Weather is the short-term condition of the lower atmosphere. It covers precipitation, temperature, humidity, wind direction, wind speed, and atmospheric pressure. These conditions change from minute to minute, hour to hour, and day to day. Weather changes quickly; climate changes slowly. On any given Tuesday, the temperature and rain in your city are weather. That Tuesday might be unusually hot or cold, but it is just one data point. Climate is the average of those conditions over 30 years or more. One way to hold the distinction: climate is what you expect; weather is what you get. The average July temperature in a city is a climate number; the temperature on a specific day is weather. The distinction matters because it shapes how claims about global warming are read. A single storm, heat wave, or cold snap is weather. The pattern those events form over decades is climate. When someone points to a snowy week as evidence against a warming planet, they are confusing the two timescales. Weather forecasts look ahead days or weeks. Climate projections look ahead decades or centuries.
A record-breaking cold winter does not disprove global warming. The January 2019 polar vortex, which brought extreme cold to parts of the United States, was a short-term weather event. It happened inside a much larger, long-term warming trend. The polar vortex is a large area of low pressure and cold air that normally sits over the poles. Occasionally it weakens and pushes cold air southward, causing a cold snap even as the global average temperature rises. This event was a reminder that weather and climate operate on different timescales.
A warming planet does not mean it will never snow or freeze. Such events become less frequent over time. Climate change can also produce heavier snow and rainfall, because warmer air holds more moisture. The mechanism is straightforward: warmer air can carry more water vapor, and when conditions are right, that vapor falls as heavier precipitation. For example, a storm in a warmer climate can drop more snow because the air holds more moisture, even if the overall number of snowstorms declines. This means that a warming world can see both fewer snowstorms and heavier ones when they occur.
The overwhelming majority of scientists, 97%, agree that climate change is real and largely caused by human activity. A change in climate can lead to changes in weather patterns.
Climate is measured by long-term averages of weather observations, often over 30-year periods. The 30-year period is a standard used by meteorologists. These averages are called Climate Normals. The observations come from satellites, weather stations, and other instruments. Over time they reveal patterns and trends that a single season cannot show. This smoothing process is what allows scientists to distinguish climate change from natural variability. For instance, a single hot summer does not indicate a warming trend, but a series of hot summers over decades does.
Human-induced warming reached approximately 1°C above pre-industrial levels in 2017. It has been increasing at around 0.2°C per decade. The global climate has changed before, but it is now changing much faster due to human activities like burning fossil fuels. The speed of the current change is what makes it different from natural shifts in the past. Natural climate shifts, such as ice ages, occur over thousands of years. The current warming is happening over decades, which is much faster.
Scientists can predict climate trends but not specific weather events. Climate models project future warming with confidence. Daily forecasts remain inherently uncertain because small variations in the atmosphere compound quickly. For example, a forecast for next week can change dramatically even a day ahead, while a projection for the next century is based on the physics of the atmosphere and oceans.
