Basic Greenhouse Facts
This is the some of the information we need to understand what is printed in books and papers.
The International Panel on Climate Change 2005 reported the results of 30 years of research by the scientific community. It convincingly shows that human activities are responsible for global warming and set a stabilisation target of 2°C. In their report made four years earlier they acknowledged that temperatures would rise 1.4-5.8°C relative to 1990 levels. Now, in this recent report, they have revised the earlier assessment to double that figure!
2°C would result in heavy damage for the earth's ecosystems.
The consequences would be so dire that we have to stay below that if
our civilisation is to remain intact.
The average global temperature is already 0.6°C above pre-industrial levels. At current rates of CO2 emission we will reach 2°C well before the middle of this century.
The trend is very clear in the diagram - often called the hockey stick. It was assembled from tree rings, ice cores and coral. There is a slight but perceptible downward trend pointing to an ice age in about 10,000 years, then at the start of the industrial era around 1850 temperatures begin to rise with ever-increasing acceleration.
The Earth has buried surplus stores of carbon at great depth to keep the planet at workable temperature of 15°C, and we have taken these stores and burnt them. They can be measured in various ways:
The concentration of CO2 in the atmosphere is measured in ppm [parts per million]. CO2 in 1800 was 280ppm, now it is 385ppm. This does not include methane that is a 21 times more powerful greenhouse gas than carbon. Levels of atmospheric methane in the recent past have not risen above 750ppb, but now stand at 1,780ppb. This is equivalent to adding an additional 45ppm of carbon to the current level.
Including all greenhouse gasses we are now close to 425ppm. The important point is the ever-increasing output since 1950, clearly indicated on the left. When the growing emissions from permafrost and other tipping point concentrations are added, it is clear that the current rate of increase will continue into the future. Recent evidence shows that the rate of increase has recently risen by 50%.
Humans have released about 40,000 million tonnes of greenhouse gasses in 2004. It has been calculated that altogether the total over 200 years of industrialisation has been about 2,300 billion (2.3 trillion US) tonnes.
This means that the tipping point could already be behind us,
because a more than 2 degree rise is now inevitable.
Ice cores over three kilometers long reached air bubbles that became trapped 800,000 years ago. They show that the range of CO2 has laid in the past between 180ppm and 300. We have now broken through that upper limit to 380ppm plus the impact of other gases including methane and fluorocarbons.
We have to stay below 400ppm of CO2 if we are to keep average temperatures from finally stabilising under 2°C. There is a flywheel effect, so that if we stop at 400+ the concentration would still drift to a peak of 470±, and thus to a temperature of nearly 3°C and a possible maximum of 11°C. Even at the lower temperatures this is sufficient to start the irreversible melting of the Greenland ice and many other dire consequences.
We should remember that the earth's mean temperature when life began was 12°C. It has risen as the sun's heat has increased, yet during glaciations (when life was most fertile and abundant) the temperature returned to 12°C, our present average is 16°C and over the next few decades is expected to reach 20°C.
The rate of increase of CO2 is now 15ppm/decade and increasing. This rate of change is probably the most scary thing. It is too fast for the Earth to cope with. On a crowded planet, we have little capacity to adapt to changes that are much faster than anything in human experience.
A second method of calculation is by weight. In the last 300 years land-use changes have released 180 PgC [billion tons carbon], mostly from the tropics, and over 290 PgC from fossil fuel. Of the total 470 PgC the atmosphere has absorbed only 180 PgC, leaving 130 PgC in the oceans and 160 PgC in trees and soil. The latter is still acting as a CO2 sink, but could easily become a source as temperature rises.
That could happen before middle of century, if not before.
At this time the total amount in the atmosphere is 750 PgC, with a slightly larger amount is being held in the world's oceans and 550 PgC remaining in tropical forests and soils. We can see that it would have a profound effect on temperature were much of it to be released.
Also, we should not forget that we have changed about half the earth's land surface from natural forest into farmland, scrub and desert, which reduces the earth's capacity to regulate itself.
The amount of carbon we have already released is about same as caused the Eocene hot event 55M years ago. The geological record suggests that this caused the temperature to rise about 8°C.
Source of Carbon Dioxide
The following are US figures. About 40% of emissions come from burning fossil fuels for electricity, 93% of which comes from coal. About 20% of CO2 emissions come from internal-combustion engines, including trains and trucks. 13% come from trucks, aviation 7.5% and buildings 12%.
One gallon of petrol produces 20 pounds of CO2
one litre produces 2 kilos.
Coal emits around 1.7 as times as much CO2 as does natural gas and 1.25 times as much as oil. For the typical household, a metric ton of carbon equals about 10,000 miles of driving at 25 mpg, or one year of home heating or four months of electricity. The average family consumes 25,000 tons annually compared to China and India that consumes one eighth of that - for the time being! This is our "ecological footprint".
If car manufacturers were to improve gas mileage by only 3 mpg, the US would save a million barrels of oil every day, and drivers would save $25 billion in fuel costs annually.
Drivers in Los Angeles and New York alone wasted 600 million gallons of gas while just sitting in traffic. This one laziness translates to 7.5 million tons of carbon dioxide.
In 2004, Australia emitted greenhouse gases equivalent to 565 million tonnes of carbon dioxide. This was about 1.4% of global emissions. But our annual emissions of 28 tonnes per person are among the highest in the world.
We are such big emitters because so much of our electricity comes from coal rather than nuclear or hydro, because of the high levels of emission associated with the rural and mineral commodities we export and because we still clear more land than most countries.
Under the Kyoto Protocol - which we signed but haven't ratified - we agreed to limit our average annual emissions in 2008 to 2012 to 108% of their level in 1990. By 2004, our total emissions had grown by just 2%, but only from land clearing - a trick we can pull only once. In truth, emissions increased by 35% over the 14 years.
This increase comes from population growth, rising standard of living and growing exports of resources. The production and use of energy (both power houses and transport) accounts for almost 70%. Agriculture - mainly methane emitted by farting and burping animals - accounts for more than 16%. The rest from land clearing, industrial processes and methane from rotting waste in dumps.
These levels of emission are down to you and me because they are part of our standard of living. Big companies may do most of it, but they do it for our ultimate benefit.
The average household produces about eight tonnes of carbon dioxide a year. Electricity accounts for half of this. About 80% of the electricity comes from coal and only 8% from renewables One third comes from natural gas, wood for 16% and solar for less than 1%.
Our appliances (fridges, freezers, washing machines, clothes dryers, dishwashers, vacuum cleaners, televisions, computers etc) account for 30% of the household energy, which is more than half the emissions.
Heating and cooling account for almost 40% per cent of all the energy used, yet make up less than 15% of household emissions. This is mainly because the proportions of homes using gas and electricity for space heating are about equal, but electric systems produce up to six times more greenhouse emissions than an efficient gas central heating system.
Over the past decade, the proportion of homes with air-conditioning has almost doubled to 60%. Most use electricity. It is the cooling system that has the biggest effect - evaporative cooling using a quarter of the power required by a refrigerated system.
After these heating water is worth almost 30% because 40% use gas and 5% are solar, though solar could provide as much as 90%
Transport accounts for more than 13% of the nation's greenhouse emissions. Road transport makes up almost 90% of this, with civil aviation 6% and the rest from sea and rail.
Cars account for 60% of transport emissions. 80% people use a car to get to work and more than 90% for day-to-day travel.
I hope this has given you a few clues on how you could reduce your own emissions. The broader conclusion, however, is that we won't get far until our governments get serious about using an emissions trading scheme or a carbon tax to encourage energy efficiency.To the top