Friends ask me how I am able to hike so fast in the mountains. My secret is not to wear a lot of heavy clothing. Even when it is 40°F, I will wear just one layer. However, I choose black for that layer, knowing that black will absorb more heat from the Sun than any other color.

Color also plays a significant role in determining Earth's surface temperature. New studies establish just how important color is to understanding the climate change debate.

The Black Carbon–Global Warming Link
The climate change debate is almost entirely focused on atmospheric carbon dioxide. However, as I wrote in Weathering Climate Change, the increase in atmospheric carbon dioxide is just one of several human factors contributing to the global warming observed over the past 70 years. 1 Other important greenhouse gases include methane, nitrous oxides, chlorofluorocarbons, and hydrofluorocarbons.

Because it is not a greenhouse gas, black carbon is a frequently overlooked contributor to global warming. Black carbon indirectly influences the global mean temperature by darkening otherwise highly reflective surfaces.

Snow and ice reflect sunlight at a 50 to 70 percent efficiency rate. When black carbon soot falls on snow and ice, it can reduce sunlight reflectivity down to just 5 to 20 percent. This reduction causes the snow and ice to absorb more heat from the Sun, which increases the atmospheric temperature above the snow and ice. When the reduction melts away the snow and ice, it exposes the ground below where the reflectivity of sunlight ranges from 5 to 30 percent.

For many years, climatologists have sought to understand why parts of the Canadian and Siberian Arctic are warming at rates about five times greater than the global average. Climatologists now know that black carbon—aerosols and soot—is  the major contributor.2 Where does all this black carbon come from?

Arctic Black Carbon Sources
Climatologists once thought that black carbon in the Arctic came from the heating of homes and commercial buildings in the Arctic, gas flaring on Arctic oil fields, and from Arctic wildfires.3 However, the total contribution from these indigenous sources came up woefully short. Consequently, a team of three atmospheric chemists analyzed surface black carbon measurements and aerosol optical properties from six Arctic data collection stations. 4

The three atmospheric chemists used Lagrangian trajectory models to calculate the movement of air parcels delivering black carbon aerosols from receptor sites. Their calculations yielded the back trajectories of the black carbon air parcels. The team showed that for five of the six Arctic surface monitoring sites the dominant transport pathway was the movement of black carbon particulates emitted in India, Bangladesh, southeastern Asia, and eastern China over Central Asia into the high Arctic. The delivery of black carbon soot emissions in the Indo-Gangetic plain reached the high Arctic in as little as seven days.

Arctic Warming Danger
In a previous Today's New Reason to Believe article, I explained the grave danger the warming of the Arctic poses for human civilization. Already, the majority of the Arctic's summer sea ice mass has melted away and the beginning of winter sea ice mass loss has been observed. I explained how any significant loss of winter sea ice mass would bring on the next ice age and with it global climate instability. Clearly, preserving the Arctic winter sea ice mass serves the best interests of humans in all the world's nations.

Mitigating Arctic Warming
The source of the black carbon soot emissions in southern and eastern Asia is not difficult to identify. It is the burning of coal. In the short term, it is not feasible for these nations to transfer energy production from coal to hydro, wind, solar, and nuclear. However, they could transfer their energy production from coal to natural gas.

Natural gas energy production yields no black carbon emissions. Furthermore, compared to electricity generation from burning coal, the burning of natural gas releases only half the amount of greenhouse gases into the atmosphere.

Currently, both India and China are building new coal power plants. Meanwhile, North America is sitting on huge natural gas reserves, reserves they could make available to these Asian nations. The substitution of natural gas for coal would substantially reduce the world's carbon footprint and eliminate most of the world's black carbon emissions while economically viable noncarbon sources of energy—such as thorium nuclear power generation, hydro, geothermal, and more efficient solar power generation—are developed and scaled up. Humans possess the knowledge and capability to mitigate Arctic warming, and with cooperation on an international scale we can help ensure a better, economically viable future for all.

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Endnotes

1. Hugh Ross, Weathering Climate Change (Covina, CA: RTB Press, 2020), 23–38.
2. S. J. Doherty et al., "Light-Absorbing Impurities in Arctic Snow," Atmospheric Chemistry and Physics 10, no. 23 (December 9, 2010): 11647–80, doi:10.5194/acp-10-11647-2010; Mark C. Serreze and Roger G. Barry, "Processes and Impacts of Arctic Amplification: A Research Synthesis," Global and Planetary Change 77, issue 1–2 (May 2011): 85–96, doi:10.1016/gloplacha.2011.03.004; M. Sand et al., "Response of Arctic Temperature to Changes in Emissions of Short-Lived Climate Forcers," Nature Climate Change 6, no. 3 (March 2016): 286–89, doi:10.1038/nclimate2880.
3. Patrik Winiger et al., "Siberian Arctic Carbon Sources Constrained by Model and Observation," Proceedings of the National Academy of Sciences, USA 114, no. 7 (February 14, 2017): E1054–E1061, doi:10.1073/pnas.1613401114; P. Winiger et al., "Source Apportionment of Circum-Arctic Atmospheric Black Carbon from Isotopes and Modeling," Science Advances 5, no. 2 (February 13, 2019): eaau8052, doi:10.1126/sciadv.asu8052.
4. J. Backman, L. Schmeisser, and E. Asmi, "Asian Emissions Explain Much of the Arctic Black Carbon Events," Geophysical Research Letters 48, no. 5 (March 15, 2021): id. e2020GL091913, doi:10.1029/2020GL091913.