Global-mean sea-level rise will drive impacts and adaptation needs around the world's coasts over the 21st century and beyond. A key element in assessing these issues is the development of scenarios (or plausible futures) of local relative sea-level rise to support impact assessment and adaptation planning. This requires combining a number of different but uncertain components of sea level which can be linked to climatic and non-climatic (i.e., uplift/subsidence of coastal land) factors. A major concern remains about the possibility of significant contributions from the major Greenland and Antarctic ice sheets and this must be factored into the assessments, despite the uncertainty. This paper reviews the different mechanisms which contribute to sea-level change and considers a methodology for combining the available data to create relative (or local) sea-level rise scenarios suitable for impact and adaptation assessments across a range of sophistication of analysis. The methods that are developed are pragmatic and consider the different needs of impact assessment, adaptation planning, and long-term decision making. This includes the requirements of strategic decision makers who rightly focus on low probability but high consequence changes and their consequences. Hence plausible high end sea-level rise scenarios beyond the conventional Intergovernmental Panel on Climate Change (IPCC) range and which take into account evidence beyond that from the current generation of climate models are developed and their application discussed. Continued review and development of sea-level scenarios is recommended, starting with assimilating the insights of the forthcoming IPCC AR5 assessment.

[1] Quantifying uncertainty in regional climate change projections is important for a range of reasons. We examine the sensitivity of regional climate change probabilities to various uncertainties. We use a simple probabilistic energy balance model that samples uncertainty in greenhouse gas emissions, the climate sensitivity, the carbon cycle, ocean mixing, and aerosol forcing. We then propagate global mean temperature probabilities to General Circulation Models (GCMs) through the pattern-scaling technique. In order to combine the resulting probabilities we devised regional skill scores for each GCM, season (DJF, JJA), and climate variable (surface temperature, and precipitation) in 22 world regions, based on model performance and model convergence. A range of sensitivity experiments are carried out with different skill score schemes, climate sensitivities, and emissions scenarios. It was shown that whether skill scores as applied in this paper were used or not, makes little difference to regional climate change probabilities. However, both these approaches provide more information than simply using the multi-model ensemble average. For temperature change probabilities, emissions scenarios uncertainty tends to dominate the 95th percentile whereas climate sensitivity uncertainty plays a more important role at the 5th percentile. The sensitivity of precipitation change probabilities to the tested uncertainties are region specific, but some conclusions can be drawn. At the 95th percentile, the uncertainty that tends to dominate is emissions scenarios, closely followed by GCM weighting scheme and the climate sensitivity. At the 5th percentile, GCM weighting scheme uncertainty tends to dominate for JJA, but for DJF all uncertainties have similar proportionate influence.Citation: Dessai, S., X. Lu, and M. Hulme (2005), Limited sensitivity analysis of regional climate change probabilities for the 21st century,

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Climate data and information is central to understanding the risks of climate change and to planning for adaptive actions to reduce such risks. The multi-scale, multi-disciplinary and multi-stakeholder nature of climate change impacts, vulnerability and adaptation require effective and sustained collaboration between the providers and users in order to ensure the relevance, practicality and applicability of climate data and information. The Nairobi Work Programme (NWP) on impacts, vulnerability and adaptation to climate change was launched as a mechanism under the United Nations Framework Convention on Climate Change (UNFCCC) to engage stakeholders, facilitate knowledge sharing and collaboration, and catalyze targeted actions on adaptation. The NWP has engaged a wide array of stakeholders, providers, users and knowledge intermediaries for climate data and information. Through discussions under the NWP, Parties to the UNFCCC recognized that there is an urgent need to improve the provision and delivery of climate information, particularly in developing countries. Improvement in the availability of and access to high quality observed climate data and climate scenarios, practical guidance for the use of climate information, and the systematic documentation and wide dissemination of good practices in applying climate information to support adaptation are all identified as priority areas of work. These clearly defined priorities, together with synergies among relevant initiatives, represent considerable opportunities to enhance the provision and delivery of climate information and services, particularly within the context of the development and implementation of the Global Framework for Climate Services (GFCS).