Physical science findings relevant to climate change adaptation Richard Jones, Met Office Science Fellow/Visiting Professor, School of Geography and Environment

We have clear evidence that: The world has warmed and many aspects of the climate have changed The observed warming is mostly caused by emissions of greenhouse gases from human activities Climate models can be used to predict temperature changes from future increases in greenhouse gases Clear trends are not seen in all climate variables and in some areas data coverage is poor and does not allow calculation of trends, especially in the case of precipitation and extremes Context

Temperature data extends to some extremes but precipitation data coverage is much more variables

And in some cases daily precipitation or even temperature data is largely absent or unavailable, e.g. northern and central Asia and many parts of Africa

Old weather data records in Mauritius However, in many places data do exist but are not readily available, especially in digital formats

The evidence-base for anthropogenic climate change is clear, with significant changes already observed and more to come So the climate is changing and many human and natural systems are sensitive to climate The information presented so far is sufficient to motivate responses, i.e. to build resilience or plan adaptation – but is often insufficient to design interventions Regional climate scenarios

© Crown copyright Met Office The first level of regionalisation – continental-scale observed, simulated and future temperature ranges with human and natural forcings Significant regional temperatures rises are predicted Again, confidence comes from the models’ responses to observed forcing

Some clear signals on changes in average seasonal precipitation – consistent messages from CMIP3/5 Blue–increase Brown–decrease Green–no change in average

Projected change in heavy rainfall Number of days in the future exceeding baseline 90%ile daily precipitation

© Crown copyright Met Office So what are we confident or uncertain about at regional scales … We are confident that: Temperatures and sea-level will increase regionally within reasonably well-defined bounds Precipitation will change in many regions – warming increases water vapour which will lead to more and heavier rainfall in many regions We are uncertain about: Precipitation changes in some regions Some smaller-scale phenomena such as tropical cyclones, wind-storms

… and how close are we to developing regional climate baselines and scenarios? Climate, at a given location or in a given region, is defined as the expected behaviour of a wide-range of weather phenomena e.g. how many summer days are expected to be above 34°C? what is the heaviest rainfall event expected in a five-year period? The information presented so far is thus clearly insufficiently detailed both in terms of its temporal and spatial characteristics To provide the additional detail refinement of this information for a particular location or decision-making context is required

An important issue: Decision-making is constrained by practical considerations (time-scales, costs) which require decisions to be taken with far from ideal information: So clear statements of the limitations of information are important: Decisions will need to be made using incomplete or poor information. Other important issues: Systems are generally sensitive to a range of non-climate drivers and their importance relative to the climate drivers needs to be assessed Barriers to decision-making can include the structure of institutional frameworks and inappropriate communication channels Decisions will require information on a range of physical and non-physical factors which can be as or more important than physical climate changes Climate information relevant to decision-making

Some context on applying climate information for impacts and adaptation assessment Impacts and adaptation assessment information needs are broad, diverse and often detailed. Some example applications: Management of transport infrastructure Hydrology/hydraulic modelling for urban flood prediction Defining drought indices for climate change impacts on crops Storm-surge modelling for coastal protection The information requirements for these applications will be very different as will the quality of the available climate data

Some climate information requirements for assessing impacts Multiple climate variables are often needed Information can be required at high temporal and spatial resolution Temporal details can involve the daily timescale to capture maxima/minima and sub-seasonal variability Fine spatial details are often needed to be able to realistically represent the physical system being studied Thresholds of some of the climate variables can be important

Main messages on climate information for impacts and adaptation Detailed predictions (climate change information we can use locally with confidence) enable clear messages to be obtained on impacts and can provide guidance on the potential or requirement for systems to adapt The climate information need to be sufficiently detailed and representative of current and future climate for establishing robust messages on impacts and adaptation Detailed – implies the temporal and spatial scale should be appropriate to the system being studied Representative – implies that the information should be reliable, if possible, or at least cover the range of plausible (non-falsifiable) outcomes

Summary The direction and likely ranges of many aspects of area-averaged regional climate change are clear and motivate the need for adaptation Additional information (e.g. more complete baseline information, disaggregation of regional climate predictions) is required to provide the detail needed to assess vulnerability and impacts and planning resilience or adaptation responses These assessment will involve multiple information streams which will have different levels of confidence – both climate and non-climate To identify a system in need of adaptation and then assess possible interventions requires in depth understanding of its climate sensitivities and the other physical and non-physical factors which influence the system