The climate is constantly changing, and scientists know that human activity has played a major role in the changes we are experiencing. Climate change encompasses more than just a warming world; it impacts the availability of food and water, the health of ecosystems, transportation systems, wildlife, and much more. It is vitally important that we work together to limit global temperatures to no more than 2°C above pre-industrial levels.
The most widely accepted theory about the cause of climate change is that the buildup of greenhouse gases in the atmosphere is causing the Earth to warm. When these gases accumulate, they act like a blanket around the planet. Sunlight (mostly short-wave radiation) hits this blanket, and it gets trapped. The Earth then emits a different type of radiation (long-wave infrared) back into the air. This is what causes the greenhouse effect. These gases are released from the breakdown of plants and animals, by human activities, and through natural processes such as volcanic eruptions.
These natural processes have always had some impact on the Earth’s temperature, but over time they are becoming a larger and larger factor in our climate. The current high level of greenhouse gas concentrations is unprecedented in thousands, and perhaps millions, of years of historical data.
Humans have produced a significant amount of these greenhouse gases, mainly through the burning of fossil fuels such as coal and oil. Those emissions are now building up in the atmosphere at an ever-increasing rate. The accumulation of these gases has already caused the Earth to warm by more than 1°C above pre-industrial levels.
As these changes continue, they are expected to cause more and more disruptions to the world’s natural systems and to our lives. We are now crossing climate thresholds that may not be reversible, including the melting of Arctic permafrost and glaciers, and the loss of ocean ice cover.
We must make substantial, immediate reductions in our emissions to avoid passing these thresholds and preventing the worst impacts of climate change.
Climate change is causing many other changes in addition to warmer temperatures, including a shift toward drier areas with less rainfall and more droughts, hotter, wetter areas with more heavy rain events, and altered wind patterns that will lead to more frequent and intense storms.
While the effects of climate change will be felt everywhere, they will be most profound in poor and vulnerable communities. These are the people who will be most likely to lose their homes, be displaced by wildfires or flooding, face malnutrition and insect-borne diseases, or die from heat stress. The climate crisis also exacerbates existing inequalities between the richest and poorest nations, with those who have the resources to cope more able to shield themselves from its consequences.
The best way to protect against the risks of climate change is for all nations to join together to slash emissions of carbon dioxide and other greenhouse gases by roughly half by 2030 and stop adding them altogether by 2050. Delays of just a few years are likely to guarantee that we will not reach this goal, and we will have no chance of limiting warming to 1.5°C.