Climate change is the long-term average warming of the planet’s atmosphere and oceans. It’s happening because human activities are releasing more greenhouse gases into the air, including carbon dioxide and methane.
The concentrations of these gases are already higher than at any time since the beginning of the industrial age. It’s largely due to burning fossil fuels, such as coal, oil and gas.
This has a powerful effect on the weather. For example, it increases the amount of heat absorbed by the ocean, which can lead to changes in ocean temperature and a rise in sea level. It also can affect the timing of flora and fauna species’ life cycles.
These effects can be very serious. For instance, heat waves are becoming more frequent and severe in many areas. This can cause serious harm to people and communities.
There are many reasons for climate change, but the most important is the increase in greenhouse gas concentrations. These gases trap the sun’s heat, like the glass in a greenhouse, so they warm up the Earth.
They’ve been doing so for decades, and are increasing rapidly. That’s why scientists say we’re seeing a rise in global temperatures that is unprecedented in the history of the world.
Temperatures have risen by an average of 2.2 degrees Fahrenheit, or 1.2 degrees Celsius, over the past 150 years. The Arctic has warmed the most, by 4 degrees Fahrenheit since the 1960s.
Some skeptics have attempted to explain climate change away with other natural factors. But scientific analysis shows that these factors can’t be relied on to fully explain the observed temperature changes of the last several decades, and that human activities are the primary driver.
The best evidence of human-caused warming comes from measurements of the concentrations of carbon dioxide in the atmosphere, which have climbed by more than 10 billion tonnes since the Industrial Revolution, mostly because of the burning of fossil fuels such as coal, oil and gas. This change is corroborated by a large range of other observations, including those from satellites and weather stations on land, in the ocean and above the atmosphere.
It’s difficult to know exactly how much of this warming is human-induced because so many factors are involved. But scientists have devised a simple statistical climate model to determine the most likely causes of observed temperature changes.
This model combines the most important human and natural forces that can cause a shift in Earth’s climate, such as changes in greenhouse gas concentrations, aerosols emitted by volcanic eruptions, solar output, and other natural changes.
Those causes have all shifted the climate system in ways that affect the Earth’s weather, and are therefore important for understanding how and why we’re experiencing climate change now.
These changes are causing extreme weather events, such as heat waves and droughts. These can wreak havoc on communities and ecosystems, and they have already caused millions of dollars in damages.
Extreme weather events will become more frequent and severe in many places as the Earth’s temperature continues to rise. These events will damage property and crops, cause health problems and even result in death. The resulting losses will disproportionately impact the poorest and most vulnerable countries.