“While we’ve talked about how the overall amount of that radiation has to balance the warming sunlight, the radiation is actually spread over a spectrum of different wavelengths. Think of those like “colors,” although not visible to our eyes. Water vapor, the most significant greenhouse gas, intercepts only some colors, but because it blocks almost 100 percent of those it does, adding more water vapor to the atmosphere won’t make the insulation much thicker—it would be like putting another layer of black paint on an already black window. But that’s not true for carbon dioxide. That molecule intercepts some colors that water vapor misses, meaning a few molecules of CO2 can have a much bigger effect (like the first layer of black paint on a clear window). So the greater potency of a CO2 molecule depends upon relatively obscure aspects of how it, and water vapor, intercept heat radiation—another example of why the details are important when attempting to understand human influences on the climate.”