Climate Literacy: The Essential Principles of Climate Sciences summarizes the most important principles and concepts of climate science. It presents information that individuals and communities need to understand Earth’s climate, impacts of climate change, and approaches for adapting and mitigating change. This article provides background science- content knowledge for understanding Essential Principle 5: Our understanding of the climate system is improved through observations, theoretical studies, and modeling.
Essential Principle 5 describes specific methods with which scientists study the climate system. These approaches follow the same methods and principles of all scientific research, have demonstrated their reliability over time, and have withstood the rigorous process of scientific peer review. Climate researchers virtually all agree that human activities are altering the climate system but how do scientists know what they know?
Scientists recording data on Sperry Glacier. Photo courtesy of glaciernps, Flickr.
The iterative process of scientific research – from the collection of observations, review of prior research, analysis of data, modeling of various scenarios, and communication of findings – needs to be understood in order to throw light on the processes of science. Because so few people know an active scientist (let alone a climate scientist), and many researchers do not communicate their research to nontechnical audiences, it is important to understand some of the basics of the work of climate scientists. These ideas are not unique to climate science; all areas of scientific research share common themes such as
- How data is collected through a wide range of tools and techniques.
- How data is rigorously checked for quality and accuracy, and what scientists mean by “uncertainty” in the data they collect.
- How models are developed and fine-tuned, with outputs from various models to increase the accuracy of the models.
- Why “peer review” publications are such an important part of the scientific research process, even though these articles are usually very technical and often hard to understand by a non-expert.
Scientists have used these principles to develop global climate models (GCMs) to describe how the atmosphere, the oceans, the land, living things, ice, and energy from the Sun affect each other and Earth’s climate. Thousands of climate researchers use global climate models to better understand how global changes, such as increasing greenhouses gases or decreasing Arctic sea ice, will affect the Earth. The models are used to look hundreds of years into the future, so that they can predict how our planet’s climate will likely change.
The following concepts are fundamental to understanding Principle 5. You can click on a concept to find the background knowledge to help you understand the concept.
Note: For additional ideas and resources for teaching each of the Essential Principles of Climate Sciences go to the Climate Literacy & Energy Awareness Network. Another good introduction to the seven essential principles is Earth: The Operator’s Manual, an hour-long film shown on PBS and based on the book of the same name by Richard Alley. The entire film is available but the site also provides short segments for teachers to preview and download (free, simple registration required), both with closed captioning for ESL and science comprehension support. A video from the U.S. Environmental Protection Agency (EPA), Climate 101 (second row, middle) explores what climate change is, signs or indicators that the planet is warming, and why it matters. Watch the video to learn more about the causes and effects of climate change and practical solutions to reduce carbon dioxide and other greenhouse gas emissions. An excellent rebuttal of climate change skeptics can be found in Why the Global Warming Skeptics Are Wrong (published 2/22/2012).
Concept A. The components and processes of Earth’s climate system are subject to the same physical laws as the rest of the Universe. Therefore, the behavior of the climate system can be understood and predicted through careful, systematic study.
Concept B. Environmental observations are the foundation for understanding the climate system. From the bottom of the ocean to the surface of the Sun, instruments on weather stations, buoys, satellites, and other platforms collect climate data. To learn about past climates, scientists use natural records, such as tree rings, ice cores, and sedimentary layers. Historical observations, such as native knowledge and personal journals, also document past climate change.
Concept C. Observations, experiments, and theory are used to construct and refine computer models that represent the climate system and make predictions about its future behavior. Results from these models lead to better understanding of the linkages between the atmosphere-ocean system and climate conditions and inspire more observations and experiments. Over time, this iterative process will result in more reliable projections of future climate conditions.
Concept D. Our understanding of climate differs in important ways from our understanding of weather. Climate scientists’ ability to predict climate patterns months, years, or decades into the future is constrained by different limitations than those faced by meteorologists in forecasting weather days to weeks into the future.
Concept E. Scientists have conducted extensive research on the fundamental characteristics of the climate system and their understanding will continue to improve. Current climate change projections are reliable enough to help humans evaluate potential decisions and actions in response to climate change.
You can also see where these concepts are found in national standards documents as well as in common misconceptions in the Standards and Curriculum Connections article.
Concept A. The components and processes of Earth’s climate system are subject to the same physical laws as the rest of the Universe. Therefore, the behavior of the climate system can be understood and predicted through careful, systematic study.
Scientists share certain basic beliefs and attitudes about what they do and how they view their work. These have to do with the nature of the world and what can be learned about it. Science presumes that the things and events in the universe occur in consistent patterns that are comprehensible through careful, systematic study. Scientists believe that through the use of the intellect, and with the aid of instruments that extend the senses, people can discover patterns in all of nature.
Science also assumes that the universe is, as its name implies, a vast single system in which the basic rules are everywhere the same. Knowledge gained from studying one part of the universe is applicable to other parts. For instance, the same principles of motion and gravitation that explain the motion of falling objects on the surface of Earth also explain the motion of the moon and the planets. With some modifications over the years, the same principles of motion have applied to other forces – and to the motion of everything, from the smallest nuclear particles to the most massive stars, from sailboats to space vehicles, from bullets to light rays.
Scientists strive to make sense of observations of phenomena by constructing explanations for them that use, or are consistent with, currently accepted scientific principles. Such explanations may be either sweeping or restricted, but they must be logically sound and incorporate a significant body of scientifically valid observations. The credibility of scientific theories often comes from their ability to show relationships among phenomena that previously seemed unrelated (American Association for the Advancement of Science 1990).
To figure out the future of climate change, scientists develop and use tools to measure how the Earth responds to change. Some of these tools are global climate models. Using models, scientists can better understand how the Earth works and how it will react to change in the future. These models take into account all the parts of the Earth system including
- animals and plants (the biosphere)
- oceans, lakes, and rivers (the hydrosphere)
- icebergs, glaciers and ice sheets (the cryosphere)
- air (the atmosphere)
- volcanoes and moving continents (the geosphere)
Related Resources
In the Field: Scientists at Work
This series of 20 articles details the work of scientists in the Arctic and Antarctica.
Understanding Science: How Science Really Works
This site provides resources and strategies that enable K-16 teachers to reinforce the nature of science throughout their science teaching and offers clear and informative explanations of scientific endeavors for students and the general public.
Process of Science
This web resource contains 16 modules describing various aspects of scientific inquiry, data analysis, peer review, ethics and more.
How We Know What We Know About Our Changing Climate: Scientists and Kids Explore Global Warming
This acclaimed children’s book (age 12 and up) by Lynne Cherry and photojournalist Gary Braasch is appropriate for classroom use. The authors approach climate change from the perspective of the scientists who are exploring the world to discover more about Earth’s climate history.
Concept B. Environmental observations are the foundation for understanding the climate system. From the bottom of the ocean to the surface of the Sun, instruments on weather stations, buoys, satellites, and other platforms collect climate data. To learn about past climates, scientists use natural records, such as tree rings, ice cores, and sedimentary layers. Historical observations, such as native knowledge and personal journals, also document past climate change.
Scientists rely on accurate, standardized measurements to study change, whether those changes are in weather, climate, organisms, or the solar system beyond Earth. Today there are arrays of sophisticated instruments on the ground, in and under the water, in the air and in space recording data about our planet. While there are some gaps in the data coverage, in many areas the biggest challenge is actually the storage and analysis of the terabytes of data streaming off satellites and other instruments.
Scanning electron microscope (SEM) image of a pollen granule. Anne Bahnweg - 'Space invaders.' Photo courtesy of Engineering at Cambridge, Flickr.
To investigate the extent, speed, and effects of historical climate changes locally and globally, scientists rely on data collected from tree rings, ice cores, pollen samples, and the fossil record. Computers are used to detect possible patterns and cycles from these data.
Trees contain some of nature’s most accurate evidence of the past. Their growth layers, appearing as rings in the cross section of the tree trunk, record evidence of floods, droughts, insect attacks, lightning strikes, and even earthquakes. Each year, a tree adds to its girth, the new growth being called a tree ring. Tree growth depends upon local conditions such as water availability. Because the amount of water available to the tree varies from year to year, scientists can use tree-ring patterns to reconstruct regional patterns of drought and climatic change. This field of study, known as dendrochronology, was begun in the early 1900s by an American astronomer named Andrew Ellicott Douglass.
A tree ring consists of two layers: a light-colored layer grows in the spring and a dark-colored layer in late summer. During wet, cool years, most trees grow more than during hot, dry years and the rings are wider. Drought or a severe winter can cause narrower rings. If the rings are a consistent width throughout the tree, the climate was the same year after year. By counting and examining the rings of a tree, scientists can accurately determine the age and health of the tree and the growing season of each year.
Modern dendrochronologists seldom cut down a tree to analyze its rings. Instead, core samples are extracted using a borer that’s screwed into the tree and pulled out, bringing with it a straw-size sample of wood about four millimeters in diameter. The hole in the tree is then sealed to prevent disease.
Related Resources
Climate Change: Striking a Solar Balance (3:35)
This NASA video reviews the role of the sun in driving the climate system. It uses colorful animations to illustrate Earth’s energy balance and how increased greenhouse gases are creating an imbalance in the energy budget, leading to warming. The video also reviews how the NASA satellite program collects data on the sun.
How to talk to an OSTRICH: Global Warming Stopped in 1998! (2:37)
From Earth: An Operator’s Manual
Geoscientist and climate expert Richard Alley connects the dots of temperature to show the difference between short-term trends and long term direction. He uses milestones of his own life to make this key argument personal and memorable.
How to Talk to an Ostrich: Who says CO2 heats things up? (1:47)
From Earth: An Operator’s Manual
Some seem to think that the heat-trapping properties of carbon dioxide are exaggerated or are just a scientific phenomenon. But after World War 2 it was the US Air Force that studied CO2 most carefully: it’s heat-trapping properties could interfere with heat-seeking missiles. As the video says, “the atmosphere doesn’t care whether you study it for warring, or warming. Adding CO2 turns up the planet’s thermostat.”
CO2 in the Ice Core Record (3:01)
From Earth: An Operator’s Manual
This video segment, from the PBS NOVA program ‘Earth: The Operators’ Manual’ featuring climate expert Richard Alley, shows how ice cores stored at the National Ice Core Lab provide evidence that ancient ice contains records of Earth’s past climate – specifically carbon dioxide and temperature.
Can You Read a Tree?
In this informational text, readers learn how scientists use cross sections from trees to reconstruct past climates. The text also introduces readers to Methuselah, a nearly 5,000-year-old bristlecone pine tree in California and the oldest known living tree in the world.
Polar Vision
A set of seven short, classroom-ready video segments highlighting the work of climate scientists in polar regions. From the Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado.
Concept C. Observations, experiments, and theory are used to construct and refine computer models that represent the climate system and make predictions about its future behavior. Results from these models lead to better understanding of the linkages between the atmosphere-ocean system and climate conditions and inspire more observations and experiments. Over time, this iterative process will result in more reliable projections of future climate conditions.
A scientific model is any simplified representation of a natural phenomenon based on observations. Most children build models of the solar system in school to gain a deeper understanding of the relationships between planets and the sun. There are various types of climate models. Some focus on certain things that affect climate such as the atmosphere or the oceans. Models that look at few variables of the climate system may be simple enough to run on a personal computer. Most models take into account many factors of the atmosphere, biosphere, geosphere, hydrosphere, and cryosphere to model the entire Earth system. They take into account the interactions and feedbacks between these different parts of the planet. Earth is a complex place and so many of these models are very complex too. They include so many mathematical calculations that they must be run on supercomputers, which can do the calculations quickly. All climate models must make some assumptions about how the Earth works, but in general, the more complex a model, the more factors it takes into account, and the fewer assumptions it makes.
One example important to understanding climate change is modeling sea ice (frozen ocean water) processes. Information about sea ice can come from field camps, aircraft, and satellites. However, data from these sources are limited. Sensors cannot account for all characteristics of sea ice anytime and anywhere. Furthermore, the record of sea ice data has a limited history. Satellite observations date back only to the mid-1970s; other observations, such as ship records, may go back as far as the late 19th century, but they are sparse. Moreover, these data cannot predict the future of sea ice extent.
Sea Ice Patterns. Taken during NASA's two-year shipborne investigation to study how changing conditions in the Arctic affect the ocean's chemistry and ecosystems. Photo courtesy of NASA Goddard Photo Stream, Flickr.
To fill in the gaps in knowledge about sea ice, scientists use models to simulate sea ice processes. These models allow scientists to reconstruct historical patterns of sea ice and predict future changes. Due to the complex nature of the models, they are run on computers. Mathematical sea ice models are primarily used to study the important processes involved in the evolution of sea ice and are used for long-term climate studies. However, models are also used to provide short-term operational forecasts (one to five days) for ocean vessels in sea ice-covered regions, as well as seasonal forecasts (one to three months) to aid in planning. The U.S. Navy, for example, runs an operational sea ice model, the Polar Ice Prediction System (PIPS), to provide short-term forecasts of Arctic sea ice.
There are currently several complex global climate models that are used to predict future climatic change. At the National Center for Atmospheric Research (NCAR), researchers have developed the Community Climate System Model (CCSM), which is so complex that it requires about three trillion mathematics calculations to simulate a single day on planet Earth. It can take thousands of hours for a supercomputer to run the model. The model output, typically many gigabytes large, is analyzed by researchers and compared with other model results and with observations and measurement data. While no scientific model is perfectly accurate, they each provide some valuable insight into the working of natural systems. Like other scientific efforts, computer modeling improves over time with the combined work of many scientists and peer review.
Related Resources
Going With the Floe: A One-Time Drifter
This article describes a researcher’s history of studying sea ice and the dynamic nature of observed changes to the sea ice in the polar regions.
Concept D. Our understanding of climate differs in important ways from our understanding of weather. Climate scientists’ ability to predict climate patterns months, years, or decades into the future is constrained by different limitations than those faced by meteorologists in forecasting weather days to weeks into the future.
The climate where you live is called regional climate. It is the average weather in a place over more than 30 years. To describe the regional climate of a place, people often tell what the temperatures are like over the seasons, how windy it is, and how much rain or snow falls. The climate of a region depends on many factors including the amount of sunlight it receives, its height above sea level, the shape of the land, and how close it is to oceans. Since the equator receives more sunlight than the poles, climate varies depending on distance from the equator.
While the weather can change in just a few hours, climate changes over longer timeframes. Climate events, like El Nino, happen over several years, small-scale fluctuations happen over decades, and larger climate changes happen over hundreds and thousands of years. The amount of solar radiation, the chemistry of the atmosphere, clouds, and the biosphere all affect Earth’s climate.
Climate models have been developed from weather forecast models by coupling them with models of the ocean, land surface, vegetation, cryosphere, and other processes, so as to represent the complexity of the climate system. Changes in the means and extremes of temperature and precipitation in response to increasing greenhouse gases can be projected over decades to centuries even though the timing of individual weather events cannot be projected (Gardiner 2008).
Concept E. Scientists have conducted extensive research on the fundamental characteristics of the climate system and their understanding will continue to improve. Current climate change projections are reliable enough to help humans evaluate potential decisions and actions in response to climate change.
Global climate models are used to predict what will happen to Earth’s climate in the future. Groups like the Intergovernmental Panel on Climate Change (the IPCC) compare the results from several different climate models as they figure out what is most likely to happen. But how do scientists know whether a model’s predictions are correct? How do they figure out whether the model is doing a good job at predicting the future of climate change?
To figure out whether a climate model is doing a good job, scientists test the model against a time period for which actual measurements of Earth’s climate are available, the past 100 years for example. The results from the model are compared with the actual measurements of real climate. If the model and the actual measurements are similar, then the mathematics equations in the model that are used to describe how Earth works are probably quite accurate. If the model results are very different from our records of what actually happened, then the model needs some work.
There are still some uncertainties about our future climate because there are processes and feedbacks between different parts of the Earth that are not fully understood. These are difficult to include in the models until they are better understood. For example, the effects of clouds on climate is known to be a large, however it is not fully understood. So scientists are researching clouds to ensure that climate models are as accurate as possible (Gardiner 2011).
Another uncertainty in these predictions of future climate is not related to natural processes. Instead, the uncertainty is just how much pollution humans will be adding to the atmosphere in the future. Innovations that stop or limit the amount of greenhouses gases that are produced, laws and rules that change the amount of pollutants that are released, and how the growing human population lives in the future are all somewhat unknown. To deal with this, climate models are often run several times, each time with different amounts of pollution and development by humans.
Related Resources
Changing Planet
From the tropics to the Arctic Ocean, “Changing Planet” explores the impact that climate change is having on our planet. Each of the 15 videos, 3-5 minutes long, follows scientists in the field who are studying the dramatic impacts of rising temperatures in the air, in the water and on land. Designed specifically for classroom use, each report has a lesson plan and activities created by the “Windows to the Universe” team at the National Earth Science Teachers Association.
Climate Change: How Do We Know?
This page from the NASA’s Eyes on the Earth Global Climate Change web site provides an overview of the most compelling research that supports human-induced and rapid climate change.
RealClimate
Read real-time discussions of emerging climate science and policy, written by climate scientists.
References
American Association for the Advancement of Science. 1990. Science for All Americans Online. Retrieved September 22, 2011 http://www.project2061.org/publications/sfaa/online/chap1.htm
Gardiner, L. 2008. Modeling the Future of Climate Change. Windows to the Universe, National Earth Science Teachers Association. Retrieved September 21, 2011 http://www.windows2universe.org/earth/climate/cli_models.html
Gardiner, L. 2010. Accuracy and Uncertainty in Climate Models. Windows to the Universe, National Earth Science Teachers Association. Retrieved September 21, 2011 http://www.windows2universe.org/earth/climate/cli_models4.html
Kimberly Lightle wrote this article. She received her PhD in science education at The Ohio State University and is principal investigator of Beyond Weather and the Water Cycle, Beyond Penguins and Polar Bears, and the Middle School Portal 2 projects. Email Kim at beyondweather@msteacher.org
Copyright September 2011 – The Ohio State University. This material is based upon work supported by the National Science Foundation under Grant No. 1034922. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This work is licensed under an Attribution-ShareAlike 3.0 Unported Creative Commons license.
