Acid rain damage, scrubbers, monitoring and models

Climate models are computer programs built from physical, chemical and biological equations. Fed with data from satellites and stations, such as gas emission levels, they predict ranges. For example, a model run in which CO₂ keeps rising can give a rounded range of about 1.5 to 2 °C of extra warming, with changed rainfall patterns and more extreme weather; the range depends on the emission assumptions and is not a forecast for a given date. A model gives ranges with uncertainty, not exact dates. The Paris Agreement of 2015 aims to hold global warming well below 2 °C above pre-industrial levels. Forecasts matter for health (pollution and UV warnings), agriculture (when to plant and harvest) and ecosystems (protecting sensitive species). A forecast of “30% chance of a heat wave” is a probability, not a certainty. Example: coral bleaching happens when corals expel the symbiotic algae that feed them because the water is too warm, and they lose their main food. Forecasts of marine heat waves can help managers reduce other stresses on a reef, for example by limiting local pollution. They cannot prevent the heat itself, and bleaching can still be severe.