Heaven, Earth and science fiction

It has long been known, through study of ice cores, that there is a strong correlation between atmospheric CO2 and temperature in the last 600,000 years. In more recent times technology has been developed enabling accurate measurement of both atmospheric CO2 and temperature. These measurements show a close correlation between them.

IPCC records and their sources are very clear. What they show is that in the past 160 years temperatures have fallen three times during short periods totalling about 50 years but that since 1860 the trend has been an increase in global temperature of about 1ºC. Since 1998 there has been a relatively steep rise in annual temperatures, not a fall and, yes, this too coincides with a significant increase in man made CO2 emissions. See graphs here and here.

Plimer asserts that, as would be expected in a cooling world, there has been no retreat of glaciers and the IPCC has no evidence of this. Rather than shrinking, Arctic sea ice is expanding and this is evidenced by a thriving polar bear population. The discovery of drowned polar bears was not due to lack of sea ice on which they could rest, hunt and eat but due to a storm. No citation is given for these assertions.

Photographic evidence of alpine and other glacier retreat is clear and seem to be uncontested by anyone other than Plimer who, presumably, regards such evidence as forgeries. The fact is that there is clear recorded evidence that glaciers on every continent are retreating. This gives particular cause for concern on at least two significant points:

1. the threat to long term maintenance of water flows in rivers fed by glaciers; and
2. the on going ability of glaciers to prevent ice sheets in Greenland and Antarctica from collapse in turn causing sea level rises.

Obviously the IPCC accepts visual evidence of glacial retreat and accurate measurement of the extent to which it has occurred - as is made clear in IPCC Technical Paper VI.

The National Snow and Ice Data Centre (NSIDC) publishes records of the Arctic area covered by sea ice for each year since 1979. This information clearly shows that the underlying trend continues to show a decline in the area covered by sea ice. It is true that from year to year this varies and in 2008-09 the area covered by ice did increase.

What Plimer studiously ignores, is that this increase of 710,000 sq km is an increase above the record low ice coverage recorded in 2007, and is 420,000 sq km below the 1979-2009 average area covered by ice. Consequently, average ice cover continues to decline as, importantly, does its thickness, suggesting rapid melting in following years.

Rather than accept Plimer’s claim that sea ice cover in the Arctic is growing, the US Geological Survey (USGS) is of the view that present trends indicate that in summer it may completely disappear by 2030. The implications of this are serious. At present, increasingly thin sea ice covers about 14.58 million sq km of the Arctic reflecting solar energy back into space. In the absence of this area of sea ice much of this energy would be absorbed by the sea and its coastal fringes, causing the ice cover to melt more extensively and rapidly each year.

This could increase the speed with which Greenland glaciers and the covering ice sheet melt. Collapse of the ice sheet would bring about a dangerous rise in sea levels, producing flooding of shorelines bordering the North Atlantic Ocean.

Regarding the polar bear, the facts are very different from those stated by Plimer. Far from thriving, in 2006 the Canadian Wildlife Service reported that the polar bear population of Hudson Bay had fallen by 22 per cent. The USGS has also reported that increasing retreat of sea ice from the northern shoreline of Alaska threatens the survival of polar bears and that, without sea ice, they are doomed to extinction, possibly by 2050. The US Government has now declared them an endangered species.

Polar bears have evolved to rely on food, mainly seals, sourced from beneath the sea ice where they swim. Seals surface at openings in the ice to breath fresh air and use it to rest on. Most bears can and do swim 60km or so in search of extensive areas of off-shore sea ice. However, melting sea ice causes it to recede to 160-200km off the Alaskan coast, well beyond their reach. In attempting to reach the sea ice in search of food, bears go beyond their endurance and, as reported by The Times, become exhausted and drown.