© Crown copyright Met Office Essentials of Climate Modelling and Intro to PRECIS RCM Data Analysis and postprocessing workshop Malaysian Met. Department, Nov 2012

© Crown copyright Met Office Essentials of Climate Modelling The goal of this session is a brief introduction to: the PRECIS regional climate model the climate system climate variability modelling of the climate system climate of the past projection of future climate

© Crown copyright Met Office PRECIS

© Crown copyright Met Office What is PRECIS? Providing REgional Climates for Impact Studies It can be applied to any area of the globe Used to generate detailed projections of future climate A simple user interface to set up and run an RCM Runs of the freely available Linux operating system PRECIS also provides utilities for users to manipulate RCM output

© Crown copyright Met Office The PRECIS user interface

© Crown copyright Met Office The components of PRECIS The RCM User interface to design and configure RCM experiments Display and data processing software Lateral boundary conditions Training course and materials Technical and Scientific Support web forum Website (

© Crown copyright Met Office Why was PRECIS developed? * UNFCCC requirement for all countries to assess their national vulnerability and plans for adaptation. * RCMs resolve local details and provide realistic extreme events for impact studies which can contribute to this assessment. * This meets the need for countries more vulnerable to climate change to generate their own national scenarios of climate change for use in impact studies. * Additionally, the PC version of PRECIS addresses the UNFCCC requirement on the UK to assist in capacity building and technology transfer.

© Crown copyright Met Office What is a Regional Climate Model? Mathematical model of the atmosphere and land surface (and sometimes the ocean) ‘High’ resolution: Produces data in grid cells < 50km in size Spans a limited area (region) of the globe Contains representations of many of the important physical processes within the climate system Cloud Radiation Rainfall Atmospheric aerosols Soil hydrology Etc.

© Crown copyright Met Office Boundary conditions Limited area regional models require meteorological information at their edges (lateral boundaries) These data provide the interface between the regional model’s domain and the rest of the world The climate of a region is always strongly influenced by the global situation These data are necessarily provided by global general circulation models (GCMs) or from observed datasets with global coverage (re-analysis experiments)

© Crown copyright Met Office Future developments * Continuously upgraded to new processors/new Linux * PRECIS version 2.0 – the HadRM3P RCM driven by CMIP5/AR5 GCMs * PRECIS version 3.0 – the HadGEM3-RA RCM (derived from the HadGEM3 GCM) driven by CMIP5/AR5 GCMs

© Crown copyright Met Office The Climate System

© Crown copyright Met Office Weather and climate Weather: the fluctuating state of the atmosphere around us Climate: the averages, variations and extremes of weather in a region over long periods of time

© Crown copyright Met Office The climate system

© Crown copyright Met Office Planetary energy balance A planetary object intercepts a circle (of radius R) of incoming solar energy S as S  R 2 A (for Albedo) of which is reflected Energy absorbed is balanced by radiation to space. Hence, S  R 2 (1-A) = 4  R 2 2  T 4 4 therefore T = (S(1-A)/4   T = Temperature  = Stefan-Boltzmann constant See the “Stefan-Boltzmann Law” for more information

© Crown copyright Met Office Planetary energy balance For the Earth, S is 1365 Wm -2 and A is 0.3, predicts 255 K (~ -18˚ C) In fact, the mean surface temperature of the Earth is 287 K (~ +14˚ C) What accounts for the difference of ~33K?

© Crown copyright Met Office The Greenhouse Effect 1. Sunlight passes through the atmosphere 2. It warms the Earth 3. Infrared radiation (IR) is given off by the Earth 5....but some IR is trapped by gases in the air, thus reducing the cooling effect Most IR escapes to outer space and cools the Earth…

Greenhouse gases Various trace gases and aerosols intercept reflected longwave radiation and re-emit in all directions Water vapour is the biggest contributor (~30 of ~33 K) Other important gases are CO 2 (~2 K), CH 4 and N 2 O (total ~1 K) Aerosols (including cloud droplets) do similar H2OH2O CH 4 CO 2 N2ON2O

© Crown copyright Met Office Indicators of the human influence on the atmosphere during the industrial era

© Crown copyright Met Office Climate variability

© Crown copyright Met Office Radiative forcing is a simple measure of the effect of a climate change mechanism There are various mechanisms that cause the climate to change Radiative forcing Natural climate drivers External Internal Anthropogenic climate drivers The enhanced greenhouse effect The effect of anthropogenic aerosol

+ © Crown copyright Met Office Natural variability of climate External radiative forcings Solar radiation changes Volcanic eruptions Internal climate variability ENSO (El Niño Southern Oscillation) NAO (North Atlantic Oscillation) MJO (Madden-Julian Oscillation)

© Crown copyright Met Office The effect of the Mt. Pinatubo eruption (June 1991) on global temperature

© Crown copyright Met Office The enhanced greenhouse effect The effect of anthropogenic aerosols direct effect (scattering of incoming solar radiation) indirect effect (affecting the radiative properties of clouds) Land-use change (agriculture, deforestation, reforestation, afforestation, urbanisation, traffic, …) Human-induced climate variations

The direct effect of aerosol Effect climate directly via their interaction with solar radiation and indirectly via their effect on clouds. The scattering of radiation causes atmospheric cooling, whereas absorption can cause atmospheric warming Aerosols are particles suspended in the atmosphere For example; dust, soot, sea salt, pollen, sulphates

Some sunlight reflected More sunlight reflected – cooling effect Brighter clouds‘Normal clouds’ Relatively clean lower atmosphere Polluted lower atmosphere The indirect effect of aerosol

Additional warming if all anthropogenic emissions of sulphur dioxide are cleaned up Emission policies: unexpected consequences Reducing pollution can lead to more rapid warming with large regional consequences Pollution from anthropogenic aerosols over China

© Crown copyright Met Office Climate feedbacks Feedbacks occur when a change in our climate has an impact which changes our climate further They either amplify the effect of the initial forcing (a positive feedback) or reduce it (a negative feedback) Examples: Water vapour (+) Albedo (+) Methane hydrates (+) Permafrost methane (+) Clouds (+ and –) …and possibly other feedbacks we don’t know about yet

How do we quantify the response of the climate? The response of the climate system to radiative forcings is complicated by: feedbacks the non-linearity of many processes different response times of the different components to a given perturbation We can use numerical models of the climate system as a means to calculate the climate response

© Crown copyright Met Office Climate models

© Crown copyright Met Office Climate models A global climate model (GCM) is a model of the climate system. The advective (relating to motion) and thermodynamical (relating to heat) evolution of atmospheric pressure, winds, temperature and moisture (prognostic variables) are simulated, while including the effects of many other physical processes. Other useful meteorological quantities (diagnostic variables) are derived consistently within the model from the prognostic variables, such as precipitation, evaporation, soil moisture, cloud cover and many more.

© Crown copyright Met Office Main components of global climate models Atmosphere and ocean dynamics Model grid Physical parameterizations Initial conditions of the model Boundary conditions (e.g. land sea mask, orographic height, vegetation and soil characteristics)

The three dimensional model grid © Crown copyright Met Office Vertical exchange between layers of momentum, heat and moisture Horizontal exchange between columns of momentum, heat and moisture Vertical exchange between layers of momentum, heat and salts by diffusion, convection and upwelling Orography, vegetation and surface characteristics included at each grid box surface Vertical exchange between layers by diffusion and advection

© Crown copyright Met Office Parameterization of physical processes Important processes occur in the atmosphere on scales smaller than those which are resolved by the grid of the dynamical part of the model. The effects of these unresolved (sub-grid scale) processes are deduced from the large scale state variables predicted by the model (wind, pressure, temperature, moisture). This procedure is called parameterization.

Initial and boundary conditions All climate models require information about the initial state of the atmosphere at the beginning of the climate model experiment. These are the initial conditions of the model experiment. The three dimensional grid of a GCM has no lateral (North- South, East-West) boundaries. The upper boundary is the end of the atmosphere where it contacts outer space. The lower boundary is either the surface of the land or the bottom of the ocean. As such the GCM requires information about the topography of the Earth’s surface, called surface boundary conditions.

© Crown copyright Met Office The World in Global Climate Models

SampleHadley Centre Global Climate Model FORTRAN program code

© Crown copyright Met Office 20 th Century climate

Variations of the Earth’s surface temperature for the past 160 years El Nino

© Crown copyright Met Office 1999 La Nina 1998 El Nino 2010 Met Office – CRU Global average surface temperatures

Variations of the Earth’s surface temperature for the past 1000 years

+ © Crown copyright Met Office Natural influence alone

+ © Crown copyright Met Office Human and natural influence combined +

© Crown copyright Met Office Predicting climate change

Predicting Climate Change Emissions Atmospheric Concentrations CO2, methane, sulphates, etc Global Climate Change Temperature, rainfall, sea level etc Regional Detail Mountain effects, islands, extreme weather etc Scenarios from population, energy, economics models and mitigation Regional climate models or statistical downscaling Coupled global climate models Carbon cycle and chemistry models Impacts models Preparing climate scenarios from model projections Methods of applying global or regional model output The climate scenario Impacts Flooding, agricultural yields etc

Range of emissions Range of global warming Range of regional climate change Range of impacts Range of concentrations The classic “cascade of uncertainty”

Impact that we wish to avoid Regional climate change that may cause this impact Global climate change that may cause this range of regional climate change GHG concentrations that may cause this range of climate change Emissions that may lead to this range in concentrations Upper bound: very likely to lead to this impact Lower bound: very unlikely to lead to this impact

© Crown copyright Met Office Temperature increases by 2100 Global average 5.5 ºCGlobal average 1.9 ºC Land areas are projected to warm more than the oceans with the greatest warming at high latitudes

© Crown copyright Met Office Precipitation changes by 2100 Some areas are projected to become wetter, others drier with an overall increase projected

... And in conclusion This presentation is intended as a brief overview of the climate system and climate modelling. For more in-depth training, consider registering for the free online course in the science of climate change and modelling at This is a joint effort of the University of Oxford Continuing Education Department and the Met Office Hadley Centre consisting of 8 interactive online units intended for an educated (but non-scientist) audience. This presentation is intended as a brief overview of the climate system and climate modelling. For more in-depth training, consider registering for the free online course in the science of climate change and modelling at This is a joint effort of the University of Oxford Continuing Education Department and the Met Office Hadley Centre consisting of 8 interactive online units intended for an educated (but non-scientist) audience.

© Crown copyright Met Office Questions