I have deleted what I wrote in 2009 because I am no longer happy that it is valid. I relied far too much on the objectivity of the 2007 IPCC report. I am no longer content to rely on this until I can carry out credibility checks on its stance.
We are given to understand that anthropogenic carbon-dioxide emissions will lead to increases in global temperatures, with potentially catastrophic consequences. But is this true? This claim consists of several parts,
1) That global average temperatures are observed to be increasing;
2) That CO2 levels in the atmosphere are increasing, and will be double the pre-industrial level by about 2060 to 2080 if current trends continue;
3) That increases in atmospheric CO2 are anthropogenic;
4) That increasing CO2 leads to increases in global average temperature, specifically that doubling from the pre-industrial 278 ppm to 556 ppm will cause the global average temperature to increase by 3.2 deg.C (plus or minus 1 deg.C);
5) That the resulting increase in global average temperature (for CO2 levels increased to 556 ppm) will lead to severe effects on the climate which will be seriously adverse for human life.
I have now independently examined the credibility of claims (1), (2) (3) and (4).
In September 2019 I have conducted a brief review of measured global average temperature data (see here) and concluded that claim (1) is borne out.
Claims (2) and (3) are addressed by a simple model of my own here. The result is that claims (2) and (3) are borne out.
In 2016 I produced my own simple model addressing Claim (4). I have taken down this model for corrections. It will return shortly.
However, in September 2019 I have addressed Claim (4) by carrying out a review of the physical basis of the IPCC climate models. The claim that CO2 can directly account for the observed global average temperature increase is weak. Agreement with measured temperature increases is crucially dependent upon assumed feedbacks which appear to have poor physical basis. Moreover the claimed agreement is achieved by tuning parameters. Read my detailed critique here.
Note that, despite the positive feedbacks in the IPCC models, these models are stable, as I demonstrate here.
That leaves Claim (5), the crucial bit - the implications of CO2 increases and temperature rise. This has defeated my attempts at a simple independent check, and will probably continue to do so. The claim that (say) a 2 deg.C increase in global average temperature would be severely adverse for human kind is entirely dependent upon climate models which are extremely complex, unverifiable and highly uncertain. How much faith should one have in them? It is not even clear to me that, as regards the planet as a whole, a temperature increase of this magnitude might not be beneficial. (Inevitably, though, some regions would be adversely impacted). In particular, increased CO2 concentrations will improve the growth rate of most vegetation, with significant implications for feeding the world population.
My critique of global average temperature increase data here
My critique of IPCC climate change models here. The science is NOT settled!
My demonstration that the IPCC climate models are stable here.
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So, no energy being wasted here, then.