The plant life on this planet did just fine with the 280 PPM they had since before the appearance of homo sapiens up to the beginning of the Industrial Revolution. The portion of the CO2 put there by humans is the difference between the 280 ppm pre-industrial value and the 420 ppm we have now. (420-280)/280 = 1.5, so we have made a 50% increase in the amount of CO2 in the Earth's atmosphere. Pretty impressive considering (off the top of my head) that probably 90% of that was put there in the last 50 years
FIRST, there remains no linkage or proof that CO2 levels have any effect upon global AVERAGE temperatures, now, or at any time in the past millions to billions of years. What we have is some recent coincidence, but only over the past couple-few hundred years. Following charts will illustrate this;
Charts taken from this search page results;
DuckDuckGo. Privacy, Simplified.
duckduckgo.com
NOTE; That for most of Earth's history there has been CO2 levels several times higher than present and often average global temperatures have not match the levels of CO2, hence no linkage of CO2 causing higher temperatures. However there is a better case for higher temps causing higher levels of CO2.
SECOND, if you were familiar with greenhouse agriculture methods , you would know that most operate at levels more around 800ppm to 1200ppm and with no detriment to the humans working in those greenhouses.
THIRD: If you were competent at math you'd know that at 280ppm, where most plants are just barely surviving, the ratio of CO2 to other elements of the atmosphere; nitrogen, oxygen, argon, etc.; is about 1 to 3,570. At 400ppm(+/-) that ratio is now 1 to 2,500. If you were competent at basic science, especially chemistry and physics, you'd know that one part(molecule) retaining a slight temperature increase can not pass that same amount of heat retention onto 2,499 other molecules.
BTW, by comparison, oxygen is at 210,000 ppm, but about four billion years ago it was near zero. It took nearly two billion years of activity by those first lifeforms,
Stromatolite
en.wikipedia.org
... transforming the carbon of CO2 into growth expansion and releasing O2(oxygen) into the atmosphere before the first of fauna(animal life) could appear. Along with other forms of flora - plant lifes. The rest is planetary/natural history.
FINALLY, science is not based upon consensus of opinion of "scientists", but on facts and data along with resulting hypothesis that can be replicated to prove the conclusions. If you know of valid lab tests that have shown one part of CO2 causing a temperature rise in the other 2,499 parts of the atmosphere, please present. Science can and does have proofs. Doubt it, ... try denying gravity by stepping off of a forty story rooftop.