Yet more Hockey Sticks to get rid of
This is Figure 1.4 on page 6 of David MackKay’s book, Sustainable Energy: Without The Hot Air (2008).
David MacKay has been criticised for a number of things including over-simplification but, as he makes clear in the book, his purpose was merely to sketch out what may and may not be possible. He has even been described a a shill for the nuclear power industry. However, is there any argument that can be made that is capable of subverting the message of the above image? As the author himself says:
“I think something new may have happened between 1800 AD and 2000 AD. I’ve marked the year 1769, in which James Watt patented his steam engine.”
The increase of CO2 in the atmosphere since the Industrial Revolution has been affected by economic output and wars etc., but overall it appears to be super-exponential – a J-curve – a Hockey Stick.
Whether it be the the number of bacteria in a petri dish or number of collisions in a nuclear chain reaction, unless or until raw materials run out (now there’s an interesting thought), the growth in numbers is exponential (i.e. it doubles in a fixed period of time). In some cases, super-exponential growth can occur (i.e. whereby the doubling-time gets shorter) – which is what has happened to the rate at which humans are pumping CO2 into the atmosphere (as shown above).
Exponential curves are everywhere in Nature. This is because positive feedback loops are everywhere too. Positive feedback loops cause rate of change to accelerate; whereas negative feedback loops cause any change to be eliminated. Therefore positive feedback loops can cause exponential growth (e.g. population) or exponential decline (e.g. sea ice).
Ice melting in the Arctic Ocean
Sea ice in the Arctic has been melting for over 30 years. However, it is not just extent that is important; volume, thickness and persistence (age) are all relevant also. With the benefit of measurements of all of these parameters it has become clear that the IPCC was wrong to ignore positive feedback mechanisms: In the case of melting sea ice; any reduction in ice cover means that ice (that reflects a lot of the Sun’s energy) is replaced by water (that absorbs much more of the Sun’s energy). The warming water makes the ice melt faster. Therefore, it is hardly surprising that the disappearance of ice from the Arctic is now predicted to occur at an earlier date than was thought likely even 10 years ago. See: http://www.arctic.noaa.gov/future/sea_ice.html
So, the reason we keep finding these Hockey Stick graphs is because they are there. They are not noise; they are signal. The are not the product of an over-active imagination or statistical trickery; they are real. Nature is sending us a message; and the message is Wake Up!