Climate Literacy Handbook: Principle 4
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| Principle 4. Climate varies over space and time through both natural and man-made processes. |
Essential Principle 4 relates to some of the differences between weather and climate, climatic processes such as the El Nino/Southern Oscillation that influence natural climate variability, and abrupt climate change, which can be triggered by naturally occurring dynamics. Understanding climate variability is critically important in helping scientists tease apart natural variation from human-induced climate change.
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Concept 4a. Climate is determined by the long-term pattern of temperature and precipitation averages and extremes at a location. Climate descriptions can refer to areas that are local, regional, or global in extent. Climate can be described for different time intervals, such as decades, years, seasons, months, or specific dates of the year. |
Comparing climates of different planets is useful in developing perspective on climate in general. For the Earth, one of the most widely used climate classification systems in the world, the Köppen climate classification was developed by Wladimir Köppen around 1900 and is rooted in the concept that native vegetation is the most accurate expression of climate. Thus, climate zone boundaries are delineated by vegetation distribution, but also take into consideration seasonality and average annual, monthly temperatures and precipitation. The Köppen system has been updated several times over the years, most recently in 2007.
Articles in Depth:
- History of contributions of planetary studies to the science of climate change
- Global distribution of precipitation
- Daily and annual cycles of temperature
Teaching Aids and External Resources:
- Climate ClassificationA short article about the Köppen system by professor Michael Ritter.
- Lesson: Geographical RegionsA grades 5-8 appropriate lesson that takes a hands-on approach to defining geographical regions, including those based on climatic variables. From the National Geographic Society.
- Simulation: Water Vapor CirculationThis simulation from NCAR shows the circulation of water vapor around the Earth over the course of a year, which helps scientists study global wind patterns and the development of cyclonic storms.
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Concept 4b. Climate is not the same thing as weather. Weather is the minute-by-minute variable condition of the atmosphere on a local scale. Climate is a conceptual description of an area’s expected weather conditions and the extent to which those conditions vary over long time intervals. |
Many people share the misconception that weather and climate are basically the same. When climate is defined too simply as “average weather”, this can reinforce this misconception. In fact, while climate and weather are related, there are very different processes at work for the two and they must be studied in different ways.
Articles in Depth:
- Climate
- Weather
Teaching Aids and External Resources:
- What is the Difference Between Weather and Climate?A short article from NCAR. Links on the left allow for more in-depth exploration of both concepts.
- Lesson: Differences Between Climate and WeatherA grade 6-8 appropriate activity in which students collect data on local weather changes and examine how they relate to local climate. Excellent background material on weather and climate differences for teacher use. From UCAR.
- Interactive: Climate and Weather Variability Graph This NOAA tool allows the investigation of processes that contribute to climate and weather variability at different time scales (days, months, decades, centuries).
- Interactive: Exploring Weather & Climate Change Through the Powers of 10This interactive timeline from NOAA relates key climate and weather processes to important events in human history. Clicking on each node of the timeline leads to additional information.
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Concept 4c. Climate change is a significant and persistent change in an area’s average climate conditions or their extremes. Seasonal variations and multi-year cycles (for example, the El Niño Southern Oscillation) that produce warm, cool, wet, or dry periods across different regions are a natural part of climate variability. They do not represent climate change. |
On land, especially at high latitudes and elevations, seasonal changes that occur during the normal course of the annual cycle’s yearly dance are somewhat predictable. Precipitation and temperature patterns occur at more or less the same time each year, with organisms and the land itself responding to the seasonal fluctuations.
The ocean retains and releases heat differently than land. While the annual cycle still is important throughout the ocean, its surface waters are separated from colder, deeper water by a thermocline. The upwelling of cold waters, especially along the equator in the eastern half of the Pacific basin, can be blocked when sea level is high, resulting in warm events.
From the Climate TimeLine, NOAA:
Scientists examining sea surface temperatures (SST) for patterns in the heating and cooling of the ocean systems have identified variability that influence climate and fisheries. One, centered in the north Pacific and most commonly called the Pacific Decadal Oscillation or PDO, seems to have return periods of 15 to 25 years, and of 50 to 70 years. The other, the North Atlantic Oscillation (NAO), has a dominant period of 12 years (Deser, 1993 ), and as its name implies, it is centered in the North Atlantic. There is ongoing debate within the research community on whether or not El Niño (ENSO) and other climate patterns such as the Pacific Decadal Oscillation are in fact really oscillations or something else. Instruments used to track decadal variability and climate patterns include thermometers, rain gauges, and stream gauges. Sea Surface Temperature (SST) is particularly important in tracking ENSO and other ocean oscillations.
Articles in Depth:
- El Niño, La Niña and the southern oscillation
Teaching Aids and External Resources:
- Animation: Visit an El Nino Observing SystemThis flash animation provides a student-accessible overview of the Tropical Atmosphere Ocean (TAO) project from NOAA, which uses an array of buoys to gather data about El Niño and La Niña.
- Lesson: Climate VariabilityIn this activity, students use playing cards to simulate climate variability and come to understand that long-term climate averages are the result of significant annual climate variability. Excellent background material on weather and climate differences for teacher use. From UCAR.
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Concept 4d. Scientific observations indicate that global climate has changed in the past, is changing now, and will change in the future. The magnitude and direction of this change is not the same at all locations on Earth. |
Just as climates across the Earth vary widely, the changes that accompany recent climate change are also varied. While globally there is a warming trend, some regions are getting wetter and cooler, while others are getting warmer and drier. It was once thought that climate was generally steady, even-keeled, but we now know that climate change can occur abruptly, as it has many times in the Earth’s past.
From the Climate TimeLine, NOAA:
Over the course of Earth's 4.55 billion orbits around the sun, there were periods when major continental ice sheets were dominant and periods when temperatures were higher and so were sea levels. Some researchers theorize that during a prolonged icehouse period between 850-550 million years ago the world was dominated by ice. This has been called the "Snowball Earth Hypothesis." Other researchers claim that the geologic record does not support the theory of a one prolonged period of 300 million years, but rather was between two and four periods of glaciation with sustained "interglacial" warm periods lasting tens of millions of years
Articles in Depth:
Teaching Aids and External Resources:
- Interactive: Regional Climate Change Impacts on the U.S.An interactive map of the U.S. allows for the exploration and comparison of key regional findings of a 2009 report from the U.S. Global Change Research Program.
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Concept 4e. Based on evidence from tree rings, other natural records, and scientific observations made around the world, Earth’s average temperature is now warmer than it has been for at least the past 1,300 years. Average temperatures have increased markedly in the past 50 years, especially in the North Polar Region. |
Because records of temperature and precipitation using thermometers, rain gauges and the like have only been methodically used for a few centuries at best, proxies allow scientists to extend the study of climate back thousands and even hundreds of thousands of years. Proxies are inferred values (such as temperature or precipitation) made from other direct measurements (like pollen).
Proxy data is derived from pollen deposited in lakes, air bubbles and dust trapped in ice, bits of vegetation packed away in packrat middens, information captured in the annual rings of trees and corals. From these, scientists are able to piece together reconstructions of past climate variability and, on occasion, abrupt change.
Articles in Depth:
- Climate Change Timeline
- Earth's climatic history
Teaching Aids and External Resources:
- Wikipedia: Proxy (climate)A short article about the use of proxies in climate studies, with links to additional information.
- NOAA Paleoclimatology ProgramThis NOAA website is a treasure trove of data, background information and educational resources about various paleo proxies.
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Concept 4f. Natural processes driving Earth’s long-term climate variability do not explain the rapid climate change observed in recent decades. The only explanation that is consistent with all available evidence is that human impacts are playing an increasing role in climate change. Future changes in climate may be rapid compared to historical changes. |
A generation after John Tyndall developed the theory and conducted observations that led to the concept of the greenhouse effect, Svante Arrehenius (1859-1927) in Sweden made calculations on “the influence of carbonic acid in the air upon the temperature of the ground". His interest was motivated by the observation that burning coal, which was widespread across Europe, added carbonic acid (CO2) to the air. His calculations suggested that adding CO2 could cause the planet to warm, in effect amplifying the effect of greenhouse gases already naturally in the atmosphere.
Articles in Depth:
- Carbon dioxide
- Causes of climate change
Teaching Aids and External Resources:
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Concept 4g. Natural processes that remove carbon dioxide from the atmosphere operate slowly when compared to the processes that are now adding it to the atmosphere. Thus, carbon dioxide introduced into the atmosphere today may remain there for a century or more. Other greenhouse gases, including some created by humans, may remain in the atmosphere for thousands of years. |
Moving greenhouse gases from the atmosphere into terrestrial and oceanic sinks is a process so slow it is difficult to comprehend. Understanding that this movement relies on the process of diffusion is a good entry point to this topic. As a result, unlike water vapor which has a very short residence time, CO2 can be in the atmosphere for thousands of years. The geologic processes sequestering atmospheric carbon into sedimentary rocks, like limestone, take hundreds of millions of years. The severity of climate change will depend not only on the magnitude of human greenhouse gas emissions but also on the potential for irreversibility.
Susan Solomon's paper below describes computer models which estimate that warming generated by current carbon dioxide emissions will persist for as long as 1,000 years after emissions stop. While the removal of atmospheric carbon dioxide does decrease radiative forcing, a long lag time ensues due to a slower loss of heat to the ocean. As a result, atmospheric temperatures do not drop significantly for a long period of time.
Articles in Depth:
Teaching Aids and External Resources:
- Solomon et al. 2009: Irreversible climate change due to carbon dioxide emissions
- NOAA: Global Carbon CycleA short article describing in detail how natural processes move carbon between the atmosphere, ocean, and land.
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