Climate models, forecasts, and impacts

Scientists forecast climate change using data and climate models. Measurements show Earth's average surface temperature is now about 1.3 °C warmer than in the late 1800s when averaged over recent years, with individual hot years such as 2024 even warmer and the fastest warming in recent decades, and global sea level has risen about 20 centimeters since 1900 and now rises about 4 millimeters per year, as ocean water expands when it warms and as glaciers and ice sheets melt. Global climate models divide the atmosphere, ocean, land, and ice into many three-dimensional grid boxes and use the laws of physics to calculate how energy, water, and air move among them over time. Scientists test models by checking whether they reproduce past climates, such as the warming of the last century or conditions during the last ice age, and then run them with different scenarios of future greenhouse gas emissions. The Intergovernmental Panel on Climate Change (IPCC) summarizes the results: by 2100, warming is projected to be about 1.5 °C above preindustrial levels if emissions fall very quickly to net zero, and roughly 4 °C or more if emissions keep rising strongly. Projected impacts include more frequent and intense heat waves, heavier downpours in many regions, more severe droughts in others, continued sea level rise that threatens coastal communities, shrinking snowpack that reduces water supplies, and stress on ecosystems such as coral reefs. Effects vary by region, and the biggest uncertainty in end-of-century forecasts is how much greenhouse gas humans will emit, not whether warming will continue.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report