Climate is usually defined as average weather, so climate change and weather are intertwined. Observations show that the weather is always changing, and the statistics of weather changes over time reflect the characteristics of climate change. While weather and climate are closely related, there are important differences. Scientists are often asked: If they cannot predict the weather a few weeks from now, how can they predict the climate 50 years from now? This is actually a common phenomenon that confuses weather and climate. The chaos of the weather makes it difficult to predict what will happen in a few days. However, predicting climate change (that is, long-term average weather) based on changes in atmospheric composition or other factors is a very different and relatively easy problem to solve. For example, it is impossible to predict the exact age at which a person will die, but we can safely say that the average age of death in industrialized countries is about 75. Another common confusion between weather and climate is the denial of global warming by a single cold winter or a lower temperature in one part of the planet. Extreme heat and extreme cold are always present, although their frequency and intensity vary with the climate. But when weather conditions are averaged over time and space, the data clearly show that the world is warming.
A diagram of the components of the climate system,
their processes, and their interactions.
Meteorologists devote a great deal of their work to observing, understanding and predicting the evolution of weather systems day by day. Using the physical concepts that determine atmospheric motion, warming, cooling, rainfall, snowfall and water evaporation, meteorologists have largely succeeded in predicting the weather over the next few days. One of the main factors that limit the predictability of weather after a few days is the fundamental dynamic characteristics of the atmosphere. In the 1960s, meteorologist EdwardLorenz discovered that small differences in initial conditions can make a big difference in the final forecast. This is known as the butterfly effect. A butterfly flapping its wings in one place (or some other tiny phenomenon) could, in theory, then change the weather in a distant place. At the heart of this effect is chaos theory, the study of how small changes in certain variables make complex systems present obvious random results.
Chaos theory does not, however, imply complete disorder. For example, slightly different conditions during the development of a storm system may change the date of arrival of the storm system or its exact path, but the average temperature and precipitation (i.e., climate) in that region and over that period will remain the same. Since an important problem facing weather forecasting is how to know all the conditions at the beginning of the forecast period, climate can be considered to be related to the background conditions of the weather. More specifically, climate can be thought of as related to the state of the entire earth system, including the atmosphere, land, oceans, snow, ice, and life (see Figure 1), which together form the global context that determines weather conditions. For example, it affects the weather along Peru's coast. Ennius determined the limits of stochastic effects on the development and variation of weather conditions. La Nina identified a different range of limits.
Another example is the familiar contrast between summer and winter. The change of seasons is due to the different geographical characteristics of the energy absorbed and radiated by the earth system, in particular the increasing greenhouse gas effect of trapping heat near the ground, which is determined by the amount of carbon dioxide and other greenhouse gases in the atmosphere. Forecasting climate change over the next 50 years due to changes in greenhouse gases is a very different and much easier problem to solve than forecasting the weather in the coming weeks. In other words, it is much easier to predict long-term variations due to changes in atmospheric composition than to predict individual weather events. For example, we cannot predict the outcome of a coin or a die, but we can predict the statistical outcome of many rolls.
While many factors continue to influence the climate, scientists have determined that human activity has become a major force and is responsible for most of the warming observed over the past 50 years. Anthropogenic climate change is mainly caused by changes in the amount of greenhouse gases in the atmosphere. In addition, changes in atmospheric particulates (aerosols) and changes in land use also contribute to climate change. With climate change, the probability of certain types of weather events is affected. For example, as the average temperature of the earth increases, the frequency and intensity of some weather events are increasing (such as heat waves and heavy rainfall), while the frequency and intensity of others are decreasing (such as extreme cold weather events).
Chaos theory does not, however, imply complete disorder. For example, slightly different conditions during the development of a storm system may change the date of arrival of the storm system or its exact path, but the average temperature and precipitation (i.e., climate) in that region and over that period will remain the same. Since an important problem facing weather forecasting is how to know all the conditions at the beginning of the forecast period, climate can be considered to be related to the background conditions of the weather. More specifically, climate can be thought of as related to the state of the entire earth system, including the atmosphere, land, oceans, snow, ice, and life (see Figure 1), which together form the global context that determines weather conditions. For example, it affects the weather along Peru's coast. Ennius determined the limits of stochastic effects on the development and variation of weather conditions. La Nina identified a different range of limits.
Another example is the familiar contrast between summer and winter. The change of seasons is due to the different geographical characteristics of the energy absorbed and radiated by the earth system, in particular the increasing greenhouse gas effect of trapping heat near the ground, which is determined by the amount of carbon dioxide and other greenhouse gases in the atmosphere. Forecasting climate change over the next 50 years due to changes in greenhouse gases is a very different and much easier problem to solve than forecasting the weather in the coming weeks. In other words, it is much easier to predict long-term variations due to changes in atmospheric composition than to predict individual weather events. For example, we cannot predict the outcome of a coin or a die, but we can predict the statistical outcome of many rolls.
While many factors continue to influence the climate, scientists have determined that human activity has become a major force and is responsible for most of the warming observed over the past 50 years. Anthropogenic climate change is mainly caused by changes in the amount of greenhouse gases in the atmosphere. In addition, changes in atmospheric particulates (aerosols) and changes in land use also contribute to climate change. With climate change, the probability of certain types of weather events is affected. For example, as the average temperature of the earth increases, the frequency and intensity of some weather events are increasing (such as heat waves and heavy rainfall), while the frequency and intensity of others are decreasing (such as extreme cold weather events).
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