Climate Change

25 Nov 2019 

There can no longer be any doubt that climate change is real and that global warming is already now having a harmful effect on human communities in many parts of the world.  There is also a great deal of pressure to reduce CO2 output (and hopefully methane output as well) by substituting renewable energy sources for fossil fuels and reducing overall energy use. These will, if successful, slow down and possibly arrest the harmful effects of global warming.  However, there are two much more fundamental changes that are required if there is to be any real prospect of reversing global warming.  These are:

1) reduction in the global human population;

 2) increasing the efficiency of photosynthesis by widely grown plants which would enable greatly increased consumption of CO2. 

It is worth pointing out that these two changes will, on evolutionary timescales, most probably happen anyway.  It is likely that, as global warming continues unabated,  there will be epidemics and starvation and warfare on a very large scale and that the world population will indeed decrease.  Over an evolutionary timescale, hundreds of thousands or millions of years, plants will also evolve to make use of the raised CO2 levels by having an increased efficiency of photosynthesis.  However, it would be greatly in the interests of the human population that now exists that these changes should be brought about by less catastrophic means and over a hugely shorter timescale. 

A reduction of the human population

The average family size is decreasing particularly in wealthier communities and increasing standards of living is one attractive option for reducing population growth. In recent years contraceptive implants (for example Etenogestrel) have been developed that,  given subcutaneously, can prevent pregnancy for up to five years. Making these available universally and free of charge could make a substantial further impact. Unfortunately, there would be opposition to such a move from some religious groups who continue to regard humanity as an endangered species.

Increasing the efficiency of photosynthesis

The current efficiency of photosynthesis is roughly one per cent of the energy provided by the sun to plants.  I have been told at a meeting, but cannot quote the source, that the upper theoretical limit of photosynthetic efficiency is ten per cent.  George Porter, a distinguished photochemist, pointed out many years ago in his  1995 Rajiv Gandhi memorial lecture that increasing the efficiency to five per cent would allow all the energy and food needs of the planet to be met on the acreage that is currently being planted.  Undoubtedly achieving this would not be easy.  The primary enzyme concerned, rubisco, is notoriously inefficient and it has proved difficult to change it.  However, the idea - even put forward by some distinguished scientists - that evolution would have provided greater efficiency, if feasible, is incorrect.  The efficiency of photosynthesis must balance the amount of carbon dioxide available and highly efficient photosynthesis in a time of low CO2 levels would simply drive the CO2 levels even lower and cause the plants to die.  Therefore the need for this highly efficient photosynthetic plant is only temporary and once the CO2 levels have been brought down again it would need to revert to the previous less efficient photosynthetic mechanism. 

There should be a real Manhattan project-scale effort put into the project of raising the efficiency of photosynthesis as this would on its own rapidly solve the climate problem.  It is therefore particularly depressing that the Green movement still continues campaign against the genetic modification of plants for reasons that are difficult to fathom.  One hopes that wider counsels and more common sense can be brought to bear.