This presentation is less specifically about what is being projected - since that is the province of the Intergovernmental Panel on Climate Change. The IPCC is still working on its Third Assessment, and while there is much already much comment about what IPCC is likely to say, I’ll not try to pre-empt their findings here. Rather, I will explore with you the current climate or environment - into which these assessments are being fed. First of all I will talk a little about climate change itself and also climate variability. We will then look at the pathways for minimizing climate impacts, a little about what the international community is doing about it all and to conclude, something on challenges.

Impacts related to climate change are often couched in terms of monotonic trends towards a set of conditions that will be less beneficial to life on this planet. For the most part this depiction is well justified as examples in Figure 1 graphically illustrate.

However climate change may be even more complex than these relatively simple or straightforward examples suggest. When we talk about climate change, we must also think about its consequences on natural climate variability.

We are all familiar with the evidence of climate variability. Simply put, climate variability is the sum of the statistical frequencies and biases of particular weather events for a location or homogeneous region. Some regions may be prone to droughts, others to floods, tropical storms and so on (Figure 2). Traditionally these statistics including the biases towards a particular type of climate were considered to be fixed within definable limits and only changed on relatively long time scales, e.g. with the onset and retreat of ice-ages. We now know that climate can vary on virtually all time scales and in practice the distinction between climate change and climate variability has become rather arbitrary. Perhaps as an outcome of this, we have seen an increasing tendency to see the term climate ‘change’ reserved for change due to human influences. Convenient though this distinction may seem, the reality is that separating climate change from climate variability, whatever the causes, is an exceedingly difficult scientific problem. Climate change then may also mean a change in the normal patterns of weather and climate for different regions throughout the globe, i.e. a change in climate variability. The most important conclusion to be drawn from this assertion is that, because the frequency of extremes in a statistical distribution is usually very sensitive to changes in the shape of the distribution, climate change may also lead to a significant change in the frequency of extreme events. Remember now that we are talking of changes on time scales of months, seasons and years as opposed to monotonic trends that may not result in significant impacts until 20 or 50 years hence.

The principal aim of a fully comprehensive climate agenda might be expressed then as the improvement of our knowledge of climate, and the underlying causes of its spectrum of spatial and temporal ability, for the betterment of humanity within the overall constraint of sustainable development.

If we consider the centre-line of the diagram above, we can think of a period of climate forcing (leading to a drought, flood, storm etc.) that has a climate impact on a region of the globe and the communities within it depending on the sensitivities to the forcing and its events. Note that we distinguish here between sensitivity and vulnerability, and the reason for this will become clear.

The impact of a climatic event can be modified in several ways. Following the onset of a particular impact, the immediate response is to alleviate the impact (e.g. through relief measures). In a more considered timeframe, one can take the lessons learnt and build resilience in the affected community through adaptation strategies that will reduce future impacts of this type.

An alternative action or response is to attempt to reduce the onset of the event itself or forestall its further development. This we term here as mitigation. In view of the inherent difficulty in effectively controlling the climatic environment, except on very small space scales, mitigation by itself is apt to be an inadequate response to climate change and variability. Nevertheless, such measures cannot be ignored.

Ahead of an event, one can take account of known or expected sensitivities to the type of event, by developing applications and adaptation strategies that when implemented will reduce the severity of negative impacts or optimize the benefits of positive impacts. Note that the absence of an action of this type leaves a heightened vulnerability to the event or a lost opportunity. Note also the distinctions between reactive, proactive and mixed actions.

We can now begin to populate the pathway chart in Figure 3 with programmes, conventions and organizations according to their principal focus of activities. Note however, that the above examples are only a very small sub-set of the very large number of possible inclusions. Environmentally related meetings of the UN system now draw interest from groups numbering in the thousands.

The keystone of all the activity, however, is the minimization of vulnerability, which can also be expressed in a positive sense as the maximization of opportunity.

The original raison d’être of the World Meteorological Organization was to develop the global infrastructure for improving weather forecasts - this is now embodied in its basic programme called the World Weather Watch. As our knowledge of climate and its influences on human activities have grown, WMO is rapidly developing a framework for providing services to user communities on a range of climate topics. Critical to the success of such a Climate Watch are the GCOS for coordinating the data requirements and inputs from a wide range of sources, and the CLIPS for ensuring the outputs meet the needs of the user communities.

The success to which we will meet the challenges posed by this very complex set of issues will be determined in large part by factors that are outside the realm of climate science - but that is not to say that scientists can or should remove themselves from the debate. Two of these ‘external’ factors that loom largest are those of 'globalization' and 'commercialization'. Both are clearly changing the traditional roles of national governments, while at the same time bearing down new responsibilities on the private sector. In this changing world, the principle of "user pays" does not always sit well with the need to maintain or strive for social equity. This is especially true in developing countries. The role of the media is especially challenging since the packaging of a complex story is often at odds with the demands to "keep it simple". Scientists are often not adept at selling their message. So it is only through good communication, between scientists and media producers, writers and directors - including a mutual understanding of each other’s strengths and constraints that will we see the true message getting through to politicians, decision-makers and society at large.