Sorry Jeb Bush, It’s Not ‘Arrogant’ To Say Climate Change Is Real. It’s True.

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Jeb Bush claimed that the science is unclear as to how much humans contribute to global warming. The United Nations climate change research organization, however, has deemed it “extremely likely” that more than half of the observed temperature increase since 1950 is due to human activities.

At an event in New Hampshire, The fifth assessment report goes into more detail on specific amounts of warming. Over that 1951 to 2010 period, there was a total rise in temperature of 0.6 degrees Celsius, or about one degree Fahrenheit. Human-caused emissions of greenhouse gases such as carbon dioxide “likely” (66 percent to 100 percent probability) caused between 0.5 and 1.3 degrees C of warming in total. Other human activities such as the release of aerosols have had more of a cooling effect, because they scatter and block sunlight as it reaches the atmosphere; this effect totaled between -0.6 and 0.1 degrees C.

Natural influences, including things like changes in the sun’s output and volcanic eruptions, have had little effect — between -0.1 and 0.1 degrees C. Internal variability, which refers to natural fluctuations in temperature, also only accounted for a change between -0.1 and 0.1 degrees C.

Here’s a visual version of these numbers, from the IPCC’s report.

warming contributions

The top bar represents the observed warming since 1951 — how much hotter it has actually become, according to the planet’s numerous weather stations. Below that in green is the warming due to greenhouse gas emissions; the yellow bar represents other anthropogenic — human-caused — activities like aerosol emissions, and the orange bar combines those two human sources. At the bottom are the relatively small contributions from natural sources like the sun and volcanos, and internal variability.

To be clear, all —> Read More