Climate Change refers to the long-term average temperature of Earth and its oceans increasing due to extra heat in the climate system, which is caused by increased levels of ‘heat-trapping’ greenhouse gases in the atmosphere. Human activities such as burning fossil fuels (coal, oil and gas) and deforestation increase the level of these gases. Other contributing factors include cyclical changes in ocean patterns, volcanic activity and variations in the Sun’s radiation output. These factors are known as ‘radiative forcings’ and are measured in the global climate models used to predict future changes.
Complex computer simulations of the climate system reveal that when a combination of all radiative forcings are added together, they match longer-term trends in observed temperatures quite well. This shows that human activities account for most of the observed warming since 1950, though there is some year-to-year variation that may not be due to any particular forcing.
As the climate warms, more extreme weather events are expected to occur. These include more frequent and intense flooding, rising sea levels, warmer oceans, and longer and more severe droughts. Climate change will also impact water systems by causing more intense and prolonged rainfall events, and changing the amount of water available for crops and wildlife.
Some regions will be more affected by Climate Change than others. Those in low-income communities and countries with fewer resources to adapt will be at greater risk. Those who depend on the natural environment for food, shelter and livelihood will be especially vulnerable to its impacts.
People living in urban areas will face health risks from increased temperatures, more frequent and intense heat waves, decreased air quality, and other impacts resulting from climate change. This includes children, pregnant women, older adults, and those with chronic conditions such as heart disease.
Observed Climate Change is due to the release of heat-trapping greenhouse gases by human activities such as burning fossil fuels (coal, gas and oil), deforestation and agriculture. The gases accumulate in the atmosphere and trap more heat from the Sun, which warms the climate system.
The climate has changed rapidly over the past few decades and is getting warmer. This is because humans have released huge amounts of heat-trapping greenhouse gases into the atmosphere – carbon dioxide, methane and other volatile organic compounds, as well as sulphur oxides and volatile particulates. These emissions have raised global atmospheric temperatures and altered regional weather patterns, including ocean and atmospheric circulation and seasonal rainfall conditions.
The majority of scientists agree that Climate Change is real, and it has been caused by humans. There is a high level of scientific consensus that more than 100% of observed warming over the past 150 years can be attributed to human causes. This is because a natural cooling effect from volcanoes and solar variations could not have cancelled out such a large proportion of human-caused warming. This is why more than 100 countries have signed the Paris Agreement to reduce carbon dioxide emissions and help protect humanity from climate change.