Our world is also full of chemical changes that take place every day. A phase change is a change in state or form in which no new substance forms. This is a special kind of physical change called a phase change. If you dissolve sugar in a glass of water, you can evaporate the water to get back to the solid sugar. For example, when liquid water freezes and forms ice, you still have water. Physical changes can almost always be reversed. These changes can be classified as either physical changes or chemical changes. Open Professional Learning × Close Professional LearningĮvery day, matter undergoes changes. But how quickly seas will rise and how dangerous the weather might get still depends on which path the world opts to take.Open Educational Resources × Close Educational Resources Sea levels will continue rising for hundreds or thousands of years, and the Arctic will be practically free of sea ice in at least one summer in the next 30 years. In every scenario, warming will continue for at least a few decades. But it does show how choices today will affect the future. The climate report cannot tell us which scenario is most likely - that will be decided by factors including government policies. By 2100, the average global temperature is a scorching 4.4C higher. The global economy grows quickly, but this growth is fuelled by exploiting fossil fuels and energy-intensive lifestyles. Current CO 2 emissions levels roughly double by 2050. Scenario 5 – Avoid at all costs: 4.4C by 2100 By the end of the century, average temperatures have risen by 3.6C. Countries become more competitive with one another, shifting toward national security and ensuring their own food supplies. On this path, emissions and temperatures rise steadily and CO 2 emissions roughly double from current levels by 2100. In this scenario, temperatures rise 2.7C by the end of the century. Progress toward sustainability is slow, with development and income growing unevenly. Socioeconomic factors follow their historic trends, with no notable shifts. CO 2 emissions hover around current levels before starting to fall mid-century, but do not reach net-zero by 2100. Scenario 3 – Middle of the road: 2.7C by 2100 But temperatures stabilize around 1.8C higher by the end of the century. It imagines the same socioeconomic shifts towards sustainability as SSP1-1.9. In the next-best scenario, global CO 2 emissions are cut severely, but not as fast, reaching net-zero after 2050. This first scenario is the only one that meets the Paris Agreement’s goal of keeping global warming to around 1.5 degrees Celsius above preindustrial temperatures, with warming hitting 1.5C but then dipping back down and stabilizing around 1.4C by the end of the century. Extreme weather is more common, but the world has dodged the worst impacts of climate change. Investments in education and health go up. Societies switch to more sustainable practices, with focus shifting from economic growth to overall well-being. The IPCC’s most optimistic scenario, this describes a world where global CO 2 emissions are cut to net zero around 2050. Scenario 1 – Most optimistic: 1.5C by 2050 Each scenario is labelled to identify both the emissions level and the so-called Shared Socioeconomic Pathway, or SSP, used in those calculations. Emissions increase when land is converted from forest to agricultural land. Education can affect the rate of technology developments. For example, a rise in population is assumed to lead to higher demand for fossil fuels and water. But the calculations are also meant to capture socioeconomic changes in areas such as population, urban density, education, land use and wealth. The scenarios are the result of complex calculations that depend on how quickly humans curb greenhouse gas emissions. climate panel report released on August 9 th, 2021, about the physical science of climate change uses five possible scenarios for the future.
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