Climate change refers to long-term changes in the average weather patterns that define Earth’s local, regional and global climate. These changes are driven by human activities, such as burning fossil fuels and unequal land use, that alter the natural balance of energy that governs Earth’s climate.
The human-caused greenhouse gas emissions that build up in the atmosphere act like a blanket, trapping extra heat near the Earth’s surface and driving warming. As humans burn more fossil fuels and emit more greenhouse gases, their atmospheric concentrations have risen dramatically over the past century. Scientists can measure these changes using data from observations of the atmosphere, oceans and land surfaces. They also study ancient air and water samples that have been stored in sediments or ice cores.
Rising temperatures increase the intensity and frequency of severe weather events, such as heavy rains, heat waves and drought. This impacts food and water security, human health and the natural ecosystems on which we depend. It is estimated that about 1.1 degrees Celsius of warming has already occurred compared to pre-industrial temperatures and it will worsen unless we take immediate action.
We can avoid many harmful impacts by limiting warming to below 1.5 degrees Celsius. This would reduce risks such as the loss of Arctic sea ice, avoid the triggering of some climate tipping points (e.g. when the permafrost in the arctic melts, releasing carbon into the atmosphere) and significantly reduce the chance of the destruction of coral reefs.
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