In the 1990s, he proposed a theory to explain how
slight changes in solar activity could cause large changes in global temperature.
Not exact matches
Periods of volcanism can cool the climate (as with the 1991 Pinatubo eruption), methane emissions from increased biological
activity can warm the climate, and
slight changes in solar output and orbital variations can all have climate effects which are much shorter
in duration than the ice age cycles, ranging from less than a decade to a thousand years
in duration (the Younger Dryas).
The paper he wrote together with Friis - Christensen
in which he found a correlation between
solar activity and clouds had a «
slight» flaw: it ignored that the period of the study coincided with a big El Nino, and that large scale
changes in ocean surface temperature are going to have an effect on cloud formation.
The Little Ice Age following the Medieval Warm Period ended due to a
slight increase
in solar output (
changes in both thermohaline circulation and volcanic
activity also contributed), but that increase has since reversed, and global temperature and
solar activity are now going
in opposite directions.
During the late 20th Century the El Ninos has a greater effect on the jet positioning than they do now and the only variable to have
changed is the level of
solar activity which appears to have coincided with a
slight warming of the stratosphere (previously cooling) and an intensification of the inversion at the tropopause which then redirects more energy back downward
in the polar high pressure cells.