Answer to Question 1
ANSWER: On a sunny day, Earth's surface warms by absorbing more energy from the Sun and the atmosphere than it radiates, while at night Earth cools by radiating more energy than it absorbs from its surroundings.
Answer to Question 2
ANSWER: The main cause of global warming is thought to be the greenhouse gas CO2, whose concentration has been increasing primarily due to the burning of fossil fuels and deforestation. However, increasing concentrations of other greenhouse gases, such as methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs) have collectively been shown to have an effect approaching that of CO2. Overall, water vapor accounts for almost 60 percent of the atmospheric greenhouse effect. CO2 accounts for 26 percent, methane 7 percent, and remaining greenhouse gases 7 percent.
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