In IPCC’s Fifth Assessment Report (AR5) of last year, they stated the following:
“It is extremely likely [95 percent confidence] more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together.”
‘More than half.’ That sounds like a pretty conservative guess. Well, they end up going further than that. Much further.
What caused global warming over the last 60 years or so, according to the IPCC? Apparently, human ‘greenhouse gas’ emissions alone (100%):
“The best estimate of the human-induced contribution to warming is similar to the observed warming over this period … The observed warming since 1951 can be attributed to the different natural and anthropogenic drivers and their contributions can now be quantified. Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5°C to 1.3 °C over the period 1951−2010, with the contributions from other anthropogenic forcings, including the cooling effect of aerosols, likely to be in the range of −0.6°C to 0.1°C.”
That should be a net range of anthropogenic ‘contributions’ to the general global temperature rise between 1951 and 2010 of 0.6 to 0.7°C.
So, then, what did not contribute at all (0%) to that same general warming, according to the IPCC? Apparently, natural external factors like solar activity, and natural internal factors like ocean cycles:
“The contribution from natural forcings is likely to be in the range of −0.1°C to 0.1°C, and from internal variability is likely to be in the range of −0.1°C to 0.1°C.”
That should make up a total natural contribution to the general global temperature rise between 1951 and 2010 of exactly 0°C. Continue reading