Discriminating against tar sands in the name of curbing carbon emissions makes sense, but is also a distraction from a bigger question about how much fossil fuel humankind can safely burn.
A calculation of the carbon dioxide emissions embedded in global crude oil reserves shows that burning these would pump out more CO2 than many scientists and world leaders have deemed safe to the climate, after including additional emissions from deforestation and burning coal and gas.
Simply maintaining present levels of crude oil consumption over the next several decades would have the same effect, implying a present carbon over-spend.
But many environmentalists have demonised a particular type of crude oil from tar sands in Canada and Venezuela, which involves high energy costs to pump oil from a thick, sandy mixture.
Burning gasoline derived from tar sands emits 10-25 per cent more CO2 than conventional crude, but focusing on tar sands neglects the other 91 per cent of world crude reserves, according to BP energy statistics, not to mention all other fossil fuels.
A panel of European Union experts votes on Thursday on whether to support a carbon label on gasoline refined from tar sand crude oil, mirroring similar efforts by Californian legislators under the US state's low carbon fuel standard.
If approved, the EU label would make refiners think twice about using tar sands crude, given that they already face targets to cut CO2 emissions embedded in their fuel products.
A label is clearly a good idea, improving transparency over the environmental implications of our energy choices.
But a more important, and politically more difficult, step is to address coherently all the fossil fuels which the world's economy depends on - which implies either preparing for more sea level rise, erratic rains and heatwaves, or writing down the assets of the world's biggest energy companies.
A useful framing discussion for the environmental impact of fossil fuels is a letter published in the journal Nature three years ago.
The authors calculated that humankind could safely emit a cumulative 1,440 billion tonnes of CO2 from 2000-2050 to have a 50 per cent chance of world surface temperatures rising this century by no more than two degrees Celsius, compared with pre-industrial levels.
The two degrees threshold is a target derived more politically than scientifically: governments have formally referred to it as a safety limit at successive UN climate summits.
Some experts say that two degrees warming or more will lead to the eventual collapse of the Greenland icesheet over centuries, raising sea levels by seven metres. Observations support more dangerous heatwaves, volatile rainfall and sea level rise with higher, global average temperatures.
It is widely acknowledged that the target is barely achievable, and that at present the world is on track for more than three degrees average surface warming by the end of the century.
In the last decade, cumulative (and still rising) CO2 emissions from burning fossil fuels and net land use change including deforestation were about 337 billion tonnes, according to BP and Global Carbon Project estimates.
That leaves 1,100 billion tonnes CO2 of the estimated available budget left over the next four decades.
In other words, annual emissions at 2010 rates (36.5 billion tonnes CO2 from land use change and fossil fuels) would consume the remaining budget by 2040, a decade early.
Viewing the role of crude oil, consumption in 2010 was 87 million barrels per day, according to BP energy statistics.
That's equivalent to nearly 14 billion tonnes of CO2 emissions annually (calculated using a U.S. Environmental Protection Agency conversion of 0.43 tonnes of CO2 emissions for an average barrel of crude, accounting for emissions only from burning, not producing, the oil).
If maintained through 2050 (actually predicted to rise in the medium-term), such road fuel emissions would consume half the calculated available CO2 budget.
That would require a cut in present annual CO2 pollution from burning coal and gas (by about a third from 20 billion tonnes in 2010), implying that some power plants would have to be closed and burgeoning shale gas discoveries left unexploited.
A similar view is obtained by calculating the CO2 emissions from simply burning all of the (conservatively) estimated proven crude oil reserves, including tar sands, at 1,526 billion barrels.
The conclusion is that the European Commission and Californian efforts are very worthwhile, taking a first step to measuring and so limiting CO2 emissions from road fuel.
But a franker discussion about plans for all crude oil and other fossil fuels is needed, given that the balance sheets of the world economy and of energy companies presently assume the environmental cost of burning these at almost zero, even in Europe which has a carbon price, but at near all-time lows.
If EU member state experts approved the tar sands measure by a majority on Thursday, and it were subsequently approved by the European Parliament (as expected), the label would be adopted as an amendment of an existing law, the Fuel Quality Directive.
A stalemate is more likely where it is neither approved nor voted down, meaning a compromise would be voted on by EU environment ministers within three months, again before scrutiny by Parliament.
A compromise may be around the level of extra CO2 emissions attributed to gasoline from tar sand crude: the oil lobby estimates this at about 11 per cent more than average crude, some academics at 15-20 per cent more, and the European Commission at 22 per cent.
This story was originally published by Reuters. Reproduced with permission.