Query: At present, climate forecasts even as little as six weeks ahead can be diametrically the opposite of what actually occurs, even if the forecasts are limited to a small region of the planet.'

Relevant passages:
Meteorology <=SEP=> Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics , with a major focus on weather forecasting . The study of meteorology dates back millennia , though significant progress in meteorology did not occur until the 18th century . The 19th century saw modest progress in the field after weather observation networks were formed across broad regions . Prior attempts at prediction of weather depended on historical data . It was n't until after the elucidation of the laws of physics and , more particularly , the development of the computer , allowing for the automated solution of a great many equations that model the weather , in the latter half of the 20th century that significant breakthroughs in weather forecasting were achieved .   Meteorological phenomena are observable weather events that are explained by the science of meteorology . Meteorological phenomena are described and quantified by the variables of Earth 's atmosphere : temperature , air pressure , water vapor , mass flow , and the variations and interactions of those variables , and how they change over time . Different spatial scales are used to describe and predict weather on local , regional , and global levels .   Meteorology , climatology , atmospheric physics , and atmospheric chemistry are sub-disciplines of the atmospheric sciences . Meteorology and hydrology compose the interdisciplinary field of hydrometeorology . The interactions between Earth 's atmosphere and its oceans are part of a coupled ocean-atmosphere system . Meteorology has application in many diverse fields such as the military , energy production , transport , agriculture , and construction .   The word `` meteorology '' is from Greek μετέωρος metéōros `` lofty ; high ( in the sky ) '' ( from μετα - meta - `` above '' and ἀείρω aeiro `` I lift up '' ) and - λογία - logia '' - logy '' , i.e. `` the study of things in the air '' .

Ensemble forecasting <=SEP=> Ensemble forecasting is a method used in numerical weather prediction . Instead of making a single forecast of the most likely weather , a set ( or ensemble ) of forecasts are produced . This set of forecasts aims to give an indication of the range of possible future states of the atmosphere . Ensemble forecasting is a form of Monte Carlo analysis . The multiple simulations are conducted to account for the two usual sources of uncertainty in forecast models : ( 1 ) the errors introduced by the use of imperfect initial conditions , amplified by the chaotic nature of the evolution equations of the atmosphere , this is often referred to as sensitive dependence on the initial conditions ; and ( 2 ) errors introduced because of imperfections in the model formulation , such as the approximate mathematical methods to solve the equations . Ideally , the verified future atmospheric state should fall within the predicted ensemble spread , and the amount of spread should be related to the uncertainty ( error ) of the forecast . In general , this approach can be used to make probabilistic forecasts of any dynamical system , and not just for weather prediction .   Today ensemble predictions are commonly made at most of the major operational weather prediction facilities worldwide , including :  National Centers for Environmental Prediction ( NCEP of the US )  European Centre for Medium-Range Weather Forecasts ( ECMWF )  United Kingdom Met Office  Météo-France  Environment Canada  Japan Meteorological Agency  Bureau of Meteorology ( Australia )  China Meteorological Administration ( CMA )  Korea Meteorological Administration  CPTEC ( Brazil )  Experimental ensemble forecasts are made at a number of universities , such as the University of Washington , and ensemble forecasts in the US are also generated by the US Navy and Air Force . There are various ways of viewing the data such as spaghetti plots , ensemble means or Postage Stamps where a number of different results from the models run can be compared .

Weather forecasting <=SEP=> Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location . Human beings have attempted to predict the weather informally for millennia , and formally since the nineteenth century . Weather forecasts are made by collecting quantitative data about the current state of the atmosphere at a given place and using scientific understanding of atmospheric processes to project how the atmosphere will change .   Once an all-human endeavor based mainly upon changes in barometric pressure , current weather conditions , and sky condition , weather forecasting now relies on computer-based models that take many atmospheric factors into account . Human input is still required to pick the best possible forecast model to base the forecast upon , which involves pattern recognition skills , teleconnections , knowledge of model performance , and knowledge of model biases . The inaccuracy of forecasting is due to the chaotic nature of the atmosphere , the massive computational power required to solve the equations that describe the atmosphere , the error involved in measuring the initial conditions , and an incomplete understanding of atmospheric processes . Hence , forecasts become less accurate as the difference between current time and the time for which the forecast is being made ( the range of the forecast ) increases . The use of ensembles and model consensus help narrow the error and pick the most likely outcome .   There are a variety of end uses to weather forecasts . Weather warnings are important forecasts because they are used to protect life and property . Forecasts based on temperature and precipitation are important to agriculture , and therefore to traders within commodity markets . Temperature forecasts are used by utility companies to estimate demand over coming days . On an everyday basis , people use weather forecasts to determine what to wear on a given day . Since outdoor activities are severely curtailed by heavy rain , snow and wind chill , forecasts can be used to plan activities around these events , and to plan ahead and survive them . In 2014 , the US spent $ 5.1 billion on weather forecasting .