Non-greenhouse factors such as changes in solar output cannot alone explain the rise in global temperature over the past 50 years.

Judge as of July 2010 against the scientific assessment literature, chiefly IPCC AR4 (2007) and the major national academy reports. True: those assessments conclude that natural or non-greenhouse factors (solar output, volcanic activity, internal variability) cannot on their own account for the global warming of roughly the past 50 years. Mostly true: the assessments support this, with a minor difference in the period or factors named. Mostly false: the evidence was inconclusive or contested in the main assessments. False: authoritative assessments found that non-greenhouse factors could fully explain the warming.

Set before the research began.

1. E1 AR4 SYR Synthesis Report - 2.4 Attribution of climate change IPCC (Fourth Assessment Report, Synthesis Report)

   “very likely that it is not due to known natural causes alone. During this period, the sum of solar and volcanic forcings would likely have produced cooling, not warming.”

2. E2 TS.4.1 Advances in Attribution of Changes in Global-Scale Temperature in the Instrumental Period: Atmosphere, Ocean and Ice IPCC (Fourth Assessment Report, Working Group I, Technical Summary)

   “Attribution studies show that it is very likely that these natural forcing factors alone cannot account for the observed warming (see Figure TS.23).”

3. E3 9.7 Combining Evidence of Anthropogenic Climate Change IPCC (Fourth Assessment Report, Working Group I, Chapter 9) · 1 January 2007

   “This warming took place at a time when non-anthropogenic external factors would likely have produced cooling. The combined effect of known sources of forcing would have been extremely likely to produce a warming.”

4. E4 Global Warming - NASA Science NASA Earth Observatory · 3 June 2010

   “Changes in the brightness of the Sun can influence the climate from decade to decade, but an increase in solar output falls short as an explanation for recent warming.”

The IPCC AR4 Synthesis Report states the observed warming is very likely not due to known natural causes alone, and that over this period combined solar and volcanic forcings would likely have produced cooling (E1). The AR4 Working Group I Technical Summary and Chapter 9 say natural forcing factors alone very likely cannot account for the observed warming, and that non-anthropogenic factors would likely have produced cooling (E2, E3). NASA's June 2010 material says increased solar output falls short as an explanation for recent warming (E4). As of July 2010 these assessments support the proposition.