The condition of Arctic sea-ice in September, the time of year when the ice recedes most because of summer melting, will become known towards the end of 2011 when all the tests have been conducted. A less routinely publicised index is the coverage of sea-ice each January, when the ice is around its maximum. This, however, has now been recorded and published for over thirty years, since the development of advanced satellite reconnaissance in the 1970s made possible the accurate measurement of sea-ice in 1979.

The figures for January 2011 are intriguing in two respects. The first is is that there is something of a cyclical process at work, over a period of four to five years, with peaks and troughs in the size of the area covered by ice.  In the 2006-09 period, for example, the ice cover actually rose about 6%. A shift on this scale, which surely reveals a pronounced cooling effect, would seem to cast great doubt on the phenomenon of climate change. If it were to continue, then global warming would cease to be a worry; the task then would be to start preparing for a new ice age.

It is in this context that the second figure is so important - for these very short-term variations disguise a much more pronounced thinning and loss of the ice-cover over three decades. The full thirty-three record from 1979-2011, allowing for the fluctuations, shows average ice-cover declining at a rate of about 3% per decade. Moreover, and this is the reason for the smattering of media attention in recent weeks, the ice-cover figure for January 2011 is below the level for 2006 - and the lowest ever recorded.

The three impacts

Among the most important developments in climate science is the recognition that climate change is having singularly asymmetric effects. There is no certainty that extreme events (such as Russia’s heatwave and wildfires or Pakistan’s floods in 2010, or the current east African drought) are signs of more violent weather that stem from a more energetic atmosphere; but what is becoming clear is that some parts of the world will be far more affected by climate change than others (see "A world in hunger: east Africa and beyond", 27 July 2011).

In general, the main oceanic regions away from the poles will warm up more slowly than the continental land-masses, which will tend to dry out. The consequences for food production, on present trends, will have huge social, political and economic consequences. The impact on the North Polar region, often termed the “near-Arctic”, will also be profound (see Øyvind Paasche, "The new Arctic: trade, science, politics", 7 April 2011). The degree of warming of this region has three potential consequences, two of which are related to positive feedback.

The first is that as sea-ice melts, larger stretches of open water absorb more solar radiation, warming up and thereby increasing the rate of melting. The second is that progressive melting of the permafrost releases large amounts of methane (marsh gas) from decaying vegetation (and methane is a far more potent climate-change gas than carbon dioxide). The third consequence - more long-term than immediate - is the risk of an accelerated loss of the Greenland ice-cap, leading to substantial sea-level rises worldwide and many other climate consequences for the Atlantic rim countries (see Øyvind Paasche, “After glaciers: a new climate world”(12 October 2009).

The near Arctic region signals advance warning to the planet of what is to come, like the canaries that coal-miners used to keep as a warning of potential explosions. At the same time, the core problem that climate change heralds - and the reason why preventing it must be a global priority - that it could increase hugely the social and economic stress on the tropics and sub-tropics, including most of the world's most impoverished and marginalised societies.

This means in practice that the main emitters have to move to ultra-low-carbon economies (under 20% of current emissions) within by around 2030; a shift that must be combined with protracted and large-scale programmes of assistance that enable developing economies to establish a model that fuses economic emancipation and environmental sustainability (see "The climate peril: a race against time", 13 November 2009).

The three blocks

If the argument for such radical action on climate change has yet to make a breakthrough, three factors have been responsible. The first and all-embracing one is institutional: namely, that current political and economic systems are badly equipped to facilitate the effective mitigation of climate change - which requires economic transformation in the short term, with all its immediate impact, to avoid much greater problems in the long term.

The second factor is political: namely, the “lost decade” at the start of the 21st century, when the world's most powerful state was in the hands of climate change-deniers. Of all the toxic legacies of the George W Bush administration, that may well turn out to be the worst (see "Climate change: a failure of leadership", 8 May 2009).

The third factor is systemic: namely, the fact that responding to climate change requires an integrated approach that embraces environmental, economic and security aspects in a single analysis.

The publication of a report by a leading parliamentary committee in the United Kingdom (the defence select committee) on 2 August 2011 is another missed opportunity in this respect: in assessing the state’s “strategic defence and security review” (SDSR), the committee - even though it includes some written evidence on climate change from the Oxford Research Group and others - hardly addresses the issue.

The report has many words about how the decline in Britain’s defence capabilities makes it hard to maintain the country’s influence in the world; but it fails to appreciate the fundamentally changed context that global environmental constraints imply (see "Climate change and global security", 2 January 2003).

Britain could in principle play a major role in pushing the world community towards a more sustainable and equitable system, but “defence” in the conventional sense of the word will not be at the core of that process. The national-security strategy (NSS) published in 2010 contained glimmers of recognition here, but such forward thinking now seems to be receding. If the reversal proves a harbinger of a repeat “lost decade”, then the world’s really dangerous times will move nearer and start to become unavoidable.