Solar Irradiance since 1874 Revisited

We reconstruct the solar irradiance since 1874 employing an evolved version of previously published models and improved sunspot and facular data. A good correlation between reconstructed irradiance and Earth’s global air temperature on time scales longer than the solar cycle is obtained and, in contrast to many earlier models, solar irradiance does not on average lag behind global temperature prior to 1975, although the exact time lag between the two quantities depends somewhat on details of the reconstruction. Since that epoch, however, air temperatures have increased by 0.2 K, whereas solar irradiance has risen a disproportionately smaller amount. Therefore, unless the influence of solar variability on Earth is very strongly non-linear, at least this most recent temperature increase reflects the influence of man-made greenhouse gases or non-solar sources of natural variability.