# How much sunlight would I need to block to stop / reverse climate change?

Using this handy dandy graph, I estimate that by the time climate change forces a response we will need to reverse 2° Celsius of heating.

The method for temperature control is described in here - a sunlight blocking satellite.

What percent of the sunlight destined for Earth needs to be reflected/redirected?

The question above presupposes 1%. But where I live there is a 14° variance in temperature which happens over 8 hours (1.75° per hour). The satellite would block light 24 hours per day so by my calculations we could cool the Earth 2°C in 5 days.

1% cooling x 1.75° x 24 hours x 5 days = 2.1°

I assume my math is wrong. But assuming we want to cool the earth over 20 years, what percent of sunlight actually needs to be reflected?

• You should just edit out your math parts, they aren't really valid science. – kingledion Jan 18 '18 at 1:38
• Heating is not measured in degrees, but in Watts.... you want to change the energy flows (Joules per second) – L.Dutch Jan 18 '18 at 5:54

According to NASA's energy budget, the Earth is absorbing 0.6 W/m$^2$, average worldwide over a whole year. This is the energy addition that is causing global warming. The Earth receives from the sun 340.4 W/m$^2$, average over the planet and year. Divide the two, and you see that we need to reduce incoming radiation by 0.2%.