How do we know climate change is caused by humans?

Global warming (or climate change) has been a hot topic for years. But now we are starting to see its effects in our everyday lives. Extreme storms, like hurricanes, are becoming more common. Sea levels have risen by about 9 inches since the late 1800s, causing flooding in coastal areas. Ice sheets and glaciers are melting at alarming rates. The ocean has become about 30% more acidic, which is harming sea creatures. Wildfire activity has doubled due to hot and dry conditions. Plants and animals around the world are facing extinction. But how do we know that these effects are happening because of global warming? And how do we know that humans caused it?

Ever since the industrial revolution in the 1800s, humans have burned large amounts of fossil fuels. This releases gases, including carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). These gases released during the burning of fossil fuels are called “greenhouse gases”, or GHGs. Greenhouse gases exist naturally in our atmosphere. Their job is to hold heat inside the atmosphere so that the warmth life needs to survive doesn’t escape into space. Imagine them as Earth’s blanket, just thick enough to keep the planet warm. However, burning fossil fuels has made this greenhouse gas “blanket” become too thick. This traps extra warmth and causes the planet to heat up.

Now, global warming might be difficult to notice on your own. It happens relatively slowly. So we are more likely to pay attention to the daily changes in weather, instead of the long-term changes in climate. But scientists can help. They measure many indicators of global warming to help us understand how and why Earth’s climate is changing.

Temperature and carbon dioxide

Scientists have carefully measured the changes in global temperature over the last 55 years. They do this using weather stations, satellites, and ocean buoys. Before these tools, we also estimated global temperature from past records. This allows scientists to track how Earth’s temperature has changed since we started burning fossil fuels. Scientists also measure the amount of carbon dioxide in the atmosphere and how this has changed over time. One way they do this is using ice cores. Ice cores are samples of ancient ice that trapped carbon dioxide from when the ice first froze long ago. They tell us what Earth’s climate was like thousands of years ago. By comparing modern data and ice core data, we can see how much humans have really affected the Earth's climate.

So what have scientists found? Earth’s average global temperature has risen sharply since we began burning fossil fuels. In recent years, the climate is about 1.5 degrees Celsius hotter than it was in the late 1800s. It might not sound like much, but that change has massive effects on our planet! Carbon dioxide levels are much higher now compared to any point in the past 800,000 years. Also, the amount of carbon dioxide in our atmosphere is rising 100 times faster than it ever did in the past. The rapid recent warming goes hand in hand with the increases in carbon dioxide in our atmosphere. As carbon dioxide levels rise, so does global temperature. All this change has happened only after we started burning fossil fuels.

More evidence for climate change

Scientists are also measuring many other effects of climate change. For example, plants and animals are starting to behave in ways we have never seen. As temperatures rise, growing seasons are shifting. Flowering plants are blooming at unusual times. Birds are migrating earlier in the spring and moving to cooler habitats. Coral is bleaching due to heat stress, leading to the decline of reefs that many ocean species depend on. The usual patterns we see in nature are being disrupted and ecosystems are thrown out of balance.

All these changes are linked to higher global temperatures. As humans continue to raise carbon dioxide levels, the effects of climate change are only getting worse. Tracking these effects gives us even stronger evidence that climate change is real and caused by humans.

What can we do?

Climate change might seem scary. But learning about climate change, why it’s happening, and its effects is an important first step toward solving the problem. Although people around the world have started to act to slow climate change, we still have a long way to go.

Did you know that corporations create most of the greenhouse gas emissions? Governments need to make laws that hold these companies responsible for what they do. To help with this, it’s important to support leaders and companies that are trying stop the burning of fossil fuels. We need to switch to renewable energy sources, like wind or solar power. You can also help by using less energy, recycling, sharing rides, and using public transportation. Your voice and actions make a difference!

Sources

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