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  • People Changing Climate. Basics

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      People Changing Climate. Basics

      Greenhouse gases emitted from cars, planes, factories and power plants are changing the Earth's climate, and contributing to global warming.

      We still do not know exactly how sensitive the Earth's climate is to these human activities, but we know they make our planet warmer. In this text you can learn how our actions affect the climate of our planet, how the climate may change in the future and what consequences this could have for the lives of people, animals and plants. You can also learn what we can do to slow down or stop climate change.

      people changing climate, logo

      Photo: NASA

      Scientific material: Author: Camilla Schreiner - CICERO (Centre for International Climate and Environmental Research - Oslo) - Norway. Scientific reviewers: Andreas Tjernshaugen - CICERO, Norway - 2004-01-20 and Dr. Knut Alfsen - Statistics Norway, Norway - 2003-09-12. Educational reviewer: Nina Arnesen - Marienlyst School, Oslo, Norway - 2004-03-10. Last update: 2004-03-27.

      Worksheets: Authors: Ellen K. Henriksen and Camilla Schreiner - University of Oslo, Norway. Scientific reviewer: Andreas Tjernshaugen - CICERO, Norway - 2004-01-20. Educational reviewer: Nina Arnesen - Marienlyst School, Oslo, Norway - 2004-03-10. Last update: 2004-03-27.

      • 1. Man-made climate change?

        1. Man-made climate change?

        For the first time in human history, people are changing the Earth’s climate by emitting so-called greenhouse gases into the atmosphere. The main cause is the dramatic increase in the use of fossil fuels (coal, oil and natural gas) since the Industrial Revolution.

        Past climate change

        The Earth’s climate is always changing. Only 20,000 years ago, much of Northern Europe was covered in an enormous glacier that was up to three kilometers thick! The Alps and the Pyrenees mountains were covered with smaller ice caps. Sudden climate shifts happened quite frequently during the Ice Age, and made the ice expand or contract. In the cold climate south of the ice-covered areas, small groups of people hunted reindeer, wild horses, and bison.

        People living in the Ice Age left behind stone tools and fantastic cave paintings but their way of life was about to disappear. Over thousands of years, the Earth’s orbit around the sun changed, summers became warmer and the ice began to melt. The Ice Age ended around 10,000 years ago. Since then, the climate in Northern Hemisphere has been warmer and far more stable. Over the last 10,000 years the climate has been milder and people have developed agriculture, cities, and civilization – which would have been far more difficult during the Ice Age.

        cave painting of a wild horse

        1. CAVE PAINTING: Painting of a wild horse from the Lascaux cave in France, painted about 12,000-17,000 years ago. When the Ice Age ended, people’s way of life changed and they stopped making cave paintings.
        Photo: Artchive.com

        We will always be at risk of unexpected and unpleasant climate changes resulting from natural causes. For example, around 400 years ago Europe experienced a relatively cold period called the Little Ice Age (but not as cold as a real ice age). What is different about the situation today is that we risk rapid changes in climate caused by people. Because of our increasing emissions of CO2 and other greenhouse gases, we expect that over the next hundred years we will see the fastest warming of the Earth since the end of the Ice Age.

        From local to global problems

        As long as we humans have existed on Earth, we have affected the environment around us. In the past, the effects of our hunting or agricultural activities on the environment were local. This changed with the Industrial Revolution which began round 1750 and accelerated in the 1800s and 1900s. A revolution is a dramatic social change.

        The Industrial Revolution took place when people began to mass produce goods in large factories using machines that ran on energy from coal, and later using oil, natural gas, and electricity. This made it much easier for people to produce goods and helped the development of modern technology. In pre-industrial times – that is, the time before the Industrial Revolution – there were no trains, cars, planes, electric lights, factories, telephones, or televisions.

        fossil fuels

        2. FOSSIL FUELS: Before the industrial revolution, all ships were powered by oars or sail. The first ships with an engine were powered by steam produced from coal. Photo: The NOAA Photo Library

        The more we produce and consume, the more we affect the environment around us. Over the last 50 years we have seen clear signs that humans affect the environment of the entire planet. We are creating environmental problems that are not only local but also global. One of these global environmental problems is man-made climate change, also known as global warming.

        Global climate change

        Man-made climate change occurs because we emit greenhouse gases into the atmosphere. These emissions come from many sources, including factories and agriculture that supply us with food and other material goods, power plants which provide us with electricity and cars and planes that take us where we need to go.

        Greenhouse gases affect the Earth’s climate by increasing the greenhouse effect. This is a natural phenomenon where water vapor, carbon dioxide and other gases in the atmosphere allow sunlight to pass reach the Earth's surface, but then absorb much of the reflected heat from the Earth that otherwise would have escaped to outer space. Without the natural greenhouse effect, the average temperature would be about minus 18°C, and the Earth would be uninhabitable (choose the topic Lower atmosphere if you want to read more about the greenhouse effect).

        greenhouse effect

        3. THE GREENHOUSE EFFECT: Sunshine (visible light) enters the atmosphere freely (yellow radiation in the left side of the figure). Some of it is immediately reflected by clouds, dust in the atmosphere and shiny surfaces (yellow radiation in the middle of the figure). The rest heats the Earth. Greenhouse gases in the atmosphere slow down the escape of heat back to outer space (red radiation in the figure).

        Emitting greenhouse gases in large amounts increases the concentration of these gases in the atmosphere. This increases the greenhouse effect so that more heat is trapped by the atmosphere. This increases the temperature of the atmosphere and changes the Earth's climate.

        About this Page:

        Author: Camilla Schreiner - CICERO (Centre for International Climate and Environmental Research - Oslo) - Norway.
        Scientific reviewers: Andreas Tjernshaugen - CICERO, Norway - 2003-09-15 and Dr. Knut Alfsen - Statistics Norway, Norway - 2003-09-08.
        Educational reviewer: Nina Arnesen - Marienlyst School, Oslo, Norway - 2004-03-10.
        Last update: 2004-03-27.

      • 2. What will a warmer world be like?

        2. What will a warmer world be like?

        A warmer global climate will definitely mean more than just more sweat! It may, for example, change wind and rain patterns and it may lead to rising sea levels. These changes will affect plant and animal life as well as human health – not to mention our homes, agriculture, businesses and economies.

        Climate change

        The future climate will be determined partly by how much greenhouse gases we emit, which is in turn determined by future population size, fossil fuel consumption, etc. The Intergovernmental Panel on Climate Change (IPCC) (read more about IPCC here) has identified how much we can expect the climate to change (read more about future emissions here). If nothing we do not take action to limit emissions of greenhouse gases, the IPCC says that by 2100 we can expect:

        • the mean surface temperature to increase by 1.4–5.8 °C compared to 1990
        • the sea-level to rise between 9 and 88 cm
        • 5–20% more rain and snow
        • more extreme weather, such as cloudbursts and heat waves, which in turn will cause flooding, landslides, drought, and forest fires, and
        • wind and ocean currents to change direction, which can cause local climate changes.

        thunder and lightning

        1. Thunder and lightning: Climate change may lead to more extreme weather, such as more frequent thunderstorms. Photo: The NOAA Photo Library

        Find out more about
        IPCC's future scenarios here.

        The reason that scientists do not know whether the temperature will increase by a little more than one degree or up to six degrees is that, first, they do not know how much we will emit in the future, and second, it is still uncertain how sensitive the climate on Earth is to emissions of greenhouse gases.

        Moreover, the above figures are averages for the entire planet. This means that some places may become much warmer, while others may change little, or even become cooler. But the degree of climate change a particular country faces has little to do with how much it has emitted. Greenhouse gases are well mixed with the other gases in the air. After they are emitted, they do not stay in the same place, but rather spread out throughout the atmosphere. Once they are there, they stay a long time. This is why it is not true that the biggest emitters will suffer the biggest climate changes. The most serious consequences of an increased greenhouse effect are just as likely to show up in places far away from where the emissions originated.

        What are the consequences of global warming?

        The impacts of global warming will vary from place to place. The weather can be drier or wetter, warmer or colder, or more or less windy. Europe will generally become warmer, particularly in the winter. In Northern, Eastern, and Central Europe, increased rainfall and heavier showers will make flooding a bigger problem, at the same time as we can expect more frequent drought in the southern parts of the continent because of less rainfall and more evaporation. The maps show how the climate may change in Europe.

        predicted temperature change

        2. HOTTER ALL OVER: How temperatures could change in Europe during this century because of global warming. The left map shows mean temperatures throughout the year, measured with thermometers, during the period 1961-1990. The right map shows what the mean temperatures could be during the years 2071-2100, according to one climate model. The numbers are uncertain and another model might get somewhat different results. Also, the results depend on how much greenhouse gases will be emitted to the atmosphere. Source: Sweclim/Naturvardsverket http://www.naturvardsverket.se/index.php3?main=/dokument/fororen/klimat/klimat/varmare.html

        predicted precipitation change

        3. BOTH WET AND DRY: How precipitation (rain and snow) could change in Europe during this century because of global warming. The left map shows changes in winter precipitation. The right map shows changes in summer precipitation. These maps are made by a climate model. The numbers are uncertain and another model might get somewhat different results. Also, the results depend on how much greenhouse gases will be emitted to the atmosphere. Source: Sweclim/Naturvardsverket http://www.naturvardsverket.se/index.php3?main=/dokument/fororen/klimat/klimat/varmare.html

        Animals and plants must find new places to live

        Changes in climate also affect the living conditions of animals and plants – both for individual species and for entire ecosystems. Many species will not thrive if their habitats become drier, colder, wetter, or warmer. Some will migrate to new habitats, others may die out. The most vulnerable species are those that are specially adapted to particular areas. A warmer climate will cause species and ecosystems to move towards the poles and up the mountains. Species that already live in northern or alpine regions are particularly vulnerable, since their habitats will be encroached upon and they will have no place to go: species that live in the mountains cannot move higher up once they reach the top. In the polar regions, the sea ice will melt earlier in the spring and form later in the fall, with serious consequences for species that live on or around the sea ice (for example, the polar bear and some seal species).

        Observations have shown that the warming over the last 30 years has already affected animal and plant life in Europe. For example, some bird and butterfly species have expanded their habitats; a study of the spring growth of several plant species shows that budding and flowering started 2–5 days earlier per decade over the last 50 years; the spring migration of birds and egg laying has started 2–5 days earlier for each decade; and species that are specially adapted to a particular climate have moved an average of 6 km toward the poles, or 6 meters higher in altitude, per decade.

        mountain goat

        4. HIGHER GROUND: When the climate is warming, mountain-living species move to higher ground. This is a North American mountain goat (Oreamnos americanus)

        A crucial factor for how animal and plant life will survive is how fast the warming actually occurs – since the longer time they have to adapt, the greater the chance that they will be successful. Rapid global warming and sudden climate changes give the species less time than if the changes occur slowly and gradually.

        polar bear

        5. THINNER BEARS: The polar bear is threatened by climate change. It specializes in catching seal on the edges of the sea ice around the North Pole, and shorter seasons with ice cover will give the polar bear a shorter hunting season. Studies show that polar bears have a lower body weight than before. Photo: NOAA Photo Library

        About this page:

        Author: Camilla Schreiner - CICERO (Centre for International Climate and Environmental Research - Oslo) - Norway.
        Scientific reviewers: Andreas Tjernshaugen - CICERO, Norway - 2004-01-20 and Dr. Knut Alfsen - Statistics Norway, Norway - 2003-09-12.
        Educational reviewer: Nina Arnesen - Marienlyst School, Oslo, Norway - 2004-03-10.
        Last update: 2004-03-27.

      • 3. How can we hinder man-made climate change?

        3. How can we hinder man-made climate change?

        We can hinder man-made climate change by emitting less greenhouse gases such as CO2. The less we emit, the less warming there will be in the future.

        bikers

        1. Cycling: The fewer greenhouse gases we emit, the less warming there will be in the future.
        Photo: Corel Gallery.

        Burning less fossil fuels

        People can slow down and eventually stop the climate change we have already started. But the climate system reacts slowly. The gases we have already emitted will keep affecting the climate for many years to come – even if we work hard to limit our emissions. Reducing emissions will slow down the rate of climate change, but the climate will keep changing as long as we live. Our children and grandchildren, however, will be able to fully enjoy our efforts we make today to limit emissions.

        The most important thing we can do to hinder climate change is to burn less fossil fuel so that we emit less CO2.

        Technological improvements and lifestyle changes can reduce the amount of energy we use on transportation, heating, cooling, lighting, appliances that run on electricity, industrial production and so on.

        Using sources of energy other than fossil fuels can reduce emissions of greenhouse gases considerably. Alternative energy sources include renewable sources such as wind power, solar power, hydroelectric power, biomass burning (as along as new trees and vegetation are planted to compensate) and nuclear power, although this is controversial for other reasons.

        Technological innovation may give us new energy sources that will replace fossil fuels in the future. For example, cars may run on hydrogen instead of gasoline. Hydrogen engines do not emit CO2 but to produce hydrogen we need lots of energy. If this energy comes from coal, oil or gas then we could end up with CO2 emissions just as big as if cars were still running on gasoline.

        Can’t we just filter out the CO2?

        Many types of pollution can be “cleaned up” by using filters. Today, however, there is no cleaning technology that can effectively remove CO2 emissions from furnaces, power plants and engines at a reasonable enough cost. Both governments and private companies in many countries are working to develop cost-effective technologies that can capture CO2 from burning coal, oil or gas before it is released into the atmosphere. It can then be stored far underground, for example in empty oil wells.

        Each year the oil company Statoil stores about 1 million tonnes of CO2 1000 meters under the ocean floor in a sandstone formation in the Sleipner gas field in the North Sea. The CO2 is separated from the natural gas and injected into the sandstone that is found under the ocean floor. This sandstone formation has room for at least 600 billion tons of CO2, which is roughly equivalent to the emissions from all of the power plants in Europe for the next 600 years.

        Two obstacles must be overcome before this technology can be applied on a large scale. First, we must be sure that the storage areas really are safe and the gas will not leak out. Second, the price of capturing and storing CO2 must drop to levels low enough that industry can afford to use the technology. Today no one knows whether or when CO2 can be captured and stored at a reasonable price. And in any case, the process can only be used for large, single sources of emissions – such as power plants and factories. Emissions from smaller, dispersed sources – such as cars, planes, paraffin stoves or gas ovens – cannot be reduced using this technology.

        natural gas at the Sleipner field

        2. Into the seabed: Natural gas is extracted from the seabed at the Sleipner field in the North Sea. CO2 is separated from the rest of the gas and pumped back into a layer of sandstone nearby. Illustration : Alligator Film/BUG

        Reduce emissions of other greenhouse gasses

        We can also reduce emissions of greenhouse gases from sources other than fossil fuels.

        • By stopping deforestation, we can avoid the release of CO2 to the atmosphere. Today deforestation is especially prevalent in tropical regions where forests are cut down to make grazing lands or raise crops.
        • Rubbish dumps (land fills) release the powerful greenhouse gas methane (CH4) from rotting organic waste. By capturing this gas and using it as fuel, we get both heat and reduced emissions of greenhouse gases.
        • Agriculture contributes to emissions of CO2, methane and nitrous oxide (N2O). More environmentally sound farming methods can reduce these emissions.
        • Many types of industrial manufacturing release greenhouse gases, especially those that contain fluorine. These emissions can be reduced using new production methods.

        Trapping CO2 from the atmosphere

        We can also increase the absorption of CO2 in forests, land and the sea.

        • When we plant forests where previously there was an open landscape, CO2 from the atmosphere is absorbed by the growing trees. However, increasing the absorption of CO2 in this way is so limited that it cannot make up for more than a fraction of the emissions that we humans are responsible for. Planting forests can also create problems – in some cases, it encroaches upon agriculture or destroys the habitats of wild animal and plant species that thrive in the existing landscape.
        • The oceans absorb large amounts of CO2 from the atmosphere. One proposal is to increase this absorption by fertilizing phytoplankton which bind carbon through photosynthesis. The effectiveness of such a step has not been documented, and phytoplankton growth after fertilization can have other, unfortunate, consequences.

        planting trees

        3. Forests: Plants take up CO2 when they photosynthesise so planting trees increases the amount of CO2 removed from the air. Photo: Corel Gallery.

        Greenhouse gases come from a large number of sources, so many different steps are needed to limit their emissions. However such large amounts come from fossil fuels that effective strategies need to focus on these fossil fuel emissions.

        Why burning wood does not contribute to climate change

        When we use fuel from biomass, such as wood or wood chips, energy is released in the form of heat, and carbon is returned to the atmosphere in the form of CO2. If new trees grow where the other trees were cut down for wood, the new trees will absorb CO2 from the atmosphere and bind it in new biomass. This re-establishes balance in the CO2 cycle. Over time, the amount of CO2 in the atmosphere will be constant. This is why biofuels are considered to be CO2-neutral.

        energy from biomass

        4. Energy from biomass: Biofuels are considered to be CO2 neutral. Photo: Corel Gallery.

        About this page:

        Author: Camilla Schreiner - CICERO (Centre for International Climate and Environmental Research - Oslo) - Norway.
        Scientific reviewers: Andreas Tjernshaugen - CICERO, Norway - 2004-01-20 and Dr. Knut Alfsen - Statistics Norway, Norway - 2003-09-12.
        Educational reviewer: Nina Arnesen - Marienlyst School, Oslo, Norway - 2004-03-10.
        Last update: 2004-03-27.