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Climate change and the enhanced greenhouse effect

Climate change on Earth is not a new phenomenon; there have been many ice ages and warm periods. Based on our understanding of this natural variation, we might expect to be entering a cooler period. However, this is not the case. This is attributed to the enhanced greenhouse effect.

What is the Greenhouse Effect?

As the name implies, the atmosphere around the Earth acts rather like the glass in a greenhouse, ensuring energy balance and conservation. The purpose of a greenhouse is to create favourable conditions that allow delicate plants to grow and this is what the atmosphere does for us.

  • The Sun produces light across a wide spectrum including short wavelengths.
  • The atmosphere is not equally transparent to all wavelengths.
  • Visible light reaches the surface of the earth and much of it is absorbed by the soil and vegetation. The absorbed energy produces heating.
  • As a result the energy is emitted from soil and vegetation as thermal radiation i.e. long wavelength light
  • Most of the thermal radiation is absorbed by certain gases in the atmosphere. These gases are known as the Greenhouse gases, of which CO2 is the most important.
  • The total amount of energy within the atmosphere increases – leading to an increase in temperature.
  • An equilibrium temperature is reached when the loss of heat energy at the top of the atmosphere equals the incoming energy received from the Sun.

The greenhouse effect is essential to life on Earth. It is necessary to maintain a climate that permits water to exist in a liquid state. Without the greenhouse effect we would freeze. The average global temperature would be approximately 30˚C lower and would not be favourable to life as we know it.
The problem is the enhanced greenhouse effect; too much energy is being trapped, leading to climate change. If this were to continue it would cause major changes to our country and indeed our planet.

The majority of scientists believe that human activity is a significant contributor to an increase in climate variability. This includes the burning of fossil fuels, destruction of rain forests, exploitation of new croplands and overgrazing of grassland – causing extra CO2 to be released. As a result our climate is becoming warmer and more variable, with Ireland, for example, experiencing more severe storms.

Carbon dioxide is present naturally in the atmosphere. It is vital for the growth of plants. However human activities are generating additional CO2 in the atmosphere. The rate of CO2 increase has accelerated in the last few decades.

Factors affecting climate change

Besides the enhanced greenhouse effect there are many other factors that aggravate climate change. For example, the melting of the polar ice results in less of the sun’s energy being reflected back to space; this in turn raises the temperature and causes even more ice to melt. This is an example of positive feedback.

Another example of positive feedback can be seen in our oceans. The oceans act as a large reservoir for CO2 and determine the atmospheric concentration to a large extent. CO2 solubility decreases as the temperature rises.

What other gases contribute to the greenhouse effect?

Greenhouse gases are gases in the atmosphere that trap radiant energy. There are many of them but the most important are:

Water vapour is responsible for most of the greenhouse effect. However, the amount of water vapour in the atmosphere is in response to climate rather than the driver of climate change.



Methane is produced by many processes including digestion of cellulose  by bacteria in wetlands, in rice fields and in the intestines of ruminants and termites. Methane is often released during the extraction of crude oil. Nitrous oxide is a by-product of some industrial processes. It is also produced by bacterial action on nitrogen compounds in the soil; this effect is greatly increased by the use  of fertilisers whether natural or manufactured. Ireland has high emissions of methane and nitrous oxide per head of population compared to other developed countries.
Other greenhouse gases include ozone (O3), CFCs and HFCs. Ozone is formed in the upper atmosphere by the action of ultraviolet radiation on oxygen. 
Many of these gases are not easily removed from the atmosphere and therefore have long residence times. For example, CO2 can persist, and continues to influence climate, for hundreds of years.

Effects on sea level.

There are four major reservoirs of freshwater ice on Earth: Arctic ice which is sea based and Antarctic ice, the Greenland Ice shelf and Permafrost/Glaciers which are all land based. Melting Arctic sea ice makes little difference to sea level as this ice is floating. Melting land based ice however makes a big difference. Evidence suggests the land ice in the polar regions is melting and adding large volumes of fresh water to the ocean; this causes a rise in sea levels with consequent effects on the  environment. The IPCC – The Intergovernmental Panel on climate change – estimates a rise of between 18 and 59 cm in sea levels during this century, and that sea levels will continue to rise for hundreds of years due to the time scales required for the energy to reach the deep oceans.
Global Climate Models forecast an increase of 1.8 to 4.0˚C in global temperatures over the next century, compared to 0.6˚C in the last century. These models represent our most advanced estimates of future events.
In many cases, it is the rate of environmental change that is the real issue. Species are generally very resilient to slow changes and can adapt over time. However, climate change is happening at such a rapid rate that species may not have sufficient time to react and adapt.
Tree species are slow to adapt. They take time to re-establish themselves in areas with more suitable conditions. Some animal/bird species are more adaptable than others. For example, cod and other fish species have moved further north in search of cooler waters during the last twenty five years or so.
Marine species such as coral are even more sensitive to temperature changes. Corals grow very slowly, but are easily bleached by warmer water, excessive ultraviolet radiation, pollution or changes in salinity. If coral polyps and their associated plankton are killed by adverse conditions then the calcium carbonate structures that they build around themselves become pale in colour.

Our effect on global warming

How can we measure our effect on the Earth’s climate? One way is to calculate our Carbon Footprint – this is a measure of the amount of carbon dioxide we produce per year. In 2005, the average carbon footprint per Irish person was 16,850 kg, compared to that in the UK where it was around 11,000 kg per person. Secondly we can look at the Food miles/kilometres associated with our food. Strawberries and other foods produced in Ireland do not require nearly as much energy to get to our tables as those imported from abroad. Consumer demands for such products out of season greatly increases the energy used in transport.  The mode of transport is also a significant factor .

What can we do about it?

The answer is simple: we need to reduce our demand for fossil fuels; this requires major and difficult changes in our lifestyle. We also need to make more use of energy sources that are renewable such as wind, wave, hydroelectric, geothermal and biofuels which can supply some of our needs. We also need to conserve energy more efficiently by using lower energy products at home and in work or school. We all have to reduce our CO2 emissions in order to protect our planet.
The Environmental Protection Agency (EPA) is an independent public body established under the Environmental Protection Agency Act, 1992. The EPA regulates and polices activities that might otherwise cause pollution. It ensures there is solid information on environmental trends so that necessary actions are taken. The EPA’s priorities are protecting the Irish environment and ensuring that development is sustainable. It employs over 290 people who work in ten locations throughout the country.
The other main instruments from which it derives its mandate are the Waste Management Act, 1996, and the Protection of the Environment Act, 2003. The EPA has a wide range of functions to protect the environment. Its primary activities include:

  • Environmental licensing
  • Enforcement of environmental law
  • Environmental planning and guidance
  • Monitoring and reporting on environmental quality – air, water, waste, noise, land and soil
  • Environmental research

The EPA’s function is to protect and improve the natural environment for present and future generations, taking into account the environmental, social and economic principles of sustainable development.