Global Warming The recent gradual warming of the

Global Warming The recent gradual warming of the Earth’s atmosphere largely as a result of human activity.

Contents • • • Evidence – Pollen analysis – Dendrochronology – Ice-core analysis – Sea-floor analysis – Radiocarbon dating – Coleoptera – Changing sea levels – Glacial deposits – Historical records – Recent evidence for global warming Possible causes of climate change – Enhanced greenhouse effect Effects of global warming – Rising sea levels – Climatic change – Extreme events Case studies – The Amazon basin (equatorial) – The African savanna (tropical wet/dry) – Bangladesh (Monsoon) Effects on the British Isles – Coastal regions – Agriculture – Flora, fauna and landscape – Soils – Water resources – Energy use Responses to global warming – International responses – National responses: the UK – L local responses

EVIDENCE

Evidence • • • Pollen analysis – Pollen resist decay when they fall into peat bogs – Different species of plant prefer different climatic conditions – Pollen is a good way of finding out climatic conditions as only mature plants produce pollen therefore the conditions were good enough for them to grow – A limitation is that pollen can be moved by animals or wind. Dendrochronology – Tree ring analysis each year a tree grows a ring on its trunk – A wide band indicates a warm wet year a narrower one indicates a cooler and drier year – Limitation is investigations have shown that trees respond more to levels of moisture than temperature – Also few trees are older than 4, 000 years Ice-core analysis – Drilling cores from areas such as Antarctica and Greenland. Carbon dioxide trapped inside =climatic indicator levels ten to be lower during cooler periods and higher in warmer Sea-floor analysis – Core samples from ocean floor reveal shifts in animal an plant populations which indicate climatic change Radiocarbon dating – Carbon is taken in by plants during photosynthesis – Carbon-14 decays at known rate carbon 12 does not decay – Therefore comparison of the levels of the two isotopes present in plant remains indicate the age at which the plant died. – Type of vegetation present at particular times indicates climate periods – Method can accurately date organic matter up to 50, 000 years old. Coleoptera – Analysis Cleoptera beetles tend to be found under different climatic conditions – Present day knowledge of present climatic range of different species and age of sediments allows past climatic conditions to be determined. Changing sea levels – Rias and fjords indicates rising (eustatic) sea levels flooding glacial and river valleys. Glacial deposits – Show records of ice advance during colder periods and retreat during warmer times. Historical records – Cave paintings, depth of grave digging in Greenland diaries, documentary evidence of events Recent evidence for global warming – Rising average temperatures

Possible causes

Possible causes of climate change • Theories: – Variations in solar activity(sunspot activity) – Changes in the Earth’s orbit and axial tilt (which affect the amount of solar radiation reaching the surface) – Meteorite impact – Volcanic activity (increasing dust in the atmosphere) – Plate movement (redistribution of land masses) – Changes in oceanic circulation – Changes in atmospheric composition, particularly the build-up of carbon dioxide and other greenhouse gases (the enhanced greenhouse effect) • Enhanced greenhouse effect

Effects

Effects of global warming • • • Rising sea level – Sea level rise in 20 st century has been 1. 5 cm – But in 21 st could rise between 5 -10 cm in a decade – Sufficient enough to cause serious flooding in coastal areas and increased erosion – Low lying countries such as Bangladesh and Netherlands and Bangladesh, and many pacific and Indian Ocean islands, rising sea levels will have catastrophic consequences. – Cost of flood defences – British estuaries may need defences similar to the Thames Barrier Climatic change – Many places will experience warmer summers – Continental areas could see reduced rainfall – They could end up producing desert like conditions in places previously good for agriculture, such as Spain – Some climatologist believe that if global warming leads to changes in the pattern of ocean currents UK could have a much colder climate – Changes in vegetation, wildlife and agriculture. – Populations would diminish – Mass migrations as people search for areas to grow crops Extreme events – Heat waves, floods, droughts and storms will all last longer and show increasing intensity – Higher temperatures = increased evaporation over oceans = greater global precipitation

Effects on the British Isles

Effects on the British Isles • • • Coastal regions Agriculture Flora, fauna and landscape Soils Water resources Energy use

Responses

Responses to global warming • International responses – Carbon credits – Post Kyoto • National responses: the UK – – – Domestic front Carbon Trust Scotland woodland creation schemes Climate change and Sustainable Energy Act Climate change bill 5 year carbon targets • Local responses – – Insulating Recycling Using energy wisely Using public transport

Arguments for global warming • Climate change has happened before but now humans are the dominant factor affecting it. • Can talk about evidence Dendrochronology. . . • Hockey stick

Arguments against global warming • • Vested interest of scientists. It is argued that scientists exaggerate the effects of global warming because they receive funds from environmental companies. Unreliability of computer climate models. It is argued that these models are not able to predict tomorrow’s weather. So how can they predict long-term climate change? There are other factors involved in global warming. It is argued that human activities are not the only cause of global warming. People in fossil fuel industries will lose their jobs.

Case studies The Amazon Basin (equatorial) Location: South America Lies within equatorial climate zone and covers an area of some 8, 235, 430 km 2, mainly in Brazil Predicted impacts of climate change on this region: An increase in temperature of 2 -3ºC by 2050 A decrease in precipitation during the dry season last up to 4 months More intense rainfall will be experienced during the wet season. Sea levels are currently rising by some 5 mm per year along the delta Amazon Up to 40% of plant species may no longer be viable in the Amazon rainforest by 2080 if predicted climate changes occur As the dry season lengthens trees will have more time to dry out so there is likely to be increased incidence of spontaneous Problems of hydraulic cycle The African savanna (tropical wet/dry) Location: North Africa tropical wet/dry savanna climate is experienced over a huge area of Western African surrounding the rainforests to the north and south of the equator. Savanna lands likely to experience an increase in temperature of some 1. 5 degrees by 2050. Surrounding sea temperatures are not expected to rise to the same extent (0. 6 -0. 8 degrees), resulting in greater temperature differential between land sea. Precipitation expected to increase by 15% within the savanna lands closer to the equator but might decrease by 10% in areas towards the northern and southern fringes of the climate zone, for example in the Horn of Africa. This is likely to be due partly to the Sahara heating up more than the Atlantic Ocean, causing more moisture to be drawn in from the ocean during the wet season Bangladesh (monsoon) Location: Bangladesh country in South Asia Population is over 150 million in 2008 Most densely populated countries in the world Poorest nations it is the most illprepared. To face challenges Likely to be seriously effected by global warming. Predicted effects include: Increase in average temperatures of 1. 5 -2. 0 digress calicoes by 2050 Increase of 10 -15% in annul precipitation by 2050. 20% increase in river discharge Because of glacial melt from Himalayas