What is Climate Change?

Climate Change refers to a number of changes in Earth’s atmosphere and surface that are caused by human activities. It includes the warming of the atmosphere and oceans, melting of snow and ice and the changing of weather patterns. These changes have major impacts on people, wildlife and the natural environment.

The climate changes we are seeing are the result of long-lived greenhouse gases being released into the air by human activities. When these gases reach the atmosphere they absorb and trap some of the sun’s heat, instead of allowing it to escape into space. This warming of the atmosphere and oceans is known as the Greenhouse Effect.

Some of the gases released by human activity into the atmosphere are carbon dioxide, methane, nitrous oxide and sulfur dioxide. These gases are also found in the atmosphere as a result of volcanic eruptions, plant and animal respiration, and changes in ocean and atmospheric circulation. The amount of greenhouse gas in the atmosphere is controlled by a natural process called the carbon cycle. This process continually moves carbon between different reservoirs – the ocean, the biosphere, and fossil fuels. Carbon is stored in these reservoirs by plants and animals, or by decomposition, volcanic eruptions, fires and landslides. When these reservoirs are changed, the concentration of carbon in the atmosphere is also affected.

There are many natural factors that affect the climate, but scientists have concluded that the rapid warming that has been seen in recent decades cannot be explained by these alone. The most significant factor is the increased level of heat-trapping greenhouse gases in the atmosphere. The most important of these is carbon dioxide, which is produced when fossil fuels are burned for energy. Other sources of emissions are burning solid waste, clearing forests, fertilizing crops and producing some industrial products.

Rising temperatures are causing many other changes. The Arctic is melting; glaciers and snow are retreating; sea ice is shrinking; wildfires are spreading; and the ranges of many species are moving or shifting in response to the warmer conditions.

These changes threaten to have a profound impact on people’s lives and livelihoods. In the United States, for example, hurricanes, heat waves, droughts and floods are already having a significant impact. And as the climate continues to warm, these events will become more severe. In addition, many health outcomes have been linked to climate change including respiratory and cardiovascular diseases, infectious diseases and malnutrition. A review of scientific literature by experts suggests that the risks of these effects on humans are likely to be much higher than previously thought. Climate change will affect everyone, but poor countries produce fewer greenhouse gases and are at greater risk from the consequences. This means they must take action first. It is estimated that if the world’s 100 least-emitting countries take fast action now, they can reduce their emissions to safe levels within the next few decades. But if they do not, global temperatures could rise by more than 4 degrees Celsius above pre-industrial levels.

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