Global warming – the tipping point
The world is now entering a critical era in which a tipping point could arise beyond which human beings will lose the ability to stop runaway global warming.
What are the feedback processes that cause accelerated warming?
First it is necessary to understand that the build up of greenhouse gases can create feedback mechanisms – some with warming and others with cooling – effects. The important point to bear in mind is that the warming effects outweigh the cooling ones. As the quantity of greenhouse gases builds up in the atmosphere this causes effects that increase the warming. The warming itself causes effects which increasethe warming still further. The main effects are summarised below:
Rising CO2 will cause acidification in the oceans killing
plankton which sequesters carbon dioxide thus increasing CO2
concentration in the atmosphere.
Vast stores of methane (a greenhouse gas 24 times more potent than CO2) are trapped or ‘frozen’ in crystal lattice form in sea bed deposits. Rising temperatures in the oceans would release methane into the atmosphere. Methane will gradually break down into CO2 and water vapour, but CO2 has an atmospheric life measured in centuries or even millennia.
Methane is also trapped in large expanses of frozen tundra and this would be released with thawing.
As temperatures rise, the concentration of water vapour in the atmosphere rises. Water vapour is itself a very powerful
greenhouse gas. So this is also a strong and rapid feedback
process.
Increased water vapour would also cause cloud formations that have both warming and cooling effects, the overall impact of
which is uncertain. However, warmer cloud systems would
increase the energy and impact of storm events.
The effect of melting ice would be to replace a white shiny
surface which reflects heat back into space with a dark surface
absorbing heat.
Human activities, including deforestation, present farming practices which break down soil carbon and convert it to CO2 and involve large amounts of fossil fuels, industrial processes and transport using fossil fuels, have already raised the carbon dioxide concentration in the atmosphere above the level which scientists believe will cause catastrophic climate changes. This is above the level that would make a 2˚C temperature rise causing such changes, inevitable. The recorded level of CO2e (carbon dioxide equivalent) in 2006 has been measured at 420 ppm and the rate of accumulation (now at 2 ppm per year) is
accelerating. Hence the feedback dynamics outlined above indicate that not only is it an urgent necessity to stop the use of fossil fuels, but also to adopt measures that would remove CO2 from the atmosphere.
Energy saving and carbon reduction
Energy saving and carbon reduction
Solar PV panels
Most energy is derived from fossil fuels and hence any personal savings in the use of energy will reduce carbon emmissions.
Two methods of representing proportional household emissions in the UK are shown in the following charts:
The figures shown are for 2006 when the average per capita emmission was 11.6 tonnes, half of which was from direct personal emmissions – air travel 34%; household heating 26%; car use 19%; Household electricity 16%; other transport use 5%.
Emmisssions outside the household but related to househjold activities – Manufacturing and construction 40%; personal travel 29%; housing 20%; services 6%; food 5%.
The figures show that 5 tonnes (out of the total of 11.6) are caused by travel and 2.3 tonnes by manufacturing and construction.
Household electricity accounts for about 0.9 tonne and household heating 1.5 tonnes. Hence the greatest reductions are to be made from reducing travel. The impact of international air flights can be determined from the CHOOSE CLIMATE CALCULATOR .
Return flight from London to Douala (Cameroon) – 4995 km
The diagram on the left shows the results from the calculator for a return flight from London to Douala (Cameroon) – a distance of 4,995 km. Note that this resulted in a per capita emission of approximately 3.5 tonnes.
Greenhouse gas emissions from aircraft flying in and out of Britain in 2030 are estimated to then contribute nearly half the UK total. Aircraft from UK airports alone emitted 9.8 million tonnes of carbon in 2005 – equivalent to 36 million tonnes of carbon dioxide.
What level of emissions should we be aiming for? Dr Hillman, Senior Fellow Emeritas at the Policy Studies Institute (2010) suggests levels shown in the following table (note that the target for 2005 was not achieved) :
An idea of household and individual annual carbon emissions can also be obtained by measuring gas and energy use in Kw hrs, heating oil in litres and transport in Km then using the following chart:
Do not include miles travelled as a passenger in a car
Another assessment can be made with this CARBON CALCULATOR
Further information can be obtained from the National Energy Foundation
Anyone considering solar heating might find the following links useful:
There is also information on ENERGY EFFICIENT HOMES and CARBON FOOTPRINTING on the National Energy Foundation web site.
