It is only 5 % - why the human addition to carbon dioxide load matters?

The people denying that human influence has little or nothing to do with climate change invariably point out that the addition by humans represents only 5 % of the total production of carbon dioxide at any given moment. Surely, such a small increment cannot have an effect attributed to it.

Another group of people say that the climate change problem is only caused by rich industrialized nations, and has nothing to do with population growth in poor areas of the world. The richest 10 % of the world’s population cause 1/3 of all greenhouse gas emissions while poorest 50 % emit only 15 % of world’s total human-emitted carbon dioxide.

Both of these statements are drastically wrong, and below I try to indicate why. In both cases the ultimate reason is the disturbance of the carbon cycle. In undisturbed nature the carbon cycle is in equilibrium. The carbon dioxide produced in the respiration of all organisms is used up in the photosynthesis and oxygen is produced.

A 5 % increase in carbon dioxide production, because of fossil fuel use, generates a huge disequilibrium, which we now see as climate change. In undisturbed nature, the disequilibrium would slowly (in hundreds to thousands of years) be corrected by an increase of green vegetation to generate a new equilibrium. The 5 % disequilibrium is so huge than the return to equilibrium lasts a long time if it is possible at all. Tipping point can be caused by the disequilibrium such that the temperature increase is so large that a net increase in photosynthesis cannot be achieved. In such a case temperature increase just continues and as worst, Earth becomes similar to Venus.

A disturbance of the carbon cycle can also result from the increased use of land by humans. This is what is currently happening in poor areas, where population increases. The carbon dioxide uptake and oxygen production by green plants is currently decreasing, mainly because of deforestation (but also as agricultural land erodes or is turned to human settlements). This causes similar worsening of the climate change situation as the fossil fuel use of the industrialized nations.

We live in one world with limits, and we should all work for the wellbeing of the planet. We should stop blaming others, which is the easy thing to do, and instead aim at reducing inequality and excessive consumption.