Things I Should Remember From High School Science
greenhouse effect
gases in Earth's atmosphere trap heat from the sun and keep it from radiating back into space; certain gases like carbon dioxide, methane, nitrogen, and water vapor are very effective "greenhouse gases" even tho they only exist in small fractions in the atmosphere. Thus, small changes in the total amount of greenhouse gases (e.g., humans burning fossil fuels) can have an overall large impact on retained heat.
feedback processes
where the effect (or output) of one thing (phase, part of the system) becomes the cause (or input) of some other part of the system
albedo
the reflectivity of a surface, as measured by the light or heat energy reflected; light-colored surfaces are more reflective than dark-colored surfaces (dark surfaces absorb more heat energy)
planetary boundary
"the outer bounds of the Holocene-like Safe Operating Space that defines the limit within which humanity can safely operate without causing significant disruption to the environment" (PHC Report p. 4)
planetary health
"the state of the Earth system in terms of its ability to maintain stability, resilience, and life-support functions" and "how well the planet sustains the conditions necessary for human and ecological well-being" (PHC Report p. 4)
plate tectonics
the idea or theory that Earth's lithosphere (the outer layer of the solid Earth including the crust and mantle) is mosaic of moving pieces, or plates (Bjornerud 2005: p. 207)
positive feedback processes
self-perpetuating (vicious or virtuous) processes that can easily spiral out of control (ex: temperature warming and sea ice melting due to albedo)
Gaia hypothesis
James Lovelock and others' "proposal that the Earth can be viewed as a super organism with the capacity to regulate its body chemistry and temperature"; "vie that Earth's near-surface environment has been largely controlled buy biological activity" (p. 15 & 203 in Bjornerud 2005)
Safe Operating Space
"Earth system state that enables humanity to develop and thrive for generations to come"; "Holocene-like conditions" that ensure that "crucial Earth system processes remain within boundaries that support global stability, resilience and life-support functions" (PHC Report p. 4)
zone of increasing risk
Earth system conditions "where the likelihood for damage increases as the boundary transgression continues"; the yellow-orange colors in the PB framework images (PHC Report p. 4)
biodiversity
the amount and extent of living species on Earth or in a particular ecosystem; biodiversity contributes to functional integrity ("the diversity of life and life forms"; PHC Report p. 34) of an ecosystem
negative feedback mechanisms
self-correcting or balancing processes (ex: body temperature regulation via sweating)
biogeochemistry
"study of the movement and exchange of elements and compound (e.g., carbon and water) through the biosphere, atmosphere, hydrosphere, and solid earth" (glossary of Bjornerud 2005: p.200) - examples include water cycle, carbon cycle, nitrogen cycle, etc.
high risk zone
Earth system conditions that portend a "higher risk of triggering both the loss of systemic life support functions and irreversible changes to the functions that regulate Earth's livability"; the red-purple colors in PB framework images (PHC Report p. 4)
stability and resilience
stability is the Earth's "ability to not disrupt relatively constant conditions over long periods" (PHC Report p. 9) and "Earth's long-term planetary-scale stability can be attributed to...negative feedback mechanisms that operate across many spatial and temporal scales" (Bjornerud p. 14); resilience is the ability to withstand and recover from disturbances and return to a comparable pre-disturbance stage
photosynthesis
how plants take in carbon dioxide and water and, in the presence of sunlight, create sugars (stored carbon) and oxygen
leverage points
"where a small change in one thing can make a big difference to the whole system" (Earth for All p. 3)
reservoir and residence time
tipping point and tipping element
tipping point is a "critical threshold...beyond which change becomes self-perpetuating leading to substantial, widespread, frequently abrupt and often irreversible impacts", while a tipping element is a "critical subsystem" of the Earth that can "trigger significant changes in the overall Earth system if their thresholds are crossed" (PHC report p. 4)
"drivers of transgression"
human activities that directly influence the control variables and cause the breaching of planetary boundaries and push Earth out of a Safe Operating Space; bonus question: What are some of the largest "drivers of transgression" of the PBs?
evapotranspiration
how plants contribute to the water cycle: plants draw up water through their roots and vascular system and transpire excess water to the air through stomata, small holes in their leaves, some of the water that lands on plants also evaporates into the air
The Limits to Growth (1970 book)
presented the results of the World3 computer simulation model of population growth, fertility, mortality, industrial output, food, and pollution and project the growth (and decline) of these subsystems over time; concluded that unlimited growth on a physically finite planet is incompatible with long-term human well-being; the LtG BAU scenario has been surprisingly accurate
thermodynamics
the study of the relationship between heat and other forms of energy; bonus question: why do we care about thermodynamics?
control variable
"representative indicator to estimate the state or condition" of a planetary boundary process (PHC Report p. 4); akin to a dashboard indicator monitoring vehicle performance in a car; bonus question: how many control variables are included in the Planetary Boundaries framework?
life-support functions
the Earth system processes necessary for life to exist on the planet, including maintaining suitable temperature ranges, moisture regimes, light and seasonal patterns, nutrient cycling, and climate moderation/modulation