example of cause and effect essay pdf

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

10.8 Cause and Effect

Learning objectives.

• Determine the purpose and structure of cause and effect in writing.
• Understand how to write a cause-and-effect essay.

The Purpose of Cause and Effect in Writing

It is often considered human nature to ask, “why?” and “how?” We want to know how our child got sick so we can better prevent it from happening in the future, or why our colleague a pay raise because we want one as well. We want to know how much money we will save over the long term if we buy a hybrid car. These examples identify only a few of the relationships we think about in our lives, but each shows the importance of understanding cause and effect.

A cause is something that produces an event or condition; an effect is what results from an event or condition. The purpose of the cause-and-effect essay is to determine how various phenomena relate in terms of origins and results. Sometimes the connection between cause and effect is clear, but often determining the exact relationship between the two is very difficult. For example, the following effects of a cold may be easily identifiable: a sore throat, runny nose, and a cough. But determining the cause of the sickness can be far more difficult. A number of causes are possible, and to complicate matters, these possible causes could have combined to cause the sickness. That is, more than one cause may be responsible for any given effect. Therefore, cause-and-effect discussions are often complicated and frequently lead to debates and arguments.

Use the complex nature of cause and effect to your advantage. Often it is not necessary, or even possible, to find the exact cause of an event or to name the exact effect. So, when formulating a thesis, you can claim one of a number of causes or effects to be the primary, or main, cause or effect. As soon as you claim that one cause or one effect is more crucial than the others, you have developed a thesis.

Consider the causes and effects in the following thesis statements. List a cause and effect for each one on your own sheet of paper.

• The growing childhood obesity epidemic is a result of technology.
• Much of the wildlife is dying because of the oil spill.
• The town continued programs that it could no longer afford, so it went bankrupt.
• More young people became politically active as use of the Internet spread throughout society.
• While many experts believed the rise in violence was due to the poor economy, it was really due to the summer-long heat wave.

Write three cause-and-effect thesis statements of your own for each of the following five broad topics.

• Health and nutrition

The Structure of a Cause-and-Effect Essay

The cause-and-effect essay opens with a general introduction to the topic, which then leads to a thesis that states the main cause, main effect, or various causes and effects of a condition or event.

The cause-and-effect essay can be organized in one of the following two primary ways:

• Start with the cause and then talk about the effects.
• Start with the effect and then talk about the causes.

For example, if your essay were on childhood obesity, you could start by talking about the effect of childhood obesity and then discuss the cause or you could start the same essay by talking about the cause of childhood obesity and then move to the effect.

Regardless of which structure you choose, be sure to explain each element of the essay fully and completely. Explaining complex relationships requires the full use of evidence, such as scientific studies, expert testimony, statistics, and anecdotes.

Because cause-and-effect essays determine how phenomena are linked, they make frequent use of certain words and phrases that denote such linkage. See Table 10.4 “Phrases of Causation” for examples of such terms.

Table 10.4 Phrases of Causation

The conclusion should wrap up the discussion and reinforce the thesis, leaving the reader with a clear understanding of the relationship that was analyzed.

Be careful of resorting to empty speculation. In writing, speculation amounts to unsubstantiated guessing. Writers are particularly prone to such trappings in cause-and-effect arguments due to the complex nature of finding links between phenomena. Be sure to have clear evidence to support the claims that you make.

Look at some of the cause-and-effect relationships from Note 10.83 “Exercise 2” . Outline the links you listed. Outline one using a cause-then-effect structure. Outline the other using the effect-then-cause structure.

Writing a Cause-and-Effect Essay

Choose an event or condition that you think has an interesting cause-and-effect relationship. Introduce your topic in an engaging way. End your introduction with a thesis that states the main cause, the main effect, or both.

Organize your essay by starting with either the cause-then-effect structure or the effect-then-cause structure. Within each section, you should clearly explain and support the causes and effects using a full range of evidence. If you are writing about multiple causes or multiple effects, you may choose to sequence either in terms of order of importance. In other words, order the causes from least to most important (or vice versa), or order the effects from least important to most important (or vice versa).

Use the phrases of causation when trying to forge connections between various events or conditions. This will help organize your ideas and orient the reader. End your essay with a conclusion that summarizes your main points and reinforces your thesis. See Chapter 15 “Readings: Examples of Essays” to read a sample cause-and-effect essay.

Choose one of the ideas you outlined in Note 10.85 “Exercise 3” and write a full cause-and-effect essay. Be sure to include an engaging introduction, a clear thesis, strong evidence and examples, and a thoughtful conclusion.

Key Takeaways

• The purpose of the cause-and-effect essay is to determine how various phenomena are related.
• The thesis states what the writer sees as the main cause, main effect, or various causes and effects of a condition or event.

The cause-and-effect essay can be organized in one of these two primary ways:

• Start with the cause and then talk about the effect.
• Start with the effect and then talk about the cause.
• Strong evidence is particularly important in the cause-and-effect essay due to the complexity of determining connections between phenomena.
• Phrases of causation are helpful in signaling links between various elements in the essay.

Writing for Success Copyright © 2015 by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

CauseEffect Essay

In the realm of academic writing, the cause and effect essay stands as a fascinating exercise that delves into the intricate web of connections between events, actions, and outcomes. This genre of composition seeks to explore the underlying relationships between various elements, shedding light on the ripple effects that shape our world. In this article, we’ll take an in-depth look at cause and effect essay examples, uncovering their essence, and providing you with a comprehensive guide to master the art of crafting these insightful pieces.

1. Cause and Effect Essay Structure

Size: 255 KB

2. Great Topics for Cause and Effect Essay

3. Cause and Effect Essay Example

Size: 102 KB

4. Cause and Effect Essay Template

Size: 29 MB

5. Cause and Effect Essay Definition

Size: 60 KB

6. College Cause and Effect Essay

Size: 27 KB

7. Persuasive Cause and Effect Essay

Size: 205 KB

8. Simple Cause and Effect Essay

Size: 168 KB

9. Best Cause and Effect Essay

Size: 425 KB

10. Cause and Effect Essay Cheat Sheet

Size: 85 KB

11. Patterns Cause and Effect Essay

Size: 617 KB

12. Formal Cause and Effect Essay

Size: 309 KB

13. Printable Cause and Effect Essay

14. Editable Cause and Effect Essay

15. Organization Cause and Effect Essay

Size: 337 KB

16. Cause and Effect Essay Practice

What is a Cause and Effect Essay?

A cause and effect essay is a type of expository writing that investigates the relationships between events, actions, or phenomena. It aims to uncover the reasons (causes) behind a particular occurrence and highlight the resulting consequences (effects). By examining these connections, writers can offer readers a deeper comprehension of how various factors interplay within a given context.

How to write a Cause and Effect Essay

Before we embark on this enlightening journey of crafting a cause and effect essay, let’s outline the fundamental steps that will guide us through the process. By following these steps, you’ll be equipped to create a structured and compelling essay that reveals the intricate patterns behind seemingly unrelated events.

Step 1: Choosing a Topic

Select a topic that piques your interest and is conducive to cause and effect analysis. It could be a social issue, scientific discovery, historical event, or any subject that offers a fertile ground for exploration.

Step 2: Conducting Research

Gather relevant information through various sources, such as books, articles, case studies, and scientific methods . Observe behaviors , identify key elements, and understand the context surrounding your chosen topic.

Step 3: Developing a Thesis Statement

Craft a clear and concise thesis statement that outlines the main objective of your essay. This statement should encapsulate the cause-and-effect relationship you aim to explore.

Step 4: Organizing Your Essay

Create an outline that serves as the skeleton of your essay. Choose from different outline formats, such as chronological, categorical, or sequential, depending on the nature of your topic. This will help you arrange your ideas logically and maintain a coherent flow throughout your essay.

What’s the difference between cause and effect and correlation?

While cause and effect imply a direct relationship between events, correlation suggests a statistical association. Cause and effect delve into the mechanism behind an outcome, whereas correlation focuses on the simultaneous occurrence of two variables.

Can I use first-person pronouns in a cause and effect essay?

Generally, it’s recommended to maintain an objective tone in academic writing. However, if your essay involves personal experiences or observations, carefully integrate first-person pronouns while emphasizing the cause-and-effect relationship.

How do I ensure a strong link between causes and effects in my essay?

Use appropriate verbs to establish a clear cause-and-effect connection. Verbs like “cause,” “result in,” “lead to,” “trigger,” and “contribute to” help elucidate the relationships between events and their outcomes.

In the realm of academic exploration, cause and effect essays serve as invaluable tools for dissecting the complex tapestry of existence. By tracing the threads that bind events and outcomes, we gain a deeper understanding of the world’s inner workings. Armed with this knowledge and the steps outlined above, you are well-equipped to embark on your own cause and effect essay journey, unraveling the mysteries that shape our reality. So, grab your metaphorical magnifying glass and start deciphering the intricate web of cause and effect today.

CauseEffect Essay Generator

Text prompt

• Instructive
• Professional

Write a CauseEffect Essay on how pollution affects ocean life

Explain in a CauseEffect Essay the impact of social media on student productivity

Cause and Effect Essay Outline: Types, Examples and Writing Tips

20 June, 2020

9 minutes read

Author:  Tomas White

This is a complete guide on writing cause and effect essays. Find a link to our essay sample at the end. Let's get started!

What is a Cause and Effect Essay?

A cause and effect essay is the type of paper that the author is using to analyze the causes and effects of a particular action or event. A curriculum usually includes this type of exercise to test your ability to understand the logic of certain events or actions.

If you can see the logic behind cause and effect in the world around you, you will encounter fewer problems when writing. If not, writing this kind of paper will give you the chance to improve your skillset and your brain’s ability to reason.

“Shallow men believe in luck or in circumstance. Strong men believe in cause and effect.” ― Ralph Waldo Emerson

In this article, the  Handmade Writing team will find out how to create an outline for your cause and effect essay – the key to successful essay writing.

Types of the Cause and Effect Essay

Before writing this kind of essay, you need to draft the structure. A good structure will result in a good paper, so it’s important to have a plan before you start. But remember , there’s no need to reinvent the wheel: just about every type of structure has already been formulated by someone.

If you are still unsure about the definition of an essay, you can take a look at our guide:  What is an Essay?

Generally speaking, there are three types of cause and effect essays. We usually differentiate them by the number of and relationships between the different causes and the effects. Let’s take a quick look at these three different cases:

1. Many causes, one effect

This kind of essay illustrates how different causes can lead to one effect. The idea here is to try and examine a variety of causes, preferably ones that come from different fields, and prove how they contributed to a particular effect. If you are writing about World War I, for example, mention the political, cultural, and historical factors that led to the great war.

By examining a range of fundamental causes, you will be able to demonstrate your knowledge about the topic.

Here is how to structure this type of essay:

• Introduction
• Cause #3 (and so on…)
• The effect of the causes

2. One cause, many effects

This type of cause and effect essay is constructed to show the various effects of a particular event, problem, or decision. Once again, you will have to demonstrate your comprehensive knowledge and analytical mastery of the field. There is no need to persuade the reader or present your argument . When writing this kind of essay, in-depth knowledge of the problem or event’s roots will be of great benefit. If you know why it happened, it will be much easier to write about its effects.

Here is the structure for this kind of essay:

• Effect #3 (and so on…)

3. Chain of causes and effects

This is the most challenging type. You need to maintain a chain of logic that demonstrates a sequence of actions and consequences, leading to the end of the chain. Although this is usually the most interesting kind of cause and effect essay, it can also be the most difficult to write.

Here is the outline structure:

• Effect #1 = Cause #2
• Effect #2 = Cause #3
• Effect #3 = Cause #4 (and so on…)

Cause and Effect Essay Outline Example

Let’s take a look at an example. Below, you will find an outline for the topic “The causes of obesity” (Type 1) :

As you can see, we used a blended strategy here. When writing about the ever-increasing consumption of unhealthy food, it is logical to talk about the marketing strategies that encourage people to buy fast food. If you are discussing fitness trainers, it is important to mention that people need to be checked by a doctor more often, etc.

In case you face some issues with writing your Cause and Effect essay, you can always count on our Essay Writers !

How do I start writing once I have drafted the structure?

If you start by structuring each paragraph and collecting suitable examples, the writing process will be much simpler. The final essay might not come up as a classic five paragraph essay – it all depends on the cause-effect chain and the number of statements of your essay.

In the Introduction, try to give the reader a general idea of what the cause and effect essay will contain. For an experienced reader, a thesis statement will be an indication that you know what you are writing about. It is also important to emphasize how and why this problem is relevant to modern life. If you ever need to write about the Caribbean crisis, for instance, state that the effects of the Cold War are still apparent in contemporary global politics. 

Related Post: How to write an Essay introduction | How to write a Thesis statement

In the Body, provide plenty of details about what causes led to the effects. Once again, if you have already assembled all the causes and effects with their relevant examples when writing your plan, you shouldn’t have any problems. But, there are some things to which you must pay particular attention. To begin with, try to make each paragraph the same length: it looks better visually. Then, try to avoid weak or unconvincing causes. This is a common mistake, and the reader will quickly realize that you are just trying to write enough characters to reach the required word count.

Moreover, you need to make sure that your causes are actually linked to their effects. This is particularly important when you write a “chained” cause and effect essay (type 3) . You need to be able to demonstrate that each cause was actually relevant to the final result. As I mentioned before, writing the Body without preparing a thorough and logical outline is often an omission.

The Conclusion must be a summary of the thesis statement that you proposed in the Introduction. An effective Conclusion means that you have a well-developed understanding of the subject. Notably, writing the Conclusion can be one of the most challenging parts of this kind of project. You typically write the Conclusion once you have finished the Body, but in practice, you will sometimes find that a well-written conclusion will reveal a few mistakes of logic in the body!

Cause and Effect Essay Sample

Be sure to check the sample essay, completed by our writers. Use it as an example to write your own cause and effect essay. Link: Cause and effect essay sample: Advertising ethic issues .

Tips and Common Mistakes from Our Expert Writers

Check out Handmadewriting paper writing Guide to learn more about academic writing!

A life lesson in Romeo and Juliet taught by death

Due to human nature, we draw conclusions only when life gives us a lesson since the experience of others is not so effective and powerful. Therefore, when analyzing and sorting out common problems we face, we may trace a parallel with well-known book characters or real historical figures. Moreover, we often compare our situations with […]

Ethical Research Paper Topics

Writing a research paper on ethics is not an easy task, especially if you do not possess excellent writing skills and do not like to contemplate controversial questions. But an ethics course is obligatory in all higher education institutions, and students have to look for a way out and be creative. When you find an […]

Art Research Paper Topics

Students obtaining degrees in fine art and art & design programs most commonly need to write a paper on art topics. However, this subject is becoming more popular in educational institutions for expanding students’ horizons. Thus, both groups of receivers of education: those who are into arts and those who only get acquainted with art […]

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons
• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

7: Cause-and-Effect Essay

• Last updated
• Save as PDF
• Page ID 5337
• Lumen Learning
• 7.1: Introduction to Cause-and-Effect Essay
• 7.2: “Cultural Baggage” by Barbara Ehrenreich
• 7.3: “Women in Science” by K.C. Cole
• 7.4: Writing for Success- Cause and Effect
• 7.5: Student Sample- Cause-and-Effect Essay

Cause And Effect Essay Guide

Cause And Effect Essay Outline

How to Create a Cause and Effect Outline - An Easy Guide

10 min read

People also read

Best Cause and Effect Essay Examples To Get Inspiration + Simple Tips

How To Write A Cause and Effect Essay - Outline & Examples

230+ Cause and Effect Essay Topics to Boost Your Academic Writing

In academic paper writing, students often tackle diverse essay types, including cause and effect essays. 

Cause and effect essays act as a gauge for how well students can use logical reasoning to understand the outcomes of different actions.

However, the most crucial element while writing this type of essay is to create an outline. 

Many students skip outlining, thinking it's time-consuming. While creating a cause and effect paper outline does take time, it actually saves more time during writing. Following a detailed plan makes the writing process easier, ensuring you don't miss key details and can draft a logical, organized essay. 

Follow the steps given in this blog for a perfect outline.

• 1. What is a Cause and Effect Essay Outline?
• 2. Cause and Effect Essay Outline Format
• 3. How to Write a Cause and Effect Essay Outline?
• 4. Cause and Effect Essay Outline Examples

What is a Cause and Effect Essay Outline?

A cause and effect essay outline is a detailed plan of action that students follow throughout the writing process. It is the key factor in writing a successful essay as it provides help in the following ways:

• It is used to organize thoughts logically.
• It makes the writing process easier and saves enough time to proofread.
• It helps the writer concentrate on the main points that need to be described in the essay.

It is not required to write full sentences at this step. Instead, state the ideas and structure them in the right order.

Furthermore, it is important to choose a unique topic before developing an outline. Check out our compiled list of good  cause and effect essay topics  to grab the reader’s interest.

Cause and Effect Essay Outline Format

Cause and effect essay outline generally follows a five-paragraph format. However, the number of body paragraphs may vary according to the topic and scope of the essay. Typically, the cause and effect essay layout contains an introduction, three body paragraphs, and a conclusion.

Here is the complete outline format structure of a cause and effect writing:

Paper Due? Why Suffer? That's our Job!

How to Write a Cause and Effect Essay Outline?

Follow the steps below to write an effective cause and effect essay outline.

• Introduction
• Body paragraphs
• Antithesis paragraph

The following is a detailed description of the steps to writing an outline.

Step 1: Cause and Effect Essay Introduction

The introduction is the first section written to give an idea of what your essay is about. It provides background information about the topic under discussion. Similarly, it also discusses the issues and focus of the essay’s main argument, along with its purpose.

Thus, try to give a general idea to the reader with the help of a  thesis statement . It is crucial to emphasize how and why the chosen event is relevant to modern life.

For example, if you are writing about the Cold War, state how it is still apparent in global politics.

Furthermore, the  essay introduction  paragraph includes the following elements.

Start With an Attention Grabber

Start your essay with a relevant, attention-grabbing hook statement. It can be in the form of a sentence, quote, anecdote, rhetorical question, or fact. The primary purpose of such a hook is to attract the audience at the beginning of the paper.

Basic Background Information

Mention some background information on the topic to get a clear picture. It will help readers understand the event and connect with the major argument. Similarly, this element is also used to understand the cause and effect before you start writing.

Thesis Statement

It is the central element while writing an introduction. Its absence will indicate that the essay lacks a focus. It is a statement of 1-2 sentences that briefly describes the major argument of the essay.

Moreover, a writer needs to discuss this idea through all the body paragraphs. Thus, make sure to craft a strong thesis statement that correlates with the outline.

Step 2: Cause and Effect Essay Body Paragraphs

The body paragraphs provide enough details and facts about the causes that led to the effects.

• Begin with  topic sentences  that indicate the first cause or effect of your topic. Also, brainstorm to describe their importance.
• Each paragraph should discuss a single cause and a single effect. Furthermore, the information must be organized in chronological or reverse order.
• Moreover, it is better to start the body paragraphs by describing causes and presenting the effects later. Analyze both the elements by explaining how and why an effect influenced the events or actions. Make sure that the content relates to the thesis statement and the overall topic.
• Use  transitional words  to connect the ideas and give relevant examples. Most writers made a common mistake of adding weak and unconvincing causes to reach the word count. As a result, it affects the essay’s credibility.
• Discuss the below elements while writing the body of your cause and effect essay.

Description of the Cause

This part requires the writer to explain the current situation clearly. It will help the reader to understand the primary argument. Thus, it is important to describe the situation in a way that prepares the reader for effect.

For example, if you are writing about the loss of privacy, that will lead to individual freedom. The focus should be on the technologies that affect freedom.

Description of the Effect

It explains to the reader the logical steps that move from cause to effect. It focuses on explaining what the multiple effects are and how we move from cause to effect.

Following the above example, the writer will explain the connection between privacy and freedom.

Explain the Cause and Effect Relationship

Here, a writer must discuss the importance of the findings. It is used to describe the short and long-term results of the effects. Also, suggest the recommendations to tackle the situation along with future prospects.

Step 3: Cause and Effect Essay Antithesis Paragraph

This paragraph will discuss the other side of the issue by identifying the major causes and effects. Also, explain the causes behind choosing a topic and how it will be relevant to modern life. 

This way, you can show the logic behind the occurrence of the two variables and their possible causes and effects.

Step 4: Cause and Effect Essay Conclusion

The conclusion paragraph aims to provide a brief summary of your essay. Thus, it should leave the audience with the feeling of completeness and make a final emphasis on the major ideas.

This section requires the writer to show how their perspective of the issue has changed by the following analysis. Also, it should further describe the positive and negative effects of the situation.

The conclusion includes the elements discussed below:

Restate the Thesis Statement

Write a few sentences that connect the body paragraphs with the thesis statement. It must also indicate how this statement has helped in proving the main argument of the essay.

Remind the Audience about the Main Points

Here you describe your general outline in strong and precise sentences. Avoid adding any new information. In case you are writing about a major event that influenced the world, such as global warming.

You should write a call to action and suggest what necessary steps need to be taken to overcome the issue.

Draft a Concluding Sentence

Like a convincing introduction; the conclusion should be catchy and compelling as well. Thus, pay attention to this section while writing a college or university essay.

Describe the research outcomes, along with the importance of the essay’s arguments.

Lastly, check out the examples available online. Consider the structure and vocabulary used by most authors to write a cause and effect essay conclusion.

Refer to the example below to better understand writing a cause and effect essay.

How to Write a Cause and Effect Essay Outline – Example

Cause and Effect Essay Outline Examples

Below are the cause and effect outline examples and samples for you to understand better.

Cause and Effect Essay Outline Template

5 Paragraph Cause and Effect Essay Outline

MLA Format Cause and Effect Essay Outline

Cause and Effect Essay Outline Sample

Cause and Effect Essay Outline on Divorce

Cause and Effect Essay Outline on Global Warming

Smoking Cause and Effect Essay Outline

Obesity Cause and Effect Essay Outline

Cause and Effect Essay Outline for College Students

Cause and Effect Essay Formal Outline

Tough Essay Due? Hire Tough Writers!

To Sum it Up! This ultimate writing guide will help you write a perfect cause and effect paper outline.

Nevertheless, not everyone can develop a cause-and-effect chain relationship between variables. Therefore, instead of risking your grades, it is better to seek professional help.

MyPerfectWords.com stands as a professional writing service, poised to support you in your academic writing tasks. In addition to our core writing services, our essay writer service offers a range of free services, including plagiarism reports, editing, and revisions.  So place your order now and get your perfect outline in no time!

Write Essay Within 60 Seconds!

Caleb S. has been providing writing services for over five years and has a Masters degree from Oxford University. He is an expert in his craft and takes great pride in helping students achieve their academic goals. Caleb is a dedicated professional who always puts his clients first.

Paper Due? Why Suffer? That’s our Job!

Keep reading

Russell Millner/Alamy

Defend Our Planet and Most Vulnerable Species

Your donation today will be triple-matched to power NRDC’s next great chapter in protecting our ecosystems and saving imperiled wildlife.

What Are the Effects of Climate Change?

A rapidly warming planet poses an existential threat to all life on earth. Just how bad it gets depends on how quickly we act.

An area flooded by Super Typhoon Noru in the Bulacan Province of the Philippines, September 26, 2022

Rouelle Umali/Xinhua via Getty Images

• Share this page block

Climate change is our planet’s greatest existential threat . If we don’t limit greenhouse gas emissions from the burning of fossil fuels, the consequences of rising global temperatures include massive crop and fishery collapse, the disappearance of hundreds of thousands of species, and entire communities becoming uninhabitable. While these outcomes may still be avoidable, climate change is already causing suffering and death. From raging wildfires and supercharged storms, its compounding effects can be felt today, outside our own windows.

Understanding these impacts can help us prepare for what’s here, what’s avoidable, and what’s yet to come, and to better prepare and protect all communities. Even though everyone is or will be affected by climate change, those living in the world’s poorest countries—which have contributed least to the problem—are the most climate-vulnerable. They have the fewest financial resources to respond to crises or adapt, and they’re closely dependent on a healthy, thriving natural world for food and income. Similarly, in the United States, it is most often low-income communities and communities of color that are on the frontlines of climate impacts. And because climate change and rising inequality are interconnected crises, decision makers must take action to combat both—and all of us must fight for climate justice. Here’s what you need to know about what we’re up against.

Effects of climate change on weather

Effects of climate change on the environment, effects of climate change on agriculture, effects of climate change on animals, effects of climate change on humans, future effects of climate change.

As global temperatures climb, widespread shifts in weather systems occur, making events like droughts , hurricanes , and floods more intense and unpredictable. Extreme weather events that may have hit just once in our grandparents’ lifetimes are becoming more common in ours. However, not every place will experience the same effects: Climate change may cause severe drought in one region while making floods more likely in another.

Already, the planet has warmed 1.1 degrees Celsius (1.9 degrees Fahrenheit) since the preindustrial era began 250 years ago, according to the Intergovernmental Panel on Climate Change (IPCC) . And scientists warn it could reach a worst-case scenario of 4 degrees Celsius (7.2 degrees Fahrenheit) by 2100 if we fail to tackle the causes of climate change —namely, the burning of fossil fuels (coal, oil, and gas) .

Tokyo during a record-breaking heat wave, August 13, 2020

The Yomiuri Shimbun via AP Images

Higher average temperatures

This change in global average temperature—seemingly small but consequential and climbing—means that, each summer, we are likely to experience increasingly sweltering heat waves. Even local news meteorologists are starting to connect strings of record-breaking days to new long-term trends, which are especially problematic in regions where infrastructure and housing have not been built with intensifying heat in mind. And heat waves aren’t just uncomfortable—they’re the leading cause of weather-related fatalities in the United States.

Longer-lasting droughts

Hotter temperatures increase the rate at which water evaporates from the air, leading to more severe and pervasive droughts . Already, climate change has pushed the American West into a severe “megadrought”—the driest 22-year stretch recorded in at least 1,200 years—shrinking drinking water supplies, withering crops , and making forests more susceptible to insect infestations. Drought can also create a positive feedback loop in which drier soil and less plant cover cause even faster evaporation.

More intense wildfires

This drier, hotter climate also creates conditions that fuel more vicious wildfire seasons—with fires that spread faster and burn longer—putting millions of additional lives and homes at risk. The number of large wildfires doubled between 1984 and 2015 in the western United States. And in California alone, the annual area burned by wildfires increased 500 percent between 1972 and 2018.

Evacuation after Hurricane Harvey in Houston, August 28, 2017

David J. Phillip/AP Photo

Stronger storms

Warmer air also holds more moisture, making tropical cyclones wetter, stronger, and more capable of rapidly intensifying. In the latest report from the IPCC , scientists found that daily rainfall during extreme precipitation events would increase by about 7 percent for each degree Celsius of global warming, increasing the dangers of flooding . The frequency of severe Category 4 and 5 hurricanes is also expected to increase. In 2017, Hurricane Harvey, a devastating Category 4 storm, dumped a record 275 trillion pounds of rain and resulted in dozens of deaths in the Houston area.

From the poles to the tropics, climate change is disrupting ecosystems. Even a seemingly slight shift in temperature can cause dramatic changes that ripple through food webs and the environment.

The lake at Jökulsárlón, a glacial lagoon in Iceland, which has grown because of continued glacial melting

Eskinder Debebe/UN Photo

Melting sea ice

The effects of climate change are most apparent in the world’s coldest regions—the poles. The Arctic is heating up twice as fast as anywhere else on earth, leading to the rapid melting of glaciers and polar ice sheets, where a massive amount of water is stored. As sea ice melts, darker ocean waters that absorb more sunlight become exposed, creating a positive feedback loop that speeds up the melting process. In just 15 years, the Arctic could be entirely ice-free in the summer.

Sea level rise

Scientists predict that melting sea ice and glaciers, as well as the fact that warmer water expands in volume, could cause sea levels to rise as much as 6.6 feet by the end of the century, should we fail to curb emissions. The extent (and pace) of this change would devastate low-lying regions, including island nations and densely populated coastal cities like New York City and Mumbai.

But sea level rise at far lower levels is still costly, dangerous, and disruptive. According to the 2022 Sea Level Rise Technical Report from the National Ocean Service, the United States will see a foot of sea level rise by 2050, which will regularly damage infrastructure, like roads, sewage treatment plants, and even power plants . Beaches that families have grown up visiting may be gone by the end of the century. Sea level rise also harms the environment, as encroaching seawater can both erode coastal ecosystems and invade freshwater inland aquifers, which we rely on for agriculture and drinking water. Saltwater incursion is already reshaping life in nations like Bangladesh , where one-quarter of the lands lie less than 7 feet above sea level.

A waterlogged road, caused by rainstorm and upstream flood discharge, in the Shaoguan, Guangdong Province of China, June 21, 2022

Stringer/Anadolu Agency via Getty Images

In addition to coastal flooding caused by sea level rise, climate change influences the factors that result in inland and urban flooding: snowmelt and heavy rain. As global warming continues to both exacerbate sea level rise and extreme weather, our nation’s floodplains are expected to grow by approximately 45 percent by 2100. In 2022, deadly flooding in Pakistan—which inundated as much as a third of the country—resulted from torrential rains mixed with melting glaciers and snow.

Warmer ocean waters and marine heat waves

Oceans are taking the brunt of our climate crisis. Covering more than 70 percent of the planet’s surface, oceans absorb 93 percent of all the heat that’s trapped by greenhouse gases and up to 30 percent of all the carbon dioxide emitted from burning fossil fuels.

Temperature-sensitive fish and other marine life are already changing migration patterns toward cooler and deeper waters to survive, sending food webs and important commercial fisheries into disarray. And the frequency of marine heat waves has increased by more than a third . These spikes have led to mass die-offs of plankton and marine mammals.

To make matters worse, the elevated absorption of carbon dioxide by the ocean leads to its gradual acidification , which alters the fundamental chemical makeup of the water and threatens marine life that has evolved to live in a narrow pH band. Animals like corals, oysters, and mussels will likely feel these effects first, as acidification disrupts the calcification process required to build their shells.

Ecosystem stressors

Land-based ecosystems—from old-growth forests to savannahs to tropical rainforests—are faring no better. Climate change is likely to increase outbreaks of pests, invasive species, and pathogen infections in forests. It’s changing the kinds of vegetation that can thrive in a given region and disrupting the life cycles of wildlife, all of which is changing the composition of ecosystems and making them less resilient to stressors. While ecosystems have the capacity to adapt, many are reaching the hard limits of that natural capacity . More repercussions will follow as temperatures rise.

Climate change appears to be triggering a series of cascading ecological changes that we can neither fully predict nor, once they have enough momentum, fully stop. This ecosystem destabilization may be most apparent when it comes to keystone species that have an outsize- role in holding up an ecosystem’s structure.

Coffee plants destroyed by frost due to extremely low temperatures near Caconde in the São Paulo state of Brazil, August 25, 2021

Jonne Roriz/Bloomberg via Getty Images

Less predictable growing seasons

In a warming world, farming crops is more unpredictable—and livestock, which are sensitive to extreme weather, become harder to raise. Climate change shifts precipitation patterns, causing unpredictable floods and longer-lasting droughts. More frequent and severe hurricanes can devastate an entire season’s worth of crops. Meanwhile, the dynamics of pests, pathogens, and invasive species—all of which are costly for farmers to manage—are also expected to become harder to predict. This is bad news, given that most of the world’s farms are small and family-run. One bad drought or flood could decimate an entire season’s crop or herd. For example, in June 2022, a triple-digit heat wave in Kansas wiped out thousands of cows. While the regenerative agriculture movement is empowering rural communities to make their lands more resilient to climate change, unfortunately, not all communities can equitably access the support services that can help them embrace these more sustainable farming tactics.

Reduced soil health

Healthy soil has good moisture and mineral content and is teeming with bugs, bacteria, fungi, and microbes that in turn contribute to healthy crops. But climate change, particularly extreme heat and changes in precipitation, can degrade soil quality. These impacts are exacerbated in areas where industrial, chemical-dependent monoculture farming has made soil and crops less able to withstand environmental changes.

Food shortages

Ultimately, impacts to our agricultural systems pose a direct threat to the global food supply. And food shortages and price hikes driven by climate change will not affect everyone equally: Wealthier people will continue to have more options for accessing food, while potentially billions of others will be plummeted into food insecurity—adding to the billions that already have moderate or severe difficulty getting enough to eat.

The poison dart frog’s survival is currently threatened by habitat loss and climate change.

Chris Mattison/Minden Pictures

It’s about far more than just the polar bears: Half of all animal species in the world’s most biodiverse places, like the Amazon rainforest and the Galapagos Islands, are at risk of extinction from climate change. And climate change is threatening species that are already suffering from the biodiversity crisis, which is driven primarily by changes in land and ocean use (like converting wild places to farmland) and direct exploitation of species (like overfishing and wildlife trade). With species already in rough shape—more than 500,000 species have insufficient habitat for long-term survival—unchecked climate change is poised to push millions over the edge.

Climate change rapidly and fundamentally alters (or in some cases, destroys) the habitat that wildlife have incrementally adapted to over millennia. This is especially harmful for species’ habitats that are currently under threat from other causes. Ice-dependent mammals like walruses and penguins, for example, won’t fare well as ice sheets shrink. Rapid shifts in ocean temperatures stress the algae that nourishes coral reefs, causing reefs to starve—an increasingly common phenomenon known as coral bleaching . Disappearing wetlands in the Midwest’s Prairie Pothole Region means the loss of watering holes and breeding grounds for millions of migratory birds. (Many species are now struggling to survive, as more than 85 percent of wetlands have been lost since 1700). And sea level rise will inundate or erode away many coastal habitats, where hundreds of species of birds, invertebrates, and other marine species live.

Many species’ behaviors—mating, feeding, migration—are closely tied to subtle seasonal shifts, as in temperature , precipitation level, and foliage. In some cases, changes to the environment are happening quicker than species are able to adapt. When the types and quantity of plant life change across a region, or when certain species bloom or hatch earlier or later than in the past, it impacts food and water supplies and reverberates up food chains.

Wildfire smoke–filled air in Multnomah County, Oregon, September 16, 2020

Motoya Nakamura/Multnomah County Communications, CC BY NC-ND 4.0

Ultimately, the way climate change impacts weather, the environment, animals, and agriculture affects humanity as well. But there’s more. Around the world, our ways of life—from how we get our food to the industries around which our economies are based—have all developed in the context of relatively stable climates. As global warming shakes this foundation, it promises to alter the very fabric of society. At worst, this could lead to widespread famine, disease, war, displacement , injury, and death. For many around the world, this grim forecast is already their reality. In this way, climate change poses an existential threat to all human life.

Human health

Climate change worsens air quality . It increases exposure to hazardous wildfire smoke and ozone smog triggered by warmer conditions, both of which harm our health, particularly for those with pre-existing illnesses like asthma or heart disease.

Insect-borne diseases like malaria and Zika become more prevalent in a warming world as their carriers are able to exist in more regions or thrive for longer seasons. In the past 30 years, the incidence of Lyme disease from ticks has nearly doubled in the United States, according to the U.S. Environmental Protection Agency (EPA). Thousands of people face injury, illness , and death every year from more frequent or more intense extreme weather events. At a 2-degree Celsius rise in global average temperature, an estimated one billion people will face heat stress risk. In the summer of 2022 alone, thousands died in record-shattering heat waves across Europe. Weeks later, dozens were killed by record-breaking urban flooding in the United States and South Korea—and more than 1,500 people perished in the flooding in Pakistan , where resulting stagnant water and unsanitary conditions threaten even more.

The effects of climate change—and the looming threat of what’s yet to come—take a significant toll on mental health too. One 2021 study on climate anxiety, published in the journal Nature , surveyed 10,000 young people from 10 different countries. Forty-five percent of respondents said that their feelings about climate change, varying from anxiety to powerlessness to anger, impacted their daily lives.

A patient with dengue fever, a mosquito-borne disease, in Karachi, Pakistan, where the spread of diseases worsened due to flooding, September 2022

Fareed Khan/AP Photo

Worsening inequity

The climate crisis exacerbates existing inequities. Though wealthy nations, such as the United States, have emitted the lion’s share of historical greenhouse gas emissions, it’s developing countries that may lack the resources to adapt and will now bear the brunt of the climate crisis. In some cases, low-lying island nations—like many in the Pacific —may cease to exist before developed economies make meaningful reductions to their carbon emissions.

Even within wealthier nations, disparities will continue to grow between those rich enough to shield themselves from the realities of climate change and those who cannot. Those with ample resources will not be displaced from their homes by wars over food or water—at least not right away. They will have homes with cool air during heat waves and be able to easily evacuate when a hurricane is headed their way. They will be able to buy increasingly expensive food and access treatment for respiratory illness caused by wildfire smoke. Billions of others can’t—and are paying the highest price for climate pollution they did not produce.

Hurricane Katrina, for example, displaced more than one million people around the Gulf Coast. But in New Orleans , where redlining practices promoted racial and economic segregation, the city’s more affluent areas tended to be located on higher ground—and those residents were able to return and rebuild much faster than others.

Displacement

Climate change will drive displacement due to impacts like food and water scarcities, sea level rise, and economic instability. It’s already happening. The United Nations Global Compact on Refugees recognizes that “climate, environmental degradation and disasters increasingly interact with the drivers of refugee movements.” Again, communities with the fewest resources—including those facing political instability and poverty—will feel the effects first and most devastatingly.

A flood-damaged home in Queens, New York, December 1, 2021

K.C. Wilsey/FEMA

Economic impacts

According to the 2018 National Climate Assessment, unless action is taken, climate change will cost the U.S. economy as much as $500 billion per year by the end of the century. And that doesn’t even include its enormous impacts on human health . Entire local industries—from commercial fishing to tourism to husbandry—are at risk of collapsing, along with the economic support they provide.

Recovering from the destruction wrought by extreme weather like hurricanes, flash floods, and wildfires is also getting more expensive every year. In 2021, the price tag of weather disasters in the United States totaled $145 billion —the third-costliest year on record, including a number of billion-dollar weather events.

The first wave of impacts can already be felt in our communities and seen on the nightly news. The World Health Organization says that in the near future, between 2030 and 2050, climate change is expected to cause an additional 250,000 deaths per year from things like malnutrition, insect-borne diseases, and heat stress. And the World Bank estimates that climate change could displace more than 140 million people within their home countries in sub-Saharan Africa, South Asia, and Latin America by 2050.

But the degree to which the climate crisis upends our lives depends on whether global leaders decide to chart a different course. If we fail to curb greenhouse gas emissions, scientists predict a catastrophic 4.3 degrees Celsius , (or around 8 degrees Fahrenheit) of warming by the end of the century. What would a world that warm look like? Wars over water. Crowded hospitals to contend with spreading disease. Collapsed fisheries. Dead coral reefs. Even more lethal heat waves. These are just some of the impacts predicted by climate scientists .

Solar panel installation at a floating photovoltaic plant on a lake in Haltern am See, Germany, April 2022

Martin Meissner/AP Photo

Climate mitigation, or our ability to reverse climate change and undo its widespread effects, hinges on the successful enactment of policies that yield deep cuts to carbon pollution, end our dependence on dangerous fossil fuels and the deadly air pollution they generate, and prioritize the people and ecosystems on the frontlines. And these actions must be taken quickly in order to ensure a healthier present day and future. In one of its latest reports, the IPCC presented its most optimistic emissions scenario, in which the world only briefly surpasses 1.5 degrees of warming but sequestration measures cause it to dip back below by 2100. Climate adaptation , a term that refers to coping with climate impacts, is no longer optional ; it’s necessary, particularly for the world’s most vulnerable populations.

By following the urgent warnings of the IPCC and limiting warming, we may be able to avoid passing some of the critical thresholds that, once crossed, can lead to potentially irreversible, catastrophic impacts for the planet, including more warming. These thresholds are known as climate tipping points and refer to when a natural system "tips" into an entirely different state. One example would be Arctic permafrost, which stores carbon like a freezer: As the permafrost melts from warming temperatures, it releases carbon dioxide into the atmosphere.

Importantly, climate action is not a binary pass-fail test. Every fraction of a degree of warming that we prevent will reduce human suffering and death, and keep more of the planet’s natural systems intact. The good news is that a wide range of solutions exist to sharply reduce emissions, slow the pace of warming, and protect communities on the frontlines of climate impacts. Climate leaders the world over—those on major political stages as well as grassroots community activists—are offering up alternative models to systems that prioritize polluters over people. Many of these solutions are rooted in ancestral and Indigenous understandings of the natural world and have existed for millennia. Some solutions require major investments into clean, renewable energy and sustainable technologies. To be successful, climate solutions must also address intersecting crises—like poverty, racism, and gender inequality —that compound and drive the causes and impacts of the climate crisis. A combination of human ingenuity and immense political will can help us get there.

This NRDC.org story is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the story was originally published by NRDC.org and link to the original; the story cannot be edited (beyond simple things such as grammar); you can’t resell the story in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select stories individually; you can’t republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our stories.

We need climate action to be a top priority in Washington.

Tell President Biden and Congress to slash climate pollution and reduce our dependence on fossil fuels. 

Urge President Biden and Congress to make equitable climate action a top priority in 2024

Related stories.

COP27: The Issues, the Tensions, and the Urgent Need for Unity on Climate

Mutual Aid and Disaster Justice: “We Keep Us Safe”

Climate Change at the Doctor’s Office

When you sign up, you’ll become a member of NRDC’s Activist Network. We will keep you informed with the latest alerts and progress reports.

Thousands Believe Covid Vaccines Harmed Them. Is Anyone Listening?

All vaccines have at least occasional side effects. But people who say they were injured by Covid vaccines believe their cases have been ignored.

Shaun Barcavage, 54, a nurse practitioner in New York City, said that ever since his first Covid shot, standing up has sent his heart racing. Credit... Hannah Yoon for The New York Times

Supported by

• Share full article

By Apoorva Mandavilli

Apoorva Mandavilli spent more than a year talking to dozens of experts in vaccine science, policymakers and people who said they had experienced serious side effects after receiving a Covid-19 vaccine.

• Published May 3, 2024 Updated May 4, 2024

Within minutes of getting the Johnson & Johnson Covid-19 vaccine, Michelle Zimmerman felt pain racing from her left arm up to her ear and down to her fingertips. Within days, she was unbearably sensitive to light and struggled to remember simple facts.

She was 37, with a Ph.D. in neuroscience, and until then could ride her bicycle 20 miles, teach a dance class and give a lecture on artificial intelligence, all in the same day. Now, more than three years later, she lives with her parents. Eventually diagnosed with brain damage, she cannot work, drive or even stand for long periods of time.

“When I let myself think about the devastation of what this has done to my life, and how much I’ve lost, sometimes it feels even too hard to comprehend,” said Dr. Zimmerman, who believes her injury is due to a contaminated vaccine batch .

The Covid vaccines, a triumph of science and public health, are estimated to have prevented millions of hospitalizations and deaths . Yet even the best vaccines produce rare but serious side effects . And the Covid vaccines have been given to more than 270 million people in the United States, in nearly 677 million doses .

Dr. Zimmerman’s account is among the more harrowing, but thousands of Americans believe they suffered serious side effects following Covid vaccination. As of April, just over 13,000 vaccine-injury compensation claims have been filed with the federal government — but to little avail. Only 19 percent have been reviewed. Only 47 of those were deemed eligible for compensation, and only 12 have been paid out, at an average of about $3,600 .

Some scientists fear that patients with real injuries are being denied help and believe that more needs to be done to clarify the possible risks.

“At least long Covid has been somewhat recognized,” said Akiko Iwasaki, an immunologist and vaccine expert at Yale University. But people who say they have post-vaccination injuries are “just completely ignored and dismissed and gaslighted,” she added.

In interviews and email exchanges conducted over several months, federal health officials insisted that serious side effects were extremely rare and that their surveillance efforts were more than sufficient to detect patterns of adverse events.

“Hundreds of millions of people in the United States have safely received Covid vaccines under the most intense safety monitoring in U.S. history,” Jeff Nesbit, a spokesman for the Department of Health and Human Services, said in an emailed statement.

But in a recent interview, Dr. Janet Woodcock, a longtime leader of the Food and Drug Administration, who retired in February, said she believed that some recipients had experienced uncommon but “serious” and “life-changing” reactions beyond those described by federal agencies.

“I feel bad for those people,” said Dr. Woodcock, who became the F.D.A.’s acting commissioner in January 2021 as the vaccines were rolling out. “I believe their suffering should be acknowledged, that they have real problems, and they should be taken seriously.”

“I’m disappointed in myself,” she added. “I did a lot of things I feel very good about, but this is one of the few things I feel I just didn’t bring it home.”

Federal officials and independent scientists face a number of challenges in identifying potential vaccine side effects.

The nation’s fragmented health care system complicates detection of very rare side effects, a process that depends on an analysis of huge amounts of data. That’s a difficult task when a patient may be tested for Covid at Walgreens, get vaccinated at CVS, go to a local clinic for minor ailments and seek care at a hospital for serious conditions. Each place may rely on different health record systems.

There is no central repository of vaccine recipients, nor of medical records, and no easy to way to pool these data. Reports to the largest federal database of so-called adverse events can be made by anyone, about anything. It’s not even clear what officials should be looking for.

“I mean, you’re not going to find ‘brain fog’ in the medical record or claims data, and so then you’re not going to find” a signal that it may be linked to vaccination, Dr. Woodcock said. If such a side effect is not acknowledged by federal officials, “it’s because it doesn’t have a good research definition,” she added. “It isn’t, like, malevolence on their part.”

The government’s understaffed compensation fund has paid so little because it officially recognizes few side effects for Covid vaccines. And vaccine supporters, including federal officials, worry that even a whisper of possible side effects feeds into misinformation spread by a vitriolic anti-vaccine movement.

‘I’m Not Real’

Patients who believe they experienced serious side effects say they have received little support or acknowledgment.

Shaun Barcavage, 54, a nurse practitioner in New York City who has worked on clinical trials for H.I.V. and Covid, said that ever since his first Covid shot, merely standing up sent his heart racing — a symptom suggestive of postural orthostatic tachycardia syndrome , a neurological disorder that some studies have linked to both Covid and, much less often, vaccination .

He also experienced stinging pain in his eyes, mouth and genitals, which has abated, and tinnitus, which has not.

“I can’t get the government to help me,” Mr. Barcavage said of his fruitless pleas to federal agencies and elected representatives. “I am told I’m not real. I’m told I’m rare. I’m told I’m coincidence.”

Renee France, 49, a physical therapist in Seattle, developed Bell’s palsy — a form of facial paralysis, usually temporary — and a dramatic rash that neatly bisected her face. Bell’s palsy is a known side effect of other vaccines, and it has been linked to Covid vaccination in some studies.

But Dr. France said doctors were dismissive of any connection to the Covid vaccines. The rash, a bout of shingles, debilitated her for three weeks, so Dr. France reported it to federal databases twice.

“I thought for sure someone would reach out, but no one ever did,” she said.

Similar sentiments were echoed in interviews, conducted over more than a year, with 30 people who said they had been harmed by Covid shots. They described a variety of symptoms following vaccination, some neurological, some autoimmune, some cardiovascular.

All said they had been turned away by physicians, told their symptoms were psychosomatic, or labeled anti-vaccine by family and friends — despite the fact that they supported vaccines.

Even leading experts in vaccine science have run up against disbelief and ambivalence.

Dr. Gregory Poland, 68, editor in chief of the journal Vaccine, said that a loud whooshing sound in his ears had accompanied every moment since his first shot, but that his entreaties to colleagues at the Centers for Disease Control and Prevention to explore the phenomenon, tinnitus, had led nowhere.

He received polite responses to his many emails, but “I just don’t get any sense of movement,” he said.

“If they have done studies, those studies should be published,” Dr. Poland added. In despair that he might “never hear silence again,” he has sought solace in meditation and his religious faith.

Dr. Buddy Creech, 50, who led several Covid vaccine trials at Vanderbilt University, said his tinnitus and racing heart lasted about a week after each shot. “It’s very similar to what I experienced during acute Covid, back in March of 2020,” Dr. Creech said.

Research may ultimately find that most reported side effects are unrelated to the vaccine, he acknowledged. Many can be caused by Covid itself.

“Regardless, when our patients experience a side effect that may or may not be related to the vaccine, we owe it to them to investigate that as completely as we can,” Dr. Creech said.

Federal health officials say they do not believe that the Covid vaccines caused the illnesses described by patients like Mr. Barcavage, Dr. Zimmerman and Dr. France. The vaccines may cause transient reactions, such as swelling, fatigue and fever, according to the C.D.C., but the agency has documented only four serious but rare side effects .

Two are associated with the Johnson & Johnson vaccine, which is no longer available in the United States: Guillain-Barré syndrome , a known side effect of other vaccines , including the flu shot; and a blood-clotting disorder.

The C.D.C. also links mRNA vaccines made by Pfizer-BioNTech and Moderna to heart inflammation, or myocarditis, especially in boys and young men. And the agency warns of anaphylaxis, or severe allergic reaction, which can occur after any vaccination.

Listening for Signals

Agency scientists are monitoring large databases containing medical information on millions of Americans for patterns that might suggest a hitherto unknown side effect of vaccination, said Dr. Demetre Daskalakis, director of the C.D.C.’s National Center for Immunization and Respiratory Diseases.

“We toe the line by reporting the signals that we think are real signals and reporting them as soon as we identify them as signals,” he said. The agency’s systems for monitoring vaccine safety are “pretty close” to ideal, he said.

Those national surveillance efforts include the Vaccine Adverse Event Reporting System (VAERS). It is the largest database, but also the least reliable: Reports of side effects can be submitted by anyone and are not vetted, so they may be subject to bias or manipulation.

The system contains roughly one million reports regarding Covid vaccination, the vast majority for mild events, according to the C.D.C.

Federal researchers also comb through databases that combine electronic health records and insurance claims on tens of millions of Americans. The scientists monitor the data for 23 conditions that may occur following Covid vaccination. Officials remain alert to others that may pop up, Dr. Daskalakis said.

But there are gaps, some experts noted. The Covid shots administered at mass vaccination sites were not recorded in insurance claims databases, for example, and medical records in the United States are not centralized.

“It’s harder to see signals when you have so many people, and things are happening in different parts of the country, and they’re not all collected in the same system,” said Rebecca Chandler, a vaccine safety expert at the Coalition for Epidemic Preparedness Innovations.

An expert panel convened by the National Academies concluded in April that for the vast majority of side effects, there was not enough data to accept or reject a link.

Asked at a recent congressional hearing whether the nation’s vaccine-safety surveillance was sufficient, Dr. Peter Marks, director of the F.D.A.’s Center for Biologics Evaluation and Research, said, “I do believe we could do better.”

In some countries with centralized health care systems, officials have actively sought out reports of serious side effects of Covid vaccines and reached conclusions that U.S. health authorities have not.

In Hong Kong, the government analyzed centralized medical records of patients after vaccination and paid people to come forward with problems. The strategy identified “a lot of mild cases that other countries would not otherwise pick up,” said Ian Wong, a researcher at the University of Hong Kong who led the nation’s vaccine safety efforts.

That included the finding that in rare instances — about seven per million doses — the Pfizer-BioNTech vaccine triggered a bout of shingles serious enough to require hospitalization.

The European Medicines Agency has linked the Pfizer and Moderna vaccines to facial paralysis, tingling sensations and numbness. The E.M.A. also counts tinnitus as a side effect of the Johnson & Johnson vaccine, although the American health agencies do not. There are more than 17,000 reports of tinnitus following Covid vaccination in VAERS.

Are the two linked? It’s not clear. As many as one in four adults has some form of tinnitus. Stress, anxiety, grief and aging can lead to the condition, as can infections like Covid itself and the flu.

There is no test or scan for tinnitus, and scientists cannot easily study it because the inner ear is tiny, delicate and encased in bone, said Dr. Konstantina Stankovic, an otolaryngologist at Stanford University.

Still, an analysis of health records from nearly 2.6 million people in the United States found that about 0.04 percent , or about 1,000, were diagnosed with tinnitus within three weeks of their first mRNA shot. In March, researchers in Australia published a study linking tinnitus and vertigo to the vaccines .

The F.D.A. is monitoring reports of tinnitus, but “at this time, the available evidence does not suggest a causal association with the Covid-19 vaccines,” the agency said in a statement.

Despite surveillance efforts, U.S. officials were not the first to identify a significant Covid vaccine side effect: myocarditis in young people receiving mRNA vaccines. It was Israeli authorities who first raised the alarm in April 2021. Officials in the United States said at the time that they had not seen a link.

On May 22, 2021, news broke that the C.D.C. was investigating a “relatively few” cases of myocarditis. By June 23, the number of myocarditis reports in VAERS had risen to more than 1,200 — a hint that it is important to tell doctors and patients what to look for.

Later analyses showed that the risk for myocarditis and pericarditis, a related condition, is highest after a second dose of an mRNA Covid vaccine in adolescent males aged 12 to 17 years.

In many people, vaccine-related myocarditis is transient. But some patients continue to experience pain, breathlessness and depression, and some show persistent changes on heart scans . The C.D.C. has said there were no confirmed deaths related to myocarditis, but in fact there have been several accounts of deaths reported post-vaccination .

Pervasive Misinformation

The rise of the anti-vaccine movement has made it difficult for scientists, in and out of government, to candidly address potential side effects, some experts said. Much of the narrative on the purported dangers of Covid vaccines is patently false, or at least exaggerated, cooked up by savvy anti-vaccine campaigns.

Questions about Covid vaccine safety are core to Robert F. Kennedy Jr.’s presidential campaign. Citing debunked theories about altered DNA, Florida’s surgeon general has called for a halt to Covid vaccination in the state.

“The sheer nature of misinformation, the scale of misinformation, is staggering, and anything will be twisted to make it seem like it’s not just a devastating side effect but proof of a massive cover-up,” said Dr. Joshua Sharfstein, a vice dean at Johns Hopkins University.

Among the hundreds of millions of Americans who were immunized for Covid, some number would have had heart attacks or strokes anyway. Some women would have miscarried. How to distinguish those caused by the vaccine from those that are coincidences? The only way to resolve the question is intense research .

But the National Institutes of Health is conducting virtually no studies on Covid vaccine safety, several experts noted. William Murphy, a cancer researcher who worked at the N.I.H. for 12 years, has been prodding federal health officials to initiate these studies since 2021.

The officials each responded with “that very tired mantra: ‘But the virus is worse,’” Dr. Murphy recalled. “Yes, the virus is worse, but that doesn’t obviate doing research to make sure that there may be other options.”

A deeper understanding of possible side effects, and who is at risk for them, could have implications for the design of future vaccines, or may indicate that for some young and healthy people, the benefit of Covid shots may no longer outweigh the risks — as some European countries have determined.

Thorough research might also speed assistance to thousands of Americans who say they were injured.

The federal government has long run the National Vaccine Injury Compensation Program , designed to compensate people who suffer injuries after vaccination. Established more than three decades ago, the program sets no limit on the amounts awarded to people found to have been harmed.

But Covid vaccines are not covered by that fund because Congress has not made them subject to the excise tax that pays for it. Some lawmakers have introduced bills to make the change.

Instead, claims regarding Covid vaccines go to the Countermeasures Injury Compensation Program . Intended for public health emergencies, this program has narrow criteria to pay out and sets a limit of $50,000, with stringent standards of proof.

It requires applicants to prove within a year of the injury that it was “the direct result” of getting the Covid vaccine, based on “compelling, reliable, valid, medical, and scientific evidence.”

The program had only four staff members at the beginning of the pandemic, and now has 35 people evaluating claims. Still, it has reviewed only a fraction of the 13,000 claims filed, and has paid out only a dozen.

Dr. Ilka Warshawsky, a 58-year-old pathologist, said she lost all hearing in her right ear after a Covid booster shot. But hearing loss is not a recognized side effect of Covid vaccination.

The compensation program for Covid vaccines sets a high bar for proof, she said, yet offers little information on how to meet it: “These adverse events can be debilitating and life-altering, and so it’s very upsetting that they’re not acknowledged or addressed.”

Dr. Zimmerman, the neuroscientist, submitted her application in October 2021 and provided dozens of supporting medical documents. She received a claim number only in January 2023.

In adjudicating her claim for workers’ compensation, Washington State officials accepted that Covid vaccination caused her injury, but she has yet to get a decision from the federal program.

One of her therapists recently told her she might never be able to live independently again.

“That felt like a devastating blow,” Dr. Zimmerman said. “But I’m trying not to lose hope there will someday be a treatment and a way to cover it.”

Apoorva Mandavilli is a reporter focused on science and global health. She was a part of the team that won the 2021 Pulitzer Prize for Public Service for coverage of the pandemic. More about Apoorva Mandavilli

Advertisement