Natural causes of climate change
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Question
Define the global energy balance.
Answer
The balance between incoming solar energy and energy radiated back to space; it sets Earth's temperature.
Question
Name two natural causes that can WARM the climate.
Answer
Higher **solar output** (sunspot cycle) and **orbital (Milankovitch) cycles**.
Question
Name a natural cause that COOLS the climate.
Answer
A large **volcanic eruption** -> sulfate aerosols -> **global dimming**.
Question
What is global dimming?
Answer
A fall in sunlight reaching the ground because particles in the air reflect or block it.
Question
How do volcanoes cool the planet?
Answer
Aerosols thrown high into the atmosphere reflect sunlight back to space, so less reaches the surface (cooling for 1-3 years).
Question
What are Milankovitch cycles?
Answer
Slow changes in Earth's orbit shape, axial tilt and wobble over tens of thousands of years that change incoming sunlight and drive ice ages.
Question
Define a positive feedback loop.
Answer
A change that **amplifies itself** -- the change triggers more of the same change.
Question
Explain the ice-albedo feedback.
Answer
Warming melts bright reflective ice; the darker surface absorbs more heat; that warms it further, melting more ice.
Question
Explain the permafrost-methane feedback.
Answer
Warming thaws permafrost, releasing methane (a greenhouse gas), which traps more heat, thawing more permafrost.
Question
What did Mount Pinatubo (1991) show?
Answer
Its aerosols cooled global temperatures by about **0.5 degrees C** for ~a year -- natural cooling / global dimming.
Question
Why is today's warming seen as mainly human, not natural?
Answer
Natural forcings are small or cooling recently, while CO2 from fossil fuels has risen sharply since ~1850, tracking the rapid warming.
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Topic 2.1 hub
Causes of global climate change
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