advancing the mitigation of Climate Change and Global Warming through Geoengineering education and research
For hundreds of years, human civilization has been changing the surface of the land through deforestation, desertification, and agriculture. Forests, grasslands, wetlands, and other natural ecosystems have been replaced with cropland. With the exception of the recent loss of ice sheets and glaciers, these land cover changes have led to increases in surface albedo. Albedo is the property of the surface of the Earth to reflect or absorb solar radiation (See NASA’s This World Is Black and White video below which describes the concept of albedo).
NASA’s This World Is Black and White. An example of how natural ecosystems carry out Albedo Modification. Courtesy of NASA’s Goddard Space Flight Center.
Hansen et al. (1998) estimated that surface alterations have led to a decrease in Earth’s radiation balance by 0.2 +/- 0.2 W/m2 (watts per square meter) since 1850 due to increases in albedo. They estimate that this has led to the cooling of the planet by 0.14 degrees Celsius.
Using a global croplands dataset (estimating croplands from 1700 to 1992) and a complex climate model that used 0.17 as an estimate of the average albedo of croplands, Mathews et al. (2003) estimated that changes in cropland area had reduced the Earth’s radiation balance by 0.15 W/m2 and temperature by 0.09 degrees Celsius.
Albedo Modification in Agriculture
Kaye and Quemada (2017) carried out a study of the albedo modification potential of cover crops (fava beans, clover, etc.) during the fallow season (the time period between the harvest and the seeding of a new season of crops). They estimated that cover crops could increase the albedo of agricultural areas from 0.17 to 0.21 (.30 on the high end). They also found that the use of cover crops could mitigate climate change by sequestering carbon in the soil and reducing the use of fertilizers. They estimated that cover crops could reduce carbon dioxide emissions by 116 to 135 g of CO2 per square meter per year. They concluded that the application of cover crops could potentially reduce agricultural emissions by 10%.
- Hansen, J.E., Sato, M., Lacis, A., Ruedy, R., Tegen, I. and Matthews, E., 1998. Climate forcings in the industrial era. Proceedings of the National Academy of Sciences, 95(22), pp.12753-12758.
Matthews, H.D., Weaver, A.J., Eby, M. and Meissner, K.J., 2003. Radiative forcing of climate by historical land cover change. Geophysical Research Letters, 30(2).