She could have added that changesin solar output have no impact on ocean acidification, the other major impact of rising carbon dioxide concentrations.
In fact these problems are similar in kind and no more intractable than those which arise in measuring inter-temporal changesin real output and expenditure.
The recent downturn in the zone's output suggests that the region is vulnerable to sudden changesin fortunes just as it was 90 years ago, when competition from South-East Asian plantations wiped out its rubber-tapping industry.