Which provides evidence that humans are causing an increase in the carbon dioxide concentration in the atmosphere?

Question

The net flux of carbon into the atmosphere without including the contribution from burning fossil fuels is negative.

The net flux of carbon out of the atmosphere without including the contribution from burning fossil fuels is zero.

The net flux of carbon out of the atmosphere without including the contribution from burning fossil fuels is negative.

The net flux of carbon into the atmosphere without including the contribution from burning fossil fuels is positive.

Answer 1

A. The net flux of carbon into the atmosphere without including the contribution from burning fossil fuels is negative