A warming climate threatens the planet’s natural systems and our ability to thrive. It is already causing glaciers and ice sheets to melt, oceans to warm faster, and heat waves to be longer and more intense. Wildlife is at risk, from polar bears in the Arctic to marine turtles in Africa. Water is at risk as well, with warmer temperatures driving increased evaporation and droughts that harm crops, limit access to clean drinking water, and increase the spread of mosquito-borne diseases like malaria.
Climate change is caused mainly by human activities, specifically the burning of fossil fuels (coal, oil and gas) that release heat-trapping greenhouse gases into the atmosphere. Those gases trap the sun’s heat that would otherwise escape into space, raising global average temperature. In the past 250 years, Earth has warmed 1.1 degrees Celsius, or 1.9 degrees Fahrenheit.
Scientists agree that humans must dramatically reduce their emissions of greenhouse gases to avoid the most harmful effects of climate change. At a minimum, they recommend that countries aim to be net zero carbon dioxide emitters by 2050. This means reducing greenhouse gas levels to as low as possible while also taking steps to remove remaining emissions from the atmosphere.
Despite the overwhelming scientific consensus, there are still many people who question the science behind climate change. Some of these skeptics have financial or political ties to the fossil fuel industry, while others have studied fields such as biology or chemistry instead of Earth, atmospheric and environmental sciences. But some skeptics, such as the physicist Richard Muller, have publicly changed their minds after reassessing historical climate data and seeing the evidence for themselves.
The vast majority of scientists understand the climate changes we are already seeing, including the loss of ice sheets and glaciers and the rising sea level, and they expect these trends to continue. They also anticipate that the frequency and intensity of extreme weather events will increase unless we take action to reduce greenhouse gas emissions.
As a result of these changes, the health risks associated with climate change are disproportionately felt by the poorest and most vulnerable communities around the world. These include those living in rural areas, island nations and coastal regions, as well as those who are most at risk of climate-related disasters and have the least capacity to cope with them.
Climate-related events like heat waves, wildfires, floods and droughts are increasingly common and intense in many parts of the world. They are already impacting people’s ability to earn a living and protect their families, and they will be much worse without urgent action. Climate change also affects the distribution of disease vectors, such as mosquitoes and ticks that carry harmful microbes from one person to another. These diseases are expected to become more widespread and severe as the climate continues to warm, because these organisms can only survive in specific environments. These conditions are also predicted to exacerbate existing health threats like malnutrition, water-borne diseases, and infectious and parasitic infections.