Climate change is already having visible effects on the world. The Earth is warming, rainfall patterns are changing, and sea levels are rising. These changes can increase the risk of heat waves, floods, droughts, and fires. A changing climate impacts crop growth and human health, while many people may need to leave their homes. It places certain species at an increased risk of extinction. The effects of climate change are real, and they are already happening. The level of climate change we will see depends on how quickly we cut emissions of dangerous greenhouse gases. Even if we were to stop all emissions today, we would not prevent some changes. However, the sooner we cut emissions, the smaller the changes will be. We know that greenhouse gases, aerosol emissions and land use affect our climate. Overall, human activity is warming our planet. Climate change can affect our climate system in lots of different ways: Our climate system is finely balanced, and small changes can have significant consequences.