Climate refers to long-term, wide-range weather patterns. Climate change is a long-term change in weather patterns. The burning of fossil fuels and wood has disrupted the carbon cycle by increasing the level of carbon dioxide in the atmosphere. As more and more carbon is converted from organic forms into carbon dioxide, the level of atmospheric carbon dioxide continues to rise. Since the beginning of the Industrial Revolution, the period in the 18th and 19th centuries where manufacturing moved into the cities, the burning of fuels has increased drastically. There has been a sharp increase in atmospheric carbon dioxide, from 280 parts per million (ppm) to over 400 ppm. When this increase in atmospheric carbon dioxide was first identified, people incorrectly assumed that because carbon dioxide is a natural component of the vast atmosphere, human behavior would not make a measurable change. Also, carbon dioxide was thought to have no effect on any important processes.Now, scientists understand that carbon dioxide is a greenhouse gas. A greenhouse gas is an atmospheric gas that reflects the Sun's rays back to Earth, trapping heat. This phenomenon is natural and helps keep the atmosphere in a warm, comfortable temperature range. However, because carbon dioxide has been rapidly added to the atmosphere, this effect has increased. The average temperature of Earth has risen along with the amount of atmospheric carbon dioxide. This process has also been referred to as global warming. The increase in temperature is having measurable global effects, including changes in rainfall patterns. Drought is more common, which affects crops as well as wild plant populations. Pollination, migration, reproduction, and other natural processes that rely on weather cues are shifting as summer seasons last longer and spring comes earlier. These changes can cause timing mistakes that impact the survival and reproduction of certain species. Weather becomes less predictable and more erratic. Some scientists hypothesize that increases in extreme weather events are the result of global warming. Large quantities of Earth's water is trapped in ice and glaciers. As temperatures rise, melting ice is pouring fresh water into the ocean, raising sea levels. In addition, warm water expands, further increasing sea levels in a feedback loop. Scientists are searching for solutions to help mitigate the effects of climate change. Curbing global carbon dioxide emissions is a critical component of most possible solutions. Alternative, renewable forms of energy to power industrialized societies may also have an impact. In addition, encouraging practices that increase carbon sequestration, or the storage of carbon dioxide or organic carbon to slow climate change, is a possible solution. One possible method of sequestration involves pumping carbon dioxide into underground cavities left empty by fossil fuel extraction. Natural processes such as photosynthesis can also assist in storing carbon. Increasing the natural occurrence of photosynthesis by methods such as providing nutrients to ocean phytoplankton may also decrease the amount of atmospheric carbon.