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Climate Change & The Data

Frequently Asked Questions

Q: What is the difference between weather and climate?

A: Weather is the set of conditions that exist over relatively short periods, usually hours or days. The conditions may be hot or cold, wet or dry, calm or stormy, etc. Weather includes events such as thunderstorms, blizzards, or persistent heat waves. A seasonal drought remains a weather event. Climate embraces averaged weather patterns over past or future time periods. Put another way, weather determines the clothes we wear to go outdoors. Climate determines the crops we plant, when we plant them, and when we harvest them.

Q: What constitutes “Climate Change”? When does a weather pattern become a change in climate?

A: Climate change is a term that includes any significant change in measures of climate, such as temperature, precipitation, even winds that lasts for several decades or longer. Climate change may result from natural factors, such as changes in the sun’s intensity and slow changes in the earth’s axis rotation and orbit around the sun. Other natural processes within the climate system include changes in ocean circulation. Human activities are now known to change atmospheric composition, principally the build-up of carbon dioxide and other gases. The burning of fossil fuels and changes to the land surface, such as deforestation and urbanization are major causes of the growth of these so-called “greenhouse gases.” These high levels of greenhouse gases correlate to measurable rises in global temperatures.

Q: How have Montana weather patterns changed over recent decades?

A: Climatologists and meteorologists often say there is no such thing as “average weather” and Montana is no exception. Quality weather gathering statistics do not extend as far back in time here as they do for other regions of the country. Nonetheless, weather extremes are broader here than perhaps any state. A -70 below zero °F was recorded at Rogers Pass in the mid 20th Century and two highs of 117 °F are also on the books, the latest in 1937 at Medicine Lake. One hundred degree temperature swings have been recorded on several occasions in a 24-hour period, the most recent -54 to 49 °F at Loma in 1972. The following site offers an excellent overview of weather extremes and events in Montana (PDF). The Montana Climate Office exhibits 50-year weather trends for five Montana cities. The general trend appears to be toward slight warming. The March mean temperatures seem markedly higher, however. For more weather pattern information, see Montana’s precipitation patterns east of the Continental Divide and the Governor’s Drought Information Advisory.

Q: Why is the term “climate change” used rather than “global warming”? Isn’t global warming the problem?

A: The terms are often used interchangeably. But according to the National Academy of Sciences (NAS), the phrase “climate change” is preferred because it helps convey that there are other changes in addition to rising temperatures. Climate change refers to any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). Global warming is an average increase in the temperature of the atmosphere near the Earth’s surface and in the troposphere. This can contribute to changes in global climate patterns. Both global warming and climate change can be caused by a variety of factors, both natural and human-induced.

Q: What are the six greenhouse gases?

A: Three of the major greenhouse gases are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), each of which is found in nature. In contrast, three of the greenhouse gases are only emitted through industrial sources: hydrofluorocarbons (HFC), perfluorocarbons (PFC), and sulphur hexafluoride (SF6). These are potent greenhouse gases and can persist in the atmosphere for many decades, but they do not occur in nature. For modeling and forecasting purposes, greenhouse gases other than carbon dioxide are converted into their CO2-equivalents.

Q: How have greenhouse gas levels in our atmosphere changed since the Industrial Revolution?

A: Since pre-industrial times, atmospheric concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) have climbed by more than 36 percent, 148 percent, and 18 percent, respectively (see the Recent Atmospheric Change page on EPA’s Climate Change site for more details). Since the Industrial Revolution, humans have added a significant amount of greenhouse gases to the atmosphere, primarily by burning fossil fuels, logging forests, and other industrial and land-use activities. Scientists have confirmed that the recent increase in atmospheric greenhouse gas concentrations is primarily due to human activity.

Q: What is Montana’s contribution to global greenhouse gases?

A: According to the Montana Climate Change Advisory Committee (MCCAC), the state emits 37 million metric tons of CO2 – or about .6 percent of total U.S. emissions. Although a small contributor among the states, the U.S. contributes about one-fourth of the world’s greenhouse gas emissions.

Q: Why aren’t methane and nitrous oxide emissions of greater concern?

A: Methane (CH4) and nitrous oxide (N2O) are greenhouse gases and are a major concern. Methane is perhaps 20-times more potent than carbon dioxide at trapping heat in the atmosphere. For modeling and forecasting purposes, methane levels are usually converted into CO2-equivalent values and may not be expressed separately. In Montana, methane is emitted by agricultural practices and livestock management, natural gas and petroleum facilities, coal mining, and wastewater management facilities. Nitrous oxide is perhaps 300-times more potent than carbon dioxide at trapping heat in the atmosphere. Emission sources in Montana are mainly through soil fertilizers and combustion of fossil fuels. As with methane, N2O levels are converted into CO2-equivalent values and may not be expressed separately.

Q: What natural factors contribute to climate change?

Natural variations within the Earth’s climate system can cause small changes over decades to centuries. Larger changes can occur through factors such as gradual changes in Earth’s orbit around the Sun, which are thought to be the key contributors in the comings and goings of past Ice Ages over many millennia. The sun’s energy can also vary over time. Large volcanic eruptions, for example, can cool the planet for a few years by spewing out particles that reflect sunlight back out to space. However, while natural variations have altered the climate significantly in the past, it is very unlikely that the changes in climate observed since the mid-20th century can be explained by natural processes alone.

Q: When will the climate change begin?

A: Many scientists believe it is already underway. The Earth has warmed 1.3°F over the past century, and it is projected by the Intergovernmental Panel on Climate Change (IPCC) to increase by an additional 3.2-7.2°F over this century. These increases may appear minor, but they are changes in the Earth’s global average temperature nonetheless. To put this in perspective, global temperatures during the last Ice Age (about 20,000 years ago) were “only” 9°F cooler than today. At the high-end of projected warming, human activities would change Earth’s climate by up to 7°F, but in the opposite direction.

Q: How will climate change likely affect Montanans?

A: Climate changes will affect all Montanans, but some more profoundly than others. The changes we have seen over recent decades are likely to continue and perhaps intensify. According to the IPCC and other sources, water availability and access is likely to change. Some reports indicate that spring run-off will occur earlier with less surface water available in some areas in late summer. Warmer temperatures are likely to bring drought conditions to certain districts, although patterns remain unclear. More forest and wildfire seasons are a likely a result of warming temperatures. And insect infestations in forests and agricultural settings may increase.Certain wildlife species may become rare or even extinct, while other species may expand their ranges. The pattern and species-mix of native vegetation may also slowly change elevations or move into new terrain. Some flora may also be lost. Certain noxious weeds will likely continue expansion.