Changing Climate GCSE Revision guide

Transcription

1 How has Earth s climate changed over the last 2.6 million years? The quaternary period is a period of time that we are currently living in. It began 2.6 million years ago. Quaternary period is an ice age Temperatures have always fluctuated. Colder periods are called glacials and warmer periods are called interglacials. We are currently living in an interglacial The Quaternary Period is divided into two epochs: the Pleistocene (2.588 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today). Although the quaternary period is an ice age, the temperature has always fluctuated, moving up and down, sometimes warmer and sometimes colder than it is today. The colder periods normally last about 100,000 years and are called glacial periods. The warmer periods normally last about 10,000 years and are called interglacial periods.

2 Scientists believe since 1880 human activities (driving cars, factories, agriculture, and air travel) have resulted in a significant artificial rise in temperature. Evidence for climate change Antarctica gives us a record of the atmosphere from years ago. Gas trapped in the ice can be measured to estimate what the climate was like thousands of years ago. Lots of 16O and Earth was colder whereas lots of 18O and Earth was warmer. Carbon Dioxide in the bubbles is another good indicator. The more CO2 the warmer the climate. This indicator shows that Earth s current temperature is high compared to the past. The expanse of sea ice in the Arctic is further evidence that our climate is changing. We have been able to measure the sea ice minimum and maximum since 1979 using satellite photos. On average the area covered by sea ice in the Arctic has become smaller by 13.3% every ten years since Global temperature data has been recorded by more than a 1000 weather stations since Maps from different years can be compares to see how climate has changed. Geological fossil evidence Plants and animals are good indicators of the environment as different species tend to favour particular climatic conditions. Evidence of past climates can be suggested by the presence of living organisms preserved as fossils. For example, the discovery of 60- million-year-old crocodiles in North Dakota, USA, suggests that the climate of the past was much warmer than it is today. Elephant-like mammals called mastodons were widespread across the USA during cold, glacial periods. Their thick woolly coats enabled them to survive the very cold conditions. Fossil mastodons have been found from Alaska to Florida, indicating that these cold periods extended across the whole of the USA. Ice cores Ice cores extracted from the Antarctic and Greenland ice sheets have proved to be an important source of information about past global temperatures. When snow falls in cold polar environments it gradually builds up layer upon layer, year upon year. The buried layers of snow are compressed and gradually turn to ice. The Antarctic ice sheet is nearly 5 km thick in places and the oldest ice at its base is thought to be 800,000 years old.

3 Scientists are able to drill deep into the ice to extract cylindrical cores from ice that is many thousands of years old. The layers of ice within a core can be dated accurately. By analysing the trapped water molecules, scientists can calculate the temperature of the atmosphere when the snow fell. This information about accurate dates and temperatures has enabled scientists to create graphs of temperature changes over the last 400,000 years. The results of this research show the fluctuating temperatures that indicate past glacial and inter-glacial periods Ocean sediments In the same way that layers of snow build up over thousands of years in a cold environment, layers of sediment do much the same thing in deep ocean basins. Scientists have been able to drill into sediments that are over 5 million years old. By studying oxygen isotopes trapped within these sediments, it has been possible to calculate past atmospheric temperatures. Historical records Historical records can provide additional evidence of climate change. Ancient cave paintings of animals in France and Spain depict nature as it was between 40,000 and 11,000 years ago, a period of time when the climate changed significantly. The problem with cave paintings is dating accurately when they were drawn. Records of extreme weather events such as floods and droughts have been used to suggest that in recent decades extreme weather events have become more frequent. Some studies have suggested that the timing of natural seasonal activities, such as tree flowering and bird migration, is advancing. (The study of natural cycles like these is called phenology.) A study of bird nesting conducted by the British Trust for Ornithology in the mid-1990s discovered that 65 species nested an average of 9 days earlier than they had in the 1970s. Swallows are arriving in the UK some 20 days earlier than they did in the 1970s. Could this be evidence of a warming world? Diaries and written observations can also provide evidence of climate change, although personal accounts can lack objective accuracy.

4 Global temperature data Look at the image. It shows temperature anomalies (variations from the long-term average) for the period This map was produced by NASA (National Aeronautics and Space Administration) using data collected from over 1000 ground weather stations together with satellite information. If you study the colour key, you should notice that there is a warming trend for most of the world. This is consistent with earlier maps produced over several decades. NASA suggests that average global temperatures have increased by 0.6 C since 1950 and 0.85 C since Weather stations are not evenly distributed across the world and some regions, especially in Africa, have a fairly sparse network. Computer programmes have been used to produce global maps like this but this does not make them absolutely accurate and reliable. Shrinking ice sheets and glaciers One of the most striking effects of the recent warming trend has been the retreat of ice sheets and glaciers. Maps and photos show that many of the world s glaciers are retreating. There is plenty of evidence from around the world of melting ice. The snows of Kilimanjaro have melted by 80 per cent since Glaciers in parts of the Himalayas could disappear by Arctic sea ice has declined in volume by 10 per cent in the last 30 years. Monitoring of the Greenland ice sheet by NASA suggests that it is shrinking. In 1910 Glacier National Park (USA) had about 150 glaciers; there are now fewer than 30. Low-level ski resorts in Europe have suffered economic hardship and some businesses have had to close due to increasingly unreliable snowfall. The Muir Glacier (Alaska, USA) has retreated by 50 km in the last 120 years. Retreat of the Columbia Glacier, Alaska, USA The Columbia Glacier has its source in the Chugach Mountains in southern Alaska. It flows for some 50 km to the sea in Prince William Sound. Its maximum thickness is 550 m. The glacier is known as a tidewater glacier because it flows directly into the sea. The Columbia Glacier is one of the most rapidly changing glaciers in the world. It has been retreating at an alarming rate since the 1980s. Between 1982 and 2014, the snout (front) of the glacier retreated by about 16 km and lost half of its thickness and volume. In the early 2000s the glacier was retreating at a staggering rate of around 30m a day, producing huge icebergs as the snout broke apart.

5 Scientists believe that the thinning of the ice may well be due to warming global temperatures. If global warming continues, it is likely that the glacier will continue to shrink. As it does so, the meltwater will contribute towards sea level rise. The extremely fast rate of retreat at the snout may be due largely to mechanical factors associated with the glacier extending into the sea, although global warming may well have played a part in making the snout unstable in the 1980s. Natural causes of climate change 1.) Milankovitch cycles. Climate change is linked to the way the earth moves around the Sun and how it wobbles and tilts as it does this. Eccentricity changes in the shape of Earth s orbit. Obliquity changes in how Earth tilts on its axis. Precession the amount Earth wobbles on its axis. Sun spots Temporary and are caused by magnetic storms. They increase the amount of energy Earth receives from the sun, causing it to warm up. Volcanic eruptions When volcanoes erupt they release huge amounts of dust containing ash, sulphur dioxide, carbon dioxide and water vapour. The dust blocks out the sunlight and contributes to a cooling effect.

6 The natural greenhouse effect The earth is kept warm and habitable because of the natural greenhouse effect. Gases in the atmosphere such as carbon dioxide and water vapour are greenhouse gases. They trap some of the sun s radiation preventing it escaping to space and therefore increasing the earth s temperature. The enhanced greenhouse effect Humans have put more greenhouse gases into the atmosphere through various activities. This makes the layer of greenhouse gases thicker and traps even more of the sun s energy.

7 Sources of Greenhouse gases. Contribution to enhanced greenhouse effect. Efficiency Source Carbon Methane Halocarbons Nitrous Oxide Dioxide 60% 15% 15% 6% Burning fossil fuels like coal and gas to make electricity. Industry, cars and deforestation. 25 times more effective than carbon dioxide. Landfill sites, rice production and farm animals times more effective than Carbon Dioxide. Air conditioning, refrigerators, aerosols and foam packaging. 250 times more efficient that Carbon Dioxide. Agricultural fertilisers and car exhausts. Human causes of climate change There is a strong link between increases in Carbon Dioxide and increases in temperature.

8 Not all countries produce the same amount of Carbon Dioxide. LIDC s emit very low levels of CO2 AC s and EDC s emit much more. China emits more than any other country but don t forget they also have the biggest population in the world! Really you should examine CO2 per capita (per person) to get a fair view. Country share of total CO2 emissions in 2011

9 CO2 emissions per capita

10 Global effects of climate change. Social Economic Environmental Reduced rainfall increases the risk of wildfires which can destroy people s homes and put lives at risk. Some areas could become so hot and dry they become impossible to inhabit. Some areas will struggle to supply enough water due to problems with water availability. Lower crop yields could increase malnutrition, ill health and death from starvation. Low lying coastal areas could be lost to flooding as sea levels rise. This could lead to migration and overcrowding in other areas. More extreme weather events mean more money has to be spent on predicting events (e.g. floods) and reducing their impacts. Areas of permafrost are melting leading to the collapse of buildings and pipelines. In farming some crops have suffered from climate change (maize crops have got smaller due to warming). Some farmers in high latitude countries are finding that crops benefit from warmer conditions. Water shortages affect ability to make power through hydro-electric. Temperatures expected to rise by C between 2005 and Warmer temperatures are causing glaciers to shrink and ice sheets like Greenland to melt. Sea ice is also shrinking, leading to loss of polar habitats. Coral reefs are suffering from bleaching due to increasing sea water temperatures. Precipitation patterns are changing warming is affecting how much rain areas get. Effects of climate change on the UK Environmental Impacts Climate o Temperature will increase o Winter rainfall may increase by 16% in parts of Western UK o Summer rainfall may decrease by 23% in parts of southern England. Extreme events o Droughts are expected to be more frequent and intense, especially in southern England. o Flooding will become more common due to increased rainfall and sea level rise. Sea level rise o By 12-76cm by 2095 o Loss of habitats, e.g. salt marsh Wildlife o Climate change will change the UK s habitat. Some species have moved North to areas with lower temperatures. This can upset the balance of natural ecosystems and lead to species extinction. Economic Tourism o Warmer weather could lead to more people staying at home for holidays and boost the UK tourism industry. o In other areas could lead to a decline, e.g. skiing in Scotland. Agriculture

11 o Warmer temperatures and longer growing season could improve productivity of some crops. o New crops (e.g. grapes) could be grown in Southern England. Perhaps with increased need for irrigation and water storage schemes. Fishing o Fishing infrastructure (e.g. ports, boats) at risk from increasingly frequent and more violent storms. o Changing fish populations in UK waters could affect fishermen s livelihoods. Social Health o Deaths from cold related illnesses may decrease but heat related illnesses will put further strain on health services. Water shortages o Drier summers will affect water availability in areas that most need it e.g. South East England where population density is increasing. Floods o Flooding may damage homes and businesses. Settlements on estuaries e.g. Portsmouth, Cardiff and low lying areas near the coast (e.g. large areas of Norfolk).

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