Could Greening the Sahara With Solar Panels Dry Out the Amazon?
Dark Panels Would Rewrite the Desert Heat Budget
Picture solar farms sprawling across the Sahara on a scale never attempted. Because photovoltaic panels are far darker than the desert's pale sand, they would soak up more sunlight and change how heat moves between the land and the atmosphere, according to an Earth-system modeling study recently highlighted in the press. The warmed surface stirs air circulation, draws in more rain, and encourages vegetation, which darkens the ground further and reinforces the warming, wetter conditions.
A Hotter, Wetter, Greener Sahara in the Model
A Northward Shift of the Tropical Rain Belt
The pivotal mechanism is a northward shift of the Intertropical Convergence Zone, the band of rising air near the equator that governs tropical rainfall. Northern Hemisphere warming alters meridional heat transport and drags this rain belt north. Moisture is redistributed: the Sahel and Sahara gain rain while vast areas of Central America, northern South America, and the tropical western Atlantic lose it, about 10% less in S20 and about 30% less in S50. The long-distance linkage travels through atmospheric teleconnections.
Drought in the Amazon, Melting Ice in the Arctic
The modeled knock-on effects are strikingly specific: drought and forest degradation in the Amazon, a rise in global surface temperature with amplified Arctic warming and further sea-ice loss from increased poleward heat transport, a northward expansion of Northern Hemisphere deciduous forests, dampened El Nino-Southern Oscillation and Atlantic Nino variability, and livelier tropical cyclone activity. Proxy evidence from the Green Sahara wet period some 6,000 years ago appears consistent with the simulations. The coverage is careful to note these are modeled outcomes, not certainties, and the hypothetical build-out is enormous, spanning more than 1 million square kilometers.
Smaller Real Farms Already Show Local Effects
Siting the Energy Transition Means Reading the Climate Fine Print
[Discussion] If a giant solar farm in your country's desert could make rainfall scarcer somewhere far away, would you still back it, and whose welfare should count most when the side effects cross borders?
