When talking about the greenhouse effect in a climate context, it really means an enhanced greenhouse effect. There is a natural greenhouse effect in the atmosphere that makes the climate so comfortable that plants, animals and we humans can survive here on earth.
Without the natural greenhouse effect, it would have been 35 degrees colder at the soil surface than it is today.
The problems caused by a changing climate are due to the fact that human emissions of different gases contribute to the enhanced greenhouse effect. The so-called greenhouse gases pass through the sun’s short-wave radiation but absorb parts of the earth’s heat radiation. Elevated levels of these gases, therefore, lead to a higher climate at the soil surface.
Water vapor and carbon dioxide, which are the most common greenhouse gases, are naturally found in the earth’s atmosphere.
Other greenhouse gases are:
- Nitrous oxide
- Sulfur hexafluoride
- Flour compounds (hydrocarbons and hydrocarbons)
The increased levels of greenhouse gases are mainly due to carbon dioxide emissions caused by the combustion of fossil fuels such as oil, coal and natural gas. Deforestation also contributes to higher levels of carbon dioxide in the atmosphere.
Carbon dioxide – contributes most to the enhanced greenhouse effect
Carbon dioxide is the greenhouse gas that contributes most to the enhanced greenhouse effect. Often the carbon dioxide content in the atmosphere can be a measure of how much greenhouse gases we can allow ourselves to emit in the future. Prior to industrialization, the carbon dioxide content in the atmosphere was about 280 ppmv (parts per million = million parts by volume).
Since then, the content has increased steadily. In 2000 it was approximately 370 ppmv. Today, we discuss which emissions lead to various large temperature increases in the future. If we do not want a major global temperature increase of more than 2º C, the carbon dioxide content in the atmosphere must be stabilized at 450 ppmv by 2100.
Global carbon dioxide emissions are largely caused by the combustion of fossil fuels, but also changing land use, especially deforestation also contributes to increased atmospheric content. The carbon dioxide is very persistent in the atmosphere and affects the climate for a very long time. In Sweden, carbon dioxide accounts for about 80 percent of greenhouse gas emissions.
Methane – from the bags, among other things
Methane is formed naturally when biological material Grazing kiss breaks down bacterially under oxygen-free conditions. In the world, the largest emissions are from rice cultivation, emissions from coal mines and natural gas, waste incineration and waste management and livestock management. Methane is formed, for example, when the cows melt the food and are released via cow’s rapes. The lifetime of methane in the atmosphere is relatively short, about 10-15 years.
Nitrous oxide (N2O) is a gas that is emitted primarily for “denitrification”. It is a process that occurs naturally in the soil of microorganisms, but which increases with the spread of fertilizers consisting of nitrogen or during combustion. About one-third of all nitrous oxide emissions are estimated to be caused by us humans. The residence time of the nitrous oxide in the atmosphere is about 150 years.
The group of fluorine compounds, unlike the other greenhouse gases, does not occur naturally in the atmosphere but is produced in an industrial way. Many of the fluorine compounds are very persistent and powerful greenhouse gases. They are comparatively powerful because they absorb radiation in a part of the infrared spectrum that was previously completely permeable. Calculated per molecule, some of them are tens of thousands of times more efficient than carbon dioxide.
There are three common groups of fluorine compounds, also called f-gases. These are:
- HFCs similar to chlorofluorocarbons CFC
- Sulfur hexafluoride (SF6) used in the electronic industry
- Perfluorocarbons, PFC, which are emitted during aluminum manufacture and also used in the electronics industry.
Emissions of these substances into the atmosphere are very small and their contribution to the greenhouse effect is therefore relatively small. However, global emissions are increasing relatively sharply, which is serious due to their strong effect and long residence time in the atmosphere. They have a lifetime of several thousand years.
O3, is a gas consisting of 3-atomic molecules of oxygen. The gas is toxic and is a health hazard when it occurs at ground level, but high up in the atmosphere fulfills the vital function of shielding from harmful solar radiation, Ozone can also act as a greenhouse gas, although we usually associate it with the problems of harmful ground-level ozone and thinning of the ozone layer. Ozone is the most short-lived greenhouse gas, with a residence time of a few weeks to a month. Since ozone levels are mainly increasing over North America and Europe, ozone in these areas is causing regional climate effects.
Aviation is a special climate impediment as it releases nitrogen oxides into the upper troposphere, where these emissions cause extensive ozone formation. It is expected that this ozone formation contributes more to the greenhouse effect than carbon dioxide emissions. Emissions from the aircraft also give rise to increased cloud formation and thus increased heating at the Earth’s surface as the clouds increase the heat-retaining capacity of the atmosphere.
Emissions in different sectors
Carbon dioxide emissions come from the burning of fossil fuels in different sectors of society. Fossil fuels are mainly used for heating and as fuel in vehicles. Emissions of other greenhouse gases such as methane and nitrous oxide largely come from agriculture and from waste.
Particles also affect
The greenhouse effect is also affected by particles in the atmosphere. Sulfate and carbon particles are the most common. The sulfate particles are derived from sulfur dioxide emissions. The particles reflect incoming sunlight, which reduces the amount of solar energy reaching the Earth’s surface. They also act as condensation cores for water vapor in the atmosphere, which affect cloud formation and precipitation. The carbon particles also absorb heat. Unlike the greenhouse gases, the residence time of the particles is very short, just a few weeks.
Carbon dioxide equivalents to compare
Today, the greenhouse effect is mainly affected by carbon dioxide emissions. It accounts for about 70 percent of the effect, while methane accounts for about 20 percent. Nitric oxide and fluorinated gases account for about 5 percent each. In order to be able to assess the effect of the different gases on the climate, for example, they take into account their relative emission volumes, ability to absorb heat radiation at different wavelengths and residence time in the atmosphere.
One usually expects a kind of carbon dioxide unit called carbon dioxide equivalents to be able to compare different greenhouse gases with each other. The magnitude is called the English GWP, Global Warming Potential and measures how much carbon dioxide would be required to achieve the same effect on the Earth’s radiation balance.