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What goes up must come down: why global rainfall is increasing

by Mark Nicholson


Urban misery in Nairobi in 2024

Kenya, Brazil, Afghanistan, even the United Arab Emirates, are just four countries to have suffered serious flooding over the last few months. Over 300 were killed by floods in Kenya, more than 55 of whom perished a few kilometres from my home when a dam broke in the middle of the night, swept away a village and buried sleeping residents in mud. Our President announced that 10th May, 2024 would be a national holiday in Kenya to commemorate the dead but it might have been more appropriate to have made the following day (a Saturday) a normal working day and got everyone to start clearing up the mess pro bono. We have far too many national holidays already in a country that is so highly indebted.


Politicians are now inclined to blame all such events on ‘climate-change’, a compound noun used so often these days that inevitably people are becoming bored of the term. They also blamed El Niño, which is a seasonal change in sea temperature in the eastern Pacific. But they were incapable of determining which the culprit was. It is easy to absolve yourself if you can blame outsiders. No one in Kenya suggested the dam burst owing to inferior construction. No one in Nairobi admitted that the urban floods were the result of the absence of road drains or the lack of any drainage in the slums, or the fact that accumulated rubbish had blocked rivers and ditches, or that all the wetlands have been drained and replaced by high-rise buildings. Nairobi was actually built on a seasonal swamp 120 years ago and is now a burgeoning metropolis of five million, totally ill-prepared for heavier rainfall.


African politicians also point out that it is the ‘West’ (plus China and India), who are responsible for most of the global carbon dioxide (CO2) emissions. While this is true, Africa is inevitably catching up. The continent’s population is rising rapidly from 228m in 1950 to 1,500 million today.  People need housing: construction means more cement and more concrete, the largest source of CO2 after fossil fuels. Concomitantly, standards of living are rising fast. Like everyone else, the growing middle class expects refrigerators, washing machines, cars and air conditioning, all of which add greenhouse gases and heat to the atmosphere.


Climate scientists can be so obsessed by carbon dioxide emissions that they are inclined to ignore the heat production of combustion engines[1]. Nairobi’s traffic jams are notorious; the urban heat production from half a million vehicles averaging 20 kph adds to the pollution.


[1] I have a similar problem with jet engines. Their CO2 emissions are easy to calculate but people forget that nearly 10,000 jets are in the air at any one time with 2+ jet engines blasting out hot air at 760 degrees C into a thin atmosphere at 11,000m at -50 degrees C.  Let no one try and tell me that that combustion heat has no effect on atmospheric temperatures


So why is rainfall increasing globally? Water, which in its gaseous phase (vapour, mist, cloud, steam etc.) is by far the most abundant greenhouse gas, responsible for at least half of the greenhouse effect on the planet. Without it, the planet would be 15 degrees C colder and largely uninhabitable. But as temperatures rise, so does water in the atmosphere. 


The European Union’s Copernicus Climate Service recently released its data showing that mean ocean temperatures were 0.3 C degrees warmer every day of the year last year, exceeding all previous records.


That increase sounds negligible but it is actually alarming and I believe, irreversible. The main effects will be:

1.     Increased evaporation from the ocean

2.     More powerful cyclones/ hurricanes

3.     Faster melting of ice, leading to sea-level rise and storm surges

4.     A breakdown in oceanic currents

5.     A reduction in marine biodiversity (e.g. coral bleaching)

Evaporation increases above freezing point as water gets warmer (although other factors such as wind speed, salinity, air pressure, surface area of the water body etc. also affect the rate of evaporation). But the atmosphere is now also warmer; so more vapour can be held before it eventually condenses, falling as precipitation (usually rain). Basic school physics tells us that a rise of one degree Celsius in the atmosphere increases the vapour-holding capacity of the air by 7 percent. So who can be surprised when rainfall and floods are getting worse worldwide? Since the global air temperature is now almost 1.5 degrees C above pre-industrial levels (the maximum 2030 goal, now unreachable in the opinion of many), this means that rainfall is likely to increase by 10 percent. And rainfall is never uniformly spread.


There is an old adage: ‘When all is said and done, there is a lot more said than done’. Nowhere is this truer than when it comes to the climate crisis.  Sadly, no one will take much notice until a super hurricane and storm surge occurs in a rich nation that puts Hurricane Katrina in the shade. As there is no sign of carbon emissions falling, we must prepare for the worst. But do we? Politicians everywhere pay lip service to the dangers of climate-change but they also know that the world economy is still dependent on fossil fuels. Mitigation and adaptation are the names of the game, rather than any real attempt to reduce carbon dioxide levels, which is not happening despite the annual hand-wringing at the UN Climate Change Conferences (COP29 is to be held this year in Baku, Azerbaijan, another oil state).


Humanity seems to be divided four ways on climate-change. The largest group are the uneducated or unaware worldwide who do not understand the issue but who, so far, are most vulnerable to the consequences.


The second group are the ‘anthropogenic climate-change deniers’. While they may at least admit to climate-change, they do not accept it is caused by human activity. They are, thankfully, insignificant in both numbers and influence but their voices are loud on social media accusing those at the other end of the scale of being alarmists. Donald Trump is one but I believe he will have to change his tune if he is re-elected.


Then there are what I term the ‘shruggers’, who are mainly in the developed countries. This group knows that climate-change and global warming are getting worse but they say there is little any individual can do about it. This is the most irresponsible group owing to their insouciance. They enjoy a high standard of living. They continue to fly and drive regularly with little or no thought to their carbon emissions, and without doing much to offset their carbon footprint[2].


[2] The internet will be responsible for over 7 percent of global CO2 emissions by 2025. Air conditioning contributes another 4 percent.

The last group includes the climate scientists and oceanographers (indeed almost all other scientists) along with a few politicians and some major names (Al Gore, King Charles, David Attenborough, etc). They believe that the threat to human existence is genuinely existential (an otherwise much overused term). Since Nairobi is the headquarters of the UN Environment Programme (UNEP), I tend to meet many more of the latter group: most of this group reckon we are way beyond the tipping point and that catastrophe is both inevitable and irreversible.


I am firmly in the latter camp and I nail my colours to the mast. Yes, I still fly, but no more than two international flights a year. I nurture the 150,000 trees I have planted over 25 years and I measure their carbon sequestration, which increases exponentially as they grow. And note it is not about planting trees; it is about raising them successfully. The world is full of tree-planting projects, which here in Kenya fail miserably because no one looks after them.  

I have said before that we ignore slow-onset catastrophes. Droughts and famines take time to develop yet kill as many or more than Rwandan genocides or tsunamis. But now we have floods as well. We continue to ignore climate change at our peril. It is affecting our lives and will do so with increasing severity. I once wrote “We ain’t seen nothing yet”: my view has yet to change.


What goes up, must come down

(including Caramelo, stranded on a rooftop in Canoas in Brazil)


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