I still remember the sensations–pounding heart, crushing headaches, confusion, and the deep dread when I put my hand on the door to the sick building I had to work in for nearly ten years. I’ve experienced high carbon dioxide levels. My body thought I was suffocating in my own exhale. This week, I find myself reliving those unpleasant times.

You see, I’m working on a sequel to Mixed In–Book Two in the Unstable States series. It’s set in the near future. When I saw this headline about record high levels of carbon dioxide, I thought, “Damn, I’m going to have to add increased carbon dioxide levels into this series.”

It’s true. There’s more carbon dioxide (CO2) in the atmosphere than ever before due to human activities such as burning fossil fuels for heating and cooling and travel and electricity, cutting down trees, pouring cement, and eating plenty of meat. This trend doesn’t look as if it’s changing anytime soon. And if, as a fiction writer, you create a future on earth, there are consequences for your characters.

It’s time to consider: what will humans on earth experience in a high carbon dioxide world?

Here’s my list:

1. Effects on food production. Plants use carbon dioxide to grow and give off oxygen. Some plants will grow bigger in a high carbon dioxide world. However, this may mean they are less nutritious. Not all plants will react the same way to more atmospheric carbon dioxide. How they take in carbon dioxide will determine if more carbon dioxide will make them giant, gangly, and less healthy. Some crops such as corn will not be affected by increased carbon dioxide while beans will have a growth enhancement.
2. Climate Impacts. This is the effect most people consider when they think of higher carbon dioxide levels. Carbon dioxide acts as a blanket and holds heat in. What will happen? Here is a detailed prediction based on each part of the globe. Coastal areas will be flooded. My series takes place in the Midwest. Displaced people might have to move here. I’m not sure Midwesterners will enjoy the crowds. Warmer temperatures could mean fewer blood clots in the elderly.
3. More rust. Yes, carbon dioxide plus water forms carbonic acid and this hastens corrosion.
4. More ocean acidity. All life depends on the proper pH balance to maintain itself. Carbon dioxide dissolves in water and when it does, it forms carbonic acid. This acid does bad things to ocean life such as dissolving shells and bleaching coral. Fish could have seizures or even lose their minds.
5. Mental challenges. Fish won’t be the only animals out of their minds. In humans,  increased anxiety and depression are associated with increased carbon dioxide in the atmosphere. Drowsiness and reduced reasoning ability also occur. This is why people should not take tests or make decisions in poorly ventilated rooms. Think about what life will be like if everywhere we go is poorly ventilated.
6. Other health implications. I worked in a building with high carbon dioxide levels due to poor ventilation and I can tell you, it’s  no fun. Skin flushing, chest pains, confusion, muscle twitches, and crushing headaches can occur if carbon dioxide levels go above 1000 ppm*. If carbon dioxide levels increase at the current rate, this will be the outside atmospheric concentration in about 300 years. Human blood pH will go down–become more acidic–just as the ocean pH decreases with too much carbon dioxide. An affected person will breathe fast and deep which sounds kind of sexy but at high levels, the person might start flapping their hands and resemble someone out of a Vonnegut novel. To get rid of the extra acid, our kidneys will need to work harder in a high carbon dioxide world. Urine will be flowing! (As a side note, slurping carbonated drinks causes the same effect and irritates your bladder and promotes urination.)
7. The heat can contribute to preterm births. 
8. Fewer mosquito bites If there is an upside, here it is. Mosquitos are attracted to the carbon dioxide in your exhaled breath. As background carbon dioxide levels rise, they have a harder time zeroing in on their prey.

Drowsy characters, panicking people,  humans flapping their hands and going to the bathroom all the time–what am I going to do with that premise? And yet, this could be the future. Can technology save us? Yes, probably, but only if we invest in it and that’s not going to happen if we live in denial of the consequences. And will everyone have the technology or only a few? I’m sure you can answer that question in your next novel. I know I’m going to have to.

*Carbon dioxide levels are usually expressed as ppm or parts-per-million. When I was a kid, the level was around 300 ppm. When I was in college it was 320 ppm or so. Today,  we have already shot past the 400 ppm level. It’s thought that once we get to 450 ppm, we will begin to see climate effects that will be difficult to reverse