Sep 5, 2022
Cooling the planet drop by drop
This summer has definitely brought home the message that water is the most pressing climate issue we currently face. Rising temperatures and extreme drought have send wild fires across the globe while floodings are threatening the subcontinent. But while water management is one of greatest challenges, it may also hold the key to our salvation when it comes to climate change.
Water plays an important role in keeping the planet cool and thereby mitigating global warming. However, climate models and measurements are almost exclusively focussed on carbon. The lack of attention for water in climate change mitigation means we are inadequate responding to the opportunity that it provides. Before I elaborate why better integrating a water perspective matters, let me briefly explain the how the water cycle interacts with climate change.
How water cools the planet
Climate change is speeding up the rate of evaporation worldwide as global temperature increase.[1] More evaporation is causing more precipitation, on average. So why are we having problems with drought? First of all, the increase in rain is unevenly distributed. Although we have more total rain, it does not rain more in all places, and also it comes down in more extreme forms, which means a lot of it is simply running off and winding up in the ocean via the big rivers (and potentially causing a lot of damage on the way).
Is the increased rate of evaporation due to climate change good or bad? The answer is both. It really depends how we respond to it.
More evaporation means more clouds, clouds cool the planet which means they act against temperature increase. Evaporation and cloud formation could be considered one of our earth systems coping mechanisms that help keep out atmosphere stable. The problem starts when evaporation gathers over large areas and comes down in massive down-pores. The answer to this problem is creating microclimates.
Microclimates: think global act local
Micro-climates occur naturally but they can easily be designed according to the same principles. How it works is that soil and plants retain, evaporate and transpire water continuously. Within the bigger water cycle these act as sub-water cycles, called micro-climates.
It all starts with rain: slowing it down, catching, storing and infiltrating it back into the ground. You see 99% of our fresh water supplies are already in the ground. When it is in the ground it does not evaporate as quickly anymore and it’s accessible when you need it. In the ground it keeps plants and trees and soil alive, so that together they can regulate the temperature and moisture levels above ground.
‘Sponge cities’ are a great example of man-made microclimates. This concept emerged in China and it consists of retaining any water where it falls on rooftops and in green areas. There’s also a Sponge city area in Berlin and it is a popular area to live in nowadays (with real estate prices to show for it).
Cumulative effect
Unlike carbon, water is easy to catch. More than technology it therefore requires a shift in mindset. For a long time, rain has been seen as a nuisance and problem. So our systems, especially in urban areas, are geared towards channelling rain away as fast as possible. Sponge cities show local benefits of the opposite strategy. At a larger scale there are also advantages.
Recent research has shown that the micro-climate provided by forests protects plants, insects and other species from extinction by buffering the effects of warming. Microclimates also protect soil health. Healthy soil is an important precondition for carbon retention and sequestration. Therefore, there are positive synergies between protecting and creating microclimates and carbon reduction efforts. At the meso level (watershed/region), promising results have been found as to the impact of microclimates on weather, notably in reducing extreme seasonal heat.
At a global level there are cumulative effects of evaporative cooling through greening. But attempts to quantify the global interaction between atmospheric changes and ecosystem transpiration remain experimental and show that it is complex. It makes sense, as there is infinite variation in the types of ground cover and their cooling capacity. The process of cooling is therefore much more dynamic than carbon sequestration.
Better policies and decisions
This matters because we take prediction by the IPCC at face value, but the truth is that the science underpinning them is under constant development. For instance, it was only recently discovered that the cooling effect of clouds is underestimated in models presently used by the IPCC.
Retaining water on land can help us slow and even reverse many of the effects of climate change. Right now, water management is mainly considered as a climate adaptation strategy and its role in mitigation is poorly understood even by the IPCC.
The lack or insufficient mention of water in climate debates and models means that measures that only reduce carbon emissions but neglect adverse effects on the water cycle, are overvalued while those solutions that have synergistic outcomes are undervalued. For instance, biofuel produced from monoculture crops has some benefits in terms of reducing the use of fossil fuel but costs a lot of water to grow and competes with natural ecosystems. On the other hand, using urban green areas for water buffering offers synergistic benefits. Introducing a water perspective into climate debates will lead to better decisions and outcomes at all levels.
Local action, citizen engagement
In order for water management and blue green solutions to be implemented at scale, we need the attention of our leaders. This is why a global movement of water keepers and protectors is emerging all over the globe. This movement is being led by indigenous leaders who have a strong tradition in protecting their ancestral lands and water rights. But they are not just calling on leaders, they are calling on citizens to. Because luckily, water offers plenty of opportunity for decentralised action at a community level.
The great thing about rain is it falls everywhere and it’s easy to catch. So ever roof, meadow, garden and sidewalk offers an opportunity to create a microclimate. We can enhance soil on our land, so that it can retain more water and plant more trees and bushes to keep it from washing away. We can dig a pond or a simple hole in the ground to retain rain longer. We can lay down a green roof on our house and place a water tank in a dark corner of the terrace. We can get together with our community and create communal rain gardens.
We need citizen engagement and community action as much as we need better decisions when it comes to water management. Because while a lot has been said in the past ten years about stepping up our efforts to reduce climate change, water actually presents a way to be more effective, given limited means.
If there is one thing I’ve learned from working and living with water, it is that you should never underestimate her power. Just like water wears down any rock over time, it can cool down the planet. I think ones we start to embrace that opportunity and start working in alliance with water we will find many solutions to other problems on the way.
Zairah Khan is the founder of BlueO2, BlueO2 is piloting community based urban water management in The Netherlands
[1] Accelerated by 2~4% per degree Celsius since 1960 according to a study by the Chinese Academy of Sciences / ETH Zurich in 2020 Improved Estimates of Changes in Upper Ocean Salinity and the Hydrological Cycle in: Journal of Climate Volume 33 Issue 23 (2020) (ametsoc.org)
