QUESTION 1
Is it the case that CO2 increased by 5% since 1998 whilst global temperature cooled over the same period (see Fig. 1)?
If so, why did the temperature not increase; and how can human emissions be to blame for dangerous levels of warming?
The government's response to this question queried whether global average temperature is an appropriate indicator of global climate, and listed circumstantial evidence for regional planetary warming.
1. What is the most appropriate measure of planetary climate?
1.1. The government’s reply says “When climate change scientists talk about global warming they mean warming of the climate system as a whole, which includes the atmosphere, the oceans, and the cryosphere”, and then adds “in terms of a single indicator of global warming, change in ocean heat content is most appropriate”.
1.2. We agree that in an ideal academic discussion, and were accurate historical data available, ocean heat content might be a better criterion by which to judge global warming than would be atmospheric temperature. Use of this indicator was first pressed strongly by Pielke (2007, 2009) as a test of the dangerous warming hypothesis, but it has not been widely publicized by the IPCC.
1.3. In any case, however, Senator Fielding’s question was predicated upon the history of IPCC’s public advice, which has consistently used the UK Hadley Centre near-surface air temperature record since 1850 as a measure of global warming. This near-surface air temperature record is the one that dominates in IPCC and government policy papers and discussion, and is the criterion of judgement that both politicians and the public are familiar with.
1. 4. As illustrated in Fielding (June 15, Fig. 1), the Hadley temperature record does not exhibit warming after 1998.