Why does temperature increase with altitude in the stratosphere, even though it decreases with altitude in the troposphere just below?
ASolar radiation directly heats the upper atmosphere more intensely at higher altitudes.
BThe ozone layer absorbs incoming ultraviolet radiation and converts that energy to heat, warming the surrounding stratospheric air.
CAir molecules are denser in the stratosphere, so they retain more heat.
DHeat from Earth's core radiates upward and warms the stratosphere from below.
The stratosphere's temperature inversion is caused by ozone. Ozone molecules (O₃) concentrated between 15 and 35 km absorb incoming UV radiation and re-emit it as heat. This internal energy source warms the stratosphere from within rather than from below. The resulting temperature inversion — warmer air above cooler air — makes the stratosphere extremely stable and prevents vertical mixing, acting as a lid on the troposphere below.
Question 2 Multiple Choice
A volcanic eruption injects sulfate aerosols into the stratosphere. Climate scientists expect these aerosols to affect global temperatures for 1–2 years. Why do stratospheric aerosols persist so much longer than similar aerosols emitted into the troposphere, which wash out within days?
AStratospheric aerosols are chemically more stable and don't react with water vapor.
BThe temperature inversion at the tropopause creates a stable lid that suppresses the vertical mixing needed to transport aerosols downward, and there is no rain to wash them out.
CStratospheric winds blow much faster, keeping aerosols suspended longer.
DAerosols in the stratosphere are smaller and lighter, so gravity affects them less.
The stratosphere's temperature inversion (warm above, cool below) makes it extremely stable — there is no convective mixing to carry aerosols downward. In the troposphere, convection, precipitation, and turbulence constantly cycle air and wash out particles within days to weeks. The stratosphere has no equivalent cleansing mechanism. This is also why ozone-depleting chemicals injected into the stratosphere persist for decades, and why geoengineering proposals involving stratospheric aerosols would have multi-year effects.
Question 3 True / False
Because nitrogen makes up 78% of the atmosphere, it is the dominant driver of Earth's surface temperature regulation.
TTrue
FFalse
Answer: False
Nitrogen (N₂) is essentially radiatively inactive — its symmetric molecular geometry means it cannot absorb or emit infrared radiation effectively. Temperature regulation is driven primarily by trace gases: water vapor, carbon dioxide, methane, and ozone collectively. CO₂, at only ~0.04% of the atmosphere, controls temperature so strongly that changes of a few parts per million drive global climate shifts. Atmospheric composition's importance is not proportional to abundance — the trace gases punch far above their weight.
Question 4 True / False
Ozone at ground level near cities is a pollutant, while ozone in the stratosphere is a protective shield against ultraviolet radiation.
TTrue
FFalse
Answer: True
Both statements are correct, but they describe ozone in very different contexts. Stratospheric ozone (15–35 km) forms naturally and absorbs UV-B and UV-C radiation that would otherwise reach the surface and damage DNA. Ground-level (tropospheric) ozone is a secondary pollutant formed when vehicle exhaust reacts with sunlight — it irritates lungs and damages plant tissue. The same molecule plays opposite roles depending on altitude, which is why 'ozone depletion' (stratospheric loss) and 'ozone pollution' (surface increase) are both problems.
Question 5 Short Answer
Why does virtually all weather — clouds, storms, rain, snow — occur in the troposphere rather than in the stratosphere, even though both layers contain gases and some water?
Think about your answer, then reveal below.
Model answer: Weather is driven by convection — the vertical movement of air driven by density differences from uneven heating. In the troposphere, the ground absorbs solar radiation and heats the air from below, creating a temperature gradient (warm below, cool above) that drives convective instability. Rising warm air carries moisture that condenses into clouds and precipitation. The stratosphere has the opposite temperature structure: warmer above, cooler below. This temperature inversion is extremely stable and suppresses vertical mixing entirely, so convective weather systems cannot form or penetrate into it.
This is why the tropopause acts as a physical ceiling for weather. Thunderstorms that grow very tall flatten out at the tropopause — they literally cannot penetrate the stable stratosphere above. Understanding each layer's temperature gradient explains why it behaves as it does: troposphere is turbulent and dynamic because it's heated from below; stratosphere is calm and isolated because it's heated from within.