Descriptions matter. As the seriousness of climate change becomes more evident, the way it is depicted will influence our response. Here are a few examples, with some potential repercussions.

The hockey stick curve

The image of a hockey stick lying on its back is often used to describe the atmospheric concentration of carbon dioxide over the last thousand years. The curved end pointing upwards at the right correlates very well with consumption of fossil fuels since the Industrial Revolution and with changes in global temperature. It is an image that has been extensively employed to refute climate deniers – how can they not see the obvious impact that human activity is having?

Certainly the strength of the relationship has helpfully convinced most people that global heating is man-made. But there is a downside: it also suggests to many that it’s entirely about CO2. A recent video by Extinction Rebellion (https://youtu.be/w3yRv1B8Y-w) is a case in point; in the video, one of the presenters claims that temperature levels were essentially benign before the 19th century because CO2 levels were flat and that if we curb CO2 emissions then climate change can be halted.

This is something of a misinterpretation. Before the 19th century, human beings were emitting greenhouse gases – mainly through agriculture – but at a level that the rest of the natural world could counter, through absorption by oceans and land. Since the IR, greenhouse gas emissions have increasingly exceeded the capacity of this natural response. But that’s all emissions, which include water vapour, methane, nitrous oxide, ozone, chlorofluorocarbons and hydrofluorocarbons (few of which I know anything about). Up until roughly the middle of the 20th century, GHG emissions from agriculture still exceeded human CO2 emissions, but the latter had broken the camel’s back, as it were.

Though CO2 is the main GHG, it’s wrong to conclude that only CO2 matters. Out of roughly 50 billion tonnes of GHG emitted annually, around 20 billion tonnes are other GHG, i.e. not CO2. We can influence global heating by reducing these other GHG – indeed, for us as individuals, our diet is probably the single biggest factor. Equally, temperatures could still rise alarmingly if we control CO2 but allow the other GHG to increase.

In the final years of the apartheid regime in South Africa, Barclays Banks was singled out for criticism in the media due to its financial involvement. Many (most?) other banks that escaped censure were also involved; they just weren’t as big as Barclays. CO2 is the Barclays of the GHG, so to speak, but all of them need to be tackled.

The budget

The budget is a metaphor used to shock governments into action. There is, according to this idea, a limited amount of GHG that we can emit before it is too late. Indicatively, we have about 500 billion tonnes left in the budget, which we will use up in around 10 years at the current rate of emissions. If we go over budget, according to this logic, then we are f****d.

Maybe shock is an effective tactic, but again there is a downside: if we declare ourselves bankrupt, we essentially give up. Yet atmospheric temperatures are not predestined to rise indefinitely. In the most optimistic scenarios of the IPCC’s latest report (August 2021), global temperatures start to fall, albeit slowly, post 2050. In later decades and centuries, the fall could be as exponential as the increase is today.

The earth is dynamic and nothing is permanent. Today’s emissions may be absorbed tomorrow: whilst CO2 itself potentially lasts for centuries, it does not follow that it has to reside in the atmosphere. Oceans, woods, or human carbon capture technology might suck it out. So let’s not despair, or ever declare ourselves bankrupt.

The overcrowded airport

Here is a better metaphor, used by the climate scientist David Mackay. Exasperated by journalists claiming that human emissions were a small fraction of those from the oceans and biosphere, Mackay compared the situation to a busy airport, one set up to deal with 1000 passengers an hour. If arrivals increase, say, to 1050 per hour, then the airport will rapidly become dysfunctional, even though the extra 50 are few compared to the original 1000.

This metaphor helpfully gets across the idea of a natural balance and our disruption of the balance. It also conveys a sense of the world’s dynamism. The metaphor could be extended – dynamic ‘feedback’ could be for the better or the worse. In the airport, fights might break out amongst frustrated travellers; in the world, rising temperatures might release methane from the oceans and permafrost. Bad news potentially. Or the airport might recruit more staff at short notice; natural mechanisms might adapt to become greener and better able to absorb GHG. Good news potentially.

This is not well understood. But in the knowledge at least that nothing will last forever, and with the prospect that our great-grandchildren might just about witness an improving climate, it is worth doing what we can and never giving up.