First, absorption helps people by preventing high-energy radiation from reaching the surface which limits our exposure to harmful radiation. The atmosphere absorbs most of the radiation from the ultraviolet region through the X-ray region. The second way in which absorption helps the earth is as a heat source for it.
*lean times (ahead). Fig. a future period of lowered income or revenue; a future period when there will be shortages of goods and suffering. (*Typically: be ~; cause ~; have ~; mean ~ .) The economy is going sour which means lean times ahead.
Lean is an expression given to any noun which is pure, trustworthy and generally not full of shit. Derived from the term to describe a non-fatty piece of steak, lean can be extended to describe a person for example. That guy is lean bro, meaning he is not full of shit and he is a cool guy.