Climate Change is the long-term average increase in global air and ocean temperature caused by human activities such as burning fossil fuels (coal, oil and natural gas), deforestation, land-use changes, and agriculture. These activities increase the amount of heat-trapping greenhouse gases in the atmosphere, which warms Earth’s surface and prevents some of the sun’s energy from escaping back into space.
Human-caused warming has already led to many observed changes such as rising global air and ocean temperatures, reduced Arctic sea ice cover, increased atmospheric and ocean circulation, and shifting global weather patterns, including changing precipitation and storm events. These climate change impacts are expected to continue and may become even more severe in the future without immediate action.
Hundreds of millions of people are already experiencing the health effects of climate change every day, from hotter temperatures and a decline in crop yields to droughts and wildfires, resulting in lower water supplies, decreased food security, and worsened living conditions. Extreme weather events like hurricanes, heat waves, and floods can also cause injuries, disrupt transportation and power systems, compromise water and wastewater services, and result in displacement.
Climate change affects everyone, but especially people who are most vulnerable. People who are poor or have preexisting medical conditions face a greater risk of injury and illness from exposure to climate stressors, such as heat, high wind speeds, or flooding. They are also less likely to have access to resources that can help them adapt to climate changes.
The Earth’s ecosystems and biodiversity are also being affected by climate change. Warmer temperatures cause plants and animals to move or abandon their habitats, which can lead to extinction. In the ocean, a warmer climate causes more acidity and can alter marine food chains. Warming waters can also trigger thermal dispersal, which can cause marine life to be transported far from their normal range. Rising sea levels and melting ice sheets can also threaten coastal communities with erosion, flooding, and storm surge.
Humans are responsible for most of the current warming because we release more heat-trapping carbon dioxide into the atmosphere than nature does naturally. If all human emissions of carbon dioxide stopped today, the world’s temperature would still rise for a few decades until ocean currents brought the excess heat stored in the deep ocean to the surface where it could be radiated back into space. It’s important to note that wealthy, industrialized nations produce more greenhouse gases than developing countries and therefore have a larger responsibility to reduce them. However, a number of these nations have been resistant to taking this responsibility.