I believe the biosphere is fragile, because over time all of the pollution us humans have made; If its from air pulloution, acid rain or even water pollution. the toxic acids over time have made the biosphere and the ozon layer weaker and more thin. which causes the biosphere to become weaker.
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The Sun is the primary source of energy for Earth's climate system is the first of seven Essential Principles of Climate Sciences.
Principle 1 sets the stage for understanding Earth's climate system and energy balances.
The Sun warms the planet, drives the hydrologic cycle, and makes life on Earth possible.