Introduction

This site is intended for a general audience seeking information about climate modeling. We want to help explain the history, uses, and simple inner workings of climate models in terms that are easy to understand for non-scientists.

Weather vs Climate

Before we can discuss climate models, it's probably a good idea to present the differences between weather and climate, and weather models and climate models. Many people seem to confuse weather and climate. Weather is the state of the atmosphere at a place and time (such as temperature, precipitation, cloudiness, wind, etc.). Climate is an average of the weather over time. Another definition of climate: the average meteorological conditions (temperature, humidity, wind speed, rainfall, etc) over time. Climate can also describe the variations in meteorological conditions of an area (such as daily maximum and minimum temperatures). Climate can be defined by the statistics at a particular location or for a region or even globally.

Weather and Climate Models

Scientists studying weather and climate increasingly use computer models. A model is a description of a system or phenomenon using abstract equations or symbols. A weather model predicts weather based on current atmospheric conditions using computer simulations and data from weather balloons, satellites, radiosonde, etc. A weather forecast from a weather model only forecasts out to about six days in advance because the atmosphere is so complex and changes so rapidly. Climate models simulate past and future climate using computer code to build a three dimensional map of the climate system that is divided up into grid boxes. Climate models can be compared against long-term observed climate data to verify the ability of models to simulate earth’s climate. Although a climate model can simulate weather events, it is not intended to simulate the exact weather on a given day; instead a climate model is intended to accurately represent the long-term weather over time in a given region.

Why bother using climate models?

If weather models are intended to accurately predict weather on a small scale over the course of a few days, and climate models are not intended to simulate actual individual events, why would we bother using climate models? Climate models can help project the future long-term, average state of the atmosphere. For example, a climate model can help answer the question: “Will the mid-western United States become more or less dry over the next century?” Many groups and organizations can use climate models to help save money and lives around the world. Some examples of these groups include: farmers, public officials, energy consultants, insurance agents, national security officials, and climate scientists.

Agriculture: Although knowing about individual rainstorms can be helpful to someone growing corn or raising cattle, knowledge about long-term changes in precipitation and temperature can help for planning for droughts and expected trends in precipitation and temperature.

Public safety: Heat waves kill about 400 people every year in the United States. Public officials may want to know if cities are likely to become warmer or cooler on average in the future in order to plan for weather events such as heat waves.

Energy: Many types of power generation need water, and climate models can help predict if regions are expected to become more or less dry over time, which can affect water availability for these power generation facilities. Additionally, long-term average cloud cover, sunlight, and wind strength can be important if developers plan to install wind farms or solar panels in an area for power generation.

Water: Water is important for agriculture, drinking, cleaning, and power generation. Government officials, farmers, and energy consultants are just a few of the people who may be interested in the long-term trends of water availability in a region.

Insurance: Insurance companies base their policies on long-term averages. Climate models can help determine if an area is more likely to experience drought, heavy rainfall, or high winds.