Metaphors help us to communicate. In the literal sense of the word, they carry us over the gap between abstract concepts and experience. As the physicist Niels Bohr reminded us, atoms can only be described by language as in poetry. Think of phrases like big bang, black hole, and warped time. In finance, we have bulls and bears, rocket scientists, and leverage. In climate science, we talk of greenhouse gases and Net Zero. The latter phrase is fast becoming the defining metaphor of our era. The term is ubiquitous - nearly 500 cities, over 1000 businesses, and around 50 global investors are committed to it.

Metaphors capture some important aspects of an issue and overlook others. Failure to remember this can easily lead to wooden-headedness, not wisdom. Moreover, words change meaning subtly over time. The example I love in finance is “speculation” – the Roman specula was a watchtower, designed to warn of risk, not to take it!  So, care is essential when interpreting any metaphor, and Net Zero is no different. Even experts can be caught out, as reported recently in the Financial Times, with Mark Carney’s “stumble” over carbon accounting.

At a basic level, Net Zero is not specific about whether we are talking about greenhouse-gas neutrality (embracing CO₂, methane, and a set of other gases) or carbon neutrality (just CO₂). This can cause confusion. The UK’s Net Zero target is set in terms of climate neutrality (by 2050), whereas China’s is set in terms of carbon neutrality (by 2060). The Paris Accord is drafted in terms of climate neutrality (sometime during the second half of this century, with 2070 the most often discussed date). That implies the UK is some 20 years ahead of the treaty, whereas China’s commitment technically remains unspecified.

Our environmental challenges go well beyond anything calculated by a simple thermometer. We need to rediscover nature and develop a new set of metaphors about our place in it.

In fairy-tale style, Net Zero infers that, by 2050, the UK has done its bit for the global climate and we can all live happily ever after. This fails to distinguish between carbon production and carbon consumption. If we simply export our carbon-intensive industries to emerging markets, global CO₂ emissions will be unchanged or conceivably increase to the extent that they are moved to more carbon-intensive centres.

Even if we clear up definitions and measuring rods, other difficulties lurk in the background. In all likelihood, the UK needs to be Net Negative well before 2050, if global climate ambitions are to be met. The longer we comfort ourselves with the Net Zero fable, the faster we shall have to put the brakes on in future. That smacks of environmental procrastination.

At a deeper level, the metaphor of the atmosphere as a machine, to be run at a specific average temperature with easy levers to pull and tweak, misrepresents the majesty and variability of nature. Our environmental challenges go well beyond anything calculated by a simple thermometer. We need to rediscover nature and develop a new set of metaphors about our place in it.

In the past, we used to describe our experience of the world in terms of organic metaphors– Lao Tzu’s river and Yahweh’s tree of life spring to mind. They were built around an appreciation of the greatness and beauty of what we have inherited. They allude to reinvigorating change today, not static future targets. They suggest diligent stewardship, enhancing our environment from season to season, and generation to generation. This is the only vision that can yield real sustainability. To achieve it, we need a lot more than a distant Net Zero; we need a Zest for Nature right now.