Medley

Causes of Climate Change - part one

Michiel Haas – the Netherlands

  1. Earth has a changing climate 

Our Earth has always had a changing climate. Warming and cooling have taken place in varying wave movements and are controlled by, among other things, the angle of the earth's axis to the sun. These periodic long-term climate changes have been described by the Serbian mathematician Milutin Milankovitch (1879-1958). The last ice age, also known as the Weichselien, ended some 11,700 years ago. This was preceded by a long period in which it was considerably colder than it is now. No trees grew in the Netherlands, a cold polar wind blew, and the oceans were about 6 degrees colder than today. According to Milutin Milankovitch, the next ice age will take place in approximately 55,000 years. Other scientists are less certain about that. But after warming irrevocably comes cooling.

  1. Earth atmosphere or climate 

The Earth has an atmosphere around it, which is bound to the Earth by gravity. This atmosphere is of great importance for life on Earth. The atmosphere tempers the sunlight, maintains the Earth's energy balance and protects against harmful radiation, such as ultraviolet radiation. This atmosphere is like a blanket around the Earth and that is why we also speak of a kind of greenhouse. That is why the temperature on Earth is pleasant. Without the atmosphere, the temperature would be -18 degrees Celsius, with this atmosphere the average temperature is +15 degrees Celsius.

The atmosphere consists of a mixture of different gases. The volume ratios of these gases in the lower layers of the atmosphere, up to about 90 km altitude, are almost constant, except for the share of water vapor.

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The atmosphere is bound to the Earth by gravity and is part of the rotation of the Earth. Without an atmosphere, life on Earth would not be possible. Because of our unbridled burning of fossil fuels we are changing the atmosphere around the Earth with all the consequences that entails. (Photo: nasa-43566 on Unsplash)

  1. Greenhouse gases

The most important greenhouse gases are:

  • Carbon dioxide CO2 - colourless and odourless gas, non-toxic, is absorbed by plants; is released by burning fossil fuels, by composting and decaying and by melting permafrost;
  • Methane CH4 - colourless and odourless gas, flammable, occurs naturally in swamps and peat and is released by melting permafrost, by forest fires and decaying material: human influence strongly through livestock farming, agriculture, landfills and burning fossil fuels;
  • Nitrous oxide N2O - laughing gas, colourless and slightly sweet-smelling gas, is used in anaesthetics, to give engines more power, emissions via agriculture, manure and fertilizer, chemical industry, waste incineration, burning fossil fuels;
  • Water vapor H2O - strongest greenhouse effect due to the large quantity in the atmosphere; increasing water vapor in the atmosphere increases the greenhouse effect, but due to cloud formation less sunlight will be absorbed, causing cooling again;
  • Chlorofluorocarbon compounds CFC's -in aerosols and in coolants of e.g. refrigerators and air conditioners, is now prohibited because of ozone layer depletion;
  • Sulfur hexafluoride SF6 - is a colourless and odourless gas, the gas is five times denser than air, it is used in electrical engineering and medical engineering;
  • Ozone O3 - a colourless to light blue gas with an unpleasant pungent odor, ozone is naturally formed in the atmosphere under the influence of electrical discharges (such as during thunderstorms) and ultraviolet radiation; the warming effect is still unknown.

Not all greenhouse gases have the same effect. Therefore, the influence of the different greenhouse gases is expressed in CO2 equivalents. The table below shows that methane has a much greater effect on warming than CO2, 28 times stronger and laughing gas is much stronger.

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Different greenhouse gases and their influence in CO2 equivalents (author: mh)

  1. Carbon cycle 

We distinguish two carbon cycles, the short cycle and the long cycle. The short cycle is the natural process of photosynthesis in which\, under the influence of sunlight, carbon dioxide is converted by plants into carbohydrates as food for the plants. Algae also absorb CO2. When plants drop their leaves, the rot releases carbon dioxide and methane, both greenhouse gases. During harvesting, the remaining residues are left on the land for composting or are burned as biofuel and CO2 is released again. However, this is the short-term carbon cycle from a year at most to several decades. This cycle does not contribute to increased greenhouse gas emissions. That is why coal-fired power stations are supplemented by wood to make them less environmentally damaging. But that is a fallacy because there are many drawbacks of this co-firing:

  1. Biomass emits more CO2 than coal. If we want to reduce the CO2 content of the atmosphere quickly then we have to consider another source of energy.
  2. Burning is very fast, forests grow slowly. Combustion releases that carbon immediately and it takes several decades before a tree of the same size is grown back and absorbs the same amount of CO2.
  3. Forests absorb CO2, but not if you burn them. That is clear. The fear is that if a forest owner can earn money by chopping down his trees and selling as biomass, the amount of forest worldwide will (even) decline faster.
  4. Co-firing of biomass is bad for biodiversity. Proponents of the co-firing of biomass claim that it is waste wood. You cannot use it constructively. But insects and microorganisms feed on dead wood, which means that biodiversity within forests is to a large extent dependent on the so-called “waste wood.”

The circulation rate of CO2 in the atmosphere is high. In about six years, all carbon dioxide in the atmosphere is absorbed and stored by terrestrial plants and oceans, to be released later by rotting.

The long-term cycle does contribute to increased greenhouse gas emissions because it releases the carbon stored millions of years ago from fossil fuels (coal, oil, natural gas). The fossil fuels were originally all organic material, but that organic material has been stored underground for a long time and thus extracted from the short carbon cycle. Now, this is released again and adds to the atmosphere, outside the natural short carbon cycle.

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You can brush up your Dutch here, text on the image only available in that language, sorry! Carbon cycle. The black numbers show how many billions of tonnes of carbon (GtC) are present in different storage sites. The purple numbers show how much carbon is exchanged between the different storage sites per year. Note: Vegetation includes all organisms. (source: Wikipedia; author Rasbak) 

  1. Greenhouse effect 

The atmosphere as a greenhouse around the Earth is necessary to make life on Earth bearable. But how does it work? Solar energy reaches the Earth in the form of visible and invisible light. When this light reaches the Earth it is converted into heat energy. This heat radiation is also called infrared radiation. Gas molecules such as water, ozone and carbon dioxide temporarily absorb the heat radiation in order to radiate in all directions later on. Part of the solar energy remains trapped in the lower ten kilometres of the atmosphere. That is the greenhouse effect.

The presence of carbon dioxide is decisive for the greenhouse effect. Carbon dioxide is present in the atmosphere in relatively high concentrations and has a molecular structure that absorbs heat well and radiates it in all directions. The other greenhouse gases also contribute, and in particular methane; some of these gases have a much greater impact on the greenhouse effect, although they occur in much smaller quantities. CO2 and CH4, in particular, make an important contribution to maintaining the radiated solar heat. That is why we often speak of CO2 equivalents; we express the other greenhouse gases in CO2eq.

  1. Increase in the greenhouse effect 

In this way, the atmosphere around the Earth ensures a constant climate on Earth. But in recent decades the average temperature on Earth has already increased by 1.0 degrees Celsius compared to pre-industrial temperatures. This can vary regionally, in the Netherlands the temperature has even risen 1.7 degrees Celsius (1) The CO2 concentration in the atmosphere has risen sharply over the past 140 years, resulting in an increased greenhouse effect. This increased greenhouse effect is almost entirely caused by the extra carbon dioxide emissions from fossil fuels, cement and methane from livestock farming and by deforestation, i.e. by man. The IPCC (the UN climate panel in which thousands of scientists from all over the world participate) is clear: man is the main cause of global warming.

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This image shows the CO2 concentration in the atmosphere of Mauna Loa, Hawaii since 1958. The fluctuation is season-dependent, in spring and summer more CO2 is absorbed, in autumn and winter it is released again in the small carbon circle. The blue line is the trend line. (source: Wikipedia; author: Delorme)

Researchers Adrian E. Raftery et al. argue in an article in Nature Climate Change (2) of July 2017 that the probability that warming will remain limited to 2 degrees Celsius by the end of this century is less than 5%. The probability that we will be able to limit the average warming to 1.5 degrees by 2100 is only 1 percent. And that was the ultimate goal of the UN climate summit (COP21) in Paris in 2015. On the other hand, the chance that the Earth will have warmed up between 2 and 4.9 degrees Celsius by 2100 is as much as 90 percent.

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On this world map, the size of the dot shows how much CO2 is emitted by the various countries. (source: Global Carbon Atlas)

  1. Human contribution 

Although the human contribution to the total annual CO2 emissions are limited, only less than 4%, this 4% extra carbon dioxide is only absorbed for 40% by land and oceans, the rest remains in the atmosphere. As a result, the share of CO2 in the atmosphere has reached a dangerously high level of 404.47 ppm today (August 2017), which is the highest level for 15-20 million years (3). A normal change of 100 ppm CO2 in the atmosphere takes about 5-20,000 years. The latest increase of 100 ppm CO2 in the atmosphere lasted 140 years.

Global warming and thus climate change is a fact. A fact that is still accompanied by many uncertainties. It is not clear how much warming there will be and what the consequences will be for us on Earth. It is also unclear what people are going to do to combat this doom scenario. It is also unknown which technological developments will be hoping to be able to reduce this warming scenario. However, It is clear what people should do to minimize the risks. All these themes will be elaborated in the following articles.

  1. Self-reinforcing effect - permafrost 

Once global warming has begun and that is the presently case, there are processes that are constantly being reinforced by further warming. A clear example of this is melting permafrost. Permafrost areas are areas that are constantly frozen and never defrost, not for centuries. But when the polar ice melts, the sunlight is no longer reflected by the reflecting white ice, but rather absorbed by dark seawater.

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These holes in the landscape are actually thawed permafrost holes. This clearly shows that permafrost is thawing in more and more places, which has major consequences for the presence of greenhouse gases in the atmosphere. (Photo: shutterstock_99314225 - Nordroden) 

This causes an increase in temperature, causing permafrost in the environment to defrost. This is why warming in the polar regions is two to three times faster than in Europe. The scientists who study permafrost in Siberia and Canada estimate that in 2100 a quarter of all greenhouse gases in the atmosphere due to human activity will come from permafrost.

This is about the same as the total emissions of the United States today. And the warmer it gets, the more permafrost will melt. A publication in Nature Climate Change (4) in the spring of 2017 shows that permafrost is more sensitive to warming than previously thought, about 20 percent more sensitive. According to the study, almost 4 million square kilometres – an area larger than India – could be affected per degree of warming.

References:

(1) Klimaatkennis paraat in 10 vragen – KNMI - https://www.knmi.nl/kennis-en-datacentrum/achtergrond/klimaatkennis-paraat-in-10-vragen

(2) Less than 2 °C warming by 2100 unlikely - Adrian E. Raftery et al. http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3352.html?foxtrotcallback=true

(3) Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years; Aradhna K. Tripati et al. - http://science.sciencemag.org/content/326/5958/1394

(4) Increased climate change risk to permafrost - Sarah Chadburn et al. april 2017 - http://www.metoffice.gov.uk/news/releases/2017/climate-targets-to-constrain-permafrost-loss

 

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