A polar bear walks along a rocky shore, looking for food. The bear would usually be on the sea ice hunting for seals, pouncing when the seal comes up to breathe. But the ice has started to melt earlier and re-form later than it has in the past. Without the sea ice, the polar bear must scavenge for other, less nutritious food.
These changes in polar sea ice are a result of climate change. But this isn’t just affecting polar bears—climate change affects everyone.
What is climate change?
The Earth's atmosphere seen from space
Photograph by NASA
Weather changes day to day—sometimes it rains, other days it’s hot. Climate is the pattern of the weather conditions over a long period of time for a large area. And climate can be affected by Earth’s atmosphere.
Our Earth is surrounded by an atmosphere made up of gases. When sunlight enters our atmosphere, some of the sun’s heat is trapped by the gas, and some bounces back out into space. By trapping that heat, our atmosphere keeps Earth warm enough to live on. Without it, our planet would be very cold, like Mars.
Earth’s climate has always naturally cycled through change, caused by how much of the sun’s energy was absorbed by the atmosphere. In fact over the past 650,000 years, the Earth has gone through seven ice ages and warming periods. Climate change describes a change in the average conditions — such as temperature and rainfall — in a region over a long period of time. NASA scientists have observed Earth’s surface is warming, and many of the warmest years on record have happened in the past 20 years.
Weather vs. Climate
Illustration of a weather forecast with text that reads 'Local Weather' next to an illustration of Earth and a thermometer with text that reads 'Global Climate'.
Weather describes the conditions outside right now in a specific place. For example, if you see that it’s raining outside right now, that’s a way to describe today’s weather. Rain, snow, wind, hurricanes, tornadoes — these are all weather events.
Climate, on the other hand, is more than just one or two rainy days. Climate describes the weather conditions that are expected in a region at a particular time of year.
Is it usually rainy or usually dry? Is it typically hot or typically cold? A region’s climate is determined by observing its weather over a period of many years—generally 30 years or more.
So, for example, one or two weeks of rainy weather wouldn’t change the fact that Phoenix typically has a dry, desert climate. Even though it’s rainy right now, we still expect Phoenix to be dry because that's what is usually the case.
Want to know more about the difference between weather and climate? Take a look at this video!
What Is Climate Change?
Alaska's Muir glacier in August 1941 and August 2004.
Alaska's Muir glacier in August 1941 and August 2004. Significant changes occurred in the 63 years between these two photos. Credit: USGS
Climate change describes a change in the average conditions — such as temperature and rainfall — in a region over a long period of time. For example, 20,000 years ago, much of the United States was covered in glaciers. In the United States today, we have a warmer climate and fewer glaciers.
Global climate change refers to the average long-term changes over the entire Earth. These include warming temperatures and changes in precipitation, as well as the effects of Earth’s warming, such as:
Rising sea levels
Shrinking mountain glaciers
Ice melting at a faster rate than usual in Greenland, Antarctica and the Arctic
Changes in flower and plant blooming times.
Earth’s climate has constantly been changing — even long before humans came into the picture. However, scientists have observed unusual changes recently. For example, Earth’s average temperature has been increasing much more quickly than they would expect over the past 150 years.
Want to know more about how we know climate change is happening? Check it all out here!
How Much Is Earth’s Climate Changing Right Now?
Graph of change in annual global temperatures, compared to the average of global annual temperatures from 1880-1899.
Graph of change in annual global temperatures, compared to the average of global annual temperatures from 1880-1899. Credit: NASA's Goddard Space Flight Center
Some parts of Earth are warming faster than others. But on average, global air temperatures near Earth's surface have gone up about 2 degrees Fahrenheit in the past 100 years. In fact, the past five years have been the warmest five years in centuries.
Many people, including scientists, are concerned about this warming. As Earth’s climate continues to warm, the intensity and amount of rainfall during storms such as hurricanes is expected to increase. Droughts and heat waves are also expected to become more intense as the climate warms.
When the whole Earth’s temperature changes by one or two degrees, that change can have big impacts on the health of Earth's plants and animals, too.
What Causes Climate Change?
A simplified animation of the greenhouse effect.
A simplified animation of the greenhouse effect. Credit: NASA/JPL-Caltech
There are lots of factors that contribute to Earth’s climate. However, scientists agree that Earth has been getting warmer in the past 50 to 100 years due to human activities.
Certain gases in Earth’s atmosphere block heat from escaping. This is called the greenhouse effect. These gases keep Earth warm like the glass in a greenhouse keeps plants warm.
Human activities — such as burning fuel to power factories, cars and buses — are changing the natural greenhouse. These changes cause the atmosphere to trap more heat than it used to, leading to a warmer Earth.
Does What We Do Matter?
This video shows how Arctic sea ice has been changing since 1984. Credit: NASA
Yes. When human activities create greenhouse gases, Earth warms. This matters because oceans, land, air, plants, animals and energy from the Sun all have an effect on one another. The combined effects of all these things give us our global climate. In other words, Earth’s climate functions like one big, connected system.
Thinking about things as systems means looking for how every part relates to others. NASA’s Earth observing satellites collect information about how our planet’s atmosphere, water and land are changing.
By looking at this information, scientists can observe how Earth’s systems work together. This will help us understand how small changes in one place can contribute to bigger changes in Earth’s global climate. analice como los dos autores enfatizan diferente
1 answer
The text provided offers a comprehensive overview of climate change and its implications, particularly through the lens of polar bears affected by melting sea ice. It highlights the distinctions between weather and climate, explains the recent trends in global temperatures, and discusses the greenhouse effect and human activities contributing to climate change.
Here's an analysis of how different authors might emphasize various aspects of this narrative:
Author A: Emphasizing Urgency and Human Impact
Narrative Style: This author might adopt a more urgent and alarmist tone, possibly focusing on the immediate consequences of climate change. They could illustrate the plight of the polar bear as a symbol of the broader environmental crisis, eliciting emotional responses from readers by emphasizing the urgency of the situation.
Human Responsibility: This author would likely stress the direct human involvement in climate change, making connections between daily activities (like driving cars or using electricity) and the larger systemic changes in Earth's climate. They might use powerful imagery or anecdotes about specific locations or communities currently suffering from climate-related disasters.
Call to Action: The emphasis would be on mobilizing collective action. They may incorporate statistics and compelling evidence about how individual actions can contribute to mitigating climate change, encouraging readers to take personal responsibility.
Author B: Focusing on Scientific Understanding and Education
Narrative Style: This author may choose a more educational and informative approach, breaking down complex scientific concepts for the reader. They could emphasize the processes behind climate change—like the greenhouse effect and historical climate cycles—focusing on imparting knowledge rather than urgency.
Systemic Approach: Instead of placing blame solely on human activities, this author may highlight the interconnectedness of Earth's systems, explaining how different factors contribute to climate change. They might present climate change as a natural phenomenon that has been exacerbated by human influence, aiming for a more balanced perspective.
Long-term Solutions: Rather than immediate action, this author might advocate for long-term strategies, such as policy changes or technological advancements, to address climate change. They may emphasize the importance of research and understanding Earth's systems to develop effective solutions.
Conclusion
In essence, while Author A’s emphasis might be on urgency and personal responsibility, aiming to galvanize immediate action against climate change, Author B would likely focus on education and systemic understanding, providing a foundation for informed long-term strategies. Both narratives hold value, as they address the complexities of climate change from different angles—one from an emotional and urgent perspective, and the other from a thoughtful and educational approach.
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