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Tuesday 25 October 2016

There is no Planet B and Ireland is not immune to climate change

Dr Conor Sweeney

Published 06/12/2015 | 02:30

‘Different parts of the Earth will see different changes in temperature’
‘Different parts of the Earth will see different changes in temperature’

Our weather is going to change, in some ways quite dramatically, in the decades ahead.

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If you thought that negotiators from 195 countries hammering out a deal to cut emissions had little enough to do with dear old Ireland - blessed with a temperate climate, cool summers, relatively warm winters and all the rain we need - then think again.

The stakes are high. World leaders are meeting to create a binding climate agreement. The aim is to keep global warming below two degrees celsius. If an agreement is not reached, the future climate will change in ways we have never experienced before - more heatwaves, droughts, extreme rain, stronger storms. The climate is a powerful force that we need to respect.

Climate change is not a new phenomenon. In fact, the climate of the Earth has always been changing. But since the industrial revolution, a new and destructive factor has been influencing the ways in which climate is changing.

That factor is Man.

Thirty years ago, the leaders of the world faced a crisis in the Earth's system. Scientists had discovered that chemicals called CFCs (Chlorofluorocarbons) -chemicals then used in fridges - were drifting high up into the atmosphere and causing a reaction that reduced ozone levels. Without the ozone to protect us, harmful UV rays from the sun were reaching dangerous levels on the surface of the Earth.

In the face of this threat to our planet, world leaders found common purpose and moved quickly to ban CFCs. As a direct consequence of this action, the ozone layer is now recovering. Humans, it seems, can fix the Earth as well as damage it.

Now, in the 21st Century, the threat to our climate comes not from CFCs but from greenhouse gases. These are gases in the atmosphere that allow energy from the sun to reach the surface of the Earth, but then trap some of the energy of the Earth from radiating back out to space.

Greenhouse gases are not all bad. Indeed, life would be difficult without them. It is because of greenhouse gases that the temperature on Earth generally stays in a range that we can live with. Without them, we would be faced with daytime temperatures of over 100 degrees, while at night the temperature would plummet to under -200 degrees.

We wouldn't last long in that climate.

The problem we face is that we are releasing extra greenhouse gases into the atmosphere and they are causing the global climate to change in ways it hasn't before. This time - unlike CFCs - it won't be so easy to ban or replace them as greenhouse gases are released when we use fossil fuels to generate electricity, heat our homes and drive our cars. They are even linked with the food that we eat.

If we continue to release greenhouse gases at the current rate, scientists estimate that the world will breach the two degrees of warming barrier within the next 50 years.

How do we know this?

In climate science centres around the world, like the one that I work in, we take huge quantities of climate data and use highly complex computer programmes to model how the climate is likely to change.

But wouldn't a bit of warming give us better summers and ease those cold winters? Not necessarily. Two degrees is the average figure - it's not the whole picture. Different parts of the earth will experience different changes in temperature.

In Ireland, our climate is strongly influenced by a current in the Atlantic Ocean, which brings warm water from Florida to the west of Ireland. This ocean current buffers us from the stronger changes in temperature that will be felt elsewhere.

Having said that, Ireland will still get warmer by around 1.8 degrees overall, with areas in the east warming more than in the west.

The real area of concern for us will be the extremes in temperature - very hot and very cold days. These extreme events have a more dramatic impact on our lives. When our climate gets warmer, extremes can change by more than the average. We will have less cold nights, less frosty days, and our number of cold spells will halve. These changes will generally be welcomed.

However, changes will also happen at the other extreme. Our hottest days will be up to four degrees hotter, meaning that we could expect to experience temperatures in the 30s, and this will have an impact on the health of our nation.

Three-quarters of weather-related deaths in first-world countries are due to extreme temperatures, mainly heatwaves: 72,000 people died in the heatwave in Europe in 2003. In a world that is two degrees warmer, Ireland can expect heatwaves to occur more frequently.

This isn't just bad for our health, it's bad for our agriculture, energy and ecosystems. Heat stress reduces crop yields, increases energy demand for cooling and can cause fish to move into deeper, colder waters.

The future won't always be warmer. Strange though it may seem, a warmer climate can cause cold weather extremes too. When the edge of the polar jet stream - a mass of cold air blowing around the North Pole - dips down over Ireland in winter, we experience bitterly cold weather. Climate change means the arctic region will become warmer in the future and this may cause the polar jet stream to move south on a more frequent basis.

Global warming also involves changes in rainfall levels and patterns. In Ireland, we usually get around 1,000mm of rain each year, although the mountains in the west get twice as much as this. Dublin actually has one of the lowest rainfall amounts in Ireland, at around 850mm per year.

In a two-degree-hotter future, Ireland will get slightly less rainfall each year. This doesn't mean that all rain showers will be lighter. Instead, there will be changes to the pattern of our rain. Summers will get drier and winters wetter.

Given that summers are going to get drier, it's not surprising to learn that we're going to have more droughts in the future too. Droughts are bad for agriculture, which will need to make greater use of irrigation. It will also impact our water reservoirs, which will need to be managed more efficiently to avoid restrictions. This further stresses a water system that is already in urgent need of upgrading.

What about when it rains? It becomes more worrying when we look at the extremes. Wet days (over 20mm rainfall) and very wet days (over 30mm rainfall) will occur more often in our future winter months. An increase in heavy rainfall events will have serious effects. In 2011, heavy rainfall in Dublin caused widespread damage and two fatalities, while in Cork in 2009, a flooding event caused tens of millions of euro in damage.

Flooding is not only caused by heavy rainfall. The string of storms in winter 2013-14 caused serious coastal damage and flooding in Ireland.

Strong winds coupled with high sea levels are the culprits here. Scientists agree that sea levels will continue to rise in the future and some research also points to an increase in intense storms in the future. Whichever way you look at it, flooding events seem set to increase.

These changes to the Irish climate are based on the presumption that the Earth's warming will be limited to two degrees. However, as things stand, we are likely to exceed that limit. To ensure that global warming stays within two degrees, we need the leaders of the world's nations to agree upon many challenging, and perhaps unpalatable, actions.

We need to act now to avoid problems that await us decades in the future.

Dr Conor Sweeney is a lecturer at UCD. He tweets @ConorSy

Sunday Independent

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