Eddie:
You say that my explanation of recovery from the Little Ice Age (LIA) was not sufficiently clear for you to understand it. This is strange because your subsequent discussion of seasons implies that you do understand what I was saying.
I explained that the climate varies in cycles (a fact known since the Bronze Age when it was pointed out by to Pharaoh by Joseph: the one with the Technicolour Dreamcoat). I explained that there are several cycles and I mentioned two of them.
I said these and other cycles must be overlaid on each other, and any AGW must be overlaid on them.
One of these cycles has a length of ~1,500 years and it has been in the warming portion of its cycle for about 300 years. Indeed, by way of illustration I pointed out;
“Around 1700, Londoners used to have “Ice Fairs” on the frozen Thames each year. The last Ice Fair was held in 1814, and the Thames has not frozen solid since.”
Clearly, this warming phase of the observed ~1,500 year cycle began long before possible GHG-induced AGW.
And I pointed out another cycle with length ~60 years. The 60 year cycle gave us cooling to 1910, cooling from 1940 to 1970, and – it seems – cooling from 1998.
All the above is empirical data: i.e. it is observed fact.
And the observed fact is that global warming stopped in 1940 but resumed in 1970. It is also an observed fact that it stopped in 1998 but we do not know if it will resume again.
We are nearing the end of the warm phase of the 1500-year-cycle, so the cooling phase of the 1500-year-cycle may have started when we reach the end of the present (cooling) phase of the 60-year-cycle. Therefore, it cannot be known if the warming from the LIA will resume (as it did in 1970) or if we are set to enter a cold phase like the LIA.
You talk of changes between decades. I fail to see why anybody would do that when considering the 1500-year-cycle. Such consideration would be a severe error. All one would compare is where one is along the phase of the cycle. Indeed, you point this out yourself when talking about the seasons (that are another climate cycle): comparing the first decade to the last decade of the twentieth century is like comparing February to May in a year.
One needs to observe the cycles and to compare like with like.
In the 1500-year-cycle, the present warm phase needs to be compared to the previous warm phase; i.e. the Medieval Warm Period when the Vikings farmed Greenland and an insect now constrained to the South of France inhabited York in the north of England.
And, in the 60-year-cycle, 1998 is like 1940 because they were years when the cycle peaked and, therefore, a cooling phase started.
I do not see how I can explain this more clearly.
In response to my correctly saying:
“…available data does not – repeat, not – support a claim that the rise in atmospheric CO2 concentration is “almost all due to human activities”.”
You reply,
“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.”
But I was talking about the “available data”. I was not discussing the “generally accepted view”.
A “generally accepted view” is not evidence that anything is correct (e.g., more people have a “view” that Santa Claus exists than there are people who accept the “view” that the rise in atmospheric CO2 concentration is “almost all due to human activities”.”). Such “views” are mere fashion, they are moderated by circumstances, and they can be very wrong (e.g., in 1930s Germany it was the “generally accepted view” that Hitler was a good guy, but it is not the “generally accepted view” in Germany today).
The isotope data are changing ratio in the direction expected from fossil fuel burning. So what? A change to the ratio must be in one direction or the other, and the ratio could be expected to alter when atmospheric CO2 concentration is changing. Importantly, the magnitude of the isotope ratio change does not fit with a claim that the isotope ratio change is caused by the human emissions of CO2.
Science is about numbers. When measurements provide numbers that do not fit a hypothesis then the hypothesis requires amendment or rejection.
You attempt to justify the “generally accepted view” by saying,
“And measurements of atmospheric CO2 over the past 50 years show a steady rise in CO2, which supports the ice core data.”
Again, so what? Nobody disputes that atmospheric CO2 has been rising in recent decades. At issue is the true cause of that rise. What some people choose to believe to be the cause does not alter the real cause (whatever that may be).
You quote a UN booklet that advocates reducing CO2 emissions.
OK, but I explained that such reductions would kill millions of people, mostly children. And I explained that it is not known what – if any – effect such reductions would have on atmospheric CO2 concentration. Indeed, I pointed out that the UN Intergovernmental Panel on Climate Change (IPCC) says this in Chapter 2 from Working Group 3 in the IPCC’s Third Assessment Report (2001) where it states, “no systematic analysis has published on the relationship between mitigation and baseline scenarios”.
In conclusion Eddie, I ask you to please keep up the debate because you, I and others may learn from rational argument of our different views.
Richard
