A 37-Year Record of Hemispheric Cloud Albedo Derived from SBUV, TOMS, and OMPS instruments Shows No Global Response in Cloudiness during El Niño Events

Quantifying global cloudiness is critical to understanding the Earth’s radiation budget and validating climate model feedbacks. We produce a long-term (1980-2016) inter-calibrated record of Hemispheric Cloud Albedo (HCA) from the suite of NOAA and NASA UV (331-380nm) sensing satellite instruments. Our derived HCA assumes a C-1 water cloud at varying cloud optical depths, a Cox-Munk surface BRDF over ocean and a lambertian surface over land.

Over the course of the 37-year record five El Nino events occur and global mean surface temperatures warm about +0.5 C. So each successive El Nino event occurs under warmer background conditions.

During the five El Nino events (1982, 1986, 1998, 2010, 2016) there was a marked positive response in HCA over the pool of warmer ocean water in the Eastern Tropical Pacific (180^oW – 100^oW, 15^o S- 15^oN) and the timing is in agreement with the Multi-variate ENSO index. However, there was an equally compensating negative HCA response in the Western Tropical Pacific. The result is that a time-series of HCA over larger areas (30^o S- 30^oN) shows no HCA response during El Nino conditions; instead, the only anomalies are from the Pinatubo and El Chichon volcanic eruptions.

There is also no detectable trend in globally averaged HCA over the 37-year record despite the warming surface temperatures. The lack of an El Nino response and the lack of an HCA trend, suggest that global cloudiness has not changed appreciably as the climate has warmed. Finally, we compare our HCA observed trends with historical CMIP5 model runs.