(The second installment in Saul Griffith's energy literacy and climate change presentation -- Ed.)
The result of our energy use:
Carbon Dioxide concentration in the atmosphere.
Scientists have now been studying the concentration of carbon dioxide in our atmosphere for more than half a century; They principally use two techniques: Direct measurement from research sites, which measure the current concentration direct from that atmosphere using highly sensitive instruments, and indirect measurement, which requires inferring the concentrations from ice-cores taken from glaciers, and from ice-cores drilled into the antarctic ice-pack.
The graph above shows the CO2 concentration as measured by different methods for the last 1,000 years.
What this graph represents is the main reason we are all becoming increasingly aware of our environmental impact. This graph tells us about how we are risking our own future.
This might be the most important plot of natural phenomena that science has ever produced. We need to keep looking at these graphs to see how we are doing. We also need to increase our confidence in the reasons for the historical variations of this graph due to natural climate cycles.
There is much earlier data: European Project for Ice Coring in Antarctica (EPICA) covers the last 650,000 years. Here scientists have determined CO2 levels by analyzing bubbles enclosed in the ice. CO2 data from 0 to 420,000 years are from earlier measurements from ice cores from Vostok station [Petit et al., 1999], and Taylor Dome [Indermühle et al., 2000]. The isotopic records indicate the sequence of six full glacial cycles [EPICA Community Members, 2004]. New CO2 data measured at the University of Bern are from ice older than 420,000 years and extend the legendary Vostok record by more than 50 percent back in time. These data confirm that the present CO2 concentrations in the atmosphere are unprecedented for at least the last 650,000 years.
Recent rate increase in atmospheric CO2 concentration
In the last 50 years, the rate of increase in CO2 has increased. The Mauna Loa studies by Roger Revelle were pioneering. Uptake of CO2 by Northern Hemisphere trees, causes seasonal variations, which can be seen at this detail. There is no denying that a rapid increase in CO2 concentrations is happening. In fact, in the last few years scientists have become concerned that the rate of increase has itself increased. This might be an indication that we've reached the limits of the earth's ecosystems ability to absorb CO2.
For reference, pre industrial concentrations were around 280 ppm. (More information on ppm concentrations from Worldchanging.)
For those people who still doubt the scientific evidence of climate change, they should pause to note that despite the complexity of the system, we can in fact measure discrete things very accurately, and whats more, by multiple techniques. Presented here are two independent observations of the same phenomena that are in very close agreement. The observations were highly separated geographically, and geologically, and this increases our confidence highly in the conclusion of rapidly rising atmospheric CO2 levels.
Where is all the Carbon?
Carbon will seek to find a chemical equilibrium. As we push more carbon into the atmosphere by burning fossil fuels, we change the equilibrium and the carbon concentrations in these various deposits changes. A Giga Tonne of Carbon (1 GtC) is 1 billion tonnes. At current rates the increase of CO2 in the ocean results in increased acidity which is reducing the ocean productivity by lowering the growth of plankton and killing coral reefs. Burning forests and deforestation release the carbon trapped in vegetation into the atmosphere. The Indonesian forest fires of recent times released as much as 0.7GtC to the atmosphere.
The thing that we try to understand when looking at this slide is the flows of CO2 through the reservoirs where it is "stored". It is comforting to note that the reservoirs are much larger than the flows, which gives us hope of slowing and even reversing
How is Human Activity changing the carbon balance?
Fossil fuels were carbonaceous things billions of years ago that over time (heat and pressure) became oil, gas, coal, and those things we generally know as fossil fuels.
We now burn those things at a rate much faster than the oceans and other natural systems can absorb them. As a measure of the natural rate at which carbon is stored via photosynthesis, the current estimates is around 40 Gigawatts (GCEP, Stanford, Exergy Flows). That is the rough rate at which new oil and coal is being made - if you wait a few million years to harvest it.
The cartoon above shows you a very simple form of the carbon picture. At the rate of 2 GtC/yr the acidity of the ocean actually increases. This implies even if we only add 2GTC to the atmosphere and consequently to the oceans we have another problem (ocean acidification) as well as the CO2 problem and climate change problem to deal with. The result of trying to force the 7GtC into the atmosphere with only 2GtC coming back out, is a net increase of 5GtC into the atmosphere yearly, consequently the CO2 concentration in the atmosphere increases.
The result of CO2 change is climate change.
The extra CO2 in the atmosphere creates something now widely known as “the greenhouse effect”. Through mechanisms described in much more detail in the resources, heat is trapped within the blanket of earth’s atmosphere and contributes to the heating of the whole planet. This is a complex phenomenon (for a great case study read about the atmosphere in the “winds of change”). This is why it will heat in some places and cool in others even when the overall, or average, trend is for global warming.
In the past 25 years (as you will have seen in Inconvenient Truth) the temperature has risen sharply, breaking all sorts of records.
Both the first two graphs of CO2 concentration in the atmosphere are rather misleading, because the y-axis does not start at zero. The first graph, for example, makes it seem as if the current CO2 concentration is almost 6 times higher than it was a thousand years ago, when it is actually 1.3 times as high. That factor of 1.3 is probably very frightening and important, but the graph itself is a bit absurd.
Over 400 World Wide Prominent Scientists Disputed Man-Made Global Warming Claims in 2007. See http://tinyurl.com/2dv6nz
The idea that the atmosphere behaves like a greenhouse is a misunderstood concept, it is not correct.
In the atmosphere water vapour is a major component (1%-4%) and it has similar optical properties to glass. The water molecule is in the form of a shallow V with two hydrogen atoms attached to the heavier central oxygen atom. It absorbs radiation by the various modes of vibration of this system and by rotation (think of it as two light balls attached to a heavy one by springs). Pure liquid water is actually blue, as it absorbs slightly in the red, though heavy water is colourless because the heavier atoms do not vibrate so readily at optical frequencies. Like the greenhouse glass, the water vapour acts as a one-way energy valve. Thus not only does water keep the planet warm, but it also maintains a fairly constant temperature. It is this greenhouse effect that makes life on earth possible.
The other and major mechanism in the greenhouse is the inhibition of convection. This is not ideal, as there is heat loss from the roof by convection. The Earth, in contrast, loses no heat by convection, but only by radiation. Convection in the oceans and atmosphere merely serves to redistribute the heat.
Find more about computer models here..