tray or ten or a thousand, but it doesn't buy you that much time.
At a constant growth rate, if the solution eventually involves spreading to multiple planets, it's just a few more centuries before we're running low on planets, almost regardless of the size of the galaxy.
And we are nowhere near reaching it. Increase in economic output with population increase is what matters.
If you have people who can't earn a living and die from hunger, it's bad. If you have people who can cook porridge out of an axe, that's good.
Loonie idle intellectuals from places like Club of Rome are first to point "let's sterilise Asians," like as if they don't see that Western material consumption was bigger than that of all "dreaded Chindonesia" combined.
Remember, those loonie first dreamed of those Malthusian horrors long before even agriculture in the West was doing well, and their prime imperative was to plainly get more resources for themselves.
I do not doubt that when we will hit the feared "Malthusian runaway" at 40B-50B people, planet's economic output would be so great that people would have hard time imagining how nutrient scarcity ever been a thing, and we will be able to "simply throw more petawatt-hours" at the problem.
Evidence for that? There's a fair selection of serious planetary scale human impacts right now - food chains, species loss, plastics, and I haven't even mentioned climate yet. I haven't heard of any of the Club of Rome calling for sterilisation of Asians either - neither have the search engines. So that seems baseless hyperbole.
The idea climate change wouldn't be an issue with "less people" is absurd. "less people" don't suddenly create viable electric cars and fusion power.
Humans have always mismanaged resources. More humans means more mismanaged resources. Not all of the planet's issues are resource management though - a selection are simply down to sheer space used - forest clearcut, development such as roads and cities built and land farmed, etc.
Electric cars are 19th century invention. It is just a matter of deciding to no longer subsidize damage caused by CO2 emissions.
Fusion is also known to be limited by the lack of funding. I've read stories about 13 year old teenagers building their own fusion reactors. The bigger challenge was getting the financial support from parents.
Climate change mitigation has never been about feasibility, it has always been about finding a solution that is immune to politics.
Wrong. Fusion reactors you can build at home are just novelties, and don't produce more power than they consume. No one has yet figured out how to actually do that, and until you can do that, fusion isn't useful as a power source. The only place we've ever seen fusion produce usable power is in a star. There's lots of research into building complex reactors to try to replicate this without needing something the size of a star, but no one's actually done it yet. It might be doable with enough funding, or it may never actually work; there's no way to say for sure.
The real problem is that too many people on this planet consume too many resources, and Americans are the worst. If most people lived in cities as dense as Tokyo and got around on trains and bicycles instead of cars, we wouldn't be having most of these problems. The amount of energy consumed per capita in America is simply unsustainable, and too many other people want to emulate this, but there's simply no way for that to possibly work on this planet: there isn't enough land or enough energy.
Sure, if we could overnight make all cars and trucks into battery EVs, replace all fossil fuel power plants with solar PV arrays (and wind farms too, since those are basically driven by solar energy too, though indirectly), and come up with some kind of storage technology to handle nighttime, high latitudes, clouds, still air, etc., then the energy aspect wouldn't be such a big deal. (Even better if we can make battery-EV airplanes.) But we're not there yet, and it's not likely we'll be there for quite a while unfortunately.
And even if we did accomplish that, that still doesn't solve the space problem. There just isn't enough room for everyone to have a big suburban house in a nice place with mild weather, and drive a personal vehicle everywhere. But if we tore down our car-based cities and rebuilt some just like Tokyo with that kind of density (and honestly, it really isn't as dense even as Manhattan; there's a lot more tall skyscrapers in NYC), then we actually could, while simultaneously having far, far fewer car-related deaths, and also having a much healthier population.
Any rate of active fossil fuel burning above the tiniest of baselines is going to be a net CO2 contributor.
But perhaps more importantly: why would fewer people, with the same amount of resources to share, not simply use more of them? Most efficiency improvements have been driven by rising prices due to rising demand, not awareness of climate change.
EDIT: Worth noting, this is also materially different to the extraction of fossil fuels for other purposes - like plastic.
Earth overshoot day is already in August [0] which basically means we are consuming it 1.75 times more bio resources than the carrying capacity of the Earth.
[0] https://www.overshootday.org/newsroom/past-earth-overshoot-d...
This argument has been made for hundreds of years, and for hundreds of years it's failed to pan out. Perhaps this time is different though.
"The power of population is indefinitely greater than the power in the earth to produce subsistence for man." - Thomas Malthus (1798)
~10% of Earth’s land is occupied by humans. Not all of that is arable, but humans have successfully terraformed throughout history and conceivably will become more capable with technological advances.
Malthus is not unique in his prognostications. Ehrlich’s The Population Bomb (1968) was more recent and predicted mass famine by the 1970s. Instead, we produce a massive surplus of food each year, although it’s not distributed adequately at present. This happened well after the Haber process (presumably the fossil fuel dividend you refer to) and occurred as a result of improved farming techniques, equipment, and crops.
Thanks to technological developments in the fossil fuels sector (fracking, horizontal drilling, etc.), fears about running out of oil have largely subsided. Simultaneously, advances in renewable energy sources are rapidly reducing our reliance on fossil fuels. Already, some electric grids are struggling with capacity — not because of a shortage of energy, rather due to an excess of electricity produced by renewable sources.
Although none of this points to an Earth beyond its carrying capacity, it also does not factor in further efficiency gains resulting from future technological progress. At the same time, we are attempting to develop the technology necessary to access extraterrestrial resources. Given that, even the finite resources available on Earth are not necessarily a limiting factor to growth.
Of total land area circa 10% is developed, 10% arable and a shade over 25% permanent pasture for livestock[1], and a few other minor agricultural uses. Of the rest we have forests, permafrost, deserts, mountains, marsh, scrub and other marginal land. The best crop and pasture land is long gone. What's left with potential appear to be the places we need to not lose - rainforests and such. God help everyone if we are able or need to start farming former permafrost.
Changing farming through mechanisation, artificial fertiliser and de-population of agriculture has been a steady march since WW2 (mostly). All leveraged on fossil fuel, and mostly a one-time dividend.
Past capacity as the rest close the development gap (you can't just miss that out), based on all resource use, and associated pollution - environmental overshoot - not mere calories. Not just a baseless assertion as we are assessed to be 70% beyond the ecosystem's capacity to absorb[2] right now. We've been beyond it for years. We're on borrowed time even without more development. Overshoot day[3] has gained a fair bit of publicity in recent years, but there's plenty of different measures all pointing to the same trends and issues.
With that level of accelerating overshoot, the planet can barely cope - the list of global scale and population related issues is huge. Yet coming en masse as a "surprise" is mostly to be expected given the growth curve. So there seems precious little headroom left, even if we do miraculously work to achieve zero carbon by 2050. Not expecting us to get anywhere near it any more though. Pretending population is just fine, or "growth is vital" as TFA claims is, whilst the globe does almost naff all to become sustainable is, frankly, nuts.
[1] https://en.wikipedia.org/wiki/Agricultural_land
[2] https://en.wikipedia.org/wiki/Carrying_capacity#Ecological_f...
The planet and its resources has a finite carrying capacity. Given we have most of the world in need of developing to reach the levels we enjoy, I suspect we are far past that capacity already -- though I am unlikely to live to see the consequences of that. We've used the world's most fertile land already. We've had the fossil fuel fertiliser dividend. Do we continue to grow and pretend growth is normal and necessary until we absolutely need another agriculture miracle? Or do we try and construct a future where everyone has a chance of abundance?
Even claiming innovation is partly a function of population size is far too simplistic - we've had periods where small countries were punching orders of magnitude above their population weight. There'll be little innovation if the food supply breaks.