Why are many scientists concerned about humans adding large amounts of carbon to the atmosphere by burning fossil fuels (combustion)?

Question

A.
The atmosphere has a limited capacity to absorb and recycle carbon naturally.
B.
When carbon is released into the atmosphere it floats into outer space, and is lost forever.
C.
If the atmosphere gains too much carbon, birds won't be able to fly.
D.
Carbon is a poisonous chemical, which can kill plants.

Answer 1

The correct answer is:

A. The atmosphere has a limited capacity to absorb and recycle carbon naturally.

Many scientists are concerned that the large amounts of carbon being added to the atmosphere through the burning of fossil fuels could exceed the natural processes that absorb and recycle carbon, leading to increased concentrations of greenhouse gases and resulting in climate change and other environmental impacts.