What is warming the Earth?

by Javier, August 29, 2018 in WUWT

A no-assumptions look at the global warming evidence helps clarify the possibilities.

The planet’s surface has been warming since the depths of the Little Ice Age, and particularly since ~ 1850 AD. The surface temperature record, however incomplete or uncertain, reflects this warming. Hypotheses about why the warming is taking place can be grouped into three general categories:

  1. The energy input is increasing. This is the basis of the variable solar output hypothesis.
  2. The energy output is decreasing. This is the basis of the greenhouse gases hypothesis.
  3. The transfer of heat within the system is changing. This is the basis of some hypotheses for a reduced vertical exchange in the ocean, or for changes in the oceanic currents that redistribute the heat.

A combination of these categories cannot be ruled out.

Whatever causes the temperature change must necessarily affect its rate of change, the velocity at which temperature changes over time, measured in °C/decade. A velocity that varies continuously and can be positive (warming) or negative (cooling).


Figure 1. 9-year global surface temperature rate of change (4-year averaged) in °C/decade. The Pause is indicated by the khaki box. Source: Met Office UK, HadCRUT 4.