Richard: “You ignore my explanation of why consideration of the period since 1998 is very proper.”
Best as I can make out, this is your explanation for the above: “It is simply a fact that 1998 was the year when the warming stopped”. The terms “warming” and “cooling” are relative terms and imply processes: warming or cooling in relation to what?
By way of analogy, we can experience a warm early spring period and a cool late spring period. In the absence of any knowledge of the seasons, all we can say is that one period is warmer or cooler than the other. However, since we have seasonal knowledge, we can say that one period is unseasonably warm or cool, and that the trend is upwards.
But when it comes to decadal periods, we have no such baseline, so must create one, typically the average of a 30-year historical period, such as 1951-1980 or 1961-1990. We can then relate periods such as 1998 to the present by reference to the baseline. Otherwise, all you can claim is that ‘1998 was warmer on average than 2008’, but that is not the same claim as ‘global warming stopped in 1998’.
“I explained that the “long term trend” is recovery from the Little Ice Age (LIA).”
This claim assumes some sort of ‘natural’ baseline around which the global temperature fluctuates. There is no evidence for this.
“…available data does not – repeat, not – support a claim that the rise in atmospheric CO2 concentration is “almost all due to human activities”.”
The generally accepted view that the recent rise in CO2 is mostly due to human activities is supported by comparing the proportion of the isotopes of carbon in the atmosphere between earlier and later periods. The proportion of human-produced carbon isotopes – ie produced by burning fossil fuels – has increased over the past 150-200 years and is still increasing.
And measurements of atmospheric CO2 over the past 50 years show a steady rise in CO2, which supports the ice core data.
As for mitigation, a United Nations Environment Programme booklet from 1991 has this to say: “Fortunately, opportunities abound for reducing net emissions. They all involve either reducing human-induced emissions or capturing carbon dioxide from the atmosphere and sequestering it. They include investments in low-emissions technologies, institutional and regulatory changes that discourage emissions, and a wide range of technical practices and social changes”.
But we can agree on one thing: surveys and opinion polls say nothing either for or against the science of global warming.
