Road Tax, Global Warming and the Greenhouse Effect

Tax – Something that is at the heart of everything we do in Britain. And the government is considering plans to raise the tax on the highest CO₂ emission cars (e.g. 4x4s and sports cars) from £220 per year to around £1800 per year on the grounds that they contribute most to the damaging CO₂ effects.

Let’s just look at 2 families who own the same 4×4 car. One uses the car rarely and their children do to school on the bus. They have a normal car they use most of the time. The other family relies on the 4×4 almost exclusively. However, with this proposed tax, both families would pay the same £1800 tax per year.

The government also has another proposal call “pay per mile” taxation which requires a chip to be installed in every car and the mileage would then be monitored via a GPS-equivalent system and you get sent the bill at the end of the month. Different roads would attract different fees ranging from approx £0.25 in the country to £1.25 in the city. Again, the argument is CO₂ emissions, although more discussion has been aired around improving Britain’s traffic infrastructure as a result of this plan.

However, at a simple level, we already pay tax on fuel. It accounts for approximately 65% of the price of a litre. To most people, introducing additional elaborate schemes, or draconian taxation might seem a little stupid since we already have a mechanism through which we can introduce equal taxation – simply increase the tax on fuel. Cars which use more fuel (the 4×4 and the sports car) would pay more tax as a result. Also, the more you drive the car the more tax you pay. So, the family who use the 4×4 rarely only pay tax when they are using it, and this would be lower than the family who used it all the time. Higher fuel consumption cars also mean that the owner would pay higher tax for the same distance covered as a more fuel efficient and less polluting car. We wouldn’t need to spend millions of the tax payers money introducing new technology – see track and trace – or penalise the affluent via a heavy-handed scheme.

Too simple? Maybe. But there are other forces at work since the cover story that the reason behind it is due to CO₂ emissions increasing and causing global warming isn’t exactly true. Plausible, yes, but not right. Let’s examine what global warming is all about.

The following is based on the lengthy, and sometimes technical, article on The Greenhouse Effect & Global Warming. It is also a follow-on from our earlier piece on Global Warming; Natural or not?.

What is the greenhouse effect?

Simply, the greenhouse effect is the process by which energy that is radiated from the sun is absorbed by, and, subsequently slowly released by the Earth’s atmosphere. Energy is not trapped as some people suggest, merely slowed down from bouncing straight back into space. This greenhouse, or dampening effect is what keeps the Earth’s temperature (allowing for fluctuatations and latitudinal variances) mild both day and night.

The greenhouse effect is basically a good thing as it makes living on the planet more bearable.

What is ‘global warming’?

While the greenhouse effect is the mecahnism itself, “global warming” really refers to the how much the greenhouse affect warms or cools the planet. Populist overuse and abuse has largely rendered the term “global warming” meaningless – what is really meant is “enhanced greenhouse”. Since Arrhenius began speculating a century ago about low CO₂ levels and ice ages the hypothesis of temperature relation to atmospheric carbon dioxide has drifted in and out of scientific focus. At present it is the focus of a great deal of attention. “Enhanced greenhouse” simply means the additional delay in energy loss to space induced by the tiny percentage of carbon dioxide and other greenhouse gases released by humans before those gases are removed from the atmosphere by breakdown and/or biological activity.

What about ‘climate change’ then?

That’s a different thing altogether. Change is what the climate is always doing and is the result of our planet’s orbital eccentricities, axial wobble, solar brightness variation, cosmic ray flux, etc.. There are also plausible terrestrial drivers of climate change too, including super volcanic events and tectonic movement, but these are not in the realm of anthropogenic (manmade) effects and so we won’t looking at them here.

The global mean temperature over which there has been so much obsession is only one part of climate – for example, how wet or dry the climate happens to be is probably of far greater significance than a simple mean temperature – in fact, it’s not even clear that a global mean temperature is a particularly useful metric. However, it is the cause of great angst at present so it will remain the focus of this article for that reason alone.

But, greenhouse is all about carbon dioxide, right?

Not so. The most important players on the greenhouse stage are water vapour and clouds. Carbon dioxide has been increased to about 0.038% of the atmosphere (possibly from about 0.028% pre-Industrial Revolution) while water in its various forms ranges from 0% to 4% of the atmosphere and its properties vary by what form it is in and even at what altitude it is found in the atmosphere. In simple terms, however, the bulk of Earth’s greenhouse effect is due to water vapor by virtue of its abundance. Water accounts for about 90% of the Earth’s greenhouse effect – perhaps 70% is due to water vapor and about 20% due to clouds (mostly water droplets), some estimates put water as high as 95% of Earth’s total greenhouse effect. The remaining portion comes from carbon dioxide, nitrous oxide, methane, ozone and miscellaneous other “minor greenhouse gases.” As an example of the relative importance of water it should be noted that changes in the relative humidity on the order of 1.3-4% are equivalent to the effect of doubling CO₂.

But carbon dioxide is pollution, isn’t it?

No again. Carbon dioxide is an essential trace gas that underpins the bulk of the global food web. Estimates vary, but somewhere around 15% seems to be the common number cited for the increase in global food crop yields due to aerial fertilization with increased carbon dioxide since 1950. This increase has both helped avoid a Malthusian disaster and preserved or returned enormous tracts of marginal land as wildlife habitat that would otherwise have had to be put under the plough in an attempt to feed the growing global population. Commercial growers deliberately generate CO₂ and increase its levels in agricultural greenhouses to between 700ppmv and 1,000ppmv to increase productivity and improve the water efficiency of food crops far beyond those in the somewhat carbon-starved open atmosphere. CO₂ feeds the forests, grows more usable lumber in timber lots meaning there is less pressure to cut old growth or push into “natural” wildlife habitat, makes plants more water efficient helping to beat back the encroaching deserts in Africa and Asia and generally increases bio-productivity. If it’s “pollution,” then it’s pollution the natural world exploits extremely well and to great profit. Doesn’t sound too bad to me.

So, how are humans contributing to global warming?

Humans account for approximately 3.4% of all CO₂ emitted to the atmosphere each year. Approximately half of that seems to “disappear” into absorption sinks. In fact, since the industrial revolution, humans account for approximately only 2.5% of the total greenhouse effect.

But that’s misleading as well. If it were such a simple accumulation, we could easily determine exactly how much Earth would warm from a doubling of atmospheric CO₂ (not much incidentally) and certainly that would be an improvement over the silly figures we currently read about.

Theoretically, in a dry atmosphere, carbon dioxide could absorb about three times more energy than it actually does, as could clouds in the absence of all other greenhouse gases. The temperature effect of atmospheric carbon dioxide is actually logarithmic (that means there is a diminishing response as you keep adding more).

The science bit: If we consider the warming effect of the pre-Industrial Revolution atmospheric carbon dioxide (about 280 parts per million by volume or ppmv) as 1, then the first half of that heating was delivered by about 20ppmv (0.002% of atmosphere) while the second half required an additional 260ppmv (0.026%). To double the pre-Industrial Revolution warming from CO₂ alone would require about 90,000ppmv (9%) but we’d never see it – CO₂ becomes toxic at around 6,000ppmv (0.6%, although humans have absolutely no prospect of achieving such concentrations).

So, although we’re pumping out a lot of crap (and CO₂) we’re not having that much of an impact.

So why is the planet warming so catastrophically if it’s not CO₂ then?

Who says it is warming catastrophically? Humans have only been trying to measure the temperature fairly consistently since about 1880, during which time we think the world may have warmed by about +0.6 °C ± 0.2 °C. As we’ve already pointed out, the estimate of warming is less than the error margin on our ability to take the Earth’s temperature, generally given as 14 °C ± 0.7 °C for the average 1961-1990 while the National Climatic Data Center (NCDC) suggest 13.9 °C for their average 1880-2004. We are pretty sure it was cold before the 1880 commencement of record and we would probably not handle the situation too well if such conditions returned but there has been no demonstrable catastrophic warming while people have been trying to measure the planet’s temperature. If we have really been measuring a warming episode as we think we have, then setting new records for “hottest ever in recorded history” should happen just about every year – although half a degree over a century is hardly something to write home about – so there’s really nothing exciting about scoring the highest number when looking at such a short history.

So, humans aren’t affecting the planet or its temperature?

Whoa! We didn’t say that either. Whether or not man-made emissions really affect global mean temperature is hard to quantify, but human endeavours do have significant local effects. The heat island effect (where average temperatures are higher in urban centres) or the local effect of increased water vapour from large scale irrigation schemes are good examples of this. There is also land use change which can be variable depending on latitude – replacing dark forest with wheat fields might significantly affect local albedo and cooling one region while denying shade in a more heavily irradiated region might cause ground heating through increased absorption. There are many effects in a hugely complex system, some will be negative, some positive and all represent change, although that is neither good nor bad in and of itself.

It is true that humans affect the region of their activities. However, any enhanced greenhouse derived from human activity subsequently creating a current or imminent catastrophe is not.

So why tax something that’s not actually making a quantifiable difference?

I think that’s a letter you should write to your local MP!