Climate Change

Climate change is a long-term shift in Earth's weather patterns. Today, the biggest shift is that the whole planet is getting warmer. Scientists often call this global warming. Earth's climate has changed many times before, but the warming happening now is caused mostly by people. It is one of the biggest challenges of the twenty-first century.

Climate vs. weather

Climate and weather are not the same thing. Weather is what happens outside on a single day. Climate is the average pattern of weather in a place over many years. A cold week in April does not mean the planet is not warming. Scientists study climate by looking at records from all over the world, over long periods of time.

Earth's average temperature has risen about 2 degrees Fahrenheit since the late 1800s. That may sound small. It is not. Even a small change in the average pulls summers hotter, winters milder, and storms stronger. It also melts ice that took thousands of years to build up.

The greenhouse effect

To understand climate change, it helps to understand the greenhouse effect. Some gases in the air, such as carbon dioxide and methane, act like a blanket around the planet. They let sunlight through, but they trap heat that tries to escape. This is a good thing in the right amount. Without the greenhouse effect, Earth would be a frozen ball.

The problem today is that humans have added a lot of extra greenhouse gases to the air. The blanket has grown thicker, and the planet is holding more heat than before.

What humans are doing

Most of the extra carbon dioxide comes from burning fossil fuels. Fossil fuels are coal, oil, and natural gas. We burn them to run cars, heat homes, and make electricity. When they burn, they release carbon that has been locked underground for millions of years.

Cutting down forests also adds to the problem. Trees pull carbon dioxide out of the air as they grow. When a forest is cleared and burned, that stored carbon goes back into the sky.

Farming plays a role too. Cows and rice paddies release methane, a greenhouse gas even stronger than carbon dioxide. Factories and landfills add more gases to the mix.

How scientists know

Scientists have been measuring carbon dioxide in the air since 1958 from a station in Hawaii. The level has risen every single year. Today there is more carbon dioxide in the air than at any time in the last 800,000 years. Scientists know this by drilling deep into Antarctic ice and studying bubbles of ancient air trapped inside.

Nearly every climate scientist in the world agrees on two main points. The planet is warming, and humans are the main cause. This is not a debate among experts. The debate is about the details: exactly how fast it will warm, which places will be hit hardest, and what we should do about it.

What changes on a warmer planet

A warmer planet does not just mean hotter days. Many things shift at once.

Glaciers and ice sheets are melting. In Greenland and Antarctica, huge amounts of ice are slipping into the ocean. As this ice melts, sea levels rise. Seas have already risen about eight inches since 1900, and they keep rising. Cities on coasts, such as Miami and parts of Bangladesh, face more flooding.

Warmer air holds more water, so some storms are getting stronger. Hurricanes can dump more rain. Wildfires burn hotter and spread farther in places that grow dry. Other places get heavier floods. Heat waves last longer and hurt more people.

Animals and plants are affected too. Polar bears hunt on sea ice that is shrinking. Coral reefs are bleaching and dying as ocean water warms. Some birds and butterflies now arrive in spring weeks earlier than they did 50 years ago.

What can be done

There are two main ways to respond. One is to slow the warming by adding fewer greenhouse gases. That means using less fossil fuel and more clean energy, such as solar power, wind power, and nuclear power. It means planting trees, saving forests, and building cars and homes that waste less energy.

The second way is to adapt. Cities are building seawalls, planting heat-tolerant crops, and making plans for stronger storms. Both actions matter. Slowing the warming is cheaper than living with its full effects.

Kids growing up today will see more of climate change than anyone alive before them. They will also have more tools to deal with it. The choices people make in the next few decades will shape the climate their grandchildren inherit.