Enlightenment Now: The Case for Reason, Science, Humanism, and Progress

Whenever we burn wood, coal, oil, or gas, the carbon in the fuel is oxidized to form carbon dioxide (CO2), which wafts into the atmosphere. Though some of the CO2 dissolves in the ocean, chemically combines with rocks, or is taken up by photosynthesizing plants, these natural sinks cannot keep up with the 38 billion tons we dump into the atmosphere each year. As gigatons of carbon laid down during the Carboniferous Period have gone up in smoke, the concentration of CO2 in the atmosphere has risen from about 270 parts per million before the Industrial Revolution to more than 400 parts today. Since CO2, like the glass in a greenhouse, traps heat radiating from the Earth’s surface, the global average temperature has risen as well, by about .8° Celsius (1.4° Fahrenheit), and 2016 was the hottest year on record, with 2015 coming in second and 2014 coming in third. The atmosphere has also been warmed by the clearing of carbon-eating forests and by the release of methane (an even more potent greenhouse gas) from leaky gas wells, melting permafrost, and the orifices at both ends of cattle. It could become warmer still in a runaway feedback loop if white, heat-reflecting snow and ice are replaced by dark, heat-absorbing land and water, if the melting of permafrost accelerates, and if more water vapor (yet another greenhouse gas) is sent into the air.

If the emission of greenhouse gases continues, the Earth’s average temperature will rise to at least 1.5°C (2.7°F) above the preindustrial level by the end of the 21st century, and perhaps to 4°C (7.2°F) above that level or more. That will cause more frequent and more severe heat waves, more floods in wet regions, more droughts in dry regions, heavier storms, more severe hurricanes, lower crop yields in warm regions, the extinction of more species, the loss of coral reefs (because the oceans will be both warmer and more acidic), and an average rise in sea level of between 0.7 and 1.2 meters (2 and 4 feet) from both the melting of land ice and the expansion of seawater. (Sea level has already risen almost eight inches since 1870, and the rate of the rise appears to be accelerating.) Low-lying areas would be flooded, island nations would disappear beneath the waves, large stretches of farmland would no longer be arable, and millions of people would be displaced. The effects could get still worse in the 22nd century and beyond, and in theory could trigger upheavals such as a diversion of the Gulf Stream (which would turn Europe into Siberia) or a collapse of Antarctic ice sheets. A rise of 2°C is considered the most that the world could reasonably adapt to, and a rise of 4°C, in the words of a 2012 World Bank report, “simply must not be allowed to occur.”⁴²

To keep the rise to 2°C or less, the world would, at a minimum, have to reduce its greenhouse gas emissions by half or more by the middle of the 21st century and eliminate them altogether before the turn of the 22nd.⁴³ The challenge is daunting. Fossil fuels provide 86 percent of the world’s energy, powering almost every car, truck, train, plane, ship, tractor, furnace, and factory on the planet, together with most of its electricity plants.⁴⁴ Humanity has never faced a problem like it.

One response to the prospect of climate change is to deny that it is occurring or that human activity is the cause. It’s completely appropriate, of course, to challenge the hypothesis of anthropogenic climate change on scientific grounds, particularly given the extreme measures it calls for if it is true. The great virtue of science is that a true hypothesis will, in the long run, withstand attempts to falsify it. Anthropogenic climate change is the most vigorously challenged scientific hypothesis in history. By now, all the major challenges—such as that global temperatures have stopped rising, that they only seem to be rising because they were measured in urban heat islands, or that they really are rising but only because the sun is getting hotter—have been refuted, and even many skeptics have been convinced.⁴⁵ A recent survey found that exactly four out of 69,406 authors of peer-reviewed articles in the scientific literature rejected the hypothesis of anthropogenic global warming, and that “the peer-reviewed literature contains no convincing evidence against [the hypothesis].”⁴⁶