Climate trends are atmospheric patterns such as temperature, gas concentrations, and precipitation. Meteorologists collect information to understand historic patterns, compare them to ongoing ones, and predict future weather events. This work includes analysis of information about the weather to identify trends of concern, such as warming and cooling spikes that may be indicative of climate change. When climates change, their trends shift permanently, which can have an impact on the environment and human populations.
There are a number of sources for information on historic climate trends. One is recorded data. In many nations, information about temperature and rainfall dates back to the early 20th century and sometimes even earlier, providing concrete information about what the weather was like. From the 1950s onward, information can also include radiation readings, gas concentrations, and other data that may be of interest to researchers.
Other related data comes from historical sources. Deposits of ice in the Arctic and Antarctic help researchers identify particulates that were present hundreds or thousands of years ago, thanks to closely packed snow that can be collected with core sampling technology to maintain the layers and allow researchers to study them. This can allow researchers to identify signs of volcanic eruptions and unusual warmth or cold on the basis of what was pollinating and when.
Additional sources for information on climate trends are a bit more unexpected. Researchers have used paintings, for example, analyzing the use of color, the appearance of the sky, and the presence of snow and other seasonal indicators to learn more about climate conditions when works of art were produced. Journals and other personal records can also provide insight into what temperatures were like, when it usually rained, how long snow pack remained, and so forth.
This historic information creates a baseline that researchers can use to explore climate trends. From year to year, there can be considerable variation in atmospheric data; precipitation might start early or late, weather could be unusually warm or cool, or heavy weather like tornadoes might increase or decrease. Over time, however, these phenomena will usually average out. This allows researchers to identify spikes of unusual data, like a warming climate trend that suggests temperatures are on a steady rise.
Researchers with an interest in climate conditions apply their research to the development of models to predict future climate trends. Prediction can allow nations to plan ahead for shifts that may not be avoidable. It can also highlight the consequences of some human activities on the environment, which may provide arguments for increased regulation. For example, many researchers believe that the production of greenhouse gases through industrial activity contributes to global warming trends, and recommend tighter pollution laws to limit the production and release of such gases.