My presentation today will focus on how our current understanding of the Earth's changing climate has profound implications for global stability and security. In revising and presenting the available evidence I wish to highlight three perspectives which are particularly relevant to this debate:
1. Science of climate change: What are the implications of what we know and do not know for interpreting future scenarios? How significant are "tipping points" and feedback mechanisms in interpreting the impact of climate change on our economies, societies and the Earth's life support systems?
2. Climate change as a threat multiplier: The scale and pace of climate change acts as a multiplier which could result in simultaneous and unprecedented impacts on where we can settle, grow food, maintain our built-up infrastructure, or rely on functioning ecosystems. Managing the potential disruption, displacement and adaptation to phenomena such as sea-level rise or extreme weather events, represents a profound challenge to sustainable development at the local, national and international level - both in economic and geopolitical terms.
3. Managing the risks of climate change: Uncertainty will continue to define our response to climate change. By its very nature, both in terms of its causes and its effects, climate change requires a global response. Accelerating the transition towards a low carbon future is but one dimension of reducing future risks. However, we must also develop a risk management strategy which anticipates and addresses the capacity of the international community to cope with significant disruptions to our societies which, left unaddressed, carry within them the seeds of tensions, chaos and conflict.
Underpinning the question of whether there is a link between climate change and security is the science.
Let us all acknowledge from the outset that the world does not have perfect knowledge on current or future climate change.
Determining the contribution of rising greenhouse gases in respect to an event such as the severe drought currently affecting the Horn of Africa is a challenge.
There may be a climate change signature, but there is also natural variation and wider environmental change underway, such as deforestation, land degradation and over exploitation of other natural resources such as freshwaters.
But human beings have never planned strategies or responses based on 100 per cent certainty, rather we make decisions based on risk assessments-intuitively when as an individual we cross a road, or deliberately when Governments or companies make decisions from economic planning and infrastructure to emerging security concerns.
The principal risk assessments in respect to climate change are the reports of the Intergovernmental Panel on Climate Change (IPCC), hosted by UNEP and the World Meteorological Organization.
Its work is in turn based on the research of thousands upon thousands of scientists from government and university-linked institutes from across the globe.
The fourth assessment report of the IPCC in 2007 concluded that it was "unequivocal" that the Earth is warming and that human activities play a role in this change.
Among its many findings then was that 11 of the last 12 years rank among the 12 hottest years on record.
Over the last 50 years, "cold days, cold nights, and frost have become less frequent, while hot days, hot nights, and heat waves have become more frequent."
The linear warming trend over the last 50 years of, on average 0.13°C per decade, is nearly twice that for the last 100 years. The total temperature increase from the period 1850 to 1899 to the period 2001 to 2005 has been 0.76°C.
Among the IPCC's other findings in 2007 was that storms and cyclones have become more intense over the past 30 years and that droughts, especially in the tropics and sub-tropics, have become more frequent with implications for food security.
Thermal expansion of the oceans is contributing to sea-level rise of on average 1.8 mm a year since the 1960s. Since 1978 satellites show that the extent of summer Arctic sea ice has fallen by 20 per cent.
Irrespective of the specific causes and drivers, there is clear evidence that our climate is changing and that the pace and scale of that change is accelerating in many areas.
The IPCC's fifth assessment will be released in 2013/2014, but already many teams of scientists claim the forecasts and scenarios of future climate change in the fourth IPCC assessment are being overtaken. For example, recent conclusions from the Snow, Water, Ice and Permafrost in the Arctic report of the Arctic Monitoring and Assessment Programme (AMAP), published in May, point to likely global sea-level rise of close to a meter or more by the end of the century as a result of, for example, faster melting of the Greenland ice sheets.