Dr. Hansen has completed fairly complex statistical analysis of recent climate extremes using the period from 1951 to 1980 as a baseline. He showed in his paper that the recent past has lots more extreme weather than his base case. He used statistical analysis to argue that the data was so extreme that it could not be natural. He then concluded that man caused global warming was responsible.
I am reminded of a phrase attributed to Mark Twain:
There are three kinds of lies: lies, damned lies, and statistics.
Dr. Hansen stated he used the baseline time period because it was a calm period before the storm that is recent global warming.
Dr. Hansen’s analysis could prove to be an interesting argument if his baseline period is representative of climate history. If it is not, his entire mathematical exercise is pointless.
Here is the East Anglia University Global Air Temperature Graph for the last 150 years
The baseline period used by Dr. Hansen appears to be a calm in the middle of a two storms. The period from 1911 to 1943 has a slope that is almost as steep as the slope from 1980 to 2000 and the period is 50% longer. Nowhere in the 150 years of the chart is there less temperature variation than in the baseline period used by Dr. Hansen. Conclusion: The baseline is almost certainly flawed.
Now look at the change from year to year. Wild year to year changes are scattered all throughout the chart. And since about 2002 the chart shows remarkably little change.
The East Anglia University chart seems to argue that Dr. Hansen is guilty of big time data cherry picking.
There are two additional problems with his analysis.
- Worldwide temperature data is difficult to accurately measure. The best data is Satellite data and it has only been available since 1979. Good ocean data has only been around since about 1990 and Oceans cover 70% of the Earth’s surface. Even today there are only 9 temperature sites below 60 degree S latitude. He used detailed statistical analysis that relied on relatively small changes in temperature. He cannot be sure his data is accurate.
- He has not proven that the variation he calculated is not normal climate variation. He has shown a correlation between rising temperature and severe weather….from a calm and false baseline. It is probable that his baseline is flawed and/or the temperature changes he attributes to carbon dioxide might have some other cause, natural or man made.
Yes it is warmer today than it was 150 years ago, about a degree C warmer. Is that statistically significant? Probably not? Is it wise to extrapolate from the most recent 50 year period in a climate cycle that is 2.5 million years old? I think not.
Dr. Hansen needs to demonstrate that this 50 year period is extraordinary and a new trend. This is a particularly difficult task in a system with wild natural fluctuations. His very small baseline is probably insignificant mathematically.
Is the recent past statistically unusual? I think not. You make the call. We live in the Holocene, a 10,000 year period of unusually stable climate. Here is a chart of the last 4000 years using a Greenland Ice Core prepared last year.
Wild variation here, there, and everywhere. Carbon dioxide was fairly stable until about 200 years ago. 4000 years of wild variation, 200 years of presumed carbon dioxide influence, in an unusually stable climatic era. Hmmm.
And Dr. Hansen publicly stated just last week
We now know that the chances these extreme weather events would have happened naturally — without climate change — is negligible.
The quotation states something he cannot possibly know with any degree of certainty and it implies that climate change is not natural…something he has assumed without proof of any kind. This all sounds more like religion than science to me.