evidence: Today, the Intergovernmental Panel on Climate Change (IPCC) released the Physical Science Basis report from Working Group 1, a major part of their sixth Assessment Report. This report includes the most up-to-date understanding of the climate system and climate change, providing the best scientific evidence in order to understand the past, present, and future changes to our planet from global warming. The conclusions are clear: climate change is already affecting nearly every part of the planet, and human activities are unequivocally the cause. The report, co-authored by 234 scientists from around the world, finds that we are now around 2.0°F (1.1°C) warmer than in 1850-1900, warming at a rate without precedent in at least 2000 years, possibly longer. This report confirms that the climate-driven changes occurring around the world are widespread, rapid, and intensifying. Our influence on the climate is making extreme weather and climate events—like heat waves, heavy rain, and droughts—more frequent and severe, putting more people, property, and natural resources in harm’s way. Unless there is a rapid and large-scale reduction in greenhouse gas emissions, limiting warming to a 2.7°F (1.5°C) threshold will be beyond reach. Scientists warn that the more humans drive Earth’s average temperature above this threshold, the more frequent and severe extreme weather and climate events will become.