Climate Alarmism

Effects of CO2 on the bioshere

Current CO2 levels in context

Over earths geological timescale since multicellular CO2 levels have varied far greater than anything during our lifetime. During Cambrian Explosion 540 million years ago, the begin of multicellular life CO2 levels were at around 4500ppm. Modern vascular plants emerged 400 million years ago at a CO2 level of 2000ppm. The vast forests consequently converted the abundant CO2 into oxygen and carbon plant matter, which we now know as coal. The approximate CO2 and temperature shifts that followed can be seen in the graph below. Geologically our current 15°C average surface temperature is still an ice age, just a short warm period within an ice age. Over the time period of millions of years plate tectonics and therefore shifting weather patterns affect the temperature significantly. So not every jump in temperature is related to CO2.

A serious question to ask climate alarmists is which fundamental physics have changed in a way where 1200-2000ppm is perfectly fine for life during the dinosaurs, but 400ppm is disastrously high for our time.

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CO2 role in plant growth

Research into plant growth has shown CO2 levels to be a major limiting factor in the production of biomass. At recent ice age CO2 levels of under 200ppm biomass production is down to a quarter of current growth. Pre-industrial levels of 280ppm give only 80% of current growth rates. When modern agriculture eliminated nutrient and water deficits, plant growth today is limited by CO2 levels or a too low temperature during winter. Even in remote areas without human activity satellites measured a greening, likely due to increased CO2 in the atmosphere. Operators of greenhouses found a CO2 level of 1000-1200 ppm to give the highest growth potential of plants if they have sufficient water, light and nutrients.

At the current rate of CO2 increase of 2ppm per year it would take another 300 years until earth reaches this optimal level for plant growth. This is longer than most countries have existed, and humans will have completely different lifestyles. Our current lifestyle is in no way relevant to our grand, grand, grand,... children and how they choose to live. Possibly they won't even live on earth and just see it as a great holiday destination. Over 2000ppm the toxicity of CO2 eliminates the growth potential and plants will only grow like our current 400ppm rates. But it will be difficult to even reach 1000ppm. Economical oil reserves are estimated to last only 50-100 years. Coal reserves last a few hundred years, but coal is only good for electricity generation and heating. If we invent a nuclear fusion reactor or a new type of nuclear fission power plant that's cheaper than a coal power plant then coal production will cease pretty quickly. As we increase CO2, the increased plant growth will also counter our CO2 emission and prevent any further rise.

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CO2 effect on humans

In closed rooms with bad ventilation CO2 can easily reach 1000pm. Humans who suddenly enter an atmosphere with over 1000ppm might experience a reduced mental performance, drowsiness, dizziness or headache. The US set an occupational limit of 5000ppm for an 8-hour period. The symptoms get worse with increased levels until at 70,000ppm there is a risk to become unconscious.

images sources:
https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2010.03441.x
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-10655/HLA-6723web.pdf