I am astounded at the responses that I receive from politicians regarding the current repeal of parts of the clean energy package of legislation. They continually ask for an explanation of the correlation between CO2 and climate change as if there is no relation, and it is all a great big hoax.

So let’s look at the science in straightforward terms that I hope will assist you with a better understanding, and just maybe help us all realise why the repealing of a mechanism that is successfully reducing emissions by pricing them, and scrapping the other parts of the clean energy package of legislation is absurd policy.

The scientific understanding of CO2 as a greenhouse gas (GHG) was first discovered and accepted in the late 19th century. It is a simple fact of physics.

Energy from the sun arrives as high frequency electromagnetic radiation (mostly in the visible light frequencies and above). It passes through our atmosphere with almost no interaction with atmospheric molecules. That radiation which is not reflected back to space by white surfaces (almost entirely clouds and clean ice sheets) is absorbed by the land and ocean surfaces, which consequently increase in temperature.

As you will no doubt recall from high school, all warm bodies radiate energy in the infrared region of the electromagnetic spectrum. Thus earth (both the land and ocean surfaces) is sending energy back out through the atmosphere as infrared radiation, and it is here where interaction does occur.

GHG molecules (of which CO2, water vapour, and methane are the most significant for this discussion) absorb that infrared radiation. This causes the atoms of the molecules to "excite" with electrons jumping out to higher orbits around their atomic nuclei. The molecule thus vibrates more than before, and additional molecular vibration is the measure of heat in any substance. Thus you can see immediately that additional GHGs in the atmosphere will cause atmospheric warming as infrared radiation is absorbed by these GHG molecules.

Now comes the important part. All "excited" atoms will return to their natural state, and in doing so the atoms release a pulse of infrared radiation which radiates out equally in all directions - half the radiation goes upwards, and if not interrupted by other GHG molecules, out to space. The other half goes back down to the earth's surface and is reabsorbed by land and ocean.

It is this radiative forcing that is warming the planet. Increasing the concentration of GHGs in the atmosphere will force more energy back to earth further warming the planet. Of course, with a constant/stable percentage of GHGs in the atmosphere, a stable temperature is achieved where energy arriving and leaving the earth is in balance.

The burning of fossil fuels is releasing CO2 (and other GHGs) into the atmosphere increasing the concentration from pre-industrial levels of some 280 parts per million (ppm) to more than 400 ppm, a massive increase.

Now there are additional positive feedbacks exacerbating the problem. Simple physics state that a warmer atmosphere will hold more water vapour. More water vapour (a GHG) will increase the radiative forcing as described above, causing further warming. More water held in the atmosphere will add to the severity of wet weather events.

The next positive feedback is easier to see. As the land, the oceans, and the atmosphere warm all over the earth, ice melts and we lose reflective surfaces. With less incoming radiative energy being reflected back to space, more incoming energy is absorbed by the planet, causing even further warming.

The third and potentially more serious feedback relates to how global warming will cause the release of massive amounts of trapped, and thus currently harmless methane, a short lived GHG which is however some 28 times more effective in radiative forcing. These releases are already coming from warming of tundras and the oceans where methane clathrates exist (methane trapped within an H2O lattice under very cold and/or high pressure situations). The amount of methane trapped in these clathrates is massive, and if released into the atmosphere, it would greatly increase warming and spell the extinction of life as we know it.

The influence of the warming of the globe on climate relates to the energy level within the whole system. The greater the amount of energy within the global system, the greater the intensity and frequency of atmospheric activity (ie: weather events). To appreciate the extent of this energy being added to our global system, it is easy to calculate and draw analogies. The above radiative forcing and the feedbacks are adding energy to the planet's systems at the rate of just over four Hiroshima atom bombs every second or, to be more dramatic, 400,000 Hiroshima bombs per day. That is extremely scary!

The evidence of change in our global climate (the long term average of all weather events) is already well understood and measurable. Climate modelling, with all its uncertainties and faults, is improving and calibrates well with the measured changes that have already occurred. The predictions for the future without immediate action to stop GHG emissions are indeed horrific, with the extinction of several species not out of the question.

While this is a very complex area of research, it is thorough, factual, and accepted by every National Academy of Science on the planet. The falsehoods, cherry picking of data, and out of context quotes, that perpetuate doubt, are only coming from - or as a result of - funding by the fossil fuel industry and related vested interests. Why should the highly subsidised fossil fuel burning industries be the only industries on the planet allowed to release their wastes for free into our environment?

We had an Emissions Trading Scheme (ETS) that was already law, albeit with a fixed price (that “great big toxic TAX”). It worked, and it, and the other measures of the Clean Energy Package (RET, CEFC, ARENA, Climate Authority), are all very necessary to help ensure a future for my grandchildren, and yours.

  • A wonderful piece Prof. Hood. Filed, retweeted etc. Indeed this physics was postulated in the 1820s by Jean Baptiste Fourier.

  • A very good explanation. I am giving a talk on climate change and have trouble explaining this fundamental concept in under a minute and in a way that people can grasp.

    • Bob
      Be careful how you explain radiative forcing. It's logarithmically declining and less than half that currently claimed by the IPCC. All of the IPCC models don't reflect the observed temperature rise, nor do they explain the pause in temperature rise for almost two decades.

  • I will never understand that very educated people like the contributor to this article does not understand the complexity of climate variations caused by other than CO2. The man-made CO2 components in the atmosphere has very little or nothing to-do with global temperature variations. There was no global temperature increase for the past 18 years and talking about weather events then just study the records of the river Thames in London over hundreds of years to see how the climate changed from the river being frozen for month to times where it was warm enough to go for a swim in the middle of winter with man not contributing to CO2 in the atmosphere.
    It is immoral to keep halve the global population in poverty because of a hypostatical assumption with no prove that CO2 is actually causing climate change. A 97% (IPCC) consensus is not science; science is what the science is. Solar and wind power generation is in my opinion useless expensive path back into the Stone Age of power generation.
    Until we get something better that fossil like Thorium, utilising carbon fuels with the today available modern technologies is the best way to progress. Inexpensive energy is the key factor to a modern civilisation with all the benefits that it brings.

    • The link to this article came to me by email with this delightful ad hom "Please forward to all your AGW and climate change denying mates”
      What a joke when they can’t even get weather right.
      In June with 90 per cent certainty…The global El Niño weather phenomenon, whose impacts cause global famines, floods – and even wars – now has a 90% chance of striking this year…from the ECMWF, considered one the most reliable of the 15 or so prediction centres around the world.

      In August…But the atmosphere has ”largely failed to respond” to sea surface temperatures and scientists’ confidence in an El Nino developing in 2014 has eased, says the Australian Bureau of Meteorology, whose climate models now put the chances of this happening to 50%

  • But, but the temperatures are in no way correlated to an increase in CO2! In fact the temperatures have paused and there are some indicators that they are decreasing. It is that simple and there is no fancy way to make "man" the culprit. Also, the amount of CO2 as measured at Mauna Loa in Hawaii show that its level is back to 1992 numbers.

    • Lawrence, that is exactly to the point. More and more scientist do now voicing their conclusions that does not conform to the non-scientific body called IPCC.

  • It is widely known that CO2 itself only accounts for about 1/2 % of the greenhouse gas effects on Earth. Meanwhile, 97% of the greenhouse gas effect is Water Vapor. The IPCC and all the cloned models running all over the planet make the assumption that a little bit of warming from CO2 will be magnified by causing Water Vapor to increase dramatically, and this water vapor will rise. Measurements of higher altitude water vapor show it is actually going down along with CO2 going up. Then, there is the unique property of water vapor where it turns in to water, meaning Clouds. With 62% to 70% of the Earth's suface covered by clouds at any one time, an increase in water vapor makes for more clouds, cooling the Earth. Feedback is negative.

  • Here we go again. There is no physics when it comes to global warming. The models assume a HUGE positive forcing from CO2 to water vapor, the dominate greenhouse gas in our atmosphere. Without this HUGE positive forcing, CAGW becomes a non-issue. PHYSICS? PHYSICS? Sorry, but the positive forcing to water vapor has NOTHING to do with PHYSICS. It is something that is only supported by computer models and to this date THERE IS NO EXACT SOLUTION FOR THE POSITIVE FORCING TO WATER VAPOR THE IPCC CLAIMS. FACT!