Has temperature as a function of luminosity and greenhouse gas Stack Exchange Network Stack Exchange network consists of 176 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Well, just because tau=1.87 is a GHG-invariant constant. on February 27, 2011 at … Concentrations of these greenhouse gases are measured in parts per million (ppm), parts per billion (ppb), or parts per trillion (ppt) by volume. However, water vapor does not control the Earth’s temperature, but is instead controlled by the temperature. I was asked in an email, why I brought this here, into the Water vapor vs CO2 greenhouse gas topic. Greenhouse gases warm the planet. In other words, a concentration of 1 ppb for a given gas means there is one molecule of that gas in every 1 billion molecules of air. absorption. https://www.ncdc.noaa.gov/global-warming/temperature-change Scientists know with virtual certainty that increasing greenhouse gas concentrations tend to warm the planet. This graph in essence gives the amount of greenhouse gas needed to sustain a surface temperature of 280K, given any specified amount of solar. Using models previously employed by IPCC, the implied global‐mean temperature and sea level changes are calculated out to 2500. Figure 4.35: OLR vs. CO2 and CH4 concentration for each gas individually mixed with Earth air on the dry adiabat. In computer-based models, rising concentrations of greenhouse gases produce an increase in the average surface temperature of the earth over time. While uncertainties are large, the results show that even with concerted efforts to stabilize concentrations of greenhouse gases, substantial temperature and sea level increases can be expected to occur over the next century. The surface temperature is fixed at 280K. On average, it probably accounts for about 60% of the warming effect. It’s true that water vapor is the largest contributor to the Earth’s greenhouse effect.