Causes & Effects

Causes

The big cause of climate change has been creeping up on the planet since the start of the Industrial Revolution, around 1750.

Our Planet

Climate change is a significant change in the average weather or climate that a region experiences. Climate change can be caused by natural factors such as variations in sunlight intensity. However, the term climate change is now generally used to refer to changes in our climate due to the build up of greenhouse gases (GHGs) in the atmosphere. This build up of GHGs is caused by excess emissions due to certain human activities, like burning fossil fuels for energy, transport and heating.

© Department of the Environment, Community and Local Government

Our Planet
© Department of the Environment, Community and Local Government

Our Planet

Climate change is a significant change in the average weather or climate that a region experiences. Climate change can be caused by natural factors such as variations in sunlight intensity. However, the term climate change is now generally used to refer to changes in our climate due to the build up of greenhouse gases (GHGs) in the atmosphere. This build up of GHGs is caused by excess emissions due to certain human activities, like burning fossil fuels for energy, transport and heating.

© Department of the Environment, Community and Local Government

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As manufacturing and transport used more and more fossil fuels – first coal, then oil and gas - millions of tonnes of their carbon content were released into the atmosphere as a gas, carbon dioxide (CO₂). This gas was naturally there already - indeed, its presence has helped all life on Earth. It lets sunlight through to hit the surface of the planet and particles in the air, creating the warmth that life needs. CO₂ also stops most of the warmth escaping into space again, which makes it (like some other vapours, such as methane and nitrous oxide) a ’greenhouse’ gas.

Earth has known dramatic swings of climate, some triggered at long intervals by variation in the planet’s orbit round the sun. Ireland's hillsides are strewn with rocks scattered in the passage of glaciers. But even in the 10,000 years since the last ice age, there have been periods of marked natural warming and cooling. Right now we are in an ‘interglacial’ – a mild period between ice ages. But in the last few centuries, the artificially-boosted ‘greenhouse’ has been trapping more and more heat, as carbon dioxide in the amosphere rose from 280 parts per million (ppm) before about 1750 to more than 400 ppm today.

Effects

The evidence for global warming has been gathered from many fields of science by the Intergovernmental Panel on Climate Change (IPCC). It has listed signs of warming to be found in natural systems all round the world.

Melting icebergs

There are many concerns about the melting of the Greenland Ice Sheet and the Antartic Ice Sheet. As global temperatures increase, so too does the rate that these ice sheets are melting. Sea levels have risen by about 2.8mm per year over the past decade, and recent studies indicate that water flow from these ice sheets contribute to about 0.5mm of this rise. Studies also indicate that the Antartic Ice Sheet may be losing mass, as water losses along the coastal areas of the ice sheet have begun to exceed the accumulated snowfall at the centre, where mass would usually be gained.

Melting icebergs

Melting icebergs

There are many concerns about the melting of the Greenland Ice Sheet and the Antartic Ice Sheet. As global temperatures increase, so too does the rate that these ice sheets are melting. Sea levels have risen by about 2.8mm per year over the past decade, and recent studies indicate that water flow from these ice sheets contribute to about 0.5mm of this rise. Studies also indicate that the Antartic Ice Sheet may be losing mass, as water losses along the coastal areas of the ice sheet have begun to exceed the accumulated snowfall at the centre, where mass would usually be gained.

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There are more and more lakes, and bigger ones, where glaciers have melted. Mountainsides thunder with avalanches of rocks, released by thawing ice. Along with the earlier dates in spring – of bud-burst, bird migration, first flowerings and so on – come changes in the range of plants and animals - they move northward, or up to higher, cooler land. In the ocean, there are shifts of plankton and fish, not always in ways that match predators to prey.

The IPCC has made predictions of how warming might develop in this century. If CO₂ emissions continue to rise unchecked, their level could double by the end of the century, producing a global average warming of 3°C to 4°C. That could have cataclysmic impacts on many human societies and natural ecosystems. Even in Ireland, the projection is for more than 2°C. in the next 40 years; perhaps 3°C by the century’s end. On any one day, an extra 2°C of warmth might seem little enough, but with averages come extremes. In the intricate machinery of climate, of living ecosystems and sea level, the demands on nature’s adaptation will often be hard to meet.