Climate Change FAQ
1. Is climate change the same as global warming?
Not exactly. Global warming is the increase in the average temperature of the earth’s atmosphere. Climate change refers to changes in the long-term weather conditions in a given place. The climate system is driven by the distribution of energy among air, water, and land. Changes in climate might include changes in the frequency and intensity of extreme weather, shifts in the timing of the seasons, and a rise in sea level resulting from global warming, but the word ‘warming’ can be misleading because it doesn’t encompass the whole range of climate changes that are expected.
2. What causes global warming?
Global warming is caused by ‘greenhouse gases,’ some of which occur naturally in our atmosphere, and some of which are man-made. What happens is that the sun warms the earth, and then the earth emits heat back out into space in the form of thermal, or infrared, radiation. The greenhouse gases act as a kind of blanket, absorbing radiation and blocking the heat from escaping into space, thereby warming the Earth. This “natural greenhouse effect” keeps the Earth about 30 degrees C warmer than it would be without any greenhouse gases, and so maintains temperatures warm enough for human existence. However, human activities have increased the concentration of greenhouse gases in our atmosphere by one-third above “natural” levels, which has led to increased global warming and has begun to destabilise the climate system.
3. What are greenhouse gases?
Some greenhouse gases occur naturally, such as water vapour, carbon dioxide, methane, nitrous oxide, and ozone. However, these gases are also produced by certain human activities. For example, carbon dioxide is produced from the burning of fossil fuels (oil, gas, and coal), wood, and wood products. Methane is emitted during the production and transport of coal, natural gas, and oil. Methane also results from the decomposition of organic waste in municipal solid waste landfills and the raising of livestock. Nitrous oxide is released during many agricultural and industrial activities and during combustion of solid waste and fossil fuels.
Man-made greenhouse gases are generated in many industrial processes. These include perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulphur hexafluoride (SF6). These gases are more “powerful” than many of the naturally occurring greenhouse gases, in that they last longer in the atmosphere and can trap more heat per molecule. For example, certain types of HFCs trap 9,000 to 10,000 times as much heat as carbon dioxide does. Greenhouse Gases and Global Warming Potential Values, EPA, April 2002
4. Do volcanoes contribute to global warming?
The short answer is ‘no.’ An erupting volcano throws huge clouds of particles and gases into the atmosphere. One of these gases, sulphur dioxide, is highly reflective, and will actually scatter and reflect the sun’s rays, thus decreasing the amount of energy reaching the Earth and causing short-term global cooling. However, not all volcanic eruptions, and not even all large eruptions, produce global-scale cooling. Whereas the eruption of Mt. Pinatubo in the Philippines in 1991 brought about global cooling of up to 0.3 degrees C lasting for up to two years, the eruption of El Chichon, in Mexico in 1982, had little effect. The difference might be in the location of the volcano, or in worlwide weather variations.
5. Don’t the snow and ice at the Earth’s poles also help cool the Earth by reflecting the sun’s rays?
Yes. Snow and ice, being white, have a high “albedo,” or degree of reflectivity. They reflect up to 90 percent of the sunlight they receive. Regions covered by snow and ice and having sub-zero temperatures year-round, including Antarctica, the Arctic Ocean, Greenland, northern Canada, northern Siberia, and most of the high mountain ranges in the world, make up what’s called the “cryosphere.” Without the cryosphere reflecting sunlight away from the Earth, the Earth’s atmosphere would be warmer. However, once global warming has begun and reflective snow cover begins to vanish, more sunlight will be absorbed, the atmosphere will become even warmer, more snow and ice will vanish, and so on in a self-perpetuating cycle.
6. And how does global warming cause climate change?
As the atmosphere warms, so do the oceans and the land. When sea water warms, it expands, and sea levels rise. The rising ocean and atmospheric temperatures also cause glaciers and ice sheets to melt. Land-based glaciers melt and run off into the sea, also contributing to sea level rise. That means a higher risk of flooding and coastal erosion. The warming of the oceans and atmosphere also means more evaporation of water into the atmosphere. Since water vapour is a greenhouse gas, it contributes to global warming. And more water in the atmosphere also means potentially more rain, hail, and snow.
Ocean currents transfer heat all around the globe, and play a major role in determining climate. Ocean water absorbs energy and warms more slowly than land. As it warms, its density and salinity can change (especially as runoff from glaciers adds fresh water to the oceans). These changes will cause variations in ocean currents, which will have profound impacts on climate.
7. Some people say climate change doesn’t really exist. Is the earth actually getting warmer? Is there actual evidence of climate change?
In fact, climate change sceptics represent only a tiny minority of opinion, and most of them are not scientists. Scientists working with the Intergovernmental Panel on Climate Change (IPCC), considered the world’s definitive authority on the subject, studied changes in the Earth’s atmosphere, climate, and biophysical system during the twentieth century. They found the following changes:
• Global temperature increased by about about 0.6 degrees C.
• In the Northern Hemisphere, the temperature increase during the twentieth century was greater than during any other century in the last millennium, with the 1990s being the warmest decade of the millennium.
• The number of hot days increased while the number of cold and frosty days decreased.
• The amount of precipitation and the number of heavy precipitation events increased in some areas while the frequency and intensity of droughts increased in others.
• El Niño events were more frequent, persistent, and intense in the past 20 to 30 years compared to the previous 100 years.
• Sea levels increased by 1 to 2 millimetres per year.
• Arctic sea ice became thinner and non-polar glaciers retreated.
• In the Northern Hemisphere, bird arrival, plant flowering, the animal breeding season, and the arrival of insects all occurred earlier in the year.
• The growing season in the Northern Hemisphere increased by up to 4 days per decade during the last 40 years, particularly at higher latitudes.
• The occurrence of plants, insects, birds, and fish shifted further toward the poles and upward in elevation.
These changes correspond with significant increases in the atmospheric concentrations of greenhouse gases. The IPCC found strong evidence that most of the warming observed in the past 50 years can be attributed to human activities.
While the sceptics may be in the minority, they are quite influential, often having the backing of energy, airline, manufacturing, and construction industries. Still, even the largest oil companies recognize that the burning of fossil fuels produces greenhouse gases that cause global warming. In May 2005, the executives of 13 of the largest companies in the UK, including Shell, HSBC, and BP, wrote a letter to Prime Minister Tony Blair calling for investment in new technologies to reduce carbon emissions and offering to work in partnership with government to take action against climate change.
8. What exactly is El Niño?
South American fishermen first used the term, which means “Christ Child,” to describe a warm ocean current that appears around Christmas every few years off the pacific coast of South America. The warming of the central and Eastern Pacific has been associated with changes in weather patterns, including torrential rainfall and flooding in South America, the Caribbean, and U.S. Gulf states; drought conditions in Australia, South Asia, and Southern Africa; and hurricanes in Hawaii and Tahiti.
El Niños occur at irregular intervals every two to seven years, and last between one and two years. More recently, they have occurred seven times since the mid-1980s. The period from 1990-1994 saw an unusually rapid succession of El Niños. The 1986-7 and 1997-8 El Niños were the strongest on record, resulting in loss of life, destruction of infrastructure, depletion of food and water reserves, displacement of communities, and outbreaks of disease on a larger scale than previously seen with El Niño.
Scientists do not all agree on the causes of El Niño, but they have become better at predicting and detecting El Niño conditions in recent years. It is not clear whether the increased frequency and intensity of El Niño is a result of global warming, but climate change models predict stronger El Niño events in the next 100 years.
9. What have been the patterns of climate change throughout the Earth’s history? Did greenhouse gases cause the Earth to warm up after the last ice age?
Scientists using ice cores to measure temperatures and levels of carbon dioxide found evidence of a series of major temperature fluctuations (including ice ages) during the past 400,000 years. These fluctuations have been accompanied by changes in atmospheric levels of carbon dioxide. Scientists think that the largest temperature fluctuations have been triggered by Milankovitch cycles, or variations in the Earth’s orbit that affect the amount of sunlight that reaches us. But these cycles alone are not enough to explain the temperature changes. It seems that the changes caused by variations in the Earth’s orbit were amplified by natural processes on Earth that caused a release of carbon dioxide, enhancing the greenhouse effect.
About 20,000 years ago, the Earth saw the end of an ice age. The temperature began to warm, probably because of changes in the Earth’s orbit, and about 11,000 years ago humans began building societies, cultivating food, and domesticating animals, sustained by relatively stable temperatures.
10. How do we know that the increases in greenhouse gases and changes in climate are because of human activity?
Certain greenhouse gases, like PFCs and HFCs, are produced only by human activities, and so their presence in the atmosphere can only be explained by human activity. But scientists are also able to quantify the sources of greenhouse gases, even naturally occurring ones like carbon dioxide, and measure their atmospheric concentrations. IPCC scientists have found strong evidence that most of the warming observed during the past 50 years is the result of human activities that produce greenhouse gases, such as the burning of fossil fuels.
11. Tony Blair called climate change “a challenge so far-reaching in its impact and irreversible in its destructive power, that it alters radically human existence.” Is this an exaggeration?
No. The potential consequences of climate change for human, economic, and ecological systems are so far-reaching as to be impossible to summarize briefly, but the serious impacts predicted by the IPCC can be seen in a number of areas:
In parts of the world with higher temperatures, more heat waves, and drought conditions:
• Decreased availability and quality of water
• Reduced crop yields
• Increased risk of death from heat stress and serious illness (particularly among urban poor and elderly populations) due to heat, humidity, and air pollution
• Increased heat stress on wildlife and livestock
• Increased risk of forest fires
• Increased risk of population displacement and social/political instability due to insecure water and food supplies
In parts of the world with increased precipitation, flooding, and sea level rise:
• Increased risk of flooding, landslides, mudslides, and avalanches
• More people exposed to malaria and water-borne diseases like cholera, and possible displacement of populations to refugee camps with inadequate sanitation, water, and food supplies
• Damage to infrastructure and property
• Soil erosion
• Contamination of fresh groundwater with seawater
Coastal zones and marine ecosystems:
• Reduced availability of fish because of changes in water temperature and quality, with detrimental effects for fish-dependent populations of people and animals
• Shore erosion due to flooding and sea level rise
12. Are there any beneficial effects of climate change?
Yes. The IPCC’s projections on climate change also show potential increases in crop yields in some regions, improved water supplies in global regions where water is currently scarce, fewer cold-related deaths, and reduced energy demand for space heating. However, it is unclear how far these changes will go to offset the detrimental effects of climate change.
13. Will climate change affect the whole world? What areas will be the worst affected?
It is impossible to say for certain exactly how any given area will be affected, and we cannot accurately predict the timing or probability of catastrophic events like major floods, storms, or fires. However, scientists do believe that the frequency and magnitude of extreme events will increase where temperatures increase.
Poorer developing countries will be especially vulnerable to the hazards of climate change, because a larger share of their economies is devoted to climate-sensitive sectors like agriculture, and because they lack the institutional and technological capabilities which would help them adapt to changes. Population pressures and poverty in many developing countries have also led to people living in especially hazardous places, such as on steep slopes or at the bottoms of valleys. Small island states and low-elevation coastal areas may be at the greatest risk because, while they are particularly vulnerable to sea level increases and storms, many are also less developed and therefore limited in their capability for adaptation. The Pacific island state of Tuvalu is in danger of disappearing due to sea level rise, and has already sought help from the international community to evacuate its people.
14. What kinds of change can we expect in the UK? Have there already been any changes?
The UK Climate Impacts Programme (UKCIP), which was set up by the government to assess the effects of climate change in the UK, has published a report detailing the extent of change already observed in the UK, and presenting four alternative scenarios of how climate change might affect the UK during the next 100 years, depending on levels of greenhouse gas emissions.
The report notes that the temperature of central England rose by almost 1 degree C in the twentieth century, and that the 1990s was the warmest decade in that region since records began in the 1660s. In addition, the growing season for plants in central England has lengthened by about one month since 1900. Heatwaves have become more frequent in summer, while winters have become wetter relative to summers and have fewer cold spells and frosts. Average sea level around the UK is about 10 centimetres higher than it was a hundred years ago.
UKCIP’s four scenarios for climate change in the next century do vary, but there are several key findings supported by all or most of them:
• The UK will become warmer, possibly by 2 to 3.5 degrees C, with greater warming in the south and east than in the north and west. Parts of the southeast may see warming of up to 5 degrees C by the 2080s.
• Higher summer temperatures will become more frequent as very cold winters become increasingly rare.
• Winters will become wetter and summers will become drier in all parts of the UK. Summer precipitation may decline by 50 percent or more by the 2080s, and winter precipitation may increase by up to 30 percent.
• Snowfall will decrease throughout the UK, with average snowfall over Scotland reduced by up to 90 percent by the 2080s.
• Episodes of heavy winter precipitation will become more frequent.
• Relative sea level around the UK will continue to rise, depending on the scenario and on the natural movement of land. Scotland’s sea level could rise by 58cm, while sea level in the south east may rise by between 26 and 86cm by the 2080s.
• Extreme sea levels will occur more frequently, possibly 10 or 20 times more frequently in the east. UKCIP Briefing Paper: Climate Change Scenarios for the UK
Many of these projections refer to average changes in conditions. But there may be considerable variation around those averages, including extreme hot or cold periods.
The above predictions are not absolute certainties; indeed no model can predict future climate with absolute certainty, given all the variable factors that influence it. However, the model used by UKCIP, which comes from the Hadley Centre, has been shown to perform well in representing current climate.
The UK Health Department has studied the potential effects of climate change on health, and determined that significant changes would likely include 2,000 more heat-related deaths per year; a significant increase in major disasters caused by severe winter gales and coastal flooding; 10,000 more cases of warm-weather related food poisoning per year and 5,000 more cases per year of skin cancer. Health Effects of Climate Change in the UK
15. But what about the Gulf Stream? I’ve heard that it might switch off, making the UK’s climate colder.
The Gulf Stream, a current of water that keeps northwest Europe warmer than it would otherwise be, could be affected by changes in density or salinity of water resulting from climate change. However, no current climate change models predict a shutdown of the Gulf Stream. Most models, including that used by UKCIP, show a weakening of it during the next century, but the UK climate is not expected to become cooler because of this. However, if global greenhouse gas emissions continue to increase unchecked, the possibility of much greater climate change in the more distant future does increase—including severe impacts on the Gulf Stream.
16. How reliable are these predictions about future climate?
Scientists base their climate predictions on their knowledge of past climate variations, on their understanding of the current climate system, and on computer models that can predict future climate based on a variety of factors. Many different models exist, and some are more successful than others at simulating different aspects of the climate system. Scientists can estimate the reliability of models by comparing their projections with present real climate, with reconstructions of past climate, and with other models’ projections. Several current models are good at simulating past (decades to centuries) climate changes, but most have performed poorly at modeling short-term (days to years) and regional climate. The difficulty of producing an accurate climate model lies in the vast amount of data required to reproduce all the various components of the climate system, from ocean currents to atmospheric concentrations of greenhouse gases. Many components of the system, like precipitation in unpopulated areas, aren’t well known, and some, like future greenhouse gas emissions, have to be assumed. Still, climate models are becoming more reliable all the time. New projections based on the most advanced models will be produced by the IPCC in 2007.
17. Is it too late to prevent climate change?
Because of the inherent delay in the climate system (many effects of greenhouse gas accumulations in the atmosphere are not felt immediately), the full effects of climate change will be slow to materialize, and some effects will likely be irreversible, like major melting of ice sheets and changes in ocean circulation patterns. According to the IPCC, even if greenhouse gas concentrations were stabilised, ice sheets and sea level would continue to respond to warming for many centuries. However, the IPCC also says that stabilising atmospheric concentrations of greenhouse gases by reducing emissions would “delay and reduce damages caused by climate change.” And importantly, slowing the process of global warming and climate change will give us more time to adapt to the changes. The IPCC emphasises adaptation as a necessary strategy to complement efforts to mitigate climate change.
18. I’ve read that the U.S. is the biggest single producer of greenhouse gases, and it didn’t sign up to the Kyoto protocol. If they’re not doing anything about climate change, what can the rest of us do?
It is true that the U.S. federal government did not ratify the Kyoto protocol. But that doesn’t mean that individual states and local governments aren’t taking action. For instance, on June 13, 2005, the mayors of 164 U.S. cities, led by Seattle and including Los Angeles, Boston, San Francisco, New York, and Miami, adopted the U.S. Mayors Climate Protection Agreement, which matches Kyoto’s goal of reducing greenhouse gas emissions by 7 percent below 1990 levels by 2012. Individual states are adopting climate-friendly policies, like emissions reduction targets, in growing numbers. In addition, there have been recent court actions in which state and city governments have filed lawsuits against federal government agencies and polluting corporations, claiming that pollution and global warming cause significant harm.
While the United States is the largest single polluter, it accounts for 25 percent of the world’s greenhouse gas emissions. There is still much to be done about the other 75 percent.
19. What can I do to prevent climate change? Can a single person make any difference?
Individuals can indeed take steps to combat climate change. Simple yet effective measures include walking, cycling, or using public transportation rather than driving; purchasing environment-friendly products, vehicles, and home appliances; recycling or minimising waste; and buying local foods that haven’t been transported long distances. We can also promote these practices in our communities, schools, and workplaces. And we can get involved in organisations dedicated to protecting our environment. Individually, everyone is a small part of the problem. Certainly, we can make individual contributions to the solution.
