No Planet B or How to get CO2-level back to the preindustrial level

We are faced with a big question, perhaps even the biggest question of all time for humanity:

How can we reduce today's CO2 level to pre-industrial levels of about 280 to 300 ppm. This level seems to be the level which is very comfortable for mankind - here we discuss from a citizen scientist's standpoint how to reduce CO2-content of the atmopshere and how to avoid further CO2 emission.
At first glance it seems that there are at least 4 ways where we can start:
  1. Reduce CO2 emissions by changing our partly luxurious lifestyle - this seems to be very difficult and it might last many decades.
  2. Plant trees. One of the questions there is where to plant and how to avoid self-ignition of the new trees by (e.g.) lightnings. This as well will last some decades.
  3. Expansion of nuclear energy based on nuclear power (fission) which is dangerous because of the unresolved disposal question. This is a bridging technology and should be stopped if there are enough renewable forms of energy. Anyway it avoids further CO2-emission when energy is generated.
  4. Nuclear energy due to fusion. This is a future dream of mankind to bring the real sun to Earth. Nobody knows when there will be a viable solution. It will at least take 50 years from now until a solution is in sight. And these 50 years will be moved forward in time almost every year. When available, it avoids further CO2-emission when energy is generated.
There may be other - mostly minor - ways or technologies to reduce CO2 emission or better the CO2-content of the atmosphere like carbon capture and storage (CCS). But these four above mentioned are the main issues here discussed. In particular CCS is not favoured very much due to possible problems when storing CO2 in possibly geologically not very stable ground.

In principle, we also have to ask the question of how we can reduce the world population. Because with increasing population also the emission of CO2 increases. This of course is a very ethical question and has no simple answer, if any. This is discussed within the context of increasing CO2 in parallel to the increasing world population ( It seems that the growth rate of the world population decreases so that we can reach a number which is more or less at a saturation point. Depending on the population growth model we here end up at 20 billion or 10 billion people or somewhere in between. The paper at is very interesting and has some nice issues which might surprise the reader. It will also be shown at which point of the earth the population numbers are rising the fastest. It is also interesting to see what the reason for this is, at what number the world population will stagnate.

CO2 has not only the warming effect, it also makes the oceans more acidic and thus kills part of biosphere. This goes along with the acid rain. Accordingly one should not hack the atmosphere (called abedo hacking) as Raymond T. Pierrehumbert says in this brilliantly written article ( oi/full/10.1080/00963402.2019.1654255). There is no planet B! And of course no Plan B, too!