Greenhouse effect Mountaineer Commentary

John Tyndall atmospheric sciences

Greenhouse effect

• The gases in the air we breathe
• are not entirely transparent to light and heat.
• 1.
• We see our atmosphere
• preferentially transmits different visible wavelengths
• scattering some colors more than others
• so that in the day the sky appears blue,
• but at dawn or sunset, across a wider swath of gases,
• mainly the red light gets through.
• 2.
• Laboratory experiments show
• different gases absorb heat in different amounts,
• oxygen and nitrogen being transparent
• but water vapor and carbon dioxide nearly opaque
• 3.
• which means that variations
• of water vapor and carbon dioxide
• regulate Earth’s temperature
• like a greenhouse, letting in light
• but trapping a variable amount
• of the heat that is reflected back.

Mountaineer

• “It’s hard to take air for granted
• at the top of the Weisshorn
• and easier to wonder
• why clouds stay in layers
• when you’re looking down on them from above.
• “Snow up here never completely melts
• but hot air rises
• so something must be happening to heat
• in this thinning air.
• “The leeward side of the mountain is dry
• but the windward side is green.
• Water vapor must condense out of the air
• as it’s forced to rise.
• “Mountaineers and balloonists know
• wind blows in different directions
• at different elevations.
• Barometric pressure makes this happen, or,
• if we reduce to first causes,
• sunlight and gravity.
• The atmosphere is stratified by gravity
• and heated unevenly by the sun.
• Wind is air moving in its layers
• to even out the pressure.
• “People ask me why a physicist climbs mountains.
• Even my guides won’t follow me up there.
• They think an educated man
• with a prestigious degree
• couldn’t learn anything important
• from a monstrous chunk of rock.
• But there it waits like the wise man in his cave
• impassive
• and taking nothing for granted.”