500 Factor
Intro
The 1000 factor is a factor calculated theoretically as the limit of possible increase of energy by humans, without suffering from ecocide or changes in weather patterns. This energy would naturally come from renewables.
This amount of power - if used by humans - still allows for all natural processes such as weather phenomena and natural life - to exist without any effect.
This effectively means that the human population on earth could be unfathomably larger, without negative effects on nature. If done effectively.
Weather is by far the largest current user of energy on Earth. About 25% of surface energy goes to rainmaking, and 5% to blowing wind (see #Energy Budget of the Earth below.
Of all life forms, Plants (not humans) are the largest users of energy. In particular - via solar energy capture with photosynthesis. Plants still use use only 1-2% of the incoming solar spectrum [1], and the earth's coverage with plants is about 30% [2]. Since only plants can use solar energy, and animals build ecosystems upon plant energy - the plant energy is the primary energy important to overall solar energy usage. Ie, animals do not use solar energy, outside of the heat - a component of weather. Bottom line - the amount of total energy required to sustain the ecosphere is under 1% of the total incoming radiation.
Both plants (under 1%) and Humans (0.01%) pale to the weather (30%) in terms of energy use. Fossil fuels don't even count here, as the entire store of fossil fuels is only a few days equivalent of solar energy (see 10000 Factor).
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Source: [3]]
Every 100k years, we go through ice age and hot age - where mean temperature of the earth fluctuates up to 7C [4] and ice coverage of earth increases to 25% of land mass (8% of total).
Here is the history of temperature over 500 million years - showing that global averages of temp ran anywhere from 50 to 95 F [5] - that is - fluctuating over 25C over all time.
Energy Budget of the Earth
From NASA - [6]
17% of surface energy radiates back, not part of weather (rain and wind).
Don't mess with evaporation - or you will have drought.
Thus, 17% is available for PV. This means that we could cover probably cover up to 17% of the earth with PV without changing weather. Nominally, this means that we can use about 1000x more energy than today, captured in the form of PV power without affecting climate. This is about 1/6 of the available 10000 Factor.