Climate change refers to long-term changes in Earth’s local, regional and global weather patterns. It is caused by increasing human emissions of heat-trapping greenhouse gases, and it has many significant impacts on ecosystems and living things. These impacts include shrinking glaciers and ice sheets, sea level rise, shifts in precipitation patterns, and increased frequency of extreme weather events such as hurricanes.
Several factors contribute to the Earth’s climate system, but the overwhelming majority of scientists agree that the planet is warming due to human activities. When energy from the sun reaches Earth, some of it is reflected back into space by clouds and ice, and some is absorbed by the atmosphere. But when certain atmospheric gases prevent the released heat from radiating back into space, the atmosphere acts like a greenhouse, trapping the Sun’s energy and warming Earth. Scientists call this process “global warming.”
The rapid increase in human emissions of greenhouse gases has contributed significantly to recent climate change. These gases are emitted from burning fossil fuels, clearing forests, fertilizing crops, storing waste in landfills, raising livestock, and producing some kinds of industrial products. They are also emitted naturally as a result of plant and animal respiration, volcanic eruptions, and ocean-atmosphere exchange. Fossil fuels – coal, oil and gas – are by far the largest contributor to global greenhouse gas emissions.
A warming planet is already having profound impacts, from the Arctic, where temperatures are rising twice as fast as the global average, to our backyards and beyond. In the Arctic, melting glaciers and ice sheets are contributing to sea level rise, while changing climate conditions threaten coastal ecosystems and low-lying areas. Warming and shifting precipitation patterns stress ecosystems, including fisheries, forests, and farmland. In addition, a warmer world is helping invasive and nuisance species, such as lionfish and ticks, thrive.
People are already feeling the effects of climate change, and the impact will only grow over time. The number of people displaced by disasters and other climate-related events is growing, along with their associated stresses on health, such as increased vulnerability to infectious diseases, trauma and stress, loss of social connections, and lack of access to clean water and adequate food.
Tackling climate change requires a massive undertaking involving everyone, everywhere. States are promoting clean energy industries; cities and towns are bolstering their resilience while placing equity at the forefront; businesses are committing to net-zero carbon goals; and individuals are taking action, from recycling to turning off lights and running the dishwasher with less water. All of these efforts are essential to avert the worst consequences of global warming.