Climate Science – the Basics

logo for animal agriculture climate change which includes a weather vane with cow and top

Many lines of evidence, from ice cores to marine deposits, indicate that Earth’s temperature, sea level, and distribution of plant and animal species have varied substantially throughout history. Ice cores from Antarctica suggest that over the past 400,000 years global temperature has varied as much as 10 degrees Celsius through ice ages and periods warmer than today. Before human influence, natural factors (such as the pattern of earth’s orbit and changes in ocean currents) are believed to be responsible for climate changes.

The Climate System.

Past Climate and Trends

Climate Models

Since the Industrial Revolution, human influences including fossil fuel emissions, urbanization, large-scale agriculture, deforestation and other activities have disturbed the natural system. Many scientists suspect that these activities have contributed a portion of the 1 degree Celsius increase in global average temperature over the past century and are in some part responsible for ocean warming, rising sea levels, melting glaciers and retreating sea ice.

The following resources are intended to provide a basic understanding of earth’s climate system, natural and human-related factors that influence climate change, climate variability, and weather, and an overview of regional and global trends in temperature and precipitation that influence management decisions made by animal producers. Related: How Does Climate Change Impact Animal Agriculture?

Fact sheet: Why Does Climate Change? (look below the preview box and title for a download link)

Educator Materials

If you would like to use the video, slides, or factsheet for educational programs, please visit the curriculum page for download links for this and other climate change topics.

Recommended Resources

About the Author

Pam Knox is a climatologist at the University of Georgia Athens. She has extensive experience in climate and agriculture topics. More about Pam….


This page was developed as part of a project “Animal Agriculture and Climate Change” an extension facilitation project to increase capacity for ag professionals. It was funded by USDA-NIFA under award # 2011-67003-30206.

Sources of Agricultural Greenhouse Gases

The conversation about climate change largely revolves around greenhouse gases. Agriculture is both a source and sink for greenhouse gases (GHG). A source is a net contribution to the atmosphere, while a sink is a net withdrawal of greenhouse gases.  In the United States, agriculture is a relatively small contributor, with approximately 8% of the total greenhouse gas emissions, as seen in Figure 1.

Most agricultural emissions originate from soil management, enteric fermentation (microbial action in the digestive system), energy use, and manure management (Figure 2).  The primary greenhouse gases related to agriculture are (in descending order of magnitude) methane, nitrous oxide, and carbon dioxide.

Fact sheet: Contribution of Greenhouse Gases: Animal Agriculture in Perspective (look below the preview box and title for a download link)

U.S. GHG Inventory Figure 1: U.S. greenhouse gas inventory with electricity distributed to economic sectors (EPA, 2013) 

Ag Sources of GHGs

Figure 2: U.S. agricultural greenhouse gas sources (Adapted from Archibeque, S. et al., 2012)

Animal Agriculture’s Contribution to Greenhouse Gas Emissions

Within animal production, the largest emissions are from beef followed by dairy, and largely dominated by the methane produced in during cattle digestion (Figure 3).

Greenhouse gas emissions from livestock in 2008

Figure 3: Greenhouse gas emissions from livestock in 2008 (USDA, 2011)

Excess nitrogen in agriculture systems can be converted to nitrous oxide through the nitrification-denitrification process. Nitrous oxide is a very potent greenhouse gas, with 310 times greater global warming potential than carbon dioxide.  Nitrous oxide can be produced in soils following fertilizer application. This includes both commercial, inorganic fertilizer as well as organic fertilizers like manure or compost.

As crops grow, photosynthesis removes carbon dioxide from the atmosphere and stores it in the plants and soil life. Soil and plant respiration adds carbon dioxide back to the atmosphere when microbes or plants breakdown molecules to produce energy.  Respiration is an essential part of growth and maintenance for most life on earth. This repeats with each growth, harvest, and decay cycle, therefore, feedstuffs and foods are generally considered to be carbon “neutral.”

Some carbon dioxide is stored in soils for long periods of time.  The processes that result in carbon accumulation are called carbon sinks or carbon sequestration.  Crop production and grazing management practices influence the soil’s ability to be a net source or sink for greenhouse gases.  Managing soils in ways that increase organic matter levels can increase the accumulation (sink) of soil carbon for many years.

Enteric Fermentation

The next largest portion of livestock greenhouse gas emissions is from methane produced during enteric fermentation in ruminants – a natural part of ruminant digestion where microbes in the first chamber of the stomach, the rumen, breaks down feed and produces methane as a by-product. The methane is released  primarily through belching.

As with plants, animals respire carbon dioxide, but also store some in their bodies, so they too are considered a neutral source of atmospheric carbon dioxide.

Manure Management

A similar microbial process to enteric fermentation leads to methane production from stored manure.  Anytime the manure sits for more than a couple days in an anaerobic (without oxygen) environment, methane will likely be produced.  Methane can be generated in the animal housing, manure storage, and during manure application. Additionally, small amounts of methane is produced from manure deposited on grazing lands.

Nitrous oxide is also produced from manure storage surfaces, during land application, and from manure in bedded packs & lots. Related: Archived webinar on GHG Emissions Research in Animal Ag

Other sources

There are many smaller sources of greenhouse gases on farms. Combustion engines exhaust carbon dioxide from fossil fuel (previously stored carbon) powered vehicles and equipment.  Manufacturing of farm inputs, including fuel, electricity, machinery, fertilizer, pesticides, seeds, plastics, and building materials, also results in emissions.

To learn more about how farm emissions are determined and see species specific examples, see the Carbon Footprint resources.

To learn about how to reduce on-farm emissions through mitigation technology and management options, see the Reducing Emissions resources.

Carbon Footprint

Definition: carbon footprint is the total greenhouse gas emissions for a given person, place, event or product.

Carbon footprints are created using a process called life cycle assessment. Life cycle assessment or LCA is a method of resource accounting where quantitative measures of inputs, outputs and impacts of a product are determined.

Life cycle assessment is commonly used to:

  • find process or production improvements
  • compare different systems or products
  • find the ‘hot spots’ in a product’s life cycle where the most environmental impacts are made
  • help businesses or consumers make informed sourcing decisions


Key Assumptions

boundaries of the system: each higher tier provides a more complete picture of the product’s impacts, however requires more time and resources to complete.

  1. Gate to Gate (LCA Tier I) – inventories the direct emissions for a single product of process
  2. Cradle to Gate (Tier II) – inputs are taken back to the initial extraction as natural resources up to a certain point in the product’s life such as its sale from the farm, i.e. farm gate.  This will include both direct  and indirect emissions from the product.
  3. Cradle To Grave (Tier III) – the product is followed through the consumer to its eventual recycling or disposal.

Sources of variation

Different researchers may get different results when performing a LCA on the same product. This can happen for many reasons:

  • System boundary definition
  • Inclusion/exclusion of secondary/ indirect sources
  • Inclusion/exclusion of biogenic carbon (stored in organisms)
  • Inclusion/exclusion of carbon dioxide from fuel combustion
  • Functional relationships used
  • Global warming potential indexes
  • Inclusion/exclusion of carbon sequestration

Related: Six archived webinars on the sources of animal ag ghg’s (some are general and some are species-specific)

Educator Materials

If you would like to use the video, slides, or factsheet for educational programs, please visit the curriculum page for download links for this and other climate change topics.

Recommended Reading – How Many Greenhouse Gases Does Agriculture Emit?

U.S. Agriculture Emissions

International Agriculture Emissions

Carbon Footprints and Life Cycle Analysis

Greenhouse Gas Regulations for Animal Agriculture

Visit Climate Change Regulation, Policy, and Market Opportunities


Author: Crystal A. Powers – University of Nebraska-Lincoln

This material was developed through support from the USDA National Institute for Food and Agriculture (NIFA) under award #2011-67003-30206.

Youth Ag Greenhouse Gas Educational Lab Materials Via Pork Production Scenarios

Waste to Worth: Spreading science and solutions logoWaste to Worth home | More proceedings….


Many of today’s high school students have little insight into the basic day-to-day operational decisions and challenges faced by Agricultural producers. Therefore, there is a need for the development of ag-centric and dynamic educational material. Furthermore; there is an even greater need to provide high-school instructors with innovative classroom materials and instructional tools that are conducive to the structured conveyance of ag principles. Targeting the need for these innovative ag educational materials within Arkansas classrooms, this project presents an dynamic lab activity with emphasis on introductory level subject matter about Arkansas swine production systems and the related greenhouse gas emissions. Due to the particular nature of the subject matter, the activity materials were crafted into two complementary products for practicality. The first product is a compilation of swine production reference materials including: terminology and layman definitions of Arkansas swine management strategies and the basic dynamics of greenhouse gasses (CO2, N2O, CH4) as they relate to swine production. The second product is a scenario based critical thinking exercise, implemented from a manipulative decision-tree platform.


  1. Educate students within the state of Arkansas about the various management systems intrinsic to swine production operations within their state.
  2. Provide students insight into the management obstacles that Arkansas swine producers are challenged with through balancing Carbon footprints, economic resources, natural resources, and legal compliance with production profitability and productivity

What Did We Do?

This project presents an dynamic lab activity with emphasis on introductory level subject matter about Arkansas swine production systems and the related greenhouse gas emissions. The activity materials were crafted into two complementary products for practicality. The first product is a compilation of swine production reference materials including: terminology and layman definitions of Arkansas swine management strategies and the basic dynamics of common greenhouse gasses (CO2, N2O, CH4) as they relate to this activities scope of swine production. The reference material serves as both an introduction to basic ideas and practices native to swine production and GHGs, and as a guide which aids the students in completion of the second product (lab activity).

The second product is a scenario based critical thinking exercise, implemented from a manipulative decision-tree platform. Flashcards are used to represent three specific swine management systems using a three tier hierarchy. This hierarchy is distinguished by the allocation of Categories, Components, and Options. The “Categories” are the designated ranking class and will represent three major swine production management systems: Housing Management, Waste Management, and Feed Management. The “Components’ are the first sub-order class, and are used to represent various functions/considerations that comprise each “Category” of production system. The “Options” class holds the lowest position within the hierarchy and represents the different configurations/settings for the individual “Components”. For the context of this exercise the students will act as consultants hired by a producer to design the three management systems (via the flashcards) to “best match” the producer’s desired specifications, as defined within by a supplied catalog of unique scenarios.

Graphical reference to the hierarchical structure of the manipulatives used within this project’s lab activity.

Future Plans

Implementation of this project’s developed lab-activity within Arkansas’ high school classrooms via the Arkansas Farm Bureau supported (Ag-In-the-Classroom) program.


Szymanski “Rick” Fields II, Program Associate, Biological and Agricultural Engineering, University of Arkansas Division of Agriculture Extension

Karl VanDevender, Professor-Engineer, Biological and Agricultural Engineering, University of Arkansas Division of Agriculture Extension

Additional Information


This is a NIFA funded project (Proposal # 2010-04269; Title of Proposal “Integrated Resource Management Tool to Mitigate the Carbon Footprint of Swine Produced in the U.S”)

Special thanks to Donna VanDevender (High School Science Teacher-Bauxite Arkansas) for her insight into the development of the materials and for providing the opportunity to conduct trial runs of the lab-activity.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.

Western Region Animal Agriculture and a Changing Climate

Western Region Animal Agriculture and a Changing Climate Extension Project

Our overall goal is for Extension—working with partner organizations—to effectively inform and influence livestock and poultry producers and consumers of animal products in all regions of the U.S. to foster production practices that are environmentally sound, climatically compatible, and economically viable.

Western Region Website-AACC

Farm Management Decision Aid Tools

Webcast Presentations

Fact Sheets

Regional Information

Online Certification Course

Brochures/Conference Visuals

Western Region Website-AACC

Farm Management Decision Aid Tools

Integrated Farm System Model (IFSM) and Dairy Gas Emissions Model (DairyGEM) – training presentation by Al Rotz.

Education received through either of these comprehensive model evaluations will lead to the development of more sustainable dairy and beef production systems.

The IFSM (Integrated Farm System Model) is a tool for evaluating environmental and economic effects of different farm management scenarios. The user enters information on cropping practices, facilities, equipment, the herd and other farm parameters. Sample farms of various sizes and types are provided with the model software to provide a starting point. Information generated by the model includes crop yields, feed production and use, animal production, manure handled, production costs and net return to management. The model’s environmental outputs include average annual soil balances of N, P, K and C, erosion of sediment, P runoff, nitrate leaching, emissions of ammonia, hydrogen sulfide and greenhouse gases, and the carbon footprint of the feed, animal weight or milk produced.

The Dairy Gas Emission Model (DairyGEM) is an educational tool that predicts ammonia and hydrogen sulfide volatilization, GHG emissions, and the carbon footprint of the milk produced. DairyGEM is used to study the interacting effects of management changes on major emission sources from feed production to the return of manure back to the land.

To download software and for more information about IFSM, please visit:

To download software and for more information about DairyGEM, please visit:

About the Presenter:

Dr. Al Rotz is an agricultural engineer at the USDA-ARS Pasture Systems and Watershed Management Research Unit in University Park, PA. His work focuses on the development and use of models to evaluate the performance, environmental impact and economics of alternative technologies and management strategies applied to integrated farming systems for dairy or beef production.

IFSM and DairyGEM Tool Training Presentation

(If one of the video windows is blank, please refresh the page.)

If you are interested in specific segments of the entire video tool training above for either IFSM or DairyGEM, please refer to the separate video segments below.


Introduction to both the Integrated Farm System Model (IFSM) and Dairy Gas Emissions Model (DairyGEM)


IFSM tool training (using dairy as an example)

**IMPORTANT Note: this segment also supports the use of DairyGEM


IFSM beef example and dairy example


DairyGEM Tool Training

***Note: for further instruction related to DairyGEM use, please refer to Segment 2

DeNitrification-DeComposition (DNDC) Model

DNDC (i.e., DeNitrification-DeComposition) is a computer simulation model of carbon and nitrogen biogeochemistry in agro-ecosystems. The model can be used for predicting crop growth, soil temperature and moisture regimes, soil carbon dynamics, nitrogen leaching, and emissions of trace gases including nitrous oxide (N2O), nitric oxide (NO), dinitrogen (N2), ammonia (NH3), methane (CH4) and carbon dioxide (CO2). In order to download the DNDC model files you will need to register and provide a valid email, as well as your affiliation and intended use. After registration and confirming your email you will be able to download the files from the DNDC Model Download page.

On the Download page, you will find 3 simulation models of interest.

The DNDC model – A computer simulation model for predicting crop yield, soil carbon sequestration, nitrogen leaching, and trace gas emissions in agro-ecosystems.

The Manure -DNDC Model- Ac computer simulation for predicting GHG and NH3 emissions from manure systems.

US Cropland GHG Calculator- A decision support system for quantifying impacts of management alternatives on GHG emissions from Agro-ecosystems in the U.S.

Manure and Nutrient Reduction Estimator Tool (MANURE Tool)

The MANURE Tool  provides a system to quantify methane and and other GHG emission reductions and the environmental benefits of renewable energy produced by digesters at dairy and swine operations. The tool is based upon a full and accurate assessment of baseline conditions at the animal feed operation, which is a key element of the emission reduction calculation. This tool can be used to assess the quantity of emission reductions associated with implementation of specific technologies and/or practices. More information about the tool can be found on the Manure and Nutrient Reduction Estimator site.


The COMET-FARM tool is a whole farm and ranch carbon and GHG accounting and reporting system. It is intended to help users account for the carbon flux and GHG emissions related to their farm and ranch management activities, and help them explore the impacts to emissions of alternative management scenarios. The tool guides the user through describing the farm/ranch’s management practices including alternative future management scenarios. Once complete, a report is generated comparing the carbon changes and GHG emissions between current management practices and future scenarios. More information about COMET FARM can be found on the COMET-FARM site.

Farm Smart

Farm Smart is designed to give producers the ability to access and mitigate their environmental profile, track and measure their progress, plan for future improvements and report outcomes of practice changes to customers, community members, regulators and other stakeholders. The system features 3 tools: the Farm Smart Environmental Calculator, the Farm Smart Farm Energy Efficiency tool, and the Farm Smart Decision Support tool. Go to the Farm Smart site to download these tools and for more information.

Webcast Presentations

Fact Sheets

Regional Information

United States Global Change Research Program (USGCRP) Information:



  Northern Great Plains


  Southern Great Plains








(Hint:  These links may take a few minutes to load.  If you get a black screen and there is a note on the bottom task bar that says “done”, scroll down a little.)


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Archived Past E-Newsletters

July 29, 2014 E-newsletter

July 11, 2014 E-newsletter

June 27, 2014 E-newsletter

June 13, 2014 E-newsletter

January 17, 2014 E-newsletter

November 22, 2013 E-newsletter

November 8, 2013 E-newsletter

October 11, 2013 E-newsletter

September 20, 2013 E-newsletter

September 13, 2013 E-newlsetter

August 30, 2013 E-newsletter

August 16, 2013 E-newsletter

July 19, 2013 E-newsletter

June 1, 2013 E-newsletter

May 10, 2013 E-newsletter

April 24, 2013 E-newsletter

Animal Ag Climate Change Newsletter Vol. 1, March 2012 (this may take a minute or so to load)

Online Certification Course

This online course is free and was developed to answer questions that the livestock and animal agriculture industry is facing related to climate.  Nationwide, producers and stakeholders are asking questions about climate change: Is it happening? Are unusual weather patterns and events becoming more frequent? Should we be planning and managing for the future? Where can we get un-biased information that serves the livestock and ag community?

This online course will provide valuable information from which to feel confident in answering these frequent questions. Also, the online platform eliminates the extra travel expense for professional development.

Students that take this course will learn about the areas of climate and weather trends, impacts, adaptation, mitigation, policy, climate science and effective communication. Upon completion, they can receive CEUs from multiple professional societies.

Or please contact Liz Whitefield at if you have any questions.

Brochures/Conference Visuals

 Brochure:   Animal Agriculture and Climate Change (this may take a minute or so to load)