SCI 101 Quiz 1

system

a set of interacting parts whose behavior cannot be worked out by studying any one part alone

sphere

one of the five major components: atmosphere, hydrosphere, geosphere, biosphere, anthroposphere

interaction

a transfer of energy or material from one sphere to another. Drawn as an arrow, and the arrow has a direction

emergent behavior

behavior of the whole system that could not be predicted by examining any single part. A traffic jam is the standard example

open and closed

Earth is open to energy, which flows through, and closed to matter, which cycles. There is no away.

Anthroposphere

People and everything people build and decide. The newest sphere on the list and the fastest-changing one

feedback loop

a chain in which the output travels back around and changes the thing that started it

positive feedback

amplifying. the response pushes the system further in the same direction. Not the same as beneficial

negative feedback

stabilizing. the response cancels part of the change and returns the system towards where it began

tipping point

a threshold past which a system shifts into a new state and does not easily return

hysteresis

the path back is not the path forward. Reversing the cause does not reverse the effect

albedo

fraction of incoming sunlight a surface reflects. Fresh snow about 0.80, open ocean about 0.06

energy balance

energy in equals energy out of a steady temperature. in exceeds out and the planet warms

S = 340 W / m²

sunlight arriving at the top of the atmosphere, averaged over the whole globe and the whole year

absorbed = S x (1-a)

with a = 0.30 this gives 238 W/m², the energy the planet has to shed again

greenhouse effect

gases transparent to incoming sunlight and opaque to outgoing infrared raise the altitude of escape, so the surface must be warmer to balance

33 degrees C

the gap between the predicted 255 K and the measured 288 K. That gap is the greenhouse effect

forcing against feedback

CO2 is a forcing, added directly and long lived. Water vapor is a feedback, set by temperature and gone in 9 days.

reservoir

an amount of carbon stored somewhere, measured in gigatonnes. A stock

flux

a rate at which carbon moves between reservoirs, measured in gigatonnes per year. A flow

residence time

reservoir divided by flux out. Short means fast to respond, long means anything added stays

airborne fraction

the stare of our emissions that stays in the air, currently about 45%. The rest goes to ocean and land

fast and slow cycles

fast moves 200 GtC a year and balances. Slow moves 0.3 GtC a year and sets the background. We connect them

ocean acidification

dissolved CO2 makes seawater more acidic. Surface pH has fallen from about 8.2 to 8.1, a 30 percent rise in acidity

what a sensor measures

the intensity of radiation arriving at the instrument, at particular wavelengths

the four resolutions

spatial, temporal, spectral, radiometric. You cannot maximize all four on one platform

the spatial and temporal trade

revisiting often needs a wide swath, and a wide swath means bigger pixels. They fight each other directly

NDVI

(NIR - RED) / (NIR + RED). Between -1 and +1. Above 0.6 is dense healthy vegetation, near 0 is bare ground, negative is water

atmospheric correction

removing the effect of scattering, aerosols and haze. It is a model, and it has already been applied to any product you download

measured against inferred

ask of any satellite claim: what was actually measured, what was assumed, and where would the assumption break?

anomaly

a value minus a baseline average. Change the baseline and every plotted number shifts, with nothing in the world changing

signal and noise

signal is the long-term direction. Noise is real year to year variability, not measurement error

cherry-picking

choosing start and end points that produce a chosen slope. Every value can be accurate and the conclusion still wrong

correlation and causation

two rising lines correlate. Causation needs a mechanism, and for CO2 that mechanism was measured in 1856

Thirty years

the conventional averaging period for climate, and roughly how long before the trend outgrows the wiggle

uncertainty

a quantified range, not absence of knowledge. A range that excludes zero is not an argument for delay