FAQ - Climate change
FAQ - Climate change
Some frequently asked questions about climate change
1) What is the greenhouse effect and how does it influence global warming?
2) What is the evidence?
3) Are humans contributing to global warming ?
4) What are the predicted changes in the Irish climate ?
5) What can I do about global warming ?
6) How may future climate change effect Irish forests?
7) Why is it so difficult to predict climate change ?
1) What is the greenhouse effect and how does it influence global warming?
The greenhouse effect is natural phenomenon that maintains the Earths atmosphere at a temperature range suitable for life to flourish. The sun's radiant energy warms the Earth's surface and its atmosphere. As this energy is reflected back toward space as heat, a portion is absorbed by a balance of heat-trapping gases, such as carbon dioxide and methane, which creates an insulating layer.
Global warming describes the rise in the Earth's temperature resulting from an increase in these heat-trapping green house gasses in the atmosphere. The is now convincing evidence that human activities are contributing to global warming by adding large amounts of green house gasses (GHGs) to the atmosphere. Our fossil fuel use is the main source of these gases. Every time we drive a car, use electricity from coal-fired power plants, or heat our homes with oil or natural gas, we release carbon dioxide and other heat-trapping gases into the air. The second most important source of GHGs is deforestation, mainly in the tropics, and other land-use changes.
The present concentration of carbon dioxide (CO2) in the atmosphere is higher than in the past 420,000 years or maybe even in the past 20 million years .Since pre-industrial times, the atmospheric concentration of carbon dioxide has increased by 31 percent. Over the same period, atmospheric methane has risen by 151 percent, mostly from agricultural activities like growing rice and raising cattle.
As the concentration of these gases grows, more heat is trapped by the atmosphere and less escapes back into space. This increase in trapped heat changes the climate, causing altered climate patterns.
In 1988, the United Nations Environment Programme and the World Meteorological Organization set up the Intergovernmental Panel on Climate Change (IPCC) (create link) to examine the most current scientific information on global warming and climate change. More than 1,250 authors and 2,500 scientific experts reviewers from more than 130 countries contributed to the panel's most recent report, Climate Change 2007: The Fourth Assessment Report (the full report will be released in November 2007). The IPCC Fourth Assessment Report is the most comprehensive and up-to-date evaluation of global warming. As the new benchmark, it serves as the basis for international climate negotiations.
The IPCC concluded in its Third Assessment Report, "An increasing body of observations gives a collective picture of a warming world and other changes in the climate system." The kinds of changes already observed that create this consistent picture include the following:
Examples of observed climatic changes
- Increase in global average surface temperature of about 0.6 °C in the 20th century
- Decrease of snow cover and sea ice extent and the retreat of mountain glaciers in the latter half of the 20th century
- Rise in global average sea level and the increase in ocean water temperatures
- Likely increase in average precipitation over the middle and high latitudes of the Northern Hemisphere, and over tropical land areas
- Increase in the frequency of extreme precipitation events in some regions of the world
Examples of observed physical and ecological changes
- Thawing of permafrost
- Lengthening of the growing season in middle and high latitudes
- Poleward and encroachment of plant and animal ranges
- Earlier flowering of trees
- Earlier emergence of insects
- Earlier egg-laying in birds
3) Are humans contributing to global warming?
About 75% of human induced CO2 emissions are derived from fossil fuel burning with the remainder due to land-use change, particularly deforestation.
Scientists have found significant evidence that leads to this conclusion:
- The observed warming over the past 100 years is unlikely to be due to natural causes alone; it was unusual even in the context of the last 1,000 years.
- There are better techniques to detect climatic changes and attribute them to different causes.
- Simulations of the climate's response to natural causes (sun, volcanoes, etc.) over the latter half of the 20th century alone cannot explain the observed trends.
- Most simulation models that take into account greenhouse gas emissions and sulphate aerosols (which have a cooling effect) are consistent with observations over the last 50 years.
4) What are the predicted changes in the Irish climate?
Regional Climate Models (RCM) - high-resolution general circulation models - have been developed and validated under a climate consortium for Ireland (C4i, 2004). Create link Results from a complete climate simulation for 2021-2060, using a moderate emission scenario, shows that mean monthly surface temperatures may increase between 1.25 and 1.5 ºC. Simulations using high emission predictions suggest that temperatures may increase by as much as 6 ºC over the next century. The largest increase in temperature will occur in the south-east of the country during the months of June and July. The most significant decreases (10%) in precipitation will occur in June, where there is an increased likelihood of higher evapotranspiration rates and drought problems in the south-east. The winter months are expected to experience increased rainfall, particularly in the north-west. In the future scenario, the frequency of intense cyclones over the Northern Atlantic area in the vicinity of Ireland is likely to increase by 15 %, possibly related to a general rise in sea temperatures.
5) What can I do about global warming?
Every little step helps - act now before its too late
- increasing energy efficiency standards
- encouraging the use of renewable energy sources (such as wind, solar power, forest wood or biomass energy)
- eliminating subsidies that encourage the use of coal and oil by making them artificially cheap
- protecting and restoring forests, which serve as important storehouses of carbon
- driving less and driving more fuel-efficient and less-polluting cars
- using energy-efficient appliances
- insulating homes
- using less electricity in general
Specific things you can do include:
- Switch off lights, appliances and equipment when they're not needed.
- Install energy-efficient compact fluorescent lamps.
- Divert garden and food wastes from landfill to composting (either at home or through a Council scheme).
- Make your home more comfortable by insulating draught-sealing and shading windows in summer.
- Manage home heating and cooling by setting thermostats appropriately - a couple of degrees up in summer and a couple of degrees down in winter.
- Cut hot water usage by installing a water-efficient showerhead, taking shorter showers and using cold water clothes washing.
- Switch to low greenhouse impact transport options like bicycle or public transport - or use phone or email.
- Minimise waste of packaging and materials - refuse, reduce, re-use, recycle.
- Use solar power - dry your clothes on the clothes line outside, not in a dryer.
6) How may future climate change effect Irish forests?
The changes in Ireland's climate will have a significant influence on soil and microclimate conditions and this will in turn affect the productivity of managed forests. It is clear that the long rotation length of forests will not facilitate a large enough evolutionary response time for adaptation/acclimation to the rapid changes in local climate (Andrasko, 1990). Given the long-term nature of forestry, the selection of suitable provenances or genotypes and adaptable management practices under future climate change scenarios is essential for sustainable forestry in Ireland. Research programmes should, such as CLIMADAPT, have been initiated to investigate how climate change may affect the productive and ecological functions of Irish forests and identify species suited to the predicted climate change scenarios.
Dynamic empirical or knowledge based models of forest growth have been developed to predict how plant processes respond to changing climate and the likely effects of climate change on forest productivity have been reviewed elsewhere (Cannell et al. 1989; Norby et al. 1999; Broadmedow 2002; Purser et al. 2004).
Some major changes include:
- The CO2 fertilization effect - increases in C3 photosynthesis and hence growth rate in response to higher ambient concentrations of CO2. This has been observed in European forests, however, there are other explanations for this, such as increased N deposition and changing management practices.
- Extending the growing season, higher mineralization rates, altered bud break and later senescence due to higher temperatures would result in higher productivity
- Decreased occurrence of frost may potentially lead to the introduction of frost susceptible species, such as Nothofagus or Pinus radiata
- A warmer climate may also have detrimental effects on productivity, such as an increase in pest and disease damage or higher evaporative losses, which together with reduced rainfall in the summer months may lead to increased soil moisture deficits.
- Higher wind speeds and more frequent storms may make forests more vulnerable to wind damage.
- Interactions of combined climate change factors and pollutant levels are more uncertain. For, example the combined effect of increased ozone and CO2 may result in no change in forest productivity.
7) Why is it so difficult to predict climate change?
Firstly, our understanding of the natural phenomena involved is limited: human activities that produce greenhouse gases are known, but the natural processes that release, absorb, and store these gases are not yet fully understood. The way in which carbon is transferred from one natural reservoir to another (the carbon cycle) is very complex and we have a limited understanding of how this cycle reacts to human interference.
We are also faced with another great unknown: the future of human society. How will the global population evolve? How will the poorest countries, which currently emit very low levels of CO2, develop? How will emissions evolve in economies with fewer oil and coal reserves? What decisions will be made by politicians in the future to limit emissions? Will we perhaps be able, thanks to technologies as yet uninvented, to make use of energy sources that do not emit greenhouse gases? So many questions that are, of course, impossible to answer over the course of a century.