[0:00]Geography, climate change. Many people confuse the two terms, global warming and climate change. Well, climate change is any significant change in the earth's climate over a long period. Whereas, global warming describes the sharp rise in global temperatures over the last century. Here is some climate change history. The quaternary period. This is the most recent geological time period spanning from about 2.6 million years ago to now. In the period before, Earth was much warmer and stable, before it entered a cold glacial period lasting 100,000 years. But you may be wondering, how could they possibly know something that happened 2.6 million year ago? Evidence for climate change comes from many sources, and you need to know them for GCSE geography. One, ice and sediment cores. Ice sheets are made up of layers of ice. One layer is formed each year. Scientists drill into ice sheets to get long cores of ice. By analyzing the gases trapped in the layers of ice, they can tell what the temperature was each and every year. Two, tree rings. As a tree grows, it forms a new ring each year. The tree rings are thicker in warm, wet conditions. Scientists take these cores and count the rings to find the age of the tree. The thickness of the ring will tell the scientists what the climate was like. Tree rings are a reliable source of evidence for the past 100,000 years. Three, pollen analysis. Pollen from plants gets preserved in sediment. Scientists can identify and date preserved pollen to show which species were living at that time. Scientists know the conditions that plants live in now, so preserved pollen from similar plants allow them to compare the climate. Four, temperature records. Since the 1850s, global temperatures have been measured accurately using thermometers. This gives us a reliable, but short-term record of temperature change. Historical records like harvest dates or newspaper weather reports can extend the record of climate change even further back. Now let's look at the causes of climate change. Natural causes. One, orbital change. Orbital change can affect how much solar radiation the Earth receives - the more energy, the warmer. This is based on the Earth's tilt and its orbital shape, whether it's circular or oval. Two, volcanic activity. Major volcanic eruptions eject large quantities of material into the atmosphere. Some of these particles reflect the sun's rays back out to space, so the Earth's surface is left cooler. And three, solar output. The sun's energy output is not constant, and changes due to short cycles for about 11 years. Now let's look at human causes of climate change. One, burning fossil fuels. Carbon dioxide is released into the atmosphere when fossil fuels like coal, oil, natural gas, and petrol are burnt. Farming, livestock produce a lot of methane, rice paddies also contribute to global warming. Deforestation. Plants remove carbon dioxide from the atmosphere, so when they are cut down, they stop taking in carbon dioxide. And cement production. This is made from limestone which releases carbon dioxide into the atmosphere. How to manage climate change? There are mitigation and adaptation strategies. So mitigation includes carbon capture, which is designed to reduce emissions from power stations, or planting trees, which increases the amount of carbon dioxide absorbed. Adaptation includes changing agricultural systems, since rainfall patterns and higher temperatures will affect crops, they could use biotechnology to sustain optimum conditions. Or manage water supplies. Dry areas are predicted to get drier, leading to more water shortages, so rain water and waste water can be recycled.
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