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Climate Change Evidence and Causes (2014) / Chapter Skim
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Pages 23-30

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 23...
... If all heat energy emitted from the surface passed through the atmosphere directly into space, Earth's average surface temperature would be tens of degrees colder than today. Greenhouse gases in the atmosphere, including water vapour, carbon dioxide, methane, and nitrous oxide, act to make the surface much warmer than this, because they absorb and emit heat energy in all directions (including downwards)
From page 24...
... Human activities have added greenhouse gases to the atmosphere The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased significantly since the Industrial Revolution began. In the case of carbon dioxide, the average concentration measured at the Mauna Loa Observatory in Hawaii has risen from 316 parts per million (ppm)
From page 25...
... Ice core records extending back 800,000 years show that during that time, CO2 concentrations remained within the range of 170 to 300 ppm throughout many ‘ice age' cycles  --  see page B4 to learn about the ice ages  --  and no concentration above 300 ppm is seen in ice core records until the past 200 years. 400 Figur e B3.
From page 26...
... Climate records show a warming trend Estimating global average surface air temperature increase requires careful analysis of millions of measurements from around the world, including from land stations, ships, and satellites. Despite the many complications of synthesising such data, multiple independent teams have concluded separately and unanimously that global average surface air temperature has risen by about 0.8 °C (1.4 °F)
From page 27...
... The temperature changes are relative to the global average surface temperature, averaged from 1961−1990. Source: IPCC AR5, data from the HadCRUT4 dataset (black)
From page 28...
... Thus, water vapour is treated as an amplifier, and not a driver, of climate change. Higher temperatures in the polar regions melt sea ice and reduce seasonal snow cover, exposing a darker ocean and land surface that can absorb more heat, causing further warming.
From page 29...
... particles in the stratosphere that reflect or absorb sunlight, leading to a short-term surface cooling lasting typically about two to three years. Over hundreds of thousands of years, slow, recurring variations in Earth's orbit around the Sun, which alter the distribution of solar energy received by Earth, have been enough to trigger the ice age cycles of the past 800,000 years.
From page 30...
... that humankind emits. Models project the temperature increase for a business-as-usual emissions Global average surface temperature change 6.0 scenario (in red)


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