Tuesday, December 08, 2009
Is Climate Change Man-Made?
Here is the evidence that there is such a component:
1 CO2 has increased from 280 to 380 parts per million since the Industrial Revolution began clearing forests and burning fossil carbon. About half of our releases have been reabsorbed by forests and oceans. The other half is still in the air.
Isotope studies and tree analyses confirm that plant derived carbon in the air has increased- which points back to ourselves, since we burn plants, both ancient and modern.
So we have definitely put carbon that was taken out of the air in the Carboniferous Period 360 million years ago back into the air.
My back of an envelope calculations suggest that each year we release into the atmosphere carbon that took about 60,000 years to take out. Peak Oil sites web gives a figure closer to an annual release of carbon that took between 250,000 - 1.5 million years to form. Their figure is probably nearer the truth
So there is no reasonable doubt whatsoever that we are responsible for the increase in carbon dioxide.
2 It is an observed fact that carbon dioxide is a greenhouse gas (GHG).
(Watch an experiment)
3 The "greenhouse effect" is necessary to keep the planet in a mode that sustains human life at the population levels of 6 billion.
We rely on being in the Goldilocks temperature band - not too hot, not too cold. We must be absolutely sure that we are not disturbing this equilibrium.
4 Calculations of "Radiative Forcing" for the various inputs into the planet show that the CO2 (and other GHGs) that we emit are the only explanation for the recent observed warming of the planet.
If we take greenhouse gases out of the equation, and rely on the other variables - core heat, clouds, water vapour, aerosols, volcanoes and solar variation - we cannot explain the recent changes in global temperature.
Click to enlarge.The red line is temperature observations, grey line is the model. Top left shows natural forcings, top right CO2 forcings, and below, the best match, with natural and CO2 combined.
5 All reasonable persons who look at the data with an open mind are convinced by the case that the climate scientists have put.
We observe temperature increases, GHG (greenhouse gas) increases are the only way we can explain the temperature differences, we produced the extra GHG, the consequences of continuing to do so are extremely serious, therefore we must decarbonise the economy.
6 The losers from decarbonisation - oil and mining multinationals, and free market ideologues - have fought a rearguard action, and have challenged the scientists on every point. Each and every one of their challenges have been met.
Some will never be convinced, because they are free market fundamentalists, and feel threatened by the guided market and cooperative economic measure that are necessary as a response to global warming. This idealism is the driver for the ceaseless, importunate criticism, and the current drive attacks in East Anglia and New Zealand. And possibly illegal activity in Canada.
This opposition has held up the decarbonisation for nearly two decades, but thankfully the world's leaders are now taking the first steps towards decarbonisation.
Another clear summary here.
Climate change FAQs.