With atmospheric CO2 concentrations reaching the 400 ppm level, the media and a number of alarmist scientists have set off the mega-alarm bells, claiming “record high levels” of CO2 had been reached, and that the planet is on the verge of an overdose. This is based purely on ignorance of the Earth’s history.
Worrying that 400 ppm is too high is like worrying about your fuel tank overflowing when it reaches the 1/8 mark during filling.
From a historical perspective, an atmospheric CO2 concentration of 400 ppm is actually almost scraping the bottom of the barrel. Over the Earth’s history, atmospheric CO2 concentrations have ranged from 180 ppm to 7000 ppm, see Figure 1 below. On that scale we are in fact today barely above the Earth’s record lows.
Figure 1: Atmospheric CO2 concentration is just barely above the life-sustaining levels of 150 ppm. For life to have real buffer against mass extinction, CO2 needs to be closer to 1000 ppm. Source here.
That 400 ppm is actually dangerously low is a fact the alarmists keep avoiding and suppressing. Below 150 ppm, plant-life dies off on a massive scale. The Earth actually came very close to that point many times over the last 2 million years during the ice ages. At the bottom of the last ice age just 20,000 years ago, life on the planet literally teetered on the brink when CO2 fell to a level of just 180 ppm. Do we really want to live on the brink of extinction.
It’s a fact that biologists have shown that once the atmospheric CO2 level falls below the 500 ppm level, plants really begin to suffer. Many of us have seen the video showing how plants grow faster under higher CO2 concentrations. The following charts show the growth curves of some plants as a function of CO2 concentration:
Figure 2: Plant growth vs CO2 concentration. Plants really begin to suffer once CO2 concentrations fall below 500 ppm. Source: click here.
Note that at high CO2 concentrations, such as 800 ppm, plants thrive. But as CO2 levels fall off, growth rates really start to plummet once they fall below 500 ppm. History shows that the Earth sustains much more life, i.e. is much greener and fruitful, when CO2 levels are higher, i.e. in the vicinity of 1000 ppm.
No one disputes that man’s activities have helped to increase atmospheric CO2 concentration, and it should not be in dispute that plants and life on the planet are thankful that man has done so. At 400 ppm, the planet is a safer place to be and will be even safer at 1000 ppm.
Also see here: http://www.bishop-hill.net/blog/2013/5/17/happer-on-cnbc.html