Climate Change Science

Climate change refers to long-term shifts in global temperatures and weather patterns. The science is based on: the greenhouse effect (certain gases trap infrared radiation, warming the surface); historical CO2 measurements (ice cores show CO2 at 280 ppm for 800,000 years pre-industrial, now at 420 ppm); temperature records (11 of the 12 hottest years on record have occurred since 2010); and physical consequences (sea level rise, ice melt, extreme weather). The Intergovernmental Panel on Climate Change (IPCC) synthesizes thousands of scientific studies. Current trajectory puts Earth on course for 2.5–3°C of warming above pre-industrial levels by 2100 — causing sea level rise of 0.5–1m, extreme weather intensification, agricultural disruption in tropical regions, and ecosystem collapse. The Paris Agreement (2015) aims for less than 2°C warming.