Greenhouse gases produced during the burning of fuels containing hydrocarbons – such as coal, oil and natural gas - have been linked to changes in global climate. A major source of these gases is the burning of hydrocarbon-based fuels for transportation, specifically automobile emissions. Commercial and military aircraft also burn hydrocarbon-based fuels releasing approximately the same amount of carbon dioxide as a passenger car with 1 passenger, depending mainly upon the length of flights. The dramatic increase in commercial aviation in the last 25 years (an increase of 4.6X as measured by the number of revenue passenger kilometers) has led scientists to investigate the potential role of jet plane emissions in forcing climate change, including the production of jet contrails in the upper troposphere and lower stratosphere.
Condensation trails from jets, contrails, are thin ice clouds that form from the burning of jet fuel and release of water vapor, a greenhouse gas. The key issue with contrails is that narrow trails can spread and coalesce to form significant banks of cirrus-type clouds. During the day, thick clouds that tend to form at lower altitudes absorb incoming shortwave solar radiation resulting in overall cooling at the Earth's surface. At night, in the absence of incoming solar radiation, the scenario is reversed; thick clouds trap longwave radiation emitted from the Earth's surface and an overall warming occurs. Clouds that form at high altitudes (3-18 km depending on the latitude) are usually thin and wispy (like contrails) and are relatively transparent to incoming shortwave radiation due to their lower albedo. At the same time, these clouds can absorb and re-emit longwave radiation from the Earth's surface producing an overall warming and perhaps a change in the daily temperature range.
Contrails are similar to cirrus clouds and form under specific temperatures and humidity levels; namely it must be cold and wet enough for ice to form, but not so wet that clouds form naturally. Also, once formed, clouds related to jet contrails may persist in the atmosphere altering both the absolute and range of temperature for a region. For example, the terrorist attacks of September 11, 2001 resulted in a three-day grounding of all commercial aircraft in the United States, therefore providing experimental conditions to test the question of whether contrails altered absolute and/or the range of temperatures. Comparing data from 1971 to 2000 to the temperature data collected around the time of the attacks clearly indicated the range of temperatures (that is the maximum temperature minus the minimum temperature) was significantly greater due to the lack of contrails.
The role of contrails in affecting local, regional and global climate is, however, likely more complicated and dependent on a range of variables including not only the density of air travel but yearly changes in atmospheric conditions, the altitude and length of jet travel, location of the jet stream and variation in other large-scale atmospheric processes.
Basic: The major commercial airlines and the Federal Aviation Administration have hired your firm to provide an independent forum to discuss the potential role of jet contrails in affecting climate change. Your task is to provide a comprehensive report on conditions required to produce contrails. Part of your report should focus on a detailed Earth system science analysis of the impact of contrails, perhaps highlighting specific regional or global areas where contrail formation may be most problematic.
Comprehensive: The debate about the role of contrail formation and climate change may have a dramatic impact on future aviation. If a positive feedback exists between contrail formation and temperature change (both absolute temperature and temperature range) then the effects could be magnified if projected increases in flight density occur. Does this mean a forced reduction in flight activity? Or are there other solutions? In this project your team is charged with investigating the science behind contrail formation, evaluating the evidence that supports or refutes the connection between climate change and contrails and researching possible solutions that might mitigate this problem. As part of your work you need to produce an Earth system science analysis of the effects of contrails on the Earth system.
**Note: Use of NASA's Earth Observations allows users to view cirrus clouds. Consider using the Cirrus Reflectance data from Terra/MODIS. A primer on how to use NEO is found here.
An image of contrails over the Midwest U.S. from Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured on November 25, 2006. Individual contrails are evident towards the southern part of the image. In the north, individual contrails have coalesced to form a thin but massive bank of high-altitude clouds. Watch contrails spread. Image: NASA Earth Observatory
In skies normally crosshatched with condensation trails, the only contrails seen in this image from September 12, 2001, were left by the plane returning President George W. Bush to Washington from Nebraska and several escort fighters. Image: NASA/Langley Research Center
This enhanced infrared image from the Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA's Terra satellite, shows widespread contrails over the southeastern United States during the morning of January 29, 2004. Such satellite data are critical for studying the effects of contrails. More... Image: NASA Earth Observatory
Contrails appear in the sky as workers leave the Launch Control Center after the launch of the space shuttle Discovery in Cape Canaveral, Fla., on Monday April 5, 2010. Image: NASA/Bill Ingalls
AIAA - Aerospace America Magazine
This is a good summary article from an airline industry group that discusses various details of contrail formation and climate change.
Air Traffic Shutdown Study
This website contains good graphics showing the dramatic decrease in air traffic density following the terrorist attacks of 9/11/2001.
Clouds and climate change
A report on the results of NASA research on the role of jet contrail formation and the potential impact on climate change.
Leaving a Trail - Contrails and climate change
This resource reports on work completed by NASA scientist Patrick Minnis providing a good summary of the research including graphs and images from the original resource.
Aviation and the Global Atmosphere - IPCC
An assessment by the IPCC on the impact of aviation on global climate. There are several sections related to contrails including the potential radiative forcing potential.
EPA Contrail Fact Sheet
Background information on contrail formation and impacts
Global Modeling of the Contrail and Contrail Cirrus Climate Impact
This article reviews the scientific knowledge and key problems regarding the modeling of the life cycle of contrail cirrus (including linear contrails), their global climate impact, and the validation of model simulations with suitable observational datasets.
Impact of aviation on climate in Belgium
A detailed look at the impact of aviation on atmospheric chemistry including formation of contrails. The data and analysis are for Europe with a focus on Belgium. Contains many excellent links on terminology.
Investigate conditions for contrail formation
In this applet you can control the air temperature and partial pressure of water required to form contrails.
NASA Subsonic Assessment Program (SASS)
This is a good portal to abundant data on contrail formation and climate impacts.
PBS Dimming the Sun - Contrails
An article about contrails - some basic facts and the controversies surrounding the role of contrails in climate change.
Contrails - Royal Meteorological Society
Basic information about contrails with suggestions for some activities and questions.
Digital Library for Earth System Science
The ultimate resource for Earth Science lesson plans, investigations and publications.
MY NASA DATA: Contrail Watching for Kids
In this introductory investigation, students explore the basics of contrails formation and classification.
Predicting Contrails Using an Appleman Chart
Military planners have been interested in condensation trail (contrail) forecasts since World War II. Contrails can make any aircraft easy to locate by enemy forces, and no amount of modern stealth technology can hide an aircraft if it leaves a persistent contrail in its wake. In 1953, a scientist named H. Appleman published a chart that can be used to determine when a jet airplane would or would not produce a contrail. For many years, the US Air Force Global Weather Center used a similar chart to make contrail forecasts. Teacher version
Clouds and the Earth's Radiant Energy System
Contrails can spread into cirrus clouds that reduce sunlight during the day and warm the Earth at night. This problem-based module explores cloud formation, cloud classification, and the role of clouds in heating and cooling the Earth; how to interpret TRMM images and data; and the role clouds play in the Earth's radiant budget and climate.
Physical Chemistry of Contrails
This is a 4-6 week long project that investigates the physical chemistry behind contrails.
Science Project: Contrail Studies from MY NASA DATA
Serious students, citizen scientists and regular weather watchers can use a camera and simple weather instruments to monitor and study contrails and to determine their possible environmental effects.
National Science Education Standards - Science Content Standards
The science content standards outline what students should know, understand, and be able to do in the natural sciences over the course of K-12 education.
- K-12 UNIFYING CONCEPTS AND PROCESSES
The understandings and abilities associated with the following concepts and processes need to be developed throughout a student's educational experiences:
- Systems, order, and organization
- Evidence, models, and explanation
- Constancy, change, and measurement
- GRADES 5-8 CONTENT STANDARDS
- Physical Science (Std B)
- Properties and changes of properties in matter
- Transfer of energy
- Science and Technology (Std E)
- Understanding about science and technology
- Science in Personal and Social Perspectives (Std F)
- Science and technology in society
- History and Nature of Science (Std G)
- GRADES 9-12 CONTENT STANDARDS
- Physical Science (Std B)
- Structure of atoms
- Structure and properties of matter
- Interactions of energy and matter
- Earth and Space Science (Std D)
- Energy in the earth system
- Geochemical cycles
- Science and Technology (Std E)
- Understanding about science and technology
- Science in Personal and Social Perspectives (Std F)
- Natural and human-induced hazards
- Science and technology in local, national, and global challenges
Principles and Standards for School Mathematics, National Council of Teachers of Mathematics (NCTM), 2000
This set of Standards proposes the mathematics concepts that all students should have the opportunity to learn. Each of these ten Standards applies across all grades, prekindergarten through grade 12. Even though each of these ten Standards applies to all grades, emphases and expectations will vary both within and between the grade bands (K-2, 3-5, 6-8, 9-12). For instance, the emphasis on number is greatest in prekindergarten through grade 2, and by grades 9-12, number receives less instructional attention. Also the total time for mathematical instruction will be divided differently according to particular needs in each grade band - for example, in the middle grades, the majority of instructional time would address algebra and geometry.
- STANDARD 1: NUMBER AND OPERATION
Mathematics instructional programs should foster the development of number and operation sense so that all students—
- understand numbers, ways of representing numbers, relationships among numbers, and number systems;
- use computational tools and strategies fluently and estimate appropriately.
- STANDARD 2: PATTERNS, FUNCTIONS, AND ALGEBRA
Mathematics instructional programs should include attention to patterns, functions, symbols, and models so that all students—
- understand various types of patterns and functional relationships;
- use symbolic forms to represent and analyze mathematical situations and structures;
- use mathematical models and analyze change in both real and abstract contexts.
- STANDARD 3: GEOMETRY AND SPATIAL SENSE
Mathematics instructional programs should include attention to geometry and spatial sense so that all students—
- select and use different representational systems, including coordinate geometry and graph theory;
- use visualization and spatial reasoning to solve problems both within and outside of mathematics.
- STANDARD 4: MEASUREMENT
Mathematics instructional programs should include attention to measurement so that all students—
- understand attributes, units, and systems of measurement;
- STANDARD 5: DATA ANALYSIS, STATISTICS, AND PROBABILITY
Mathematics instructional programs should include attention to data analysis, statistics, and probability so that all students—
- pose questions and collect, organize, and represent data to answer those questions;
- interpret data using methods of exploratory data analysis;
- develop and evaluate inferences, predictions, and arguments that are based on data;
- STANDARD 6: PROBLEM SOLVING
Mathematics instructional programs should focus on solving problems as part of understanding mathematics so that all students—
- build new mathematical knowledge through their work with problems;
- develop a disposition to formulate, represent, abstract, and generalize in situations within and outside mathematics;
- apply a wide variety of strategies to solve problems and adapt the strategies to new situations;
- monitor and reflect on their mathematical thinking in solving problems.
- STANDARD 7: REASONING AND PROOF
Mathematics instructional programs should focus on learning to reason and construct proofs as part of understanding mathematics so that all students—
- recognize reasoning and proof as essential and powerful parts of mathematics;
- make and investigate mathematical conjectures;
- develop and evaluate mathematical arguments and proofs;
- STANDARD 8: COMMUNICATION
Mathematics instructional programs should use communication to foster understanding of mathematics so that all students—
- organize and consolidate their mathematical thinking to communicate with others;
- express mathematical ideas coherently and clearly to peers, teachers, and others;
- extend their mathematical knowledge by considering the thinking and strategies of others;
- use the language of mathematics as a precise means of mathematical expression.
- STANDARD 9: CONNECTIONS
Mathematics instructional programs should emphasize connections to foster understanding of mathematics so that all students—
- recognize and use connections among different mathematical ideas;
- recognize, use, and learn about mathematics in contexts outside of mathematics.
- STANDARD 10: REPRESENTATION
Mathematics instructional programs should emphasize mathematical representations to foster understanding of mathematics so that all students—
- use representations to model and interpret physical, social, and mathematical phenomena.
Geography for Life: National Geography Standards, 1994
- THE WORLD IN SPATIAL TERMS
Geography studies the relationships between people, places, and environments by mapping information about them into a spatial context. The geographically informed person knows and understands:
- How to use maps and other geographic representations, tools and technologies to acquire, process, and report information from a spatial perspective
- How to use mental maps to organize information about people, places, and environments in a spatial context
- How to analyze the spatial organization of people, places, and environments on Earth’s surface
- PLACES AND REGIONS
The identities and lives of individuals and people are rooted in particular places and in those human constructs called regions. The geographically informed person knows and understands:
- That people create regions to interpret Earth’s complexity
- PHYSICAL SYSTEMS
Physical processes shape Earth’s surface and interact with plant and animal life to create, sustain, and modify ecosystems. The geographically informed person knows and understands:
- The physical processes that shape the patterns of Earth’s surface
- The characteristics and spatial distribution of ecosystems on Earth’s surface
- HUMAN SYSTEMS
People are central to geography in that human activities help shape Earth’s surface, human settlements and structures are part of Earth’s surface, and humans compete for control of Earth’s surface. The geographically informed person knows and understands:
- The characteristics, distribution, and migration of human populations on Earth’s surface
- ENVIRONMENT AND SOCIETY
The physical environment is modified by human activities, largely as a consequence of the ways in which human societies value and use Earth’s natural resources, and human activities are also influenced by Earth’s physical features and processes. The geographically informed person knows and understands:
- How human actions modify the physical environment
- How physical systems affect human systems
- THE USES OF GEOGRAPHY
Knowledge of geography enables people to develop an understanding of the relationships between people, places, and environments over time — that is, of Earth as it was, is, and might be. The geographically informed person knows and understands:
- How to apply geography to interpret the present and plan for the future
The International Society for Technology Education
From http://www.iste.org and
- BASIC OPERATIONS AND CONCEPTS
- Students demonstrate a sound understanding of the nature and operation of technology systems.
- SOCIAL, ETHICAL AND HUMAN ISSUES
- Students practice responsible use of technology systems, information, and software.
- Students develop positive attitudes toward technology uses that support lifelong learning, collaboration, personal pursuits, and productivity.
- TECHNOLOGY PRODUCTIVITY TOOLS
- Students use technology tools to enhance learning, increase productivity, and promote creativity.
- Students use productivity tools to collaborate in constructing technology-enhanced models, prepare publications, and produce other creative works.
- TECHNOLOGY COMMUNICATION TOOLS
- Students use telecommunications to collaborate, publish, and interact with peers, experts, and other audiences.
- Students use a variety of media and formats to communicate information and ideas effectively to multiple audiences.
- TECHNOLOGY RESEARCH TOOLS
- Students use technology to locate, evaluate, and collect information from a variety of sources.
- Students use technology tools to process data and report results.
- Students evaluate and select new information resources and technological innovations based on the appropriateness for specific tasks.
- TECHNOLOGY PROBLEM- SOLVING AND DECISION-MAKING TOOLS
- Students use technology resources for solving problems and making informed decisions.
- Students employ technology in the development of strategies for solving problems in the real world.