Euroviews. Are water cycles the missing piece of the climate crisis puzzle?

When we talk about the greenhouse effect (as opposed to global warming), we rarely talk about the fact that most of it is not caused by carbon dioxide. 

Yet, as a greenhouse gas, water vapour contributes 70% of the insulation that keeps solar energy within our atmosphere, at the right temperature for life. 

CO2’s impact is at around just 20% of that, though it is rising. One of the reasons for this skewed perception revolves around us not struggling to measure how much water vapour is around at any one time because it varies according to where you are. 

Meanwhile, we can measure CO2 everywhere, very accurately, because it’s homogenous and diffuses around the globe.

Only what we can measure can be counted. However, the most meaningful impacts may not be easily measurable. 

Warming is speeding up, 1.5C above pre-industrial levels already in some parts of the world, and many climate scientists worry something may be missing from the models. 

Could the answer lie in an inconvenient and forgotten, but critically important piece of climate science?

Water cycles are beautifully complex, with endless feedback loops, involving humans, plants, animals, soil, weather, and climate. 

Modelling them is a huge challenge most climate simulators, seeking clear outputs for policymakers, shy away from. The effect of CO2 by contrast is simple, and aesthetically boring, but easier to explain.

We all remember water cycles from geography classes. When wet air flow from the ocean is forced upwards by mountains, it condenses, forms rain, and goes back into the sea from rivers. 

This is the “big” water cycle. But in important parts of the world, like the Amazon or Congolese rainforests, the majority of rain comes from vegetation, the “small” water cycle. 

P