By Roger Diamond

I recently read there are proposals afoot that use a geoengineering approach to deal with climate change. Geoengineering involves making changes to the Earth’s surface and basic physical makeup on a scale that can influence large-scale systems such as weather, river flows and so on.

Humans have been geoengineering for centuries, chopping down forests, clearing land for farming, damming large rivers and in so doing capturing natural flows of energy or commodities and using these to build our complex society. However, in almost all cases these geoengineering projects have triggered a cascade of unintended environmental responses, many devastating. One example is the building of the High Aswan Dam on the Nile River, which then deprived the Nile Delta of the nutrient-laden silt (brought by annual floods) that had kept agriculture thriving in Egypt for millennia. The loss of nutrients was tackled with the widespread application of inorganic fertilisers, which then entered the Delta’s waterways and nearby Mediterranean Sea. This caused algal blooms and fish kills, which unfortunately have not kept the package tourists away!

My recent reading is of proposals by Steven Chu, the US energy secretary, to raise the Earth’s albedo by painting surfaces in light colours. Albedo is the reflectivity of a surface, where zero is total absorption (a flat ocean is near zero) and 1.0 is total reflection (snow and ice being 0.7 to 0.8). Painting cars, roads, roofs and walls white to increase the albedo, and in so doing reflect energy back into space is a very simple tactic. And there is nothing wrong with a simple solution to a simple problem. But here’s the rub — the problem, climate change, is ever so slightly a complex one. And hence this approach qualifies as simplistic. In other words, the complexity of the solution does not match the complexity of the problem.

In general, humans have been raising the Earth’s albedo for centuries, by replacing forests and shrublands with croplands and urban areas. For example, the 1 000km long and 400km wide wheatbelt of Western Australia has replaced an open eucalypt woodland with an annual grass crop of wheat that leaves the soil bare for almost eight months of the year, reflecting much of the sun’s energy straight back into space. One of the few areas in the world where the albedo has decreased substantially is Johannesburg, where grassland has been replaced by well-treed suburbs, although as the suburbs densify and roads are widened, the trees are falling foul of rooftops and tarmac and the albedo is going back up again.

So if we have been raising the Earth’s albedo for centuries, should we not be trying to reduce it. Would that extra energy stored not help drive the Earth’s weather machine? What would the slow release of that heat overnight do to influence night breezes? And if a city was cooler during the day, would that not slow the flow of cooler, fresh air from the countryside that keeps the city air breathable? These are questions that need to be answered before the truckloads of white paint are sprayed over your green lawn.

From an energy perspective, what would the greenhouse gas contributions be to lighten the roads and rooftops of our immense metropolises, versus the supposed gains from this brighter world. A lighter coloured house and car will need more heating when winter comes, meaning more greenhouse gases. Sunglass sales would soar — sure! Any other predictions I’d leave at the casino called The Future of Mankind. Is this not childlike thinking applied to something so complex nobody dares pretend they understand? What happened to logic and realism?

The philosophy behind my post this week is that complexity is deserving of some real thought. This is not a particularly clever concept on my part, yet why do people consistently want to believe in the simplistic approach, wishing somehow that the easy way will be the best way. In some cases, the solution may be simple to articulate, but this still does not mean it will be simple to apply. “Save energy” is easy to say but very hard to do. “Stop climate change — paint your roof white!” Really? You be the judge.

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