Abstract: The rise in global average temperature over the last century has halted since roughly the year 2000, despite the fact that the release of CO2 into the atmosphere is still increasing. It is suggested here that this interruption has been caused by the suspension of the near linear (+ 0.5 °C/100 years or 0.05 °C/10 years) temperature increase over the last two centuries, due to recovery from the Little Ice Age, by a superposed multi-decadal oscillation of a 0.2 °C amplitude and a 50~60 year period, which reached its positive peak in about the year 2000—a halting similar to those that occurred around 1880 and 1940. Because both the near linear change and the multi-decadal oscillation are likely to be natural changes (the recovery from the Little Ice Age (LIA) and an oscillation related to the Pacific Decadal Oscillation (PDO), respectively), they must be carefully subtracted from temperature data before estimating the effects of CO2.
Abstract: Climate has changed over the Earth’s past, is changing continuously and will do so in the future due to external and internal drivers. Some external drivers, such as the astronomic constellation of the Earth-sun system and continental shifts, have led to slow changes over long time scales. While others, for instance volcanic eruptions, may lead to fast, quasi-abrupt changes with impacts on climate over a limited time. Internal drivers like albedo, or the greenhouse effect are parts and processes of the climate system itself that may again change the climate at comparatively shorter time scales than most external drivers. [...]