- solar activity [after previously claiming such small changes in solar activity could not affect climate],
- stratospheric water vapour, "which warms the surface, has been relatively low since 2000" [climate models instead predicted an increase]
- and the El Niño–Southern Oscillation (ENSO) cycle, based on a paper from which Dr. Judith Curry concluded, "no matter what, I am coming up with natural internal variability associated accounting for significantly MORE than half of the observed warming," which is contrary to the central premise of the IPCC.
"A mix of explanations has been offered for the recent hiatus: the minimum in solar energy output in the latest 11-year sunspot cycle lasted longer than usual [after previously claiming such changes could not affect climate]; stratospheric water vapour, which warms the surface, has been relatively low since 2000 [models predicted an increase]; and the El Niño–Southern Oscillation (ENSO) cycle of warm El Niño and cold La Niña phases in the equatorial Pacific, which is known to affect global mean temperature and not just the temperature of the equatorial Pacific, has favoured the La Niña phase since the major El Niño event of 1997–98. Empirical models that fit the observed hiatus have generally relied on La Niña-related cooling to offset a large fraction of the greenhouse- induced warming. Consistently, analyses of the heat being taken up by the oceans have pointed to an increase in this heat uptake, predominantly in the Pacific, as underlying the hiatus."