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

Tiistai 5.4.2022 klo 14:40 - Mikko Nikinmaa

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.

Kommentoi kirjoitusta. Avainsanat: climate change, deforestation, carbon cycle, population growth

Human actions cause climate change even when fossil fuel use is not involved

Tiistai 22.3.2022 klo 18:24 - Mikko Nikinmaa

Although there are still many people thinking that climate change is not occurring or at least man has nothing to do with it, there are many problems that man is causing which accelerate temperature increase, and which could be avoided by human action. The points below are such, and can be very important in driving many parts of the world uninhabitable because of either too high temperature or drought or both. So, even people who do not believe that fossil fuel burning causes temperature increase, should accept that the following affect climate and that humans could take actions to combat the changes.

1. Because of massive deforestation, Amazon rainforest appears to near tipping point, where the rainforest turns to savannah. Boulton et al write in recent Nature Climate Change (Nature Climate Change 12: 271-278; 2022) how the resilience of Amazon rainforest has decreased dramatically since the early 2000s. Other studies have also indicated that whereas we have always considered Amazonas to be a carbon sink, it has recently turned into a net emitter of carbon dioxide. The major reason for carbon dioxide emissions is the widespread forest burning.

If the rainforest starts turning to savannah, naturally the first thing that happens is that the plant and animal species living in rainforest die off, so the biodiversity decreases radically. But even if this doesn’t concern the people, who deforest Amazonas, the following should. The water cycle of South America depends on the rainforest. If Amazonas turns into savannah, because more agricultural land is wanted, the whole South America dries up, and many areas become unsuitable for agriculture (too dry). So, by trying to increase agricultural area, greedy people end up decreasing it.

And because of the loss of one big carbon dioxide sink, the temperature throughout the world increases even if fossil fuels had nothing to do with climate change.

2. Two events happening to the oceans are also causing increased carbon dioxide levels and consecutive temperature increase even without the input of fossil fuel burning, and both depend mainly on human action. First, almost a half of the photosynthetic carbon dioxide use is due to the photosynthesis of (mainly unicellular) algae. Because of the pollution, it is estimated that the oceanic photosynthesis has decreased by 10-15 %. This increased carbon dioxide load is one factor affecting global temperatures, and could be avoided by human action – proper water purification. Second, world’s oceans are overfished. The global carbon cycle depends a lot on fish accumulating carbon. When they die, the accumulated carbon sinks to the bottom of the oceans and stays there for thousands of years. As overfishing reduces fish populations, this removal of carbon from ocean surface is reduced, and the reduced removal is seen as an increase in global carbon dioxide level, leading to temperature increase.

Again this takes place without any change in fossil fuel use, but is entirely human-caused.

3. There are further a couple of vicious circles, which increasingly take place, if human actions fail to limit temperature increase. Temperature increase decreases the carbon dioxide solubility in water. Thus, if temperature increases, more carbon dioxide is given up from the ocean, leading to further temperature increase etc. There are huge natural gas (methane) stores below the permafrost. Methane is a very potent greenhouse gas. If temperature increases so that permafrost starts melting, the methane below is liberated, causes further temperature increase leading to further permafrost melting and methane liberation etc.

To prevent these vicious circles from happening, climate deeds are important even today with the brutal Russian attack to Ukraine. In the best case, it can actually speed up the change from fossil fuel-based to green energy production.

Kommentoi kirjoitusta. Avainsanat: carbon cycle, Amazonas, deforestation, overfishing, permafrost, methane

Tipping Points to Vicious Circles, When We Cannot Control Temperature Rise

Torstai 5.12.2019 klo 15:23 - Mikko Nikinmaa

In the Eocene period about 50 million years ago, the mean temperature of the Earth was about 14oC higher than presently, and there was practically no ice anywhere. Further, the temperature gradient between poles and the tropics was small. This is taken by “climate deniers” to mean that human actions have little to do with temperature increase; “temperature increases as a result of natural causes”. Further, “climate deniers” maintain that human-like creatures were able to exist in Eocene conditions. Undoubtedly true, but at that time the number of human-like creatures was maximally a few million, and not more than seven billion. Close to half of the present human population lives in an area, which would be under the sea in ice-free world.

So, as a conclusion, there has been a markedly higher temperature on the earth because of natural causes, and some human-like creatures have survived it. However, this does not mean that mankind does not affect climate today, there is ample evidence on the contrary. At the worst, human actions can serve as trigger, causing a small temperature increase, which leads to tipping points with resulting vicious circles causing marked increases in temperature without any human role. Originally it was thought that the temperature rise before tipping points were likely to occur would be more than 5oC, then it decreased to 3-4 oC and the latest suggestion is that the probability for the occurrence of tipping points increases markedly, if the temperature increases 1.5-2 oC. The temperature has already increased by 1 oC from the preindustrial average, and the present promised actions to combat climate change would limit the temperature increase to approximately 3 oC. This is clearly larger temperature increase than what would be required for an increased probability for the tipping points and consecutive vicious circles of temperature increase to occur. Because of this, we have the CLIMATE EMERGENCY. Human actions matter now, but if enough of the tipping points have been reached, temperature increases no matter what we do. Below I list a couple of the tipping points with vicious circle properties, which may have been reached already.

Melting of Arctic sea ice. Recent years have seen open water in large areas of the Arctic sea. Virtually all the reports about it have been positive. Politicians have, e.g., rejoiced over the possibility of commercial shipping from Europe to Asia via the northeastern route. However, with melting sea ice one easily forgets that the white ice reflects virtually all the heat back to the sky, whereas the dark water absorbs the heat. This leads to marked acceleration of temperature increase.

Thawing of permafrost. Virtually all climate models have started with the outset that the thawing is gradual, and any effects reach significant level only a couple of hundred years from now. However, it has proven that the permafrost ice is a significant structural component of close to 20 % of the land area. Where this is the case, thawing permafrost is seen as huge craters etc. Where they occur, release of carbon (and methane) is much larger than estimated in the models. The carbon release can be double to what has been estimated.

Forest fires. The importance of forests as carbon dioxide sinks has repeatedly been emphasized. Whenever a forest burns, all the carbon it has accumulated is returned to atmosphere. Because of the hot and dry weather, the area affected by forest fires has increased markedly during recent years. In addition to forest fires, deforestation to gain agricultural land, and disease and harmul insect outbreaks especially in boreal forest decrease their carbon dioxide sink properties.

Aquatic pollution. For most of us it is unknown that about half of the Earth’s photosynthesis, i.e. carbon dioxide removal, is carried out by (mainly microscopic) algae. During recent years, the algal photosynthesis has been reduced by 10-20 % globally as the pollution of oceans has decreased the photosynthesis by algae.

Nitrous oxide production. The nitrogen fertilization, which is on the increase, increases the conversion of the fertilizers to nitrous oxide. This gas is the third most important greenhouse gas after carbon dioxide and methane. The need for nitrogen-containing fertilizers is on the increase as the fertility of agricultural land is decreasing.

Two articles in Nature have aspects of what I have written above (Lenton et al. Nature 575: 592-595, 2019; Turetsky et al. Nature 569: 32-34, 2019).

Kommentoi kirjoitusta. Avainsanat: climate change, permafrost, deforestatio, aquatic pollution