A–Z glossary
Climate change facts and risk factors, in plain English.
1
- 100-year flood
- A flood with a 1% chance of happening in any given year — not once a century. Over a 30-year mortgage that's about a 26% chance.
A
- Air Quality Index (AQI)
- A 0–500 scale of daily air pollution. Above 100 is unhealthy for sensitive groups; wildfire smoke can push it over 300.
- Aquifer depletion
- When groundwater is pumped faster than it refills, causing wells to dry up and land to sink.
B
- Base flood elevation
- The height floodwater is expected to reach in a 100-year flood. Homes built below it often need flood insurance.
- Brownfield
- Land previously used for industry that may be contaminated.
C
- Cancer cluster
- A higher-than-expected number of cancer cases in a group of people, area, or time period.
D
- Derecho
- A long-lived, straight-line windstorm that can cause tornado-like damage across hundreds of miles.
- Drought
- A long stretch of below-normal rainfall that strains water supplies, crops, and can trigger watering limits.
E
- Elevation certificate
- A document showing a building's elevation relative to flood levels; key for flood insurance pricing.
- Environmental justice
- The fair treatment of all people regarding pollution; EPA EJScreen maps where burdens are highest.
F
- FEMA flood zone
- Areas mapped by FEMA by flood risk. Zones starting with A or V are high risk.
H
- Heat island
- Urban areas that are noticeably hotter than surroundings due to pavement and few trees.
- HPSA
- Health Professional Shortage Area — a federal designation for places short on primary care, dental or mental-health providers.
I
- Insurance non-renewal
- When an insurer declines to renew a policy — increasingly common in wildfire and hurricane areas.
K
- Karst
- Landscape over soluble rock like limestone, where sinkholes form.
L
- Liquefaction
- When shaking turns saturated soil to a liquid-like state, damaging foundations during earthquakes.
M
- Mine subsidence
- Ground sinking over old underground mines; historic mine maps flag areas worth investigating.
- Modeled vs. observed data
- Observed data was measured (a test, monitor, or recorded event). Modeled data is an estimate from a risk model or projection.
N
- Nitrates
- Chemicals from fertilizer that can enter drinking water; high levels are dangerous for infants.
P
- PFAS
- 'Forever chemicals' used in industry and firefighting foam that persist in water and the body.
- PM2.5
- Fine particles in smoke and pollution small enough to enter the bloodstream.
R
- Radon
- A natural radioactive gas that seeps into basements; the 2nd leading cause of lung cancer in the US.
S
- SAIDI / SAIFI
- Utility reliability measures: average total outage minutes and average number of outages per customer per year.
- Storm surge
- Ocean water pushed ashore by a hurricane — often the deadliest part of the storm.
- Subsidence
- Gradual sinking of land, often caused by groundwater pumping or soft soils.
- Superfund site
- A heavily contaminated location the EPA has listed for long-term cleanup.
T
- Tornado Alley
- A loose region of the central US with frequent tornadoes; activity has been shifting east into 'Dixie Alley'.
- Toxics Release Inventory (TRI)
- EPA's public database of toxic chemicals released by industrial facilities.
- Transportation noise
- Sound from highways, airports and rail; federal maps give broad estimates, not indoor measurements.
W
- Wildfire smoke days
- Days when wildfire smoke, sometimes from fires a thousand miles away, makes the air unhealthy.
- Wildland–urban interface (WUI)
- Where homes meet undeveloped wildland — the highest-risk zone for wildfire home losses.