Meteorology focuses on current weather patterns to determine what the weather is likely to produce in the short term. Acclimate scientist will research weather patterns over long periods of time: thousands of years into the past in some instances. The look for what influenced the weather during various periods and try to deduct what mitigating factors caused it. Take, for example, the year without summer, back around 1812. It was finally determined much later that the eruption of Krakatoa affected the growing season in Bangor, Maine on the other side of the globe. Actually, it affected the weather around the world. They study the data and trends that caused the weather. While an active volcano erupting may cause a drastic change for a short period of time, say as much as two years, it will eventually level out and return to a more normal pattern within a few years. Studies have found that, instead of returning to normal, the temperature has slowly, but steadily, risen over the past 50 years. Worldwide, the temps have risen about 2.5° over that time. Based on the data, the current trend shows a rise of another 1.5° over the next 50 years, however, based on current data, that could come to pass within as soon as 20 years.