The greenhouse effect and global warming What are they? The causes, effects, impacts and responses

2 Key Idea – only the one Environmental abuse has serious consequences. Its causes need to be tackled to ensure a more sustainable future. But there are still 3 sections to study …..

3 Section 3 part 1 Causes of global warming and climate change: deforestation; use of fossil fuels; air pollution; agricultural change; CFCs. Consequences: rising sea levels; more hazards; ecosystem changes; new employment opportunities; changing settlement patterns; health and well being. A case study of the threats posed by global warming and climate change to one country (eg Bangladesh, the Maldives).

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5 Please visit _nat/04/climate_change/html/greenhouse.stm _nat/04/climate_change/html/greenhouse.stm

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10 THE NATURAL GREENHOUSE EFFECT The atmosphere has a number of gases, often in tiny amounts, which trap the heat given out by the Earth. To make sure that the Earth's temperature remains constant, the balance of these gases in the atmosphere must not be upset.

11 The GREENHOUSE GASES are very important and are mainly: water vapour occurs naturally in the atmosphere. carbon dioxide produced naturally when people and animals breathe. Plants and trees absorb carbon dioxide to live. Volcanoes also produce this gas. Carbon dioxide is not the same as carbon monoxide methane comes from cattle as they digest their food. The gas also comes from fields where rice is grown in paddy fields. nitrous oxide when plants die and rot, nitrous oxide is produced. ozone occurs naturally in the atmosphere.

12 THE ENHANCED GREENHOUSE EFFECT Because there are more and more greenhouse gases in the atmosphere, more heat is trapped which makes the Earth warmer. This is known as global warming. A lot of scientists agree that man's activities are making the natural greenhouse effect stronger. If we carry on polluting the atmosphere with greenhouse gases, it will have very dangerous effects on the Earth.

What are the causes of rises in Greenhouse gases

14 THE ENHANCED GREENHOUSE EFFECT Some of the activities of man also produce greenhouse gases. These gases keep increasing in the atmosphere. The balance of the greenhouse gases changes and this has effects on the whole of the planet. Burning fossil fuels - coal, oil and natural gas - releases carbon dioxide into the atmosphere. Cutting down and burning trees also produces a lot of carbon dioxide. A group of greenhouse gases called the chlorofluorocarbons, - which are usually called CFCs, because the other word is much too long! - have been used in aerosols, such as hairspray cans, fridges and in making foam plastics. They are found in small amounts in the atmosphere. They are dangerous greenhouse gases because small amounts can trap large amounts of heat.

15 Some greenhouse gases X 300 more effect on global warming than CO 2 Man-made sources of nitrous oxide include nylon and nitric acid production, the use of fertilisers in agriculture, cars with catalytic converters and the burning of organic matter. Methane is x 30 more effective than CO 2 Where does methane come from? (3 places)

16 CO 2 and temperature rise

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19 Two ways of looking at causes

The effects

21 Global Warming – some effects Since 1970, rise in:Decrease in:  Global surface temperatures Snow extent  Tropospheric temperatures Arctic sea ice  (air closest to ground level)  Global Sea Surface Temperatures Glaciers  Global sea level Cold temperatures  Water vapor  Rainfall intensity  Precipitation  Hurricane intensity  Drought  Extreme high temperatures  Heat waves Since 1970, rise in:Decrease in:  Global surface temperatures Snow extent  Tropospheric temperatures Arctic sea ice  (air closest to ground level)  Global Sea Surface Temperatures Glaciers  Global sea level Cold temperatures  Water vapor  Rainfall intensity  Precipitation  Hurricane intensity  Drought  Extreme high temperatures  Heat waves

22 Global mean temperatures are rising faster with time  Period Rate Years  /decade Warmest 12 years: 1998,2005,2003,2002,2004,2006,2001,1997,1995,1999,1990,2000

23 Global mean temperatures are rising faster with time   Period Rate Years  /decade

24 Global mean temperatures are rising faster with time     Period Rate Years  /decade

25 Annual anomalies of global average SST and land surface air temperature Sea Surface T Land Land surface temperatures are rising faster than SSTs

26 Smoothed annual anomalies for precipitation (%) over land from 1900 to 2005; other regions are dominated by variability. Land precipitation is changing significantly over broad areas Increases Decreases

27 Regions of disproportionate changes in heavy (95 th ) and very heavy (99 th ) precipitation Proportion of heavy rainfalls: increasing in most land areas

28 Projected Patterns of Precipitation Change Projected Patterns of Precipitation Change Precipitation increases very likely in high latitudes Decreases likely in most subtropical land regions This continues the observed patterns in recent trends

29 Sea level is rising: from ocean expansion and melting glaciers Sea level is rising: from ocean expansion and melting glaciers Since 1993 Global sea level has risen 41 mm (1.6 inches) 60% from expansion as ocean temperatures rise, 40% from melting glaciers Steve Nerem

30 Evidence for reality of climate change Glaciers melting Alpine glacier, Austria 1909 Toboggan Glacier Alaska 2000 Muir Glacier, Alaska

31 Global mean temperatures are rising faster with time     Period Rate Years  /decade

32 The impacts

33 Impacts on living things If the sea-levels are rising then – what might the effects be? And on people and the ecosystems? If there are more climatic hazards – what might they be? What is the impact? Where might be affected the most? Changes in rainfall – what might be the effects on the earth? On the human welfare? Rises in temperature – what would be the effects? What are the impacts on the different groups? That is the sea as well? Warming seas with more CO 2 in ( that is an acid by the way)?

34 Impacts on living things Ecosystem changes –  which would be most affected?  What would be the impacts on the world as a whole?  On people?  On ecosystem populations? Agricultural production: all bad or maybe some good?

35 One of the impacts is on human health – why?

36 Case study: Bangladesh Notice all the rivers that come down from the Himalayas – when is there the highest flow in these?

37 75% of Bangladesh is at or below just 10 metres in height.

38 Projected climate change impacts Many of the projected impacts of climate change will reinforce the baseline environmental, socio-economic and demographic stresses already faced by Bangladesh. Climate change is likely to result in: i. Increased flooding, both in terms of extent and frequency, associated with sea level rise, greater monsoon precipitation and increased glacial melt ii. Increased vulnerability to cyclone and storm surges iii. Increased moisture stress during dry periods leading to increased drought iv. Increased salinity intrusion v. Greater temperature extremes

39 So what are the issues? The ice caps in the Himalayas are melting so the spring flood carrying sediments to re-enrich the soils are slowly reducing. The storms seem to be becoming more intense The sea level is rising due to snow melt and thermal expansion. The mangrove swamps, the Sundarbans, are the largest in the world, will disappear is the sea levels rise by a mere 45cm. Without mangroves to protect the coastal behind them, much land will be washed away in storms, leaving millions homeless.

40 So what are the issues? More salt water infiltration is likely, which will make more of the land that is still above sea level, useless for growing rice, so putting more pressure on more to people to migrate. Saltwater from the Bay of Bengal already penetrates 100 kilometres inland during the dry season, and climate change is likely to exacerbate this. Pressure from an increasing population (rising at 2% pa) and rising demand for groundwater further reduces the availability of freshwater supplies for domestic and industrial purposes If sea levels rises up to one metre this century, Bangladesh could lose up to 15 per cent of its landmass and up to 30 million Bangladeshis could become climate refugees. In these areas, agriculture, industry, infrastructure, livelihoods, marine resources, forestry and biodiversity, human health, and utility services will all suffer. Such a scenario could lead to a decline in GDP of between 27 and 57 per cent. ( It is currently US$ 641 ) Given the high population density (954 per sq km) of the country as a whole, this could lead to mass climate emigration – where could they go?