Water is also essential for life, still you can drown. Yes, we had higher levels of CO2 in geological times of the earths past. The problem is, we are changing the CO2 content at a rate where ecological systems might not be able to cope with it. Also, even if the ecological systems do not collapse, just flooding of the inhabited costal regions would create enough human suffering to justify strong countermeasures against raising CO2.
interesting that you bring in human suffering. Have you thought about all the lives saved and brought into existence due to the burning of fossil fuels? I'm not much of a utilitarian, but gradual sea rise is nothing compared to the degree of poverty inflicted and number of people that would never be born if fossil fuel use were forcibly reduced. And no solar can't replace it, nor wind. The only contender is nuclear.
There is no doubt that modern civilization was only possible due to fossil fuels. But that says nothing about how long we should continue to use them. Actually its just in the last very few years that alternative energies are competitive. This is really a development which happened in the last 20 years. And solar and wind can replace fossil fuels. In 2015, 30% of the German electricity was produced by regenerative energies, up about 5% from 2014. So in the next few years, it will be the largest part of energy production. We don't have to go to 0% CO2 emissions, having 10-20% gas power plants for filling gaps is absolutely acceptable, as long as the rest is CO2-free.
