Re: Is there a connection between artificial light and gloabal warming?

If I understand you right, you're asking whether the heat and light given off by artificial lights heats up the Earth's surface by a significant amount.

Of course, lighting isn't the only artificial source of heat: we use energy to heat and cool buildings, to power cars and other vehicles, and to manufacture goods and materials. Almost all of that energy is eventually released as heat to the environment. So let's generalize your question: Does the heat released by artificial energy sources of all kinds heat up the Earth's surface by a significant amount?

The total energy consumption of humanity is roughly 10 terawatts (10 million million watts) (Fogg, 1995, p. 67). This includes all energy sources (nuclear, fossil fuels, renewable energy), used for all purposes (electricity, heating, transportation, manufacturing). Almost all of this is eventually released as heat to the environment.

The total amount of sunlight absorbed by the Earth is about 50,000 terawatts, or 5,000 times the energy used by humanity.

So you see, the amount of heat released by humanity is extremely small compared to the amount of heat released by the absorbtion of sunlight. But that doesn't quite answer the question: we want to know how artificial sources compare to global warming, which is small compared to total solar absorbtion.

The greenhouse effect reduces the atmosphere's ability to let heat at the surface escape to space. It works by trapping some of the heat released from the Earth's surface, and re-radiating it back down toward the surface again. This extra heat warms the Earth's surface. This is a natural process, but by releasing carbon dioxide and other gases into the atmosphere, we are increasing it. Estimates of the amount are not precise, but our best guess (IPCC WG1 Assessment, 2001, p. 37) is that the human contribution to the greenhouse effect supplies an extra 300 terawatts to the Earth's surface.

To recap:

So you see, the heat directly released by humans is about 30 times smaller than the extra heating caused by our contribution to the greenhouse effect, and 5,000 times smaller than the heating caused by the sun.

The answer to your question is no: the heat directly released by human activities is trivial compared to the greenhouse effect.

This does not mean that you should run your lights all night without worrying about heating up the planet. The lights themselves don't produce a significant amount of heat, but when you use more electricity, your city's electrical power plant burns more fuel and releases more carbon dioxide, and the carbon dioxide greenhouse effect does cause a measurable warming of the planet.

Sources

Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel of Climate Change. Cambridge University Press, 2001. (Everyone on the planet should read this report's "Summary for Policymakers".)

Fogg, Martyn J. Terraforming: Engineering Planetary Environments. Society of Automotive Engineers, 1995. (A rather far-out topic, but with tons of good information on planetology and climatology.)