Which of the following is a true statement?

• When heat from the sun reaches Earth, some is reflected back into space, and some is trapped by Earth's atmosphere

• When heat from the sun reaches Earth, all of it is trapped by Earth's atmosphere

• When heat from the sun reaches Earth, all of it is reflected back into space

Greenhouse gases are essential to life

• True

• False

Atmospheric CO₂ has increased by ____% since the Industrial Revolution

Since 1970, the sun's output of energy has ______, while the temperature has ______.

• decreased;increased

• increased;decreased

• decreased;decreased

• increased;increased

Only the bottom layers of the atmosphere are becoming warmer, indicating that the sun is....

• the cause of global warming

• not the cause of global warming

Since 1870, humans have put out about ______ gigatons of CO₂ into the atmosphere, and about 40% has stayed there.

After analyzing the gas content from ancient ice cores, scientists have discovered that our atmospheric ___ content is the highest it's been in almost a million years

• CO₂

• CH₄

• N₂O

• SO₂

Fossil fuels come mainly from old plants. Compared to the atmosphere, plants have higher amounts of carbon-12 and lower amounts of carbon-13. Scientists have found that the more fossil fuels we burn, the more _______ we see in the atmosphere

• carbon-12

• carbon-13

• carbon-14

• carbon-15

Volcanoes emit ~0.2 gigatons of CO₂ a year, while humans emit about ______ gigatons of CO₂ a year.

• 0.4

• 4

• 50

• 35

Deforestation ______ the amount of CO₂ in the atmosphere

• increases

• decreases

• does not affect