5.2 Deducing the culprits

Figure 14 is an interactive figure with a series of frames to illustrate the idea summed up in this title: What’s really warming the world? The interactive is credited to Eric Roston and Blacki Migliozzi, June 24, 2015. Each frame has some text and a graph. Frame 1 text reads: Skeptics of manmade climate change offer various natural causes to explain why the Earth has warmed 1.4 degrees Fahrenheit since 1880. But can these account for the planet's rising temperature? Scroll down to see show how much different factors, both natural and industrial, contribute to global warming, based on findings from NASA's Goddard Institute for Space Studies. Frame 1 is a line graph that shows temperature difference from the 1880 - 1910 Average in °F, on the y or vertical axis, ranging from -2 °F (labelled ‘Colder’) to - +2 °F (labelled ‘Hotter’). The x or horizontal axis shows time, from 1880 to 2014, and this axis intersects the y axis at 0 °F. The graph shows a line lies close to the horizontal, i.e. with values of 0 °F temperature change. From 1917, the line increases up to the final point, which must have a temperature difference of 1.4 °F in 2014. From 1930, the temperature differences are always greater than 0 °F The graph fluctuates with variation of up to about 0.7 °F from year to year. The graph is labelled ‘This line shows the measured, or “observed,” land-ocean temperature Frame 2 is titled: Is it the Earth’s Orbit? Frame 2 text reads: The Earth wobbles on its axis, and its tilt and orbit change over many thousands of years, pushing the climate into and out of ice ages. Yet the influence of orbital changes on the planet's temperature over 125 years has been negligible. Frame 2 text is the temperature difference graph from Frame 1, but has had data added to it as a separate line. This shows fluctuations in temperature, labelled ‘Orbital Changes’, i.e. the contribution to the temperature change due to Orbital Changes. This line remains close to temperature change = 0 °F, with very small fluctuations from year to year (less than ±1°F). The confidence band, labelled ‘This band shows where temperatures fall in 95% of climate observations, and shows a confidence of about ±0.5 °F – this is a typical confidence band for all subsequent frames. This graph sets the pattern for subsequent frames. Frame 3 is titled: Is it the Sun? Frame 3 text reads: The sun’s temperature varies over decades and centuries. These changes have had little effect on the Earth’s overall climate Figure 3 graph is the Frame 1 graph with temperature data added to it, labelled ‘Solar’. This line remains close to temperature change = 0 °F, with very small fluctuations from year to year (less than ±1°F) Frame 4 is titled: Is it Volcanoes? Frame 4 text reads: The data suggest no. Human industry emits about 100 times more CO₂ than volcanic activity, and eruptions release sulfate chemicals that can actually cool the atmosphere for a year or two. Frame 4 graph is the Frame 1 graph with temperature data added to it, labelled ‘Volcanic’. This line remains close to temperature change = 0 °F, with very small fluctuations from year to year (less than ±1°F). However, there are some notable dips, down to about – 0.7 °F, in years 1885, 1903, 1964, 1983 and 1992. Frame 5 is titled: Is it all three of these combined? Frame 5 text reads: If it were, then the response to natural factors should match the observed temperature. Adding the natural factors together just doesn’t add up. Frame 4 graph is the Frame 1 graph with temperature data added to it, labelled ‘Natural factors’ which is very similar to the Volcanic data on the previous frame, i.e. the line remains close to temperature change = 0 °F, with very small fluctuations from year to year (less than ±1°F). However, there are some notable dips, down to about – 0.7 °F, in years 1885, 1903, 1964, 1983 and 1992. Frame 6 is titled: So if it’s not Nature, Is it Deforestation? Frame 6 text reads: Humans have cut, ploughed, and paved more than half the Earth’s surface. Dark forests are yielding to lighter patches, which reflect more sunlight – and have a slight cooling effect. Frame 6 graph shows the frame 1 graph with temperature data added to it, labelled ‘Land Use’. This line remains close to temperature change = 0 °F, with very small fluctuations from year to year (less than ±1°F), until about 1940. From then until 2014, the temperature difference falls to about -0.2 °F. Frame 7 is titled: Or Ozone pollution? Frame 7 text reads: Natural ozone high in the atmosphere blocks harmful sunlight and cools things slightly. Closer to Earth, ozone is created by pollution and traps heat, making the climate a little bit hotter. What's the overall effect? Not much. Frame 7 graph shows the original graph with temperature data added to it, labelled ‘Ozone’. The line shows an increase in temperature differences, from about -0.1° F in 1880 to 0 °F between 1906 – 1930, increasing to positive values of about 0.2 °F by 2014. Frame 8 is titled: Or aerosol Pollution? Frame 8 text reads: Some pollutants cool the atmosphere, like sulfate aerosols from coal-burning. These aerosols offset some of the warming. (Unfortunately, they also cause acid rain). Frame 8 graph is the Frame 1 graph with temperature data added to it, labelled ‘Aerosols’. The line a steady value of about -0.1°F (with similar size fluctuations) from 1880 to about 1920, then a steady decline to about -0.8 °F by 2014. Frame 9 is titled: No, it Really is greenhouse Gases Frame 9 text reads: Atmospheric CO₂ levels are 40 per cent higher than they were in 1750. The green line shows the influence of greenhouse gas emissions. It’s no contest. Frame 9 graph is the Frame 1 graph with temperature data added to it, labelled ‘Greenhouse gases’. This line increases from 0 °F in 1880 to almost +2 °F in 2014. The rate of increase of the curve increases through this period too. Frame 10 is titled: See for yourself Frame 10 text reads: Greenhouse gases warm the atmosphere. Aerosols cool it a little bit. Ozone and land-use changes add and subtract a little. Altogether, they match the observed temperature, particularly since 1950. Frame 10 graph is the Frame 1 graph with temperature data added to it, labelled ‘Human Factors’. This matches the ‘Observed line closely’ though smoothing through the year to year variations. However, the ‘Human Factors line is mostly above the ‘Observed’ line up to about 1934, by up to about 0.3 °F. Frame 11 is titled: Compare and Contrast Frame 11 text reads: Putting the possible natural and human causes of climate change alongside one another makes the dominant role of greenhouse gases even more plainly visible. The only real question is: What are we going to do about it? This is the same graph as the previous frame, ‘See for yourself’.