You might not have come across the word Apologetics before.

It refers to the practice of defending a position or point of view against critics or opponents. It’s often used in a religious, or occasionally philosophical or political context . . . but I’m using it here in a scientific sense.

A climate change sense, to be specific.

As I’ve written before, I share the view that man-made climate change is real and occurring as a consequence of our use of fossil fuels, and also share the concerns of numerous organisations and individuals that this will have a potentially devastating effect on people everywhere, especially the world’s poorest and most vulnerable. Responding to rising sea levels, repairing after more extreme weather events, ensuring sufficient water and food supplies and managing the resulting mass migrations that are likely to occur all look set to become incredible challenges for our warming world.

What we should do about this,  is a legitimate subject for debate. Less fossil fuels ? More renewables ? More nuclear ? More tree planting ? Less deforestation ? Lower energy agriculture ? More efficient agriculture ? Less meat ? GM crops ? Geo-engineering ? Adaptation ? Tax ? Subsidies ?

It makes sense to me to do what we reasonably can to quickly decarbonise our economies, and that in the interests of fairness, most of the cost of this should be borne by the richest economies and people in the world (ie: us). This approach is broadly known as contraction and convergence. This is my opinion – everyone else will have their own.

We’re all entitled to our own opinions, but there is seemingly ever more disagreement about the facts presented in the media.

We now have a debate between climate proponents and sceptics. Hawks and doves. Doom-mongers and denialists !

You might be familiar with some of the various sceptical arguments which frequently get cited:

‘CO2 is not a pollutant – only a harmless plant food‘

‘There is no evidence the climate is warming – it may even be cooling‘

‘The Earth’s climate changes naturally, and it’s nothing to do with us‘

The first one really just comes down to the definition of pollutant and harmless – though CO2 is clearly not totally harmless (that our bodies exhale it is a clue), but it’s toxicity isn’t really the issue here.

The second is just a misrepresentation of the facts. There is ample evidence that the world has a strong warming trend – regardless of weather it’s snowing outside Boris Johnson’s window.

The third is more interesting, because, of course it’s  half true.

The planet’s climate has indeed always changed, long before we had anything to do with it, and the extent of this change has been quite remarkable.

While most of us talk about ice ages, Geologists talk about glacials – periods when there is year round ice cover at one or both poles (such as now), and inter-glacials – periods when the world is totally ice free year round. We are currently coming out of an ice age, which peaked around 22,000 years ago, with widespread ice cover across much of Europe and North America, as far south as Germany, the UK and Ireland.

Going further back there have been numerous warm and cold periods in the Earth’s history, including a period around 400-600 million years ago, when the entire planet is thought to have frozen !

These glacial periods come and go, partly driven by the presence of large land masses at one or both of the planetary poles (via plate tectonics), partly by orbital variation around the sun, and partly (most scientists believe mostly) by variation in atmospheric carbon dioxide levels.

So given all this natural variation – do the sceptics have a point ?

It’s a question of timescale.

What’s different now is that  carbon dioxide levels have been increasing at incredibly rapid rate in recent years. Measurements of ice cores from Antarctica show that atmospheric carbon dioxide levels varied between 180 and 210 ppm during recent glacials, and 280-300 ppm during recent interglacials.

But, the current concentration of carbon dioxide in the atmosphere is 391 ppm (2012), and is still rising.

We are quickly moving into atmospheric chemistry territory outside the normal range of the recent historical past – at least the last 800,000 years, and possibly much much longer. With global emissions continuing to increase year on year, ever higher levels are now effectively ‘locked-in’, no doubt triggering various tipping points and feedback mechanisms on the way.

Climate change is part of the natural state of the earth – but there seems little doubt our global use of fossil fuels is moving us quickly to somewhere new, outside the variation of the recent past, and that coming to terms with a much warmer world is going to be a significant challenge for us.

What we should do about it is going to have to be another post entirely . . . in the meantime think carefully before buying a house near sea level.

Photo by  Alastair Rae, via Wikicommons

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