In the broadest sense, Climate Change refers to human-caused changes in Earth’s natural systems – including the atmosphere and ocean – which result in higher risks for humans, nature and our economy. The scientific consensus is clear that unmitigated carbon emissions are the primary driver of global climate change. This will lead to warming of the planet’s atmosphere, ocean and land resulting in significant impacts in every region of the world.
The evidence is irrefutable. The Earth’s atmospheric greenhouse gas concentrations have been steadily increasing since human activities began in the Industrial Revolution. These increases are primarily due to burning fossil fuels, resulting in carbon dioxide (CO2) being released into the air. The CO2 concentration in the atmosphere is currently at the highest level in hundreds of thousands of years.
Scientists routinely compare patterns of observed climate change with those produced by sophisticated models of Earth’s systems, such as the atmosphere and ocean. Using a technique known as “fingerprinting”, they can identify the presence of certain influences on climate, such as natural variations in the Sun’s output or volcanic eruptions. The most distinctive fingerprint is left by fossil fuel combustion, which results in the release of CO2, heat-trapping sulphur dioxide and short-lived greenhouse gases such as methane and volatile organic compounds. These chemicals also form aerosols in the atmosphere, which scatter and reflect incoming solar radiation. They also cause the formation of low-level clouds that absorb outgoing heat, thereby warming the Earth.
In comparison, the modelled influence of all natural factors leads to a modest cooling. The IPCC’s most recent report concluded that human activities are responsible for between 104% and 110% of observed warming, with combined natural forcings accounting for a slight cooling.
Warmer temperatures also have a range of other negative impacts. For example, they increase the rate at which freshwater is withdrawn from rivers and lakes, leading to water scarcity in many regions. They also raise the risk of wildfires, such as those seen in Europe last summer. In addition, they may exacerbate the effects of extreme weather events such as floods or droughts.
Climate change threatens the survival of all life on Earth, from polar bears in the Arctic to marine turtles off the coast of Africa. Rising sea levels will affect coastal communities, while longer, more intense droughts are expected to impact food and water supplies for both people and wildlife.
The best way to limit the damage from climate change is to reduce our dependence on fossil fuels and move to a clean energy economy, with a focus on equity and sustainable development for all. This will require transforming transportation, reorienting our food system and shifting to lower-carbon lifestyles. It will also involve combatting misinformation spread by the fossil fuel industry and other wealthy interests. Without these efforts, the consequences of Climate Change will be severe and far-reaching. The time to act is now.