The author is a visiting professor and chair of the Kings Policy Institute at King's College London.
The discussion at COP 26 covered almost all the possible answers to the looming challenge of climate change, from small scale nuclear reactors to battery-powered aircraft, and from changes in human diets to the erection of protectionist barriers. One issue, however, seemed to be neglected, and that is the potential for serious gains in energy efficiency.
The story is complicated, but there are grounds for optimism. The transformation of the economy is just beginning and there is an opportunity for dramatic improvements.
There is a huge scope for efficiency gains. One recent study found that 54 per cent of electricity supply is lost before power reaches the consumer because of the inadequacies of the distribution network. According to a paper published by Lawrence Livermore National Laboratory, 68 per cent of the energy produced in the US is wasted.
The proportion of the UK's electricity supply fell before power reached the consumer because of inadequacies in the distribution network.
The world would be a long way to reducing emissions to an unthreatening level, if you cut out half of those losses.
A similar outcome would be achieved if every country and every sector of the economy could reach the lowest current levels of energy intensity - that is, the amount of energy used to produce each unit of output anywhere in the world. None of the gains requires new technology or scientific breakthroughs.
It is not easy to eliminate waste and move to the most efficient means of production.
The shape of the economy determines the energy use per unit of GDP at the national level. The UK seems to have a great record. Energy use is lower now than in 1965, despite a quadrupling of GDP in real terms. The shift in the economic activity from basic manufacturing to services is just the result of the shift in the mix of economic activity, not due to prudent use of resources or any government initiative.
India is moving in the opposite direction, away from agriculture and a rural economy to an ever more urbanised and industrialised base in which energy use and energy intensity inevitably rise.
Relative levels of efficiency at both national and sectoral levels are also determined by the age of the capital stock - that is, energy-consuming equipment deployed in industry, transport and in buildings - and the pace at which it turns over and must be replaced.
Each new generation of technology tends to be more efficient than the last — think of cars, buildings or washing machines.
The pace of the change can be pushed on by well-targeted regulations and standards. The quality of the capital stock is what determines the pattern of energy use until it is replaced. The time period for cars is typically 15 to 20 years. The lifespan for buildings, such as houses, can be a century or more.
Surges in energy prices can encourage energy savings. In prosperous developed societies, energy costs are a small fraction of total outgoings and the sensitivity of consumers to prices is conditioned by both the costs of switching to new and more efficient equipment and the fact that energy costs for most households and businesses are a small portion of total outgoings.
The impact on the volume of consumption tends to be very limited, as rising energy costs lead to complaints about the size of bills. We do not stop using the dishwashers and the cars we have already acquired.
These constraints and complexities expose why few governments have succeeded in implementing effective measures to reduce waste or improve efficiency.
There is reason for optimism. There is a wave of change in the technologies involved in the production, processing, distribution and consumption of energy because of the acceptance that climate change poses serious risks.
The storage technology should allow us to use much more of the capacity of wind and solar supplies, so much of which is wasted at the moment. Building standards will be driven by regulation. The application of smart grids and meters will allow us to use energy with more care. New factories will incorporate processes that use less power. This wholesale upgrading of the capital stock will amount to an industrial revolution.
Over 20 years, it is a reasonable bet to assume that the bulk of the capital stock of developed countries will be new or radically refurbished, pushed on regulations or price incentives.
The plan to phasing out of cars with internal combustion engines is just the beginning. If the net zero targets are to be met, then the facts, offices, and railway systems will have to be changed. The emerging economies will benefit from leapfrogging existing technologies.
The end result will be a reduction in the amount of energy used for each unit of output, and a reduction in overall consumption than would otherwise have been the case.
The question is whether the pace and extent of change will be enough to offset the impact of factors that will continue to drive demand and possibly cause emissions upwards - population growth and spread of prosperity.