Utterly ridiculous on so many levels. Carbon dioxide is not going to miraculously double the size of plants. It's like saying oxygen will double the size of animals.
Even if the premise was true, doubling the size of plants is not going to solve the climate crisis. Carbon dioxide is being built up into the atomosphere from emmissions, trapping sunlight, much the same way the glass does on a car. That heats up the planet, and shrinks the ice caps, which are responsible for reflecting the sun's rays, which only accelerates the warming. Then carbon dioxide trapped in the oceans gets released, making the problem even worse. The result is that the problem escalates quickly and exponentially until there is no turning back, and nothing can be done. The Earth's temperature rises to a point where species die out, ecosystems collapse, water levels rise, bacteria flourish in the ocean, and more extreme weather causes extensive damage and deaths. This, in turn, leads to global instablity, and the increased likelihood of war, famine, etc....
Scientists unanimously agree. Every major scientific organization does. The problem is those who stand to lose the most money, oil companies, big corporations don't give a shit. They only care about making money, and don't want the government to make drastic changes which will make them lose money. They therefore buy politicans and spread information such as that on the site you listed to create confusion, doubt, and skeptism.
