Climate is defined as a a description of the aggregate (or collective) weather conditions; the sum of all statistical weather information that helps describe a place or region. The National Weather Service says “Climate encompasses the weather over different periods of time and also relates to mutual interactions between the components of the earth system (e.g., atmospheric composition, changes in the Earth’s orbit around the sun, etc.).”
In other words, when someone looks out their window, they observe the weather, which shapes the climate each day. A single weather event, such as a lake-effect snowstorm, contributes to the overall climate but cannot define it.
The climate is a collective of weather. In other words, think about a book, and each page is one single day of the weather, and the book is called “The Climate.” This book would then encompass years of daily weather data throughout the pages.
It is important to know where the data come from to understand changes in precipitation (e.g., snowfall) and air temperature. Various atmospheric variables are measured most frequently today, including air temperature, barometric pressure, cloud type, cloud height and cloud cover, current or prevailing weather, dewpoint temperature, precipitation, sunshine, and wind speed and direction.
Nearly 15,000 stations alone in the United States record at least one of these variables listed above. The international agency responsible for worldwide climatic data is the World Meteorological Organization (WMO), located in Geneva, Switzerland.
The Intergovernmental Panel on Climate Change’s Data Distribution Center is a gateway to various data sets used to assess global climate changes. The World Data Center for Climate, part of the World Data System, includes climatological, meteorological, astronomical, oceanographic, and geophysical data sets.
NOAA’s National Centers for Environment Information (NCEI) in Asheville, North Carolina, is the main library for weather records in the United States. The U.S. Historical Climatology Network maintains a high-quality dataset for over 1,000 stations in the contiguous United States to quantify national and regional-scale temperature changes.
NCEI manages the Regional Climate Center Program, encompassing six regional offices throughout the United States. The Northeast Regional Climate Center serves Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, Delaware, New York, Pennsylvania, New Jersey, Maryland, West Virginia, and Washington D.C.
Climate Normals
Climate normals can provide insight into growing seasons for farmers, including first and last freeze dates, drought conditions, winter conditions, and energy usage for heating and cooling days. If someone walks outside and thinks the weather is hotter, colder, wetter, or drier than they remember, they think about climate normals.
Normals are another way of saying expected conditions from the recent (30-year) past. More specifically, climate normals are 30-year averages for climate variables like precipitation and air temperature.
Data consist of annual/seasonal, monthly, daily, and hourly averages. These datasets provide a baseline that compares a location’s current weather to the expected, or normal, weather.
Climate normals are continuously updated, with previous 30-year averages being 1931-1960 and 1961-1990. The WMO creates specific guidelines on calculating climate normals to be consistent worldwide.
The most current set of climate normals data is from 1991-2020. (Note that subtracting 2020 from 1991 is 29. Due to counting the full, inclusive years of 1991 through 2020, the total is 30.)
An example of using climate normals to understand air temperature in Boonville, Oneida County, NY is as follows:
• The average maximum air temperature in February 2024 was 34.2°F.
• The climate normal for February’s average maximum air temperature is 27.2°F.
• February 2024 was 7° above the climate normal. This means that February was warmer than normal.
Climate Change
What is causing air temperatures to warm? Scientists can reconstruct climate as far back as 570 million years ago on a geologic time scale. Over these periods, the climate has changed, with several ice ages occurring about 18,000 years ago, a cooling period occurring approximately 10,200 years ago, and a warming period peaking about 5,500 years ago.
The Earth then went through a warming period between years 950-1250, known as the Little Climatic Optimum or Medieval Warm Period, and then between 1250-1450, the climate widely cooled, and from 1450-1850, the Little Ice Age occurred.
By the end of the 19th century, instrumental records show the climate started to warm, and the 20th century also had both warm and cool times; however, an exceptionally warm period started in the 1980s and continues today.
The fundamental reason why the Earth’s climate undergoes changes is because change is related to how energy flows into and out of the system and how energy is exchanged within the Earth-ocean-atmosphere system.
Natural changes can affect the energy system on “short-term scales,” for example, variations in solar irradiance (or solar energy given off from the sun). It is incorrect to explain that the change in climate experienced today is solely based on these natural factors.
Our Greenhouse Planet
The greenhouse effect makes all life possible on Earth. It is a complex interchange between the Earth’s surface and the atmosphere. The atmosphere is made up of nitrogen (78.084%), oxygen (20.946%), argon (0.934%), carbon dioxide (0.042%), and other trace gases, such as neon, helium, methane, and more.
Greenhouse gases include carbon dioxide, methane, ozone, nitrous oxide, chlorofluorocarbons, and water vapor. Greenhouse gases are energy absorbers because they trap heat, with carbon dioxide, methane, and nitrous oxide contributing the most to warming.
The greenhouse effect is when the sun emits shortwave solar radiation (i.e., energy from the sun that reaches the Earth as light and heat), followed by the Earth emitting longwave radiation (i.e., giving off heat) back into the atmosphere, which is absorbed by greenhouse gases.
The Earth warms because heat is trapped near the Earth’s surface by greenhouse gases. Think of greenhouse gases acting as a blanket around the Earth. Some of the Earth’s longwave radiation, or heat, reflects back into space, but greenhouse gases (the blanket) trap the rest in the atmosphere.
This is a complicated game of “hot potato,” but without this “blanket” surrounding the atmosphere, the surface temperature would be 0°F, and all water on Earth would
be frozen.
Carbon dioxide (CO2 ) is the most important greenhouse gas because it is very good at trapping heat emitted from the Earth’s surface (longwave radiation), influencing how much the atmosphere warms.
A direct relationship, or trend, exists between increasing CO2 levels and air temperature. As CO2 levels increase, the blanket thickens, causing more heat to become trapped, which causes air temperatures to increase (or warm).
CO2 levels are higher than they have ever been recorded in the past 800,000 years. Scientists have been able to reconstruct what past climates used to be using proxy data, which are observations of other variables that serve as a substitute or proxy for the actual climatic record.
Proxies are paleoclimatological archives, such as ocean sediments, mountain glaciers, ancient soils, ice sheets, bog or lake sediments, ice cores, tree rings, written records, and archeological records.
Human Causes of Climate Warming
The question then becomes, why are CO2 levels so high? The answer is human activities.
In 1956, Gilbert Plass researched and concluded that industrial and other human activities are adding “considerably more” carbon dioxide than any natural cause. Another term often used is anthropogenic, which means changes caused or influenced by people, either directly or indirectly.
Scientists refer to this as anthropogenic changes, or human-caused changes. Human activities have increased carbon dioxide in the atmosphere by 50 percent. This means the carbon dioxide level is 150 percent of its value in 1750 (around the start of the Industrial Revolution).
Carbon is abundantly found in the Earth as fossil fuels in the form of coal, oil, and natural gas. When additional carbon dioxide is released into the atmosphere from burning fossil fuels, over time, it acts as if another blanket has been knitted and placed around the atmosphere, trapping heat from being released into space and, therefore, increasing the atmosphere’s air temperature.
The increase in the atmosphere’s air temperature is global warming. Global warming is the long-term heating of Earth’s surface caused by human activities since the pre-industrial period (between 1850 and 1900). The term is often used interchangeably with climate change, but this is incorrect.
As previously mentioned, the greenhouse effect is essential for living on Earth; however, human activities have increased the amount of greenhouse gases in the atmosphere to a point where it contains, or traps, the excess heat that would otherwise be emitted, or go, into space, which has caused the Earth’s air temperature to increase, called global warming.
Warming air temperatures have widespread physical impacts on the environment. This ranges from rising sea levels, changing weather patterns, ecosystem changes, economic impacts, health risks, and more. The long-term change in average weather patterns in any region and the world beyond is called climate change.
In other words, climate change is the long-term change being observed in weather conditions, such as precipitation, flooding, droughts, heat waves, and hurricanes. Climate change can result in more drastic events, whether that means seasons with very little snowfall or seasons with extremely high snowfall amounts.
Natural changes (e.g., variations in solar irradiance, sunspot activity, and atmospheric dust) and long-term changes (e.g., the angle of the Earth’s axis and distance from the Earth to the sun) cannot be considered solely on their own to explain why carbon dioxide levels have increased.
Human factors increase carbon dioxide emissions, which thickens the “blanket” around the Earth’s atmosphere, trapping heat and increasing air temperatures (i.e., global warming). Increasing air temperatures cause changes in weather patterns – climate change.
The NYS Climate Impacts Assessment explores current and future climate change impacts on communities, ecosystems, and the economy in New York State. Over 250 New York-based, national, and Indigenous climate science experts and representatives from communities and industries across the state contributed to the assessment.
It provides an in-depth analysis of how a changing climate impacts the state, including agriculture, buildings, ecosystems, energy, human health and safety, society and economy, transportation, and water resources.
This essay was excerpted (with minor editing) from the Tug Hill Commission‘s How Winter is Changing in the Tug Hill Region (March 2025).
Learn more about Climate Change in New York State.
Illustrations, from above: Cities create urban heat islands which can be exacerbated by climate change; Essential Climate Variables as defined by the Global Climate Observing System; there are 54 focused on the atmosphere, cryosphere, ocean, anthroposphere, biosphere, and the hydrosphere; Early 20th century snow removal crew in Churubusco in Clinton County, NY (courtesy Lawrence Gooley); Global average temperatures show that the Medieval Warm Period and Little Ice Age were not a planet-wide period but a regional phenomenon occurring near the end of a long temperature decline that preceded recent global warming (wikimedia user Ed Hawkins); Diagram of the greenhouse effect; NOAA data showing CO2 levels from 800 thousand years ago through today with orange line showing ice core data, and the red line modern instrumental data; and the impact of the greenhouse effect on Earth’s climate was succinctly described more than a century ago in this 1912 Popular Mechanics article.
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