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Explore the potential implications of climate change on major cities like London, as rising sea levels pose a threat of flooding. Understand the difference between weather and climate, the greenhouse effect, and the role of human activities in contributing to global warming.
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New Year 2150? Why might climate change mean that London and other major cities could become flooded in the future?
What is climate? Climate is not the same as weather. What is the difference? Weatheris the state of the atmosphere at a given time and place. It is measured in terms of factors such as temperature, rainfall, humidity and cloudiness. Climate is the average weather for a region over a long period of time, usually 30 years. One way to remember the difference is that “climate is what you expect, weather is what you get”. Weather can change several times a day; the climate normally takes a long time to change. What would happen if the climate changed quickly?
Is the climate always the same? Systematic recording of weather data has only occurred since the 19th century. These and other records have shown that the climate does naturally change over time. For example, paintings and diaries provide information about the ‘Little Ice Age’. This was a period of cooling from about 1300 to 1850. Many glaciers increased in size, crops were lost and major rivers, such as the Thames, regularly froze. Before the ‘Little Ice Age’, there was an unusually warm period known as the ‘Medieval Warm Period’, which lasted for about eight centuries.
What is climate change? Climate change is a natural phenomenon and normally takes place over several centuries. The term ‘climate change’ is being used now to refer to the current climate. This is because recent scientific records show that the global climate seems to be warming up more rapidly than usual. • The average global temperature has increased by 0.6°C in 140 years. • The ten hottest years for the last 100 years have occurred since 1990. • Scientists have predicted that the climate could increase by up to 6°C in the next 150 years. What could be causing this and should we be concerned?
How is the Earth warmed? Climate is affected by the conditions and components of the atmosphere. The Earth’s atmosphere acts like the glass in a greenhouse and is needed to keep the planet warm enough for life to exist. Sunlight passes through the Earth’s atmosphere and the Earth gives out infrared radiation. Certain gases trap some of this radiation in the atmosphere, which keeps the Earth warm. This is called the greenhouse effect. Having some greenhouse gases is a good thing. If it wasn’t for these gases, Earth would be too cold to live on! However, too much of a good thing can be bad.
How hot can the greenhouse effect get? The planet Venus is further from the Sun than Mercury but has an higher average temperature. Its surface can reach up to 482°C, which is hot enough to melt lead! Venus’ atmosphere is mostly made up of carbon dioxide, which traps so much of the solar radiation that the planet becomes extremely hot. The hostile climate conditions on Venus make it impossible for life to survive.
What is global warming? The term ‘global warming’ is often used in connection with climate change, but what does it mean? Global warming refers to the increase in the Earth’s temperature due to the greenhouse effect, which can cause changes in climate. However, the term ‘global warming is now being used to refer to the warmingpredictedto occur as a result of increased emissions of greenhouse gases and other human activities. This enhanced greenhouse effect may lead to significant climate change. Remember, global warming and climate change are not the same thing and should not be used interchangeably.
Why is carbon dioxide so important? Carbon dioxide is considered the most significant greenhouse gas. This is because carbon dioxide can remain in the environment over a long time, from 50 to 200 years. Any process producing carbon dioxide today could affect the climate for hundreds of years. Carbon is present in all living things and moves through the environment in a chain of reactions called the carbon cycle. Levels of carbon dioxidein the atmosphere have increased since the industrial revolution in the 19th century. How might human activities have contributed to this?
What happens when fossil fuels are burned? Fossil fuels are carbon-based materials that formed over millions of years from the remains of ancient plants and animals. Fossil fuels are burned to generate heat. This combustion reaction creates carbon dioxide and water as waste products. + + fossil fuels oxygen carbon dioxide water Greater use of fossil fuels is thought to be the main source of the increase in atmospheric carbon dioxide. Should the use of fossil fuels be limited? How would this affect our lifestyles?
What else affects greenhouse gas levels? Burning wood releases carbon dioxide into the atmosphere. Living trees also have a major impact on the atmosphere, as they produce oxygen and absorb the greenhouse gas carbon dioxide. Deforestation reduces the amount of photosynthesis taking place and so increases carbon dioxide levels. Rice farming and cattle farming produce the greenhouse gas methane. This gas is 7.5 times more effective as a greenhouse gas than carbon dioxide, but is currently in the atmosphere at much lower levels.
What is the evidence for climate change? Data collected by climate scientists can be used to answer two key questions: • Is the climate really changing rapidly? • Is human activity causing this climate change? These scientists are setting up an Automatic Weather Station on the Djankuat glacier, in the Caucasus Mountains in Russia. Monitoring glaciers has produced startling evidence about the rate at which some glaciers are melting.
How are carbon dioxide levels measured? Atmospheric carbon dioxide levels are measured around the world to detect global trends in this greenhouse gas. The standard measurement used is parts per million (ppm). In 2005, levels were around 370ppm. This means for every million parts of air, 370 parts were carbon dioxide. Research stations for monitoring atmospheric gases are usually sited in remote places. The Mauna Loa Observatory in Hawaii, is located at an altitude of 4,170 metres.
What are ice cores? Ice cores are long columns of ice that are drilled out of glaciers. Ice cores are studied to increase understanding of the history of climate as they provide data about the distant past. Air bubbles trapped in the ice are used to estimate carbon dioxide levelsthousands of years ago. This is called a proxy record. These are indirect climate measures of the climate that have not been recorded using instruments. Tree rings are another type of proxy record.
400 300 200 CO2 conc. (ppm) 100 0 400 300 200 100 0 years before present (thousands) 400 300 200 CO2 conc. (ppm) 100 0 1960 1980 2000 How different are carbon dioxide levels today? These graphs show how carbon dioxide concentrations have changed over time. Around 200 years ago, carbon dioxide levels were about 280ppm and are now about 380 ppm. According to records, this is about 27% more than at any time in the last 400,000 years. How might this affect the climate? year
0.6 0.4 0.2 difference from average temp. (°C) 0 -0.2 -0.4 -0.6 1861 1941 2001 year 400 300 200 CO2 conc. (ppm) 100 0 1960 1980 2000 year Are temperature and carbon dioxide related? The global average temperature has increased at the same time as the levels of carbon dioxide have risen. However, it is not correct to say that carbon dioxide levels have caused this temperature change, because there are other factors involved. How should the data be discussed?
How should I talk about the climate data? It is important to be very careful about the words used to discuss scientific data. Collected data shows that temperature and carbon dioxide levels in the atmosphere have increased at the same time. It might seem to make sense to say that the rise in carbon dioxide is causing the temperature rise but this is incorrect. • How do you know that it is not the temperature increase that is causing carbon dioxide levels to rise? • Can you say for certain that carbon dioxide is the only factor in the change of temperature? It is more correct to say that there appears to be a positive relationship between carbon dioxide levels and temperature.
How is climate change predicted? Scientists use experiments to explore how things works and test predictions. However, the climate is far too large and too complicated to be reproduced in a laboratory. Instead, computer models are used to represent the climate and explore the possible effects of human actions. Mathematical formulae are used to represent the separate parts of the climate system and how they interact. In models, the Earth is divided into grid squares. Using smaller squares increases the detail.
radiation from the Earth radiation from the Sun volcanoes atmosphere precipitation evaporation transpiration ice in the sea ice on land land seas and oceans rivers and lakes How is the climate modelled? There are many factors that can affect the climate. All these interactions need to be included in climate models.
Who first used maths for climate prediction? Climate modelling evolved from formulae used for weather prediction. These were created by Lewis Fry Richardson, an English mathematician. When his work was published in 1922, the predictions were not very accurate because the calculations took a long time. Richardson thought a hall full of people working on the calculations would be needed to keep up with the weather. What he really needed was a supercomputer!
What is a supercomputer? Computers were developed in the 1960s and have been getting more and more powerful ever since. The Earth Simulator centre in Japan has one of the largest computers used for climate modelling. It can work at a speed of 35,000,000,000 calculations per second! Powerful computers like this make it possible to model the complexity of the climate system.
How can I help predict climate change? Climateprediction.net is a climate modelling programme that can be run from home and school computers. • Instead of using one supercomputer, lots of smaller computers are used to run climate models.This is called ‘distributed computing’. • The project has been running since 2004 and uses over 90,000 computers worldwide. • These globes show the results of simulations to predict how the temperature may change in response to greenhouse gases.
How accurate are climate models? Within a small section of the scientific community there is still some scepticism about the accuracy of the predictions produced using climate models. Arguments against using climate models include: • Climate models do not measure local variability well. • It is difficult to model aspects of the climate like clouds. Cloud cover greatly influences surface temperature. Not including clouds in models could reduce their accuracy. • To predict the contribution of humans to climate change, the models have to make assumptions about population and economic growth. This could cause prediction errors. How are climate researchers trying to solve these problems?
How are climate models tested? Climate change researchers take several steps to make model predictions more reliable. • Data from previous climates, such as the 20th century, is entered into the model. This tests the ability of the model to reproduce known climates. • Scientists usually report a range of projections or scenarios. These can show, for example, how the climate might change if human carbon dioxide production stays the same, if it decreases or if it increases. • The International Panel on Climate Change (IPCC) is a UN organization that is responsible for assessing climate change data. They use information from different computer models to write reports for governments about the science of climate change.
What climate changes are predicted? Using data from several key sources, the International Panel on Climate Change (IPCC) have made the following projections about climate change. Key projections are that by 2100: • Mean global temperature will have increased by1.4 to 5.8°C. • Sea levelswill rise by0.09m0.88m. • There will be more precipitation (rain, snow, hail, etc.) over the northern hemisphere. • There will be more hot days and fewer cold days. How should we respond to these projections?
Why not just wait and see what happens? Some effects of climate change may not take place for decades.Would it be better to wait before taking action? The precautionary principleadvises that a lack of scientific certainty is not an argument against taking action when there is a serious threat. This can be applied to climate change. • If predictions about the human impact on climate change are correct, the results will be widespread and devastating. • Rising sea levels would flood many major cities. • Decreasing rainfalls in Africa could affect 70% of the continent’s population, leading to widespread famine. • If we delay taking action, it is likely to become impossible to avoid or reverse these climate changes.
Glossary • carbon cycle – The movement of carbon and carbon compounds through the atmosphere and ecosystem. • climate – The average weather pattern for a region over a long period of time, usually 30 years. • climate change – A significant variation in the long-term weather patterns for a region. • global warming– An increase in the average temperature of Earth. • greenhouse effect– The trapping of infrared radiation by the Earth’s atmosphere, which makes the temperature warmer than it would be otherwise. • greenhouse gas– An atmospheric gas that can trap infrared radiation. • proxy record– A natural or indirect record of climate.
