Do we need to reach absolute zero emissions to stop climate change? Is there some level of unavoidable fossil fuel emissions, that can be accepted?

When I reseach this, I find that about 44% of todays fossil emissions get reabsorbed by nature. Even if this goes down a bit, shouldn't we be able to i.e. remain at 40% of today emissions and no longer make the situation worse? f core sthere are effects that are just starting to show and will continue for a long time. But will we have stopped the initial force of this process? I read a book that claimed that even reducing the emissions by 90% would not be enought. We thus would need to switch to some form of new economic system. I am trying to understand how much in a problem we really are. For chemical processen and aviation it might never become financially vialble to use hydrogen. Same goes for methane derivatives for shipping. Concrete is another almost unsolvable climate problem.