The super short version of the problem of global climate change is as follows:
- Carbon dioxide and other greenhouse gases in the atmosphere trap heat from the sun
- People are vastly increasing the amount of greenhouse gases in the atmosphere, which means we trap more heat, which means the temperature of the planet is rising
- A fast rising temperature causes massive problems for humanity and all other life on earth
- We need to stop putting extra greenhouse gases into the atmosphere if we want a livable and sustainable world
First, there is a natural carbon cycle on the planet. Carbon is a basic physical element, found in great quantities both on the surface and in the center of the earth, though it makes up only a small proportion of all of the matter of the earth. Most of this carbon is under the surface, bound up in rocks, in the earth's core, or in fossilized plants that have been buried by the action of water, wind, and time. Then there is the carbon found on or near the surface that cycles back and forth between the air, the water, the rocks and soil, and living things. All life that we know is built out of carbon molecules, and all living things spend much of their time and energy bringing carbon into their bodies. Plants draw it from the air while animals eat other living things made out of carbon. The earth's cycle of carbon is always in flux, plants are growing and dying, animal populations rise and fall, rocks and water absorb and release it. The main point to make about the cycle is that the amount of carbon actively moving around the surface, the waters, and the atmosphere, has stayed in equilibrium for millions of years. The equilibrium amount of carbon in the atmosphere, mostly as carbon dioxide, has stayed about 300 parts per million (a quite small proportion of the air) for millions of years up until about one hundred years ago.
The problem that we face today is that people have thrown off this balance, as human activities have drastically increased the amount of carbon going into the atmosphere, much more than the natural systems and cycles can absorb. The most notorious source has been the fossil fuels of coal, oil, and natural gas. These substances once were living organisms, and were trapped underground and transformed into concentrated carbon based energy. When we burn them, we release carbon back into the atmosphere that has been out of circulation for millions of years. Another huge contributor to carbon in the atmosphere is poor land use. For example, forests are cut down, poor agricultural practices destroy soil, cows produce lots of methane (another carbon based greenhouse gas), all of which lead to the carbon stored in these places being released to the atmosphere. Industrial processes can also add carbon to the atmosphere. One such process is the production of cement. Cement is made by heating rock (limestone) that is high in carbon, leading both to a useful product as well putting more carbon dioxide into the atmosphere. The sum of these activities cause the amount of carbon in the atmosphere to rise. Today in the fall of 2017, the amount of carbon dioxide in the atmosphere has risen by a third, to 405 ppm. Current human activities are causing a continued 1 ppm increase each and every year.
Now, the biggest reason that all of this extra carbon in the atmosphere is a problem is due to the greenhouse effect. The basic analogy of the greenhouse effect is that the glass walls of a greenhouse trap some of the energy from the sun, allowing the inside of a greenhouse to be warmer than the air outside. It turns out that the earth's atmosphere does the same thing. An enormous amount of energy from the sun hits the earth, with some staying and some bouncing back into space. Carbon dioxide and other greenhouse gases in the atmosphere do the same thing as the glass in the greenhouse walls, they trap heat inside. The more greenhouse gases in the atmosphere, the warmer the earth stays. This has mostly been a great thing for life on earth, as the greenhouse effect is the reason that we have such moderate temperatures today that life on earth is so well adapted to. As mentioned in the last paragraph, carbon dioxide in the atmosphere has risen by a third, and this has trapped more heat through the greenhouse effect. So far, this rise in atmospheric carbon has increased the earth's temperature by nearly one degree Celsius. If current trends of humanity's resource and land use continue, this could reach 5 or 6 degrees Celsius (10 degrees Fahrenheit) by the year 2100. Humanity now stands at a point where we are cooking ourselves out of house and home. It is impossible to predict all the effects of this warming, but we do know that it would be catastrophic. Sea levels would rise, weather extremes of flood, drought and wildfire would increase, some ecosystems would collapse and many species would go extinct, and there would be millions of climate refugees fleeing these effects.
Put all together this makes for a very simple goal in fighting climate change, though it will be difficult and complex to achieve: humanity needs to stop putting excess greenhouse gases into the atmosphere if we want to save ourselves and our planet.