Climate Change refers to changes in Earth’s climate system that have been caused by human activities, including rising global air and ocean temperatures, melting ice sheets and glaciers, and changing weather patterns such as drought and floods. The changes are causing harm to natural and human systems. They threaten the very things we depend on for survival, including water, food, energy, transportation, wildlife, and ecosystems.
The most significant cause of climate change is the addition of extra heat-trapping greenhouse gases to Earth’s atmosphere. These gases trap the sun’s heat and prevent it from escaping back into space. Most of these gases were produced naturally, but humans now add a great deal to the atmosphere each year by burning fossil fuels like coal, oil and gas. This is contributing to the rapid increase in global temperature.
As carbon dioxide levels rise, Earth’s atmosphere becomes warmer and less able to hold heat. This is known as the greenhouse effect.
Natural processes produce and destroy greenhouse gases on a regular basis. For example, the decomposition of plants and animals produces carbon dioxide, which plants absorb during photosynthesis. This helps to stabilize atmospheric levels of CO2. However, human activities are now producing far more than these natural processes can offset, leading to the current climate crisis.
In addition to adding heat-trapping gases to the atmosphere, human activities are also reducing the amount of natural carbon storage on the planet by deforestation and land-use changes. This reduction has increased the rate of warming, threatening both natural and human-made systems.
Climate change is pushing many ecosystems toward so-called tipping points, which are thresholds beyond which irreversible changes may occur. For example, as global average temperatures warm, the Arctic and other highly sensitive ecosystems are at greater risk of losing key habitats and species. The report says that limiting warming to 1.5 degrees Celsius would require “rapid and far-reaching” transitions in energy, buildings, industry, transport and cities, as well as an end to fossil fuel use.
About half of the world’s population already experiences severe water scarcity, and this will worsen as global temperatures rise. The report notes that at 2 degrees Celsius of warming, as many as 18% of global plant and animal species could be threatened with extinction. At 4 degrees Celsius, this figure jumps to 50%.
Health risks from climate change can be particularly acute for vulnerable populations. The report identifies children, pregnant women, the elderly, and people living with mental illness as being at greater risk of heat-related health effects.
Climate change is also displacing people, which can lead to poor nutrition, trauma, lack of access to clean water, and increased vulnerability to infectious diseases. This displacement can also result in malnutrition, stress, and social unrest, and it can increase the spread of diseases such as dengue fever and West Nile virus. The report calls on governments to reduce emissions as low as possible while investing in climate-resilient development. The window of opportunity to make a difference is closing fast, the authors warn.