Recently, we have had some very cold weather during the winter. But even so, average temperatures are rising around the world. Known as global warming, almost all scientists agree that global warming is real, it is happening now, and humans are causing it.
But how can we still have cold winter weather and global warming? It's because weather and climate are two different things.
Weather Describes Current Conditions
Weather describes the conditions of the lower atmosphere, or the air close to Earth's surface. These conditions include rain or snow, temperature, humidity (or how much water is in the air), wind speed and direction, and atmospheric pressure. They can change quickly. It could be sunny, cloudy, rainy, foggy, cold, hot, windy, stormy, or snowing.
The sun influences weather by heating the lower atmosphere. Warm air rises and cold air rushes in to fill its place. This causes wind. The air holds water in its gas form, known as water vapor. The wind and the water in the air cause clouds, rain or snow, and storms to form and move.
Conditions in the atmosphere are always changing. So weather is always changing. Meteorologists are scientists who study the weather. They get information from satellites, weather stations, and instruments that float in the ocean. They try to predict the weather that is coming in the next few days or weeks. This is called a forecast. Weather forecasts are very important. They warn people of dangerous weather conditions. Big storms can cause flash flooding. Dry winds can whip up forest fires.
Climate Describes Long-term Conditions
Weather changes often and can last for days or weeks or months. Climate, however, describes the conditions in the atmosphere over a long time, usually 30 years or more. Climate can be thought of as an average of weather conditions over time. That's why a very cold winter can happen even when average temperatures are warming.
Climate conditions are different in regions of the world. Climate affects the types of plants and animals that live there.
Weather and climate are linked. In fact, a change in climate can lead to changes in weather patterns.
Human Activities Are Affecting the Climate
Climate change is not new. The climate has changed many times in Earth's history. However, it is changing much faster now than it has in the past. This time, human activities are to blame.
The biggest cause of climate change is burning coal, gas, and oil. These are called fossil fuels because they formed from plants and animals that died and were buried a long time ago. We use fossil fuels to power our cars, trucks, buses, and trains. We use them to make electricity, heat our homes, and run factories.
Burning fossil fuels releases carbon dioxide into the atmosphere. Carbon dioxide is a type of greenhouse gas. These gases are like the glass roof in a greenhouse. The gases allow heat from the sun to enter the atmosphere, but stop it from escaping. As a result, Earth gets warmer.
Global warming is already happening. In the last 100 years, Earth's temperature has risen by 0.8 degrees Celsius (1.4 degrees Fahrenheit). Arctic sea ice is melting. Glaciers are shrinking. Sea levels are rising. Extreme weather events, like floods, wildfires, and hurricanes, are becoming more common and severe. Animals and plants are moving to cooler areas.
Humans Try To Address Global Warming
Scientists first learned how greenhouse gases affect the atmosphere in the 1800s. In the late 1930s, scientists found that Earth's temperature was already rising. In the 1980s, the science was accepted and people started to take action.
In 1988, the United Nations formed the Intergovernmental Panel on Climate Change. Since then, countries have agreed to lower the amount of carbon dioxide they release to fight climate change.
In 2015, 197 countries signed the Paris Agreement. It is a pledge to stop global temperatures from rising by more than two degrees Celsius (3.6 degrees Fahrenheit). In 2017, the United States announced it would withdraw from the agreement. Only China releases more greenhouse gases than the United States.