What is climate change ?

The scientific community and governments across the world are in agreement - the climate is changing

But what is climate change ? what is causing it ? and how will it affect us ?

The climate can be described as the average weather over a period of time.  Climate change means a significant change in the measures of climate, such as temperature, rainfall, or wind, lasting for an extended period – decades or longer. The Earth's climate has changed many times during the planet's history, with events ranging from ice ages to long periods of warmth.  What’s different about this period of the earth’s history is that human activities are significantly contributing to natural climate change through our emissions of greenhouse gases. This interference is resulting in increased air and ocean temperatures, drought, melting ice and snow, rising sea levels, increased rainfall, flooding and other influences.

So what causes climate change ?

Climate change can result from natural processes and factors and more recently due to human activities through our emissions of greenhouse gases. Examples of natural factors include;

  • Changes in the sun's intensity
  • Volcanic eruptions, or slow changes in the Earth's orbit around the sun
  • Natural processes within the climate system such as changes in ocean current circulation

However, the current global aim is to tackle climate change resulting from human activities whose greenhouse gas emissions are changing the composition of the earth’s atmosphere. The Intergovernmental Panel on Climate Change (IPCC) state that ;

‘Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (produced by humans) greenhouse gas emissions’
Examples of human activities contributing to climate change include;

  • Carbon dioxide emissions through burning fossil fuels such as coal, oil and gas and peat
  • Methane and nitrous oxide emissions from agriculture
  •  Emissions through land use changes such as deforestation, reforestation, urbanization, desertification,

These emissions that are changing the composition of the earths atmosphere are termed the Greenhouse effect. For the past 200 years, the burning of fossil fuels, such as coal and oil, and deforestation have caused the concentrations of heat-trapping greenhouse gases to increase significantly in our atmosphere. These gases prevent heat from escaping to space, somewhat like the glass panels of a greenhouse. The figure below from the IPCC explains greenhouse gases.

This figures dsiplays the greenhouse gas effect whereby radiation from the sun is trapped in the earth's atmosphere by greenhouse gases.
Figure 1: The greenhouse gas effect (Source IPCC 2007)

The increased emissions to the atmosphere of greenhouse gases mean that current levels of gases far exceed their natural ranges. The figure below shows the levels of certain greenhouse gases in the atmosphere over the last 2000 years.

This figure show greenhouse gas concentrations (Co2, Mthane, Nitrous oxide) relatively stable at approximately 250 to 275 parts per million from year 0 AD to approximately mid 1700s whereby the concentration steadily increases to approximately 380 ppm in 2005.
Figure 2: Atmospheric Greenhouse Gas Level (Source: IPCC, 2007)

This rise in greenhouse gases has increased the amount of energy being trapped in the climate system.  The consequences of this are most clearly evident in the global temperature records, which show that, on average, the global temperature has increased by 0.8 degrees centigrade (ºC) above pre-industrial levels.  Continued emissions at or above current levels would cause further warming and result in changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.

What are Irelands Greenhouse gas emissions?

What Impacts will climate change have for Ireland ?

Addressing climate change