Can increasing albedo of existing ship wakes reduce climate change?

• Published in: Journal of geophysical research. Atmospheres 2016-02, Vol.121 (4), p.1549-1558
• Main Authors: Crook, Julia A., Jackson, Lawrence S., Forster, Piers M.
• Format: Article
• Language: English
• Subjects: Air pollution; Albedo; Albedo (solar); Area; Asymmetry; Atmospheric precipitations; Brightening; Bubbles; Climate; Climate change; climate modeling; Climate models; Climatology; Computer simulation; Cooling; Distribution; Geoengineering; Geophysics; Global climate; Global warming; Greenhouse gases; Hemispheric laterality; Lifetime; Loads (forces); Management; Meteorology; Northern Hemisphere; Ocean-atmosphere interaction; Oceans; Precipitation; Radiation; Radiative forcing; Reduction; ship wakes; Shipping; Ships; Simulation; Skewed distributions; Solar radiation; Surface temperature; Surfactants; Temperature; Temperature effects; Temperature requirements; Tropical climate; Variability; Wakes
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2015JD024201

Solar radiation management schemes could potentially alleviate the impacts of global warming. One such scheme could be to brighten the surface of the ocean by increasing the albedo and areal extent of bubbles in the wakes of existing shipping. Here we show that ship wake bubble lifetimes would need to be extended from minutes to days, requiring the addition of surfactant, for ship wake area to be increased enough to have a significant forcing. We use a global climate model to simulate brightening the wakes of existing shipping by increasing wake albedo by 0.2 and increasing wake lifetime by ×1440. This yields a global mean radiative forcing of −0.9 ± 0.6 Wm−2 (−1.8 ± 0.9 Wm−2 in the Northern Hemisphere) and a 0.5°C reduction of global mean surface temperature with greater cooling over land and in the Northern Hemisphere, partially offsetting greenhouse gas warming. Tropical precipitation shifts southward but remains within current variability. The hemispheric forcing asymmetry of this scheme is due to the asymmetry in the distribution of existing shipping. If wake lifetime could reach ~3 months, the global mean radiative forcing could potentially reach −3 Wm−2. Increasing wake area through increasing bubble lifetime could result in a greater temperature reduction, but regional precipitation would likely deviate further from current climatology as suggested by results from our uniform ocean albedo simulation. Alternatively, additional ships specifically for the purpose of geoengineering could be used to produce a larger and more hemispherically symmetrical forcing. Key Points Surfactant would be required to increase wake area enough to reduce temperature significantly A 0.2 albedo increase and at least ×1200 lifetime increase of wakes is required Additional ships could be used to reduce temperature further and improve coverage of forcing