To determine whether declining pollutants deserve credit for the recovery, the researchers used a 3D
atmospheric model to separate the
effects of the chemicals from those
of weather, which can affect ozone loss through winds and temperature, and
volcanic eruptions, which deplete ozone by pumping sulfate particles into the upper atmosphere.
Thus we employ here an established technique to estimate the impact
of ENSO on global mean temperature, and to incorporate the
effects of dynamically induced
atmospheric variability and major explosive
volcanic eruptions.
The most likely candidate for that climatic variable force that comes to mind is solar variability (because I can think
of no other force that can change or reverse in a different trend often enough, and quick enough to account for the historical climatic record) and the primary and secondary
effects associated with this solar variability which I feel are a significant player in glacial / inter-glacial cycles, counter climatic trends when taken into consideration with these factors which are, land / ocean arrangements, mean land elevation, mean magnetic field strength
of the earth (magnetic excursions), the mean state
of the climate (average global temperature), the initial state
of the earth's climate (how close to interglacial - glacial threshold condition it is) the state
of random terrestrial (violent
volcanic eruption, or a random
atmospheric circulation / oceanic pattern that feeds upon itself possibly) / extra terrestrial events (super-nova in vicinity
of earth or a random impact) along with Milankovitch Cycles.