examples of bibliography websites

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Cite a Website

Don't let plagiarism errors spoil your paper, citing a website in apa.

Once you’ve identified a credible website to use, create a citation and begin building your reference list. Citation Machine citing tools can help you create references for online news articles, government websites, blogs, and many other website! Keeping track of sources as you research and write can help you stay organized and ethical. If you end up not using a source, you can easily delete it from your bibliography. Ready to create a citation? Enter the website’s URL into the search box above. You’ll get a list of results, so you can identify and choose the correct source you want to cite. It’s that easy to begin!

If you’re wondering how to cite a website in APA, use the structure below.

Author Last Name, First initial. (Year, Month Date Published). Title of web page . Name of Website. URL

Example of an APA format website:

Austerlitz, S. (2015, March 3). How long can a spinoff like ‘Better Call Saul’ last? FiveThirtyEight. http://fivethirtyeight.com/features/how-long-can-a-spinoff-like-better-call-saul-last/

Keep in mind that not all information found on a website follows the structure above. Only use the Website format above if your online source does not fit another source category. For example, if you’re looking at a video on YouTube, refer to the ‘YouTube Video’ section. If you’re citing a newspaper article found online, refer to ‘Newspapers Found Online’ section. Again, an APA website citation is strictly for web pages that do not fit better with one of the other categories on this page.

Social media:

When adding the text of a post, keep the original capitalization, spelling, hashtags, emojis (if possible), and links within the text.

Facebook posts:

Structure: Facebook user’s Last name, F. M. (Year, Monday Day of Post). Up to the first 20 words of Facebook post [Source type if attached] [Post type]. Facebook. URL

Source type examples: [Video attached], [Image attached]

Post type examples: [Status update], [Video], [Image], [Infographic]

Gomez, S. (2020, February 4). Guys, I’ve been working on this special project for two years and can officially say Rare Beauty is launching in [Video]. Facebook. https://www.facebook.com/Selena/videos/1340031502835436/

Life at Chegg. (2020, February 7) It breaks our heart that 50% of college students right here in Silicon Valley are hungry. That’s why Chegg has [Images attached] [Status update]. Facebook. https://www.facebook.com/LifeAtChegg/posts/1076718522691591

Twitter posts:

Structure: Account holder’s Last name, F. M. [Twitter Handle]. (Year, Month Day of Post). Up to the first 20 words of tweet [source type if attached] [Tweet]. Twitter. URL

Source type examples: [Video attached], [Image attached], [Poll attached]

Example: Edelman, J. [Edelman11]. (2018, April 26). Nine years ago today my life changed forever. New England took a chance on a long shot and I’ve worked [Video attached] [Tweet]. Twitter. https://twitter.com/Edelman11/status/989652345922473985

Instagram posts:

APA citation format: Account holder’s Last name, F. M. [@Instagram handle]. (Year, Month Day). Up to the first 20 words of caption [Photograph(s) and/or Video(s)]. Instagram. URL

Example: Portman, N. [@natalieportman]. (2019, January 5). Many of my best experiences last year were getting to listen to and learn from so many incredible people through [Videos]. Instagram. https://www.instagram.com/p/BsRD-FBB8HI/?utm_source=ig_web_copy_link

If this guide hasn’t helped solve all of your referencing questions, or if you’re still feeling the need to type “how to cite a website APA” into Google, then check out our APA citation generator on CitationMachine.com, which can build your references for you!

APA Website Citation

- powered by chegg, create citations for free.

Website Book Journal Other

←Back to APA Citation Examples

Use the following template to cite a website using the APA citation format. There are also BibMe style guides for the MLA and Chicago styles.

Here’s a table of contents for this guide:

• Cite a website on BibMe citation generator
• Cite a website article with an author
• Cite a website article without an author
• Cite a website article without a date

How to Cite a Website in APA

Cite in websites in apa automatically with bibme.

To have your bibliography or works cited list automatically made for you, check out our free APA citation generator . Once you’re finished with your citations, you can also find help with creating an APA title page .

Citing a general website article in APA with an author

Author, A. (Year, Month Date of Publication). Article title . Website/Publisher Name. URL

Simmons, B. (2015, January 9). The tale of two Flaccos . Grantland. http://grantland.com/the-triangle/the-tale-of-two-flaccos/

Citing a general website article in APA without an author

Article title . (Year, Month Date of Publication). Website/Publisher Name. URL

Teen posed as doctor at West Palm Beach hospital: police . (2015, January 16). NBC Miami. http://www.nbcmiami.com/news/local/Teen-Posed-as-Doctor-at-West-Palm-Beach-Hospital-Police-288810831.html

Citing a general website article in APA without a date

Author, A. (n.d.). Article title . Website/Publisher Name. URL

University of California Santa Barbara. (n.d.). About UC Santa Barbara . UC Santa Barbara. https://www.ucsb.edu/about

Note that if the webpage contents are likely to change, include a retrieval date, formatted as follows:

University of California Santa Barbara. (n.d.). About UC Santa Barbara . UC Santa Barbara. Retrieved November 3, 2021, from https://www.ucsb.edu/about

How to cite from social media in APA

Apa citation example for facebook.

Author/Page Name. (Year, Month Date). First 20 words of post text [Status update]. Facebook. URL

Gates, B. (2020, December 1). 75 years after its founding, the United Nations’ work is as important as ever. In addition to working towards the [Status update]. Facebook. https://www.facebook.com/BillGates/posts/10157610753046961

APA citation example for Twitter

Author name [@twitterhandle]. (Year, Month Date). First 20 words of tweet text [Tweet]. Twitter. URL

 World Health Organization [@WHO]. (2021, January 27). Nutritious & safe food is 🔑 to achieve #HealthForAll. Together, let’s create food systems that are: 🥗 Healthy ♻️ Sustainable [Tweet]. Twitter. https://twitter.com/WHO/status/1354450281321345029

Note that if emojis are used in a tweet (or any type of social media post that you are citing), they should be included and counted as one word (but should not be italicized). Hashtags also count as one word.

APA citation example for Instagram

Author name [@username]. (Year, Month Date). First 20 words of post text [Photograph or Video]. Instagram. URL

National Geographic [@NatGeo]. (2021, January 26). Photo by @paulnicklen / I took this photo while waiting for leopard seals in Antarctica—my favorite assignment from 20 years [Photograph]. Instagram. https://www.instagram.com/p/CKg4XeSDHhG/

For more information on how to cite in APA, check out the APA style guide and  Cornell .

Important Note:

For information on how to cite other types of online sources in APA, check out the following guides:

• Online Book
• Online Magazine
• Online Newspaper
• Online Journal
• Online Encyclopedia

←Back to APA Citation Guide

“A word after a word after a word is power.” — Margaret Atwood

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When there is no date available for a webpage, use “n.d.” signifying “no date” in in-text citations, along with the author’s surname or the name of the institution.

Example in-text citation with author and no date:

(Ramsay, n.d.)

Example in-text citation with institution and no date:

(NIMH, n.d.)

Per section 10 of the APA Publication Manual , the contributor’s name (either the individual or the organization who shared the Instagram post) along with the year should be used when citing an Instagram post in an in-text citation.

Parenthetical: (Poster’s Last Name, year post was published)

Narrative: Poster’s Last Name (year post was published)

Parenthetical: (Vedika, 2022)

Narrative: Vedika (2022)

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Home / Guides / Citation Guides / Citation Basics / Annotated Bibliography Format & Examples

Annotated Bibliography Format & Examples

A complete guide to the mla & apa annotated bibliography.

If you’ve just received an assignment that requires an MLA or APA annotated bibliography, you may be wondering where to start. This guide will help answer all of your questions and includes step-by-step instructions on how to do an annotated bibliography in MLA style, as well as an APA annotated bibliography. You will also find sample annotated bibliographies, real-life examples, and opportunities to practice what you have learned.

The MLA ( Modern Language Association ) and APA (American Psychological Association) are not associated with this guide. All of the information provided here, however, offers direction for students and researchers who use these citation styles in their work.

The structures and annotated bibliography templates on this page were created by the in-house librarians at EasyBib.com.

If you’re simply looking for an example of an annotated bibliography (both in MLA format and APA format), scroll down toward the bottom of the page. We’ve included links to visuals for those of you who need help with the structure and styling of an annotated bibliography. If you’re looking for a variety of annotated bibliography topics, and you’re truly searching for the answer to, “What is an annotated bibliography?” then continue reading!

Here’s a run-through of everything this page includes:

Table of contents

What is an annotated bibliography, annotations vs. abstract, why include annotations.

• Step 1: Analyze your sources

Step 2: Write the descriptions

• Step 3a: Formatting an MLA style annotated bibliography
• Step 3b: Formatting an APA style annotated bibliography

Annotated Bibliography Templates

Using the easybib annotation tool.

A bibliography is a complete list of the sources that were used to complete a research paper or project.

Depending on the style guide you follow, you may also see this called a Works Cited (also called an MLA bibliography) or Reference List (APA format). Each listed source, or citation , shares information about the author, title, publishing year, and other details that serve to credit the original authors whose work informed your research. These details also help other students and researchers find and read the source materials.

When your research is related to a scholastic assignment, you should always verify your instructor’s requirements for the types and number of sources to include, as well as the style you should adhere to when formatting your paper and bibliography.

An MLA annotated bibliography and an APA format annotated bibliography are bibliographies that include a concise explanation, or annotation , of each listed source. Depending on the assignment, this annotation may be solely descriptive, or analytical.

An abstract and annotation should not be confused; they differ in both their substance as well as their placement in a paper.

Annotations: 

• Usually found in bibliographies at the end of a paper
• Are subjective
• Purpose is to summarize and evaluate . It should briefly communicate the work’s main point, but also discuss the background of the author or study, and the strengths/weaknesses of the work.

Abstracts: 

• Usually found in journal databases or the beginning of a paper
• Are objective
• Purpose is to summarize . It should provide a short overview of the article and communicate the main points and themes.

If you would like to learn more , this link further explores the difference between an abstract and an annotation.

This resource provides additional information on how to write a bibliography with annotations in other formats. You can also take advantage of the plagiarism checker and bibliography tools that come with EasyBib Plus to help you create your reference lists.

Before you learn how to make an annotated bibliography, you may be wondering why you need to.

Sometimes instructors want you to create and include annotations in your bibliography, either as part of an assignment or as an assignment unto itself. Understanding the purpose of this approach to your reference list can help to ensure that you gain all of the benefits that the annotated bibliography process provides.

As a student, this method will help you develop or hone your research skills, providing you with practice not only in locating sources but also in analyzing and evaluating them for relevance and quality.

Your instructor will gain insight into your research abilities, as well, allowing them to assess your work more thoroughly. If you plan to publish your research, this comprehensive approach to detailing your sources will provide readers and other researchers with a substantial directory of resources to evaluate for their own work.

Whether you’re publishing or submitting your annotated bibliography, make sure your spelling and wording is correct! If you need to brush up on any parts of speech topics, check out our interjection , determiner , and adverb pages!

Step 1: Analyze your sources 

Each annotation should be a summarization or analysis of your source. If you have been tasked with writing annotations as part of a research paper or project, begin to create both the citation and notes on the source while you identify and analyze your sources.

Not only will this approach help you to hone your research skills and identify sources that are relevant and useful for your topic, but you will also save time. When done in this manner, both your citations and annotations will be nearly complete before you begin to write the body of your paper.

Analyzing your potential sources requires a two-pronged approach that first evaluates the author, publication, and date, and then examines the content.

When conducting your initial assessment of the source, consider some of the following questions to guide your appraisal:

• What qualifies the author to write on this subject?
• Is the author affiliated with a reputable institution in this field?
• Is the author credentialed or otherwise considered an expert in this field?
• Is this source current?
• Is this the most recent edition?
• Is the publisher reputable?
• Is the journal reputable?

Once your primary evaluation is complete, you will move on the assessing the content itself. Consider some of these elements as you review each source:

• Who is the intended audience?
• Is the author presenting her opinion or interpretation as the truth, or stating facts?
• What supporting evidence does the author provide?
• Did the author perform the research, or curate and present the research of others?
• If the author used the research of others, are the sources the author cites credible?
• Are there errors or omissions of fact?
• Is the author writing objectively and without bias?

Also, consider the value each source provides to you:

• Is the information helpful for your particular assignment?
• Does it help answer your research question(s)?
• Is this source different from your other sources, or does it repeat information you already have?
• Is the source providing you with a different perspective on your topic, or changing your beliefs or thinking about your subject?

To make it easier for you to create your reference page, write your notes in the format you will be using when you construct this part of the assignment (for instance, as short phrases or complete sentences). Once you have identified all of the sources you wish to include, you will merely need to insert what you have already written on the page and write your citation, which is explained in the next section.

Click here for additional information and a supplementary annotated bibliography sample. For an MLA bibliography example (with annotations),  check out our visual example of an MLA annotated bibliography .

An annotated bibliography entry may be written either as short phrases or complete sentences. Your instructor will advise you of which approach you are required to take.

Annotations should include either:

• The main points from the source, as well as the topics covered, the approach used, and any findings.
• Or your critical evaluation.
• A standard annotation is approximately one paragraph.
• Take care not to include any unnecessary details, as the goal is to summarize each source as succinctly as possible and, in some cases, evaluate them.
• Your field of study or instructor will determine what format your annotated bibliography will use. In this guide, you’ll find examples of an MLA and an APA annotated bibliography.

Here is an annotated bibliography example MLA annotation for the book The Elements of Eloquence: Secrets of the Perfect Turn of Phrase by UK author and blogger Mark Forsyth:

The author, Mark Forsyth, examines the rhetorical devices used in the English language, analyzing the patterns and formats that create memorable quotes. He traces the history of rhetoric to the Ancient Greeks, and provides an abridged timeline, following their use and evolution through to modern day. The author also explores the broader subject of persuasion and maps out the role that the figures of rhetoric play in it. In all, he examines over thirty devices, dissecting notable passages and phrases from pop music, the plays of William Shakespeare, the Bible, and more to explore the figures of rhetoric at work within each of them. Thorough definitions accompany this examination of structure to demonstrate how these formulas have been used to generate famously memorable expressions as well as how to reproduce their effects.

Notice how the annotated bibliography MLA entry above is descriptive enough so the reader has an idea of what the source is about with just a single paragraph. For more information on annotations, check out this informative site . If you’re looking to strengthen your writing in general, reading these grammar guides could be a good start.

For guidance on creating entries in MLA format , APA format , and more styles , check out the EasyBib library of resources or try the EasyBib annotation tool—we talk about it below!

Step 3a: MLA annotated bibliography format

The MLA Style Center and the current edition of the MLA Handbook provide the following guidance for formatting an MLA annotated bibliography:

• Title your reference page as “Annotated Bibliography” or “Annotated List of Works Cited.”
• Place each annotation after its reference.
• Annotations should typically not exceed a single paragraph.
• Annotations should be indented one inch from the start of your citation.
• Double-space all text on the page.
• 1-inch margins around the page.

Sources in an annotated bibliography can be organized alphabetically by the first word in each reference (as with a normal Works Cited page), by publication date, or by subject.

For a visual example of an annotated bibliography, as well as specific annotation examples, visit the MLA annotated bibliography guide .

If you are required to share your references in a manner other than in MLA bibliography format, the EasyBib style guides can help you with many common styles. While you’re at it, check out their conjunction , preposition , and pronoun pages to help keep your paper in mint condition!

Step 3b: APA annotated bibliography format

The American Psychological Association states that your instructor should set the guidelines for your annotated bibliography, but asks that the bibliography be formatted according to their standard reference page rules (see Section 9.51 of the Publication Manual ). If your teacher has requested an APA formatted annotated bibliography, first ask them for guidelines. Otherwise, here are some quick rules for you to follow:

• Double space all text on the page.  
• Title your page “Annotated Bibliogra phy”. Bold and center the title.  
• Organize references alphabetically by the first word of each reference.  
• Only the first line of a ref erence is flush with the left margin. Any other lines after the first line should be indented ½ inch from the left.  
• Add annotations on the next line after their paired reference.   
• Fully indent annotations by a ½ inch from the left.  
• Keep annotations short. No more than one paragraph.  

For examples of a  properly formatted APA annotation, visit this guide on APA annotated bibliographies .  

In comparison to the sample annotated bibliography MLA, the APA sample formats its page elements and references differently.

Students and researchers who type their research notes can save time by using an annotated bibliography template in MLA format while reviewing and analyzing sources. By adding the relevant information into a pre-formatted template, you’ll create a resource that helps you when you begin writing your paper in addition to saving time by completing your references and summaries alongside your research.

Students who prefer to take notes by hand can employ a modified version of this approach, with an additional step required to transfer your handwritten and formatted references from your notebook to populate your reference page.

Bibliography Template for MLA

To create an annotated bibliography MLA template, copy the following details into the program in which you will take notes or hand write it on the top margin of a page in your notebook. For each source, use this template to guide you as you identify the necessary details and insert them into your notes:

• Author (Last name, First name).
• Title of source.
• Title of the container ,
• Other contributors (names and roles),
• Publication Date,
• Location of the source (such as URL or page range).
• Summary or Analysis.

The MLA 9 model for MLA works cited entries offers a single format for all source type, and a great deal of flexibility to include the information most relevant to your topic and omit that which isn’t.

Hopefully our visual annotated bibliography example in MLA above has helped. If you still have lingering questions, visit the MLA Style Center online ( linked here ). Also, here’s a guide if you’re looking for more on the related topic of MLA in-text & parenthetical citations .

Bibliography Template for APA

Students and researchers who are still asking themselves how to piece together an annotated bibliography, or still questioning what is an annotated bibliography, could probably benefit from a template, similar to the one above. This one, however, is for those of you who are tasked with creating an annotated bibliography in the style created by the American Psychological Association.

The tricky thing about this specific style though, is that every reference is styled differently. Books, websites, journal articles, newspaper articles, and many others each have their own reference structure.

For most sources though, you should look for the following, basic information:

• Type of source
• Author (last name, first name)
• Title of source/article/web page, etc.
• Title of where source was found (e.g., database name, website name, etc.)
• Other contributors (names and roles)
• Location of the source (such as URL, DOI, or page range)
• Summary or Analysis

We understand it can get tricky, and it’s very different from the Modern Language Association’s structure for references. Take a moment to either use the other handy guides on EasyBib.com or use our automatic generator to form your references in just a few clicks. Our tools help take the pain away from having to rack your brain to form references properly. Capitals, lowercase letters, italics, quotation marks, punctuation in the appropriate places, it can all be quite overwhelming. Do yourself a favor, and use the EasyBib automatic citation generator.

Even though there are a lot of different variations, here’s a commonly used structure for sources:

Author’s Last Name, First initial, Middle initial. (Year the source was published). Title of the source . Retrieved from (insert the website address here)

Underneath the reference, include your summary or analysis paragraph.

Hopefully, this page helped answer all of your “What is an annotated bibliography?” questions. If you’re seeking out an annotated bibliography generator, follow the steps above the annotated bibliography examples.

Looking for additional help with other related topics? Don’t forget about the various beneficial guides on EasyBib.com! Our APA in-text citation guide and our APA parenthetical citation guide are two of our most popular pages. Learn the ins and outs of referencing your work in the body of your paper with our thorough, complete, and reader-friendly guides.

If you are creating a bibliography in MLA format, the EasyBib MLA bibliography generator can help save you time formatting your citations and annotations correctly. You can create entries for websites, books, videos, databases, dictionary articles, and many other types of sources.

In addition to forming the citations, you can also enter your annotation text to produce the complete entry for each source. The process for this is simple. You can follow along below to practice creating one:

• First, select your source type from among the 50+ available options. For this example, we will use the acting career of Keanu Reeves as our research topic and use the movie Point Break from 1991 as our first source. To cite this film, you would select the option for “Film/Online Video.” As you follow along, pick the option that is suitable for your source if you are using a different example.
• Enter the title of your source or, if you are citing a website, you may enter the URL. (Now would be a great time to peek at how to cite websites in MLA ). After you enter the title or URL for your reference, the EasyBib citation tool will scan for titles that match it and provide you with a list of results. Select “Cite this” next to the listing that matches your source.
• You will see a citation form. This gives you the option to add additional relevant or necessary information. For our sample topic, we will specifically cite Keanu Reeves as the performer and Kathryn Bigelow as the director.
• After entering any additional details, you have the option to expand your entry and include an annotation. To do so, select “Add annotation” at the bottom of the page, and a text box will open up.

Then, type your summary or analysis into the text box. If you took notes during the research stage using the format of your paper, this might be as simple as copying and pasting your already written summary or critique. Once you have entered all of the necessary information, select “Create citation” to generate the complete entry. You can then copy and paste this into your MLA bibliography.

Here’s what it’ll look like:

Point Break . Directed by Kathryn Bigelow, performance by Keanu Reeves, 20th Century Fox, 1991.

Reeves’ role as rookie FBI Agent Johnny Utah in Point Break marks the turning point in his Hollywood film career. While he’d risen to fame due to the success of the Bill and Ted franchise, his status today as an action star began when Point Break provided him with the material to establish himself as capable of portraying more than the lovable but unserious characters of his previous starring roles. In a parallel arc, director Kathryn Bigelow’s career also sees a shift beginning with Point Break , establishing her within the traditional action genre as a serious director capable of creating high-action and visually memorable films. While Point Break leaves plenty to be desired in terms of dialogue, it afforded Bigelow and Reeves the opportunities to showcase themselves and their talent in new ways that still echo in their work today.

• Works Cited

Harner, James L.  On Compiling an Annotated Bibliography . 2nd ed., Modern Language Association of America, 2000.

MLA Handbook . 9th ed., Modern Language Association of America, 2021.

Publication Manual of the American Psychological Association . 7th ed., American Psychological Association, 2020.

“What Guidance Should I Give My Students for Preparing an Annotated Bibliography?” The MLA Style Center , The Modern Language Association, 4 Nov. 2016, style.mla.org/annotated-bibliographies/.

Visit our EasyBib Twitter feed to discover more citing tips, fun grammar facts, and the latest product updates.

Published October 18, 2015. Updated July 25, 2021.

Written and edited by Michele Kirschenbaum and Elise Barbeau. Michele Kirschenbaum is a school library media specialist and is the in-house librarian at EasyBib.com. Elise Barbeau is the Citation Specialist at Chegg. She has worked in digital marketing, libraries, and publishing.

Citation Guides

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• Block Quotes
• Citation Examples
• et al Usage
• In-text Citations
• Page Numbers
• Reference Page
• Sample Paper
• APA 7 Updates
• View APA Guide
• Bibliography
• MLA 8 Updates
• View MLA Guide

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An annotated bibliography is a list containing complete information of sources, such as journals, books, and reports, cited in the text. In addition, it provides a brief description of each source in about 100–150 words. The annotation can explain the topics covered in the source or evaluate the source. The main objective of giving the annotation is to provide the reader the importance, accuracy, and value of the source.

An example of an annotated bibliography in APA style is given below.

Lim, L. (2014). Ideology, rationality and reproduction in education: A critical discourse analysis. Discourse: Studies in the Cultural Politics of Education, 35 (1), 61–76. https://doi:10.1080/01596306.2012.739467

Lim (2014) focuses on issues of power and ideology dominant in curricular discourses of rationality to study a discourse analysis of the goals of one of the most important curricula in the teaching of thinking. He proves that political and class commitments are reproduced in the forms of thinking that are valued in societies. Through his research, Lim asserts that such curricula engage in making our understanding of what thinking and rationality are. It must facilitate the social reproduction of a specific proportion of the middle class.

If you want to evaluate or provide a description of a source you are citing, you can create an annotated bibliography. Write your annotation in 100–150 words and add it below the source for which you are providing your annotation. Remember, your annotation should provide the reader the importance, accuracy, and value of the source. Below are the guidelines and rules to be followed while writing an annotated bibliography for APA style:

Order your reference entries in alphabetical order, similar to how you would order entries in the reference list.

If you want to add an annotation to an entry, add it as a fresh paragraph below the reference entry. The annotation is indented 0.5 inches from the left margin. However, the first line of the annotation is not indented.

To format the annotated bibliography, follow the recommendations given below:

Set the left, right, top, and bottom margins to 1 inch.

Give double-line spacing.

Title the page “Annotated Bibliography.” Set it in bold.

The title should be aligned to the center of the page.

As you format reference entries, left-align all references in the annotated bibliography section. If any entry runs over more than a line, indent the subsequent lines 0.5 inch from the left margin.

Arrange all reference entries alphabetically according to the surname of the authors.

Provide your annotations below the reference entry for which you want to give your annotation. Indent annotations 0.5 inches from the left margin.

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The current warming trend is different because it is clearly the result of human activities since the mid-1800s, and is proceeding at a rate not seen over many recent millennia. 1 It is undeniable that human activities have produced the atmospheric gases that have trapped more of the Sun’s energy in the Earth system. This extra energy has warmed the atmosphere, ocean, and land, and widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.

Earth-orbiting satellites and new technologies have helped scientists see the big picture, collecting many different types of information about our planet and its climate all over the world. These data, collected over many years, reveal the signs and patterns of a changing climate.

Scientists demonstrated the heat-trapping nature of carbon dioxide and other gases in the mid-19th century. 2 Many of the science instruments NASA uses to study our climate focus on how these gases affect the movement of infrared radiation through the atmosphere. From the measured impacts of increases in these gases, there is no question that increased greenhouse gas levels warm Earth in response.

Scientific evidence for warming of the climate system is unequivocal.

Intergovernmental Panel on Climate Change

Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly 10 times faster than the average rate of warming after an ice age. Carbon dioxide from human activities is increasing about 250 times faster than it did from natural sources after the last Ice Age. 3

The Evidence for Rapid Climate Change Is Compelling:

Global Temperature Is Rising

The planet's average surface temperature has risen about 2 degrees Fahrenheit (1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide emissions into the atmosphere and other human activities. 4 Most of the warming occurred in the past 40 years, with the seven most recent years being the warmest. The years 2016 and 2020 are tied for the warmest year on record. 5 Image credit: Ashwin Kumar, Creative Commons Attribution-Share Alike 2.0 Generic.

The Ocean Is Getting Warmer

The ocean has absorbed much of this increased heat, with the top 100 meters (about 328 feet) of ocean showing warming of 0.67 degrees Fahrenheit (0.33 degrees Celsius) since 1969. 6 Earth stores 90% of the extra energy in the ocean. Image credit: Kelsey Roberts/USGS

The Ice Sheets Are Shrinking

The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost an average of 279 billion tons of ice per year between 1993 and 2019, while Antarctica lost about 148 billion tons of ice per year. 7 Image: The Antarctic Peninsula, Credit: NASA

Glaciers Are Retreating

Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska, and Africa. 8 Image: Miles Glacier, Alaska Image credit: NASA

Snow Cover Is Decreasing

Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and the snow is melting earlier. 9 Image credit: NASA/JPL-Caltech

Sea Level Is Rising

Global sea level rose about 8 inches (20 centimeters) in the last century. The rate in the last two decades, however, is nearly double that of the last century and accelerating slightly every year. 10 Image credit: U.S. Army Corps of Engineers Norfolk District

Arctic Sea Ice Is Declining

Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades. 11 Credit: NASA's Scientific Visualization Studio

Extreme Events Are Increasing in Frequency

The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events. 12 Image credit: Régine Fabri,  CC BY-SA 4.0 , via Wikimedia Commons

Ocean Acidification Is Increasing

Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30%. 13 , 14 This increase is due to humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the ocean. The ocean has absorbed between 20% and 30% of total anthropogenic carbon dioxide emissions in recent decades (7.2 to 10.8 billion metric tons per year). 1 5 , 16 Image credit: NOAA

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2. In 1824, Joseph Fourier calculated that an Earth-sized planet, at our distance from the Sun, ought to be much colder. He suggested something in the atmosphere must be acting like an insulating blanket. In 1856, Eunice Foote discovered that blanket, showing that carbon dioxide and water vapor in Earth's atmosphere trap escaping infrared (heat) radiation. In the 1860s, physicist John Tyndall recognized Earth's natural greenhouse effect and suggested that slight changes in the atmospheric composition could bring about climatic variations. In 1896, a seminal paper by Swedish scientist Svante Arrhenius first predicted that changes in atmospheric carbon dioxide levels could substantially alter the surface temperature through the greenhouse effect. In 1938, Guy Callendar connected carbon dioxide increases in Earth’s atmosphere to global warming. In 1941, Milutin Milankovic linked ice ages to Earth’s orbital characteristics. Gilbert Plass formulated the Carbon Dioxide Theory of Climate Change in 1956.

3. IPCC Sixth Assessment Report, WG1, Chapter 2 Vostok ice core data; NOAA Mauna Loa CO2 record O. Gaffney, W. Steffen, "The Anthropocene Equation." The Anthropocene Review 4, issue 1 (April 2017): 53-61. https://doi.org/abs/10.1177/2053019616688022.

4. https://www.ncei.noaa.gov/monitoring https://crudata.uea.ac.uk/cru/data/temperature/ http://data.giss.nasa.gov/gistemp

5. https://www.giss.nasa.gov/research/news/20170118/

6. S. Levitus, J. Antonov, T. Boyer, O Baranova, H. Garcia, R. Locarnini, A. Mishonov, J. Reagan, D. Seidov, E. Yarosh, M. Zweng, " NCEI ocean heat content, temperature anomalies, salinity anomalies, thermosteric sea level anomalies, halosteric sea level anomalies, and total steric sea level anomalies from 1955 to present calculated from in situ oceanographic subsurface profile data (NCEI Accession 0164586), Version 4.4. (2017) NOAA National Centers for Environmental Information. https://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/index3.html K. von Schuckmann, L. Cheng, L,. D. Palmer, J. Hansen, C. Tassone, V. Aich, S. Adusumilli, H. Beltrami, H., T. Boyer, F. Cuesta-Valero, D. Desbruyeres, C. Domingues, A. Garcia-Garcia, P. Gentine, J. Gilson, M. Gorfer, L. Haimberger, M. Ishii, M., G. Johnson, R. Killick, B. King, G. Kirchengast, N. Kolodziejczyk, J. Lyman, B. Marzeion, M. Mayer, M. Monier, D. Monselesan, S. Purkey, D. Roemmich, A. Schweiger, S. Seneviratne, A. Shepherd, D. Slater, A. Steiner, F. Straneo, M.L. Timmermans, S. Wijffels. "Heat stored in the Earth system: where does the energy go?" Earth System Science Data 12, Issue 3 (07 September 2020): 2013-2041. https://doi.org/10.5194/essd-12-2013-2020.

7. I. Velicogna, Yara Mohajerani, A. Geruo, F. Landerer, J. Mouginot, B. Noel, E. Rignot, T. Sutterly, M. van den Broeke, M. Wessem, D. Wiese, "Continuity of Ice Sheet Mass Loss in Greenland and Antarctica From the GRACE and GRACE Follow-On Missions." Geophysical Research Letters 47, Issue 8 (28 April 2020): e2020GL087291. https://doi.org/10.1029/2020GL087291.

8. National Snow and Ice Data Center World Glacier Monitoring Service

9. National Snow and Ice Data Center D.A. Robinson, D. K. Hall, and T. L. Mote, "MEaSUREs Northern Hemisphere Terrestrial Snow Cover Extent Daily 25km EASE-Grid 2.0, Version 1 (2017). Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/MEASURES/CRYOSPHERE/nsidc-0530.001 . http://nsidc.org/cryosphere/sotc/snow_extent.html Rutgers University Global Snow Lab. Data History

10. R.S. Nerem, B.D. Beckley, J. T. Fasullo, B.D. Hamlington, D. Masters, and G.T. Mitchum, "Climate-change–driven accelerated sea-level rise detected in the altimeter era." PNAS 15, no. 9 (12 Feb. 2018): 2022-2025. https://doi.org/10.1073/pnas.1717312115.

11. https://nsidc.org/cryosphere/sotc/sea_ice.html Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, Zhang and Rothrock, 2003) http://psc.apl.washington.edu/research/projects/arctic-sea-ice-volume-anomaly/ http://psc.apl.uw.edu/research/projects/projections-of-an-ice-diminished-arctic-ocean/

12. USGCRP, 2017: Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 470 pp, https://doi.org/10.7930/j0j964j6 .

13. http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

14. http://www.pmel.noaa.gov/co2/story/Ocean+Acidification

15. C.L. Sabine, et al., “The Oceanic Sink for Anthropogenic CO2.” Science 305 (16 July 2004): 367-371. https://doi.org/10.1126/science.1097403.

16. Special Report on the Ocean and Cryosphere in a Changing Climate , Technical Summary, Chapter TS.5, Changing Ocean, Marine Ecosystems, and Dependent Communities, Section 5.2.2.3. https://www.ipcc.ch/srocc/chapter/technical-summary/

Header image shows clouds imitating mountains as the sun sets after midnight as seen from Denali's backcountry Unit 13 on June 14, 2019. Credit: NPS/Emily Mesner Image credit in list of evidence: Ashwin Kumar, Creative Commons Attribution-Share Alike 2.0 Generic.

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