2.2a The Earths climate appears to be changing as a result of human activity, and future climates are uncertain
To recognise and understand that human activities produce greenhouse gasesSpecification Statement- What challenges might our future climate present us with?
What is the message?
Name as many Greenhouse gases as you can:In order, Earth's most abundant greenhouse gases are:water vapour carbon dioxide methane nitrous oxide ozone CFCs When these gases are ranked by their contribution to the greenhouse effect, the most important are:water vapour, which contributes 3672% carbon dioxide, which contributes 926% methane, which contributes 49% ozone, which contributes 37%
How much does each contribute?
Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would be on average about 33C (59F) colder than at present Human life would therefore not be possible
Water vapour is the most abundant of the greenhouse gases, and is the dominant contributor to the natural greenhouse effect. Human activity has little direct impact on the concentration of water vapour in the atmosphere; however, changes inits concentration are an indirect result of climate feedbacksrelated to the warming of the atmosphere.Astemperatures rise, more waterevaporates from ground sources - rivers, oceans, etc. Because the air is warmer, the relative humidity can also be higher, leading to more water vapour in the atmosphere. Higher concentrations of water vapour areable to absorb more thermal infrared radiation from the Earth,further warming the atmosphere. The warmer atmosphere can then hold more water vapour, and the cycle continues. This is cycle is considered a positive feedback loop. However,uncertainty exists in boththe extent and importance of this feedback loop. As water vapour increases in the atmosphere, more of it willalso condense into clouds, whichreflect incoming solar radiation away fromthe Earth's surface thereby becoming a cooling force.Water Vapour
Carbon dioxide (CO2),Carbon dioxide is released into the atmosphere through both natural and humanprocesses. Natural production and absorption of carbon dioxide is primarily through the biosphere and the oceans via the carbon cycle. Human activities such as fuel burning (coal, oil, natural gas, and wood), deforestation, cement production, and changes in land use have altered the natural carbon cycle by increasing the concentration of carbon dioxide in the atmosphere.Carbon dioxide was the first greenhouse gas found to be increasing in atmospheric concentration withconclusive measurements made in the last half of the 20th century. Carbon dioxide levels as a component of the atmospherehave increased nearly 30 percentbeginning from the late 18th century to the present time, and is now at approximately 370 parts per million (ppm) and rising. Prior to industrialization,carbon dioxide levels fluctuated near 280ppm, with seasonal variations as vegetation drew down carbon dioxide in the springand summer for photosynthesis, releasing it in the fall and winterthrough decomposition.
Methane (CH4) Which comes from both natural and human sources, is an extremely powerful warming agent - even more effective than carbon dioxide - however its lifetime in the atmosphere is brief, only about 12 years.In nature, methane is released through biological processesin low oxygen environments, such as swamplands. Human activities, including growing rice, raising cattle, using natural gas and coal mining, are increasingly adding to the level of methane in the atmosphere. As is sending waste to landfill sitesSince the beginning of the 19th century, methane levels have risen 150 percent, though the pattern of methane emissions is highly irregular and, since1990,has levelled off for reasons that are unclear.
Nitrous OxideOtherwise known as "laughing gas," is a long-lived warming gas, persisting in the atmosphere for approximately 120 years. It is produced naturally froma wide variety of biological sources in both soil and water, particularly microbial action in wet tropical forests. Human-related sources ofnitrous oxideinclude agricultural soil management, animal manure management, sewage treatment,combustion of fossil fuel, and the production of a variety of acids.It is alsoimportant to account for the various interactions between natural processes and human influences in the nitrogen cycle, since human impacts can significantly enhance the natural processes that lead to N2O formation. For example, fertilizer use andnitrogen-loaded runoff into waterwayscan enhance nitrous oxide emissions fromnatural sources. Concentrations of nitrous oxidebegan to rise at the beginning of the industrial revolution, although emissionshave been somewhatdifficult to quantify on a global scale, primarily because it isone of the least studied greenhouse gases to date.
Ozone is a highly reactive molecule composed of three atoms of oxygen. Ozone concentrations vary by both geographic location and altitude. At lower levels in the trophosphere, ozone exerts a warming force upon the atmosphere, primarily due to human processes. Automobile emissions, industrial pollution, and the burning ofvegetation increase the levels ofcarbon and nitrogen moleculeswhich - when reacting to sunlight - produce ozone, an important contributor to smog. Levels of ozone have nearly doubled since the 1800s, and have increased nearly 30 percent since the industrial revolution.In the stratosphere, a decrease inozone concentration exerts a cooling force upon the atmosphere. Much of the decline in this stratospheric ozone can be attributed to the destructive action of CFCs. As ozone continues to contribute both the warming and cooling of the atmosphere, its role in the overall enhancement of thegreenhouse effect will continue to be difficult to determine.
HalocarbonsCompounds of human origins used primarily as cooling agents,propellants, and cleaning solventsin a broad range of applications. The most familiar type of halocarbonsare thechlorofluorocarbons (CFCs); however,since it wasdiscovered that theydestroy stratospheric ozone, theyare continuing tobe phased out under the terms of the Montreal Protocol. Although levels of CFCs are declining,their long atmospheric lifetimes assure thatthey will continue to contribute to the greenhouse effect for some time.Another set of synthesized halocarbon compounds - created as substitutes to replace CFCs -are called HFCs (hydrofluorcarbons). While theyare also greenhouse gases,they are less stable in the atmosphere and therefore have a shorter lifetime and less of an impact as a greenhouse gas. Also, at lower altitudes, halocarbons function as a warming gas; however, in the upper atmosphere, they exert a cooling impact through their interaction with ozone. Therefore, the ultimate impact of halocarbons on the greenhouse effect is highly uncertain.
TaskSummarise the information about greenhouse gases into a mind map, START OFF LIKE THIS- GREENHOUSEGASESMETHANECARBON DIOXIDEOZONENITRIOUS OXIDEHALOCARBONSWATER VAPOURCFCsHFCsReleased by swampsEscapes from landfill
Describe the differences between the main source of emissions for the 3 main GHGSummarise the main causes of GHG emissions detailed in the pie chart
In 1980 there were 16 billion tonnes of carbon dioxide emissions made worldwide; emissions in 1980 were 70% of the carbon emitted in 2000.In 1980 the most carbon dioxide emissions came from the United States, China and Germany. Emissions per person from the United States were 14 times greater than those from China. Emissions depend on levels and type of industrialisation, types of transport and fossil fuel usage. Per person the most polluting territories emit 1000 times more carbon dioxide than the least polluting. Although emissions have increased greatly over years between 1980 and 2000, the distribution of emissions remains similar. CO2 EMISSIONS IN 1980
Carbon dioxide causes roughly 60% of the enhanced greenhouse effect or global warming resulting from certain gases emitted by human activities. In 2000 there were almost 23 billion tonnes of carbon dioxide emitted worldwide. Of this, 28% came from North American territories; 0.09% came from Central African territories. Emissions of carbon dioxide vary hugely between places, due to differences in lifestyle and ways of producing energy. Whilst people living in 66 territories emitted less than 1 tonne per person in 2000; more than 10 tonnes per person were emitted by people living in the highest polluting 21 territories that year CO2 EMISSIONS IN 2000
Between 1980 and 2000, 72% of territories increased their emissions of carbon dioxide, totalling 6.6 billion tonnes a year. Other territories reduced their emissions by 1.9 billion tonnes a year.The biggest increases in carbon dioxide emissions over this period were in China, the United States and India. 42% of the world population live in these 3 territories, they caused 45% of the world increases. The per person increase in emissions from the United States was over 3 times larger than Chinas, and over 4 times Indias.The largest increases in carbon dioxide emissions per person living there were in Qatar, then Bahrain.CO2 EMISSIONS INCREASED 1980-2000
Between 1980 and 2000, roughly 58 territories decreased their annual carbon dioxide emissions. Together these territories reduced annual emissions by 1.9 billion tonnes; carbon emission increases from other territories were 3.5 times greater than this decrease.Almost half of the decrease was in territories formerly in the Union of Soviet Socialist Republics, followed by Germany at 15%, Poland at 8%, and France at 6%. Decline in industrial production and factory closure contributed to