CO₂ in five minutes

A fact sheet telling you the basics of CO2 in just five minutes are given below. You can also download this fact sheet as a pdf file

What is CO₂?

CO₂ is the chemical formula for carbon dioxide, a natural part of the air we breathe. Close to 0.04 percent of the air is CO₂, and at room temperature CO₂ is a gas with no color and no odor.

CO₂ is very important biologically, because it takes part in the photosynthesis and in respiration, which are essential processes for living species. The photosynthesis is a biochemical reaction that takes place in green plants when sunlight is used to transform CO₂ and water to glucose, oxygen and energy. The opposite reaction takes place during respiration of living species; oxygen and glucose is then transformed back to CO₂ and water.

Environmental impacts of CO₂ Emissions

Increasing CO₂ emissions is mainly a result of combustion of fossil fuels like coal, oil and gas for energy production. There has been a large increase in global anthropogenic (human made) CO₂ emissions since the industrial revolution 250 years ago.

Figure 1. Global CO2 emissions.

The atmospheric CO₂ concentration has increased by one third since the industrial revolution, and today 0.038 percent of the atmosphere is CO₂. Further increase in atmospheric CO2 concentration is expected, according to the International Panel on Climate Control, IPCC. How large the increase will be is strongly dependent on which strategies that are implemented to reduce the CO₂ emissions. Scenarios for future atmospheric CO2 concentration are shown in Figure 2 together with expected increase in global temperature.

Figure 2. Scenarios for atmospheric CO2 concentration and global temperature increase. The different lines represent different models.

The Greenhouse Effect
When the radiation from the sun hits the earth, some of the radiation is reflected by the surface of the earth as infrared radiation. Some of this infrared radiation leaves the atmosphere, but some of it is reflected back to the earth, and this is the greenhouse effect.

The greenhouse effect is a natural process where some gases in the atmosphere reflect the infrared radiation back to the earth. Without this natural greenhouse effect, the global average temperature would have been -19 oC, and not +15 oC as it is today.

Figure 3. The greenhouse effect.

Water vapor is the most important gas leading to greenhouse effect, and because atmospheric water vapor concentration is hardly effected by human activity, this is referred to as natural greenhouse effect.

Gasses leading to greenhouse effect are called greenhouse gasses (GHG). If the atmospheric concentration of GHGs increases due to human activity the result will be man-made greenhouse effect. The most important GHGs leading to man-made greenhouse effect are (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF₆). The most important GHG leading to anthropogenic global warming is CO₂.

According to IPCC, there is no doubt that increasing anthropogenic CO₂ emissions are leading to global warming. The consequences of too high global warming will be melting of glaciers, leading to reduced water and food resources. The sea level will rise, and there will be more extreme weather, more draughts, and more floods. As a consequence more than 200 million humans can become climate refugees. Ecosystems will be disrupted, and 15 to 40 percent of all species can be extinct.

Acidification of the Oceans
CO₂ can be dissolved in the oceans, and increasing atmospheric CO₂ concentration will increase the amount of dissolved CO₂. The result will be acidification of the oceans, which can lead to serious consequences for species living under water.

Strategies to cut emission

A global warming of more than 2 ^oC increase in global average temperature will lead to serious consequences, and the IPCC have therefore suggested that global GHG emissions should be reduced by 50 to 85 percent by 2050. This is a tremendous challenge, especially when energy demand and fossil fuel consumption increases rapidly in developing countries like China and India. Even if we are able to keep the increase in average global temperature below +2 ^oC, there will be dramatic climate changes, especially in artic areas.

Man-made CO₂ emissions are to a large extent a result of burning fossil fuels. The most important energy sources globally are fossil fuels like coal, oil and natural gas, and when these energy sources are burned to provide heat or power, large volumes of CO₂ are released into the atmosphere.

A successful strategy to reduce man-made CO₂ emission sufficiently demands that Governments establish economic incentives and regulatory framework to strengthen research and development of new low emission technologies.

Sufficient reduction of global CO₂ emissions requires a combination of several strategies;

• The energy consumption must be reduced through enhanced energy efficiency
• The production of renewable energy must be increased
• Forest management must be improved to ensure that forests are not cut down
• CO₂ Capture and storage (CCS) must be deployed globally

Another alternative for reducing CO₂ emissions is to switch from fossil fuel energy production to nuclear energy. However, this is considered as a bad strategy due to the potential hazards related to nuclear energy production and nuclear waste. Another argument is that the potential for CO₂ emission reduction due to increased nuclear energy production is relatively small.

CO₂ Capture and Storage
A promising technology for reducing global CO₂ emissions is Carbon dioxide Capture and Storage (CCS), which has a large potential for reducing global CO₂ emissions the next decades. CCS includes three steps:

• CO₂ capture where CO₂ is removed from the flue gas from fossil fuelled power plants, refineries and large industrial factories for production of steel, ammonia, and cement.
• Transportation of CO₂ in pipelines or by ship to a storage site
• Safe underground storage of CO₂ in suitable underground geological structures.

Before CO₂ storage can be deployed on a global scale, methods and standards for CO₂ storage must be established to ensure safe storage without leakages.