Recently, one of my acquaintances, in a discussion about climate change, put forward the argument that more carbon dioxide (CO2) in the atmosphere might be a good thing, because it encouraged plant growth and hence should result in more food being available. I didn't have a ready answer, so I asked Bing AI for help. The following is the (heavily edited and reference-checked) result.
Most educated people now accept that CO2 is a gas that makes the Earth warmer. This is because CO2 traps heat from the sun and keeps it from escaping back into space; a condition called the greenhouse effect. Humans have been adding CO2 to the air by burning coal, oil, and gas for energy since the beginning of the industrial age in the early 19th century. This was carbon dioxide that has been sequestered deep in the Earth over a period of hundreds of millions of years, gradually bringing the atmosphere to what it was like a couple of centuries ago. Since then, we have returned massive amounts of this CO2 back to the atmosphere all at once, geologically speaking, with the results we are beginning to see right now. This dumping of CO2 back into the atmosphere has caused the Earth's temperature to rise by about 1 degree Celsius since the 1800s. This doesn't sound like much, but it has a big impact on the weather, the oceans, the ice, and the living things on our planet.
However, CO2 is not only a gas that makes the Earth warmer. It's also a gas that plants need to grow. Plants use CO2, water, and sunlight to make their own food in a process called photosynthesis. When plants do photosynthesis, they also make oxygen that we breathe. So more CO2 in the air means more food for plants, right? And more food for plants means more food for us, right?
Well, not so fast. The answer is not that simple. Some scientists have done experiments to see how plants react to more CO2 in the air. They have found that some plants do grow faster and bigger with more CO2, but some plants do not. It depends on what kind of plant it is, and where it grows. For example, wheat, rice, and beans like more CO2, but corn and sugarcane do not. Also, some plants can get more nitrogen from the air than others, which helps them grow better with more CO2, but some plants cannot.
More CO2 in the air does not mean only more food for plants. It also means other changes in the environment that affect plant growth. For example, more CO2 in the air means higher air and ocean temperatures, which upset normal weather patterns. This results in abnormal droughts, flooding and winds in different places. In turn, this results in less, or excessive, water in the soil, changes to soil chemistry, more bugs or diseases that damage plants, and more pollution that harms plant cells. These changes can make plant growth worse or better. It depends on how much conditions change and how these changes interact with each other.
So what does this mean for our food supply? Some scientists have used computer modelling to try to predict how much food we will have in the future with more CO2 in the air. They have used different models that use different data and assumptions. They have also used different scenarios that imagine different human responses and behaviours as conditions change. Unsurprisingly, different results have been found depending on what model and scenario is used. Some models say we will have more food in some places, but less in others. Some say we will have less food everywhere while others say we will have enough food for everyone if we share it well (not a likely proposition if history is any indication).
So what can we do about it? The answer is not easy either. But one thing we can do is to reduce our CO2 emissions by minimising fossil fuel use and utilising more renewable energy sources like solar or wind power. This can help slow down global warming and climate change and give us more time to adapt to them. We can also protect and restore our land ecosystems like forests, grasslands, and wetlands that store carbon and help regulate the climate. This can help reduce CO2 in the air and provide other benefits like clean water and greater biodiversity. And we can improve our farming practices by using less water and fertiliser, and by adopting more regenerative methods. We may also need to change what we produce, and where, to adapt to changes to conditions and make more efficient and environment-friendly use of the land. This may in turn require us to change our diets to match what the Earth is still capable of producing.
My own opinion, supported by the evidence of recent exceptional droughts, floods, hurricanes and similar climatic events in a number of the world's food-producing areas is that more CO2 in the atmosphere will result in continued warming and further devastation of food crops, resulting in a significant decline in food production.
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