What would earth’s temperature be without the greenhouse effect?

the global temperature would be minus 19 degrees celsius.
the greenhouse effect does not affect global temperatures; it only has local effect.
without the greenhouse effect, the earth’s temperature would hover just above freezing the entire year.
without the greenhouse effect, the earth’s temperature would reach 26.6 degrees celsius (80 degrees fahrenheit).
without the greenhouse effect, the north and south poles would disappear.

The global temperature would be minus 19 degrees Celsius.

Explanation:

Without the Greenhouse effect, the Earth temperature would be around 0 degrees Fahrenheit, that is, around -19 degrees Celsius. The greenhouse effect helps the Earth retain some of the radiation from the atmosphere, so, without this effect, it would be very cold.

question

which are human systems?

the amazon rain forest

the appalachian trail

the george washington bridge

the himalayas

the hoover dam

the north american free trade agreement