Jock Allison responds to a suggestion that he has erred in his interpretation of Arctic sea ice melt statistics.
Dr Tulloch of GNS Science has suggested I have made a classic error because I had considered (letter to Otago Daily Times 19.09.09) only a small part of the relevant information with regard to the Arctic sea ice melting.
Indeed I did know about his graph showing all the data for Arctic sea ice since 1979.
Despite the fact that Dr Tulloch states that the long-term rate of decline is 11% per decade, the data in the graph show variation but no decline from 1979 to about 1997.
From that time to 2007 there was a decline of 40% from about 6.9 million sq km to 4.1 million sq km at the summer minimum.
This is a big decline, but there was some recovery to 5.1 million sq km in 2009.
These are big changes over a very short time period.
However, the time elapsed from 1979, or from 1997 when the recorded decline of the Arctic sea ice started, is a microcosm in geological time as I am sure Dr Tulloch will agree, not sufficient time on which to predict that rapid increases in Arctic sea ice melts will continue, and/or that they have much to do with climate change.
I remind readers that in the early 1970s, the worry was that we were about to enter another ice age.
But I digress.
Dr Tulloch correctly notes that ice will reflect about 80% of the sun's heat back into the atmosphere, whereas dark ocean absorbs about 90% of the heat.
Some perspective is important.
While the summer minimum for Arctic sea ice has diminished markedly since 1997, the maximum area in winter only diminished slightly.
The sea area of the world is 361 million sq km.
Arctic sea ice peaks at 13 to 14 million sq km, and in summer diminishes to 4 to 7 million sq km.
This diminution, to a minimum of 2 to 3 million sq km less than the level from 1979 to 1997, might be assumed to be a diminution of 1 to 1.5 million sq km year round.
This equates to 0.28%-0.42% of ice from the total ocean area, not particularly alarming I suggest, from a potential global warming point of view.
The Antarctic sea ice reached record maximum levels in 2009 since recording started in 1979, almost 2 million sq km greater than the 1979 to 2000 average.
Further, the South Pole winter is now about 0.6degC cooler than in 1957.
In fact, if we consider the total areas at both poles as of now, the increase in the Antarctic ice almost makes up for the loss in the Arctic.
The sun shines on both expanses of ice.
Not particularly alarming from a global warming point of view.
I agree that my statement that the world has been cooling since 2002 is a significant statement that deserves more than a one liner.
At a World Climate Conference in Geneva last month, Prof Mojib Latif, the recipient of several international climate-study prizes and lead author for the IPCC, conceded that the world had not warmed for nearly a decade.
He noted that we may be in for another decade (or two) of cooling, but then warming would resume.
These are bold predictions indeed, and do not fit the IPCC models of global warming.
Back to the drawing board.
In the event of more years of cooling, when might governments suggest that some moves to reduce emissions because of the threat of catastrophic global warming might be premature? The evidence that CO2 has anything to do with global warming is not there, but that's a subject for another discussion.
Perhaps some of the climate scientists could present the evidence in a user-friendly way in this newspaper.
- Dr Jock Allison is a Dunedin-based agricultural scientist and consultant.
