With investment, the world could move to 100% renewable energy sources relatively quickly. The implications at this stage, however, would be disastrous - energy supplies for most countries would be severely limited, intermittent, and far more expensive.

The same applies to other ambitions for establishing genuine sustainability, in aerospace and other forms of transport, in manufacturing and other industries.

There are no short cuts. For the good principles of the Government’s Net Zero 2050 legislation and many of the United Nations Sustainable Development Goals to become a reality there need to be hard-nosed decisions based on a fine-grained understanding of the consequences of introducing sustainable methods and technologies.

Goals include affordable and clean energy (“by 2030, increase substantially the share of renewable energy in the global energy mix”), upgrading industry (“greater adoption of clean and environmentally sound technologies and industrial processes”) and improving city living (“paying special attention to air quality and municipal and other waste management”).

In other words, there needs to be a managed and responsible transition - making use of known technologies (like carbon capture storage when it comes to energy production) while sustainable solutions are developed to a fully workable stage. For there to be genuinely green transport and green consumption, there has to be close attention to the full picture: the carbon footprint of the manufacturing processes involved, the use of scarce materials. Water can be recycled and reused, but needs to be done in ways that involve little or no energy cost. We need agriculture to be more productive while at the same time protecting and improving the quality of soils.