South of Glasgow, northeast Montana. Photograph courtesy of Rick and Susie Graetz, University of Montana.



adaptation Actions taken to help communities and ecosystems better cope with potential negative effects of climate change or take advantage of potential opportunities.


adaptive capacity The inherent ability of a system (e.g., ecosystem or social system) to adapt to a changing environment; for example, a plant species that can survive a broader range of temperatures may have greater adaptive capacity compared to a plant that can only tolerate a narrow range of temperatures.


agribusiness An industry engaged in the production operations of a farm, the manufacture and distribution of farm equipment and supplies, and the processing, storage, and distribution of farm commodities.


agronomy The science of crop production and soil management.


annual streamflow The cumulative quantity of water for a period of record, in this case a calendar year. 


anthropogenic Originating in human activity.


aquifer A body of permeable rock that can contain or transmit groundwater.


atmospheric carbon dioxide (CO2) The amount of CO2 in Earth’s atmosphere. Although the proportion of Earth’s atmosphere made up by CO2 is small, CO2 is a potent greenhouse gases and directly related to the burning of fossil fuels. Atmospheric carbon dioxide levels in Earth’s atmosphere are at the highest levels in an estimated 3 million years and these levels are projected to increase global average temperatures through the greenhouse effect.


attribution Identifies a source or cause of something.


basis The difference between the futures market price and the local price for an agricultural commodity, measured in dollars per bushel.


base flow The portion of streamflow that is not runoff and results from seepage of water from the ground into a channel slowly over time. The primary source of running water in a stream during dry weather.


basin A drainage basin or catchment basin is an extent or an area of land where all surface water from rain, melting snow, or ice converges to a single point at a lower elevation, usually the exit of the basin, where the waters join another body of water, such as a river, lake, reservoir, estuary, wetland, sea, or ocean.


biocontrol Short for biological control; the reduction in numbers or elimination of pest organisms by interference with their ecology (as by the introduction of parasites or disease).


biodiversity The variety of all native living organisms and their various forms and interrelationships.


biomass The total amount of organic matter present in an organism, population, ecosystem, or given area.


bushel A unit for measuring an amount of fruit and grain that is equal to about 35.2 liters in the US. 


C3 and C4 plants Plants use different photosynthetic pathways (termed C3 photosynthesis or C4 photosynthesis). C4 plants evolved as an adaptation to high-temperature, high-light conditions. C4 plant growth rates increase more under hot, high-CO2 conditions than that of C3 plants and exhibit less water loss.


climate versus weather The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere behaves over relatively long periods of time (i.e., multiple decades).


climate change Changes in average weather conditions that persist over multiple decades or longer. Climate change encompasses both increases and decreases in temperature, as well as shifts in precipitation, changing risk of certain types of severe weather events, and changes to other features of the climate system.


climate oscillation See teleconnections.


commercial crops Agricultural crops that are grown for sale to return a profit, purchased by parties separate from a farm (note: not all commercial crops are commodity crops).


commodity crops Crops that are traded, and typically include crops that are non-perishable, easily storable, and undifferentiated.


commodity futures Buying or selling of a set amount of a commodity at a predetermined price and date.


confined aquifer A confined aquifer is an aquifer below the land surface that is saturated with water. Layers of impermeable material are both above and below the aquifer, causing it to be under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.


cow-calf operations Livestock operations in which a base breeding herd of mother cows and bulls are maintained. Each year’s calves are sold between the ages of 6 and 12 months, along with culled cows and bulls, except for some breeding herd replacements.


crop rotation System of cultivation where different crops are planted in consecutive growing seasons to maintain soil fertility.


cultivar A contraction of cultivated variety. It refers to a plant type within a particular cultivated species that is distinguished by one or more characteristics.


direct effect A primary impact to a system from shifts in climate conditions (e.g., temperature and precipitation), such as direct mortality to species from increased heat extremes.


direct runoff The runoff entering stream channels promptly after rainfall, exclusive of base flow. Direct runoff equals the volume of rainfall excess (e.g., total precipitation minus losses).


disturbance regime The frequency, severity, and pattern of events that disrupt an ecosystem or community; for example, a forest’s fire disturbance regime may be the historical pattern of frequent, low-intensity fires versus infrequent, high-severity fires.


drought For this report, drought is categorized in four ways: 1) meteorological drought, defined as a deficit in precipitation; 2) hydrological drought, characterized by reduced water levels in streams, lakes, and aquifers; 3) ecological drought, defined as a prolonged period over which an ecosystem’s demand for water exceeds the supply; and 4) agricultural drought, commonly understood as a deficit in soil moisture.  


dryland farming A system of producing crops in semiarid regions (usually with less than 20 inches [0.5 m] of annual rainfall) without the use of irrigation.


El Niño-Southern Oscillation (ENSO) A periodic variation in wind and sea-surface temperature patterns that affects global weather; El Niño (warming phase where sea-surface temperatures in the eastern Pacific Ocean warm) generally means warmer (and sometimes slightly drier) winter conditions in Montana. In contrast, La Niña (cooling phase) generally means cooler (and sometimes wetter) winters for Montanans.The two phases each last approximately 6-18 months, and oscillate between the two phases approximately every 3-4 yr.


ensemble of general circulation models (GCMs) Succinctly: When many different forecast models are used to generate a projection, and outputs are synthesized into a single score or average. This type of forecast significantly reduces errors in model output and enables a level of certainty to be placed on the projections. More broadly: Rather than relying on the outcome of a single climate model, scientists run ensembles of many models. Each model in the ensemble plausibly represents the real world, but as the models differ somewhat they produce different outcomes. Scientists analyze the outputs (e.g., projected average daily temperature at mid century) over the entire ensemble. Those analyses provide both the projection of the future resulting from the ensemble of models, and define the level of certainty that should be placed on that projection.


ephemeral stream A stream that flows only briefly during and following a period of rainfall in the immediate locality.


evaporation The change of a liquid into a vapor at a temperature below the boiling point. Evaporation takes place at the surface of a liquid, where molecules with the highest kinetic energy are able to escape. When this happens, the average kinetic energy of the liquid is lowered and its temperature decreases.


evapotranspiration The combined effect of evaporation and transpiration (by plants) of water, which is one of the most important processes driving the hydrologic cycle. Evapotranspiration is often analyzed in two ways, as potential evapotranspiration, which is a measure of demand for water from the atmosphere regardless of how much water is available, and actual evapotranspiration, which is how much water is actually used by plants and evaporated from water surfaces. Generally, actual evapotranspiration is driven by water availability, solar radiation, and plant type, but also affected by wind and vapor pressure. Transpiration is affected by vegetation-related factors such as leaf area and stomatal conductance, the exchange of CO2 and water vapor between leaves and the air.


fallow Cultivated land that is allowed to lie idle during the growing season; or to plow, harrow, and break up (land) without seeding to destroy weeds and conserve soil moisture.


feeder cattle Growing beef cattle between the calf stage and sale to finishing operations.


fire behavior The manner in which wildfire ignites and spreads, and characterizing the burning conditions within a single fire.


fire regime The frequency, severity, and pattern of wildfire.


fire risk The likelihood of a fire ignition.


fire severity The magnitude of effects from a fire, usually measured by the level of vegetation or biomass mortality or the area burned.


flood An overflowing of a large amount of water beyond its normal confines, especially over what is normally dry land.


flood plain An area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding.


frost days The annual count of days where daily minimum temperature drops below 32°F (0°C).


futures trading An agreement between two people, one who sells and agrees to deliver and one who buys and agrees to a certain kind, quality, and quantity of product to be delivered during a specified delivery month at a specified price. More simply, a contract to buy specific quantities of a commodity at a specified price with delivery set at a specified time in the future.


general circulation models (GCMs) Numerical models representing physical processes in the atmosphere, ocean, cryosphere, and land surface. They are the most advanced tools currently available for simulating the response of the global climate system to increasing greenhouse gas concentrations.


grain filling The period of wheat development from pollination to seed production.


greenhouse gas A gas in Earth’s atmosphere that absorbs and then re-radiates heat from the Earth and thereby raises global average temperatures. The primary greenhouse gases in Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Earth relies on the warming effect of greenhouse gases to sustain life, but increases in greenhouse gases, particularly carbon dioxide from the burning of fossil fuels, can increase average global temperatures over historical norms.


greenhouse gas emissions The discharge of greenhouse gases, such as carbon dioxide, methane, nitrous oxide and various halogenated hydrocarbons, into the atmosphere. Combustion of fossil fuels, agricultural activities, and industrial practices contribute to the emissions of greenhouse gases.


green manure Crops grown to be incorporated into the soil to increase soil quality, fertility and structure.


global warming The increase in Earth’s surface air temperatures, on average, across the globe and over decades. Because climate systems are complex, increases in global average temperatures do not mean increased temperatures everywhere on Earth, nor that temperatures in a given year will be warmer than the year before (which represents weather, not climate). More simply: Gobal warming is used to describe a gradual increase in the average temperature of the Earth’s atmosphere and its oceans, a change that is believed to be permanently changing the Earth’s climate. 


groundwater Water held underground in the soil or in pores and crevices in rock.


growing degree-days A weather-based indicator for assessing crop development. It is a calculation used by crop producers that is a measure of heat accumulation used to predict plant and pest development rates such as the date that a crop reaches maturity.


hardiness zone A geographically-defined zone in which a specific category of plant life is capable of growing, as defined by temperature hardiness, or ability to withstand the minimum temperatures of the zone. The zones are based on the average annual extreme minimum temperature during a 30-yr period in the past, not the lowest temperature that has ever occurred in the past or might occur in the future.


human agency The capacity possessed by people to act of their own volition.


hydrograph A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, or other channel or conduit carrying flow. The rate of flow is typically expressed as cubic feet per second, CFS, or ft3/s (the metric unit is m3/s).


hydrologic cycle The sequence of conditions through which water passes from vapor in the atmosphere through precipitation upon land or water surfaces and ultimately back into the atmosphere as a result of evaporation and transpiration. 


hydrology The study of water. Hydrology generally focuses on the distribution of water and interaction with the land surface and underlying soils and rocks.


indirect effect A secondary impact to a system from a change that was caused by shifting climate conditions, such as increased fire frequency, which is a result of drier conditions caused by an increase in temperature.


infiltration The movement of water from the land surface into the soil.


interception The capture of precipitation above the ground surface, for example, by vegetation or buildings.


IPCC SRES Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios. 


irrigation Application of water to soil for the purpose of plant production.


legume Any of a large family (Leguminsoae syn. Fabaceae, the legume family) of dicotyledonous herbs, shrubs, and trees having fruits that are legumes or loments, bearing nodules on the roots that contain nitrogen-fixing bacteria, and including important food and forage plants (as peas, beans, or clovers).


metrics Quantifiable measures of observed or projected climate conditions, including both primary metrics (for example, temperature and precipitation) and derived metrics (e.g., projected days over 90°F [32°C ] or number of consecutive dry days).


microclimate The local climate of a given site or habitat varying in size from a tiny crevice to a large land area. Microclimate is usually, however, characterized by considerable uniformity of climate over the site involved and relatively local when compared to its enveloping macroclimate. The differences generally stem from local climate factors such as elevation and exposure.


mitigation Efforts to reduce greenhouse gas emissions to, or increase carbon storage from, the atmosphere as a means to reduce the magnitude and speed of onset of climate change.


model A physical or mathematical representation of a process that can be used to predict some aspect of the process.


organic A crop that is produced without: antibiotics; growth hormones, most conventional pesticides, petroleum-based fertilizers or sewage sludge-based fertilizers, bioengineering, or ionizing radiation. USDA certification is required before a product can be labeled organic. 


oscillation A recurring cyclical pattern in global or regional climate that often occurs on decadal to sub-decadal timescales. Climate oscillations that have a particularly strong influence on Montana’s climate are the El Nino Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO).


Pacific Decadal Oscillation (PDO) A periodic variation in sea-surface temperatures that is similar to El Niño-Southern Oscillation, but has a much longer duration (approximately 20-30 yr). When the PDO is in the same phase as El Niño-Southern Oscillation, weather effects are more pronounced. For example, when both are in the warming phase, Montanans may experience an extremely warm winter, whereas if PDO is in a cooling phase, a warm phase El Niño-Southern Oscillation may have a reduced impact. 


Palmer Drought Severity Index (PDSI) A measurement of dryness based on recent precipitation and temperature. The Palmer Drought Severity Index is based on a supply-and-demand model of soil moisture.


Palmer Z Drought Index One of the Palmer Drought Indices; it measures short-term drought on a monthly scale. The Z-value is also referenced to the specific location, climate, and time of year.


parameter A variable, in a general model, whose value is adjusted to make the model specific to a given situation.


pathogen Microorganisms, viruses, and parasites that can cause disease. 


peak flow The point of the hydrograph that has the highest flow.


permeability A measure of the ability of a porous material (often, a rock or an unconsolidated material) to allow fluids to pass through it.


phenology The study of periodic biological phenomena with relation to climate (particularly seasonal changes). These phenomena can be used to interpret local seasons and the climate zones.


physiography The subfield of geography that studies physical patterns and processes of the Earth. It aims to understand the forces that produce and change rocks, oceans, weather, and global flora and fauna patterns.


primary productivity The total quantity of fixed carbon (organic matter) per unit area over time produced by photosynthesis in an ecosystem.


pulse cropv Annual leguminous crops yielding from 1-12 grains or seeds of variable size, shape, and color within a pod. Limited to crops harvested solely for dry grain, thereby excluding crops harvested green for food, oil extraction, and those that are used exclusively for sowing purposes. 


radiative forcing The difference between the amount of sunlight absorbed by the Earth versus the energy radiated back to space. Greenhouse gases in the atmosphere, particularly carbon dioxide, increase the amount of radiative forcing, which is measured in units of watts/m2. The laws of physics require that average global temperatures increase with increased radiative forcing. 


rangeland Land on which the historical climax plant community is predominantly grasses, grasslike plants, forbs, or shrubs. This includes lands re-vegetated naturally or artificially when routine management of the vegetation is accomplished through manipulation of grazing. Rangelands include natural grasslands, savannas, shrublands, most deserts, tundra, alpine communities, coastal marshes, and wet meadows.


RCP (representative concentration pathways) Imagined plausible trends in greenhouse gas emissions and resulting concentrations in the atmosphere used in climate projection models. This analysis uses the relatively moderate and more severe scenarios of RCP4.5 and 8.5. These scenarios represent a future with an increase in radiative forcing of 4.5 or 8.5 watts/m2, respectively. The RCP4.5 scenario assumes greenhouse gas emissions peak mid century, and then decline, while the RCP8.5 scenario assumes continued high greenhouse gas emissions through the end of the century.


resilience In ecology, the capacity of an ecosystem to respond to a disturbance or perturbation by resisting damage and recovering quickly.


resistance In ecology, the property of populations or communities to remain essentially unchanged when subject to disturbance. Sensitivity is the inverse of resistance.


resistance gene A gene involved in the process of resistance to a disease or pathogen; especially a gene involved in the process of antibiotic resistance in a bacterium or other pathogenic microorganism.


ruminants Mammals that have four stomachs and even-toed hooves.


runoff Surface runoff (also known as overland flow) is the flow of water that occurs when excess stormwater, meltwater, or other sources flows over the Earth’s surface.


scenario Climate change scenarios are based on projections of future greenhouse gas (particularly carbon dioxide) emissions and resulting atmospheric concentrations given various plausible but imagined combinations of how governments, societies, economies, and technologies will change in the future. This analysis considers two plausible greenhouse gas concentration scenarios: a moderate (stabilized) and more severe (business-as-usual) scenario, referred to as RCP4.5 and RCP8.5, respectively.


shallow aquifer Typically (but not always) the shallowest aquifer at a given location is unconfined, meaning it does not have a confining layer (an aquitard or aquiclude) between it and the surface. The term perched refers to ground water accumulating above a low-permeability unit or strata, such as a clay layer.


silage Any crop that is harvested green and preserved in a succulent condition by partial fermentation in a nearly airtight container such as a silo.


specialty crop Fruits and vegetables, tree nuts, dried fruits and horticulture and nursery crops, including floriculture. 


spring wheat A general term for wheat sown in the early spring and harvested in the late summer or early autumn of the same year.


Snow Water Equivalent (SWE) A common snowpack measurement that is the amount of water contained within the snowpack. It can be thought of as the depth of water that would theoretically result if you melted the entire snowpack instantaneously.


soil moisture A measure of the quantity of water contained in soil. Soil moisture is a key variable in controlling the exchange of water and energy between the land surface and the atmosphere through evaporation and plant transpiration. 


storage The volume of water contained in natural depressions in the land surface, such as a snowpack, glaciers, drainage basins, aquifers, soil zones, lakes, reservoirs, or irrigation projects.


streamflow (also known as channel runoff) The flow of water in streams, rivers, and other channels. It is a major element of the water cycle. 


teleconnection A connection between meteorological events that occur a long distance apart, such as sea-surface temperatures in the Pacific Ocean affecting winter temperatures in Montana. Also referred to as climate oscillations or patterns of climate variability.


test weight A measure of grain bulk density, often used as a general indicator of overall quality and as a gage of endosperm hardness to alkaline cookers and dry millers.


tillage The traditional method of farming in which soil is prepared for planting by completely inverting it with a plow. Subsequent working of the soil with other implements is usually performed to smooth the soil surface. Bare soil is exposed to the weather for some varying length of time depending on soil and climate conditions.


transpiration The passage of water through a plant from the roots through the vascular system to the atmosphere.


unconfined aquifer A groundwater aquifer is said to be unconfined when its upper surface (water table) is open to the atmosphere through permeable material.


velocity The rate of climate changes occurring across space and time.


warm days Percentage of time when daily maximum temperature >90th percentile.


warm nights Percentage of time when daily minimum temperature >90th percentile.


water quality The chemical, physical, biological, and radiological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and/or to any human need or purpose.


watershed An area characterized by all direct runoff being conveyed to the same outlet. Similar terms include basin, subwatershed, drainage basin, catchment, and catch basin.


water year A time period of 12 months (generally October 1 of a given year through September 30 of the following year) for which precipitation totals are measured.


weather versus climate See climate versus weather.


winter wheat A general term for wheat sown in the fall, persisting through the winter winter as seedlings, and harvested the following spring or summer after it reaches full maturity.