Back to the Future entry. I wanted to share the notion that our technological civilization is in a state of transition. This question of a civilization's technological future comes up in regard to alien civilizations. So far, one of the few safe speculations from scientist are the energy consumption needs of a developing civilization.

Of this reflections by physicist and media pundit Michio Kaku, I wish to note a couple of things, first the total energy consumption we have versus the output (rather downpour) solar energy provides to our planet; second the need for a civilization to develop within a certain time-frame if it is to survive statistically occurring natural catastrophes, which include meteors and the death of the sun, but also--and this is a comment I make to the article but others have mentioned (notably physicist Carl Sagan) our misuse of technology.
At the end is the link to the complete article.

Physics of Type I, II, and III Civilizations

Specifically, we can rank civilizations by their energy consumption, using the following principles:
1) The laws of thermodynamics. Even an advanced civilization is bound by the laws of thermodynamics, especially the Second Law, and can hence be ranked by the energy at their disposal.
2) The laws of stable matter. Baryonic matter (e.g. based on protons and neutrons) tends to clump into three large groupings: planets, stars and galaxies. (This is a well-defined by product of stellar and galactic evolution, thermonuclear fusion, etc.) Thus, their energy will also be based on three distinct types, and this places upper limits on their rate of energy consumption.
3) The laws of planetary evolution. Any advanced civilization must grow in energy consumption faster than the frequency of life-threatening catastrophes (e.g. meteor impacts, ice ages, supernovas, etc.). If they grow any slower, they are doomed to extinction. This places mathematical lower limits on the rate of growth of these civilizations.
In a seminal paper published in 1964 in the Journal of Soviet Astronomy, Russian astrophysicist Nicolai Kardashev theorized that advanced civilizations must therefore be grouped according to three types: Type I, II, and III, which have mastered planetary, stellar and galactic forms of energy, respectively. He calculated that the energy consumption of these three types of civilization would be separated by a factor of many billions. But how long will it take to reach Type II and III status?

Shorter than most realize.

Berkeley astronomer Don Goldsmith reminds us that the earth receives about one billionth of the suns energy, and that humans utilize about one millionth of that. So we consume about one million billionth of the suns total energy. At present, our entire planetary energy production is about 10 billion billion ergs per second. But our energy growth is rising exponentially, and hence we can calculate how long it will take to rise to Type II or III status.

http://mkaku.org/home/articles/the-physics-of-extraterrestrial-civilizations/