Fighting counterinformation - the supposed water vapour effect

Sometimes you just come across the weirdest and most pathetic arguments to support the idea that global warming does not exist, or that it is no big deal, or that it is not necessary to do anything about it, or that it is not human caused. In fact, the internet is bursting with such claims, very often coming from the same people, who apparently do not mind contradicting themselves with their own arguments.

Surprisingly, or perhaps not, many people buy into some of these arguments and in fact spread them as the gospel truth among friends and acquaintances.

So, I've decided to add another aim to this blog, namely, to counter some of the counterinformation that crowds the internet, and in the process, hopefully, give some simple arguments that people can use to convince others that this or other anti-environmental myth being spread around is wrong, or even a purposeful lie.

I'm starting by talking about water vapour, or steam.

Some campaigners argue that global warming cannot be caused by humans because the main responsible for the greenhouse effect is, by far, water vapour, and that since only 1% of vapour is human generated, then global warming is not caused by Humans.


Okay, there are a couple of true things there, as is usually the case. It is a common trick to suggest a starting point to an argument which is correct, to make credible a certain conclusion, which is reached by shadier reasoning. After all, the best lies are the ones with a basis of truth.
It is true that water vapour is responsible for most of the greenhouse effect and it is true that almost all of the water vapour comes from natural sources, for example evaporation of water from sea, lakes, and rivers, breathing by animals and plants, etc.

ALL the rest is a lie.

First mistake

To start with, the greenhouse effect is one thing. Climate change or global warming is another.

The greenhouse effect is, simply put, the atmosphere retaining the sun's energy in the form of heat, allowing us a comfortable temperature as opposed to the -200 degrees of space.
Water vapour is responsible for most, but not all of this effect.

Global warming, on the other hand, is an increase of the greenhouse effect, i.e., the atmosphere stores more of the sun's energy than before.
What this means is that, whereas water vapour is responsible for most of the greenhouse effect, it is not the main driver for its increase, i.e., it is not the main driver of global warming.

Therefore, whether Humans generate a small or a large proportion of the globe's water vapour is really not that relevant for the problem

Second mistake

We have no control over the emissions of water vapour (remember we only generate about 1% of it). Fortunately for us, even that extra 1% of vapour has little scope to increase the greenhouse effect significantly because water vapour does not stay in the atmosphere for very long. It condensates into water fairly rapidly, which means that its global warming effect is very limited in time.

But that is completely different for the other greenhouse gases, like CO2, methane, nitrous oxide and others which can warm up the atmosphere for decades or even centuries, and which are to a great extent the result of human activities.
The fact that the concentration of these gases has multiplied throughout our industrialisation, has led to an increase of the warming effect by these gases. Even if vapour stays the same, the global result will still be an increase of temperatures

Let's put this into a numerical example to make it clearer.
Imagine CO2, methane, and nitrous oxide are responsible for 10% of the greenhouse effect (not the real proportion but easier to work with). So, if the greenhouse effect makes our current temperature 200 degrees higher than the absolute zero temperature that exists in open space, then, 20 of these degrees will be due to these three gases.
Let's say that the concentration of these gases in the atmosphere doubles and we ignore all of the side effects, we might assume that our temperature will go up 20 degrees. Instead of summers with 25° C we might have to deal with 45°.

Even if these three gases are only responsible for 5% of the greenhouse effect, they will increase the temperature 10°.

And importantly, they will be responsible for 100% of the increase. Which means, we are responsible for it since we are the ones pumping more of the stuff into the atmosphere.
And because they stay in the atmosphere for very long, the effect will last decades or centuries, even without taking in feedbacks and tipping points which might be triggered.

So, it is really pointless to say water vapour is the main greenhouse gas so there's nothing we can do. It is the extra drop that makes the glass flow over. It doesn't matter it this drop happens to be water, wine, whisky, beer or milk. It will still flow over.

Mistake Three

Humans might only be responsible for 1% of the water vapour emissions, but this is not the whole story. This refers to water vapour directly generated by humans.
It 'forgets' that the higher the temperatures, the faster water evaporates. The more greenhouse gases we put out there, and the warmer they make the atmosphere, the more water vapour will be created, feeding back into the system with a vengeance.
In fact, recent studies by NASA indicate that the increased evaporation might go as far as to double the global warming effect in comparison to the warming that the other gases would generate on their own.

What about the Albedo effect?

This is a related issue to the third mistake. Albedo is the reflection of sunlight back into space. The higher the albedo, the less energy stays in the atmosphere warming it up. Areas covered with lighter colours, such as in places covered in ice, salt or light coloured sand, reflect a higher proportion of the sun's light than other areas (which is an important consideration now the north pole ice cap is going).

Clouds, which should increase in number if there is more water vapour in the atmosphere, have the same effect, reflecting sunlight and helping to keep Earth cooler. On the other hand, they also reflect energy back to Earth, avoiding it escaping back into space.

The overall result is still unclear, being one of the many difficulties in creating accurate environmental models. Some people have in fact suggested creating steam clouds to work as a sunshade as a way of fighting global warming.

Unfortunately, however, so far studies have indicated that more clouds tend to trap slightly more energy than the one they reflect back to space, so I'm afraid we should not really count on clouds to save us.