Hints of another gremlin in the greenhouse: anthropogenic sulfur

Abstract

Already there are many complicating factors (‘gremlins’) that frustrate attempts to link observed climate changes to predictions from the greenhouse hypothesis. Consequences of these ‘gremlins in the greenhouse’ (along with their possible identities) include hemispherically asymmetric cooling of the lower stratosphere (perhaps caused by asymmetric ozone destruction by chlorofluorocarbons), cooling of the tropical upper troposphere (perhaps caused by an increase in water vapor), lack of polar amplification of lower tropospheric warming (poorly modeled clouds, ocean currents, ice and snow et al.), and asymmetric warming of the lower tropospheres of the two hemispheres (differences in thermal inertias, responses to volcanic eruptions et al.). In this report, emphasis is on examining hints that the cause of the relative cooling of the Northern Hemisphere has been anthropogenic sulfur emission; it is concluded that this concept is not inconsistent with the data; however, the possibility that all observed temperature changes are natural is also not inconsistent with the data. Research needed to remove these ambiguities includes more extensive monitoring, improvements to climate models, advances in statistical analyses of time series, better definition of climatic consequences of volcanic eruptions, and focused efforts to understand and describe the major climate changes that occurred in the Northern Hemisphere c. 1940 and 1815.