Correct. While CO2 can benefit plant (and weed) growth (of biomass),
CO2 definitely does benefit plant growth. It's a scientifically proven fact. 'No CO2' equates to 'no plant growth' which equates to 'no life'.
the resulting (global warming and extreme weather) climate effects will shift climate zones instead of only adding areas that produce more biomass.
Those of us who are not 'Climate Change Deniers' understand that climate is always changing for whatever reasons. That's the nature of climate. 10,000 to 6,000 years ago, the Sahara Desert was a rich grassland. It didn't become a desert as a result of rising CO2 levels.
Also, rising levels of CO2 have the greatest benefit in water-stressed conditions. In optimal conditions, with adequate water and soil nutrients, where a doubling of CO2 concentrations results in, say, a 40% increase in plant growth, that increase could rise to 65% in drier conditions, compared to the same plants grown in the same dry conditions but without the doubling of CO2.
Biomass alone also doesn't say much about the usefulness (e.g. as a food crop). In addition to CO2, plants also need the right amount of sunlight and water with nutrients. This is not a simple process of adding only one component, CO2. There are many climate zones that will become unsuited to produce food due to the rising temperatures (and lack of water).
Biomass alone says an awful lot about the usefulness of a food crop. No biomass equates to no food. You die.
However, it must be obvious to everyone (even Greta Thunberg), that plants do not grow on CO2 alone. Of course water, and sunlight, and soil nutrients are also essential.
The nutritional quality of the food we eat varies considerably, according to soil quality and modern farming practices which tend to gradually deplete the health and quality of the soil over time. That's another issue.
I think perhaps we need a new term for 'Climate Change Alarmist'. How about, 'Benefits of CO2 Denier'.
