modeling climate change in future periods (gcm models and downscaling techniques)

Modeling Climate Change in Future Periods

(GCM models and Downscaling Techniques)

Alireza Massah Bavani, Assistant professor, University of Tehran

Climate change study steps

Understanding the concepts of climate change

Modeling climate change

in the future

Impact assessment of

climate change

Adaptation to climate change

Mitigation of climate change

The component of climate system

Monitoring the observed climate (detection of Climate

Change)

Are the changes unusual?

What makes C.C.?

Attribution of C.C.

Scio-economic scenario

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

Simple Model (MAGICC

Atmospheric-Ocean General Circulation Model

(AOGCM)

Downscaling

Impact Assessment

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Monitoring the observed climate (detection of

Climate Change)

Atmosphere and surface

Snow, ice and frozen

ground

Ocean and Sea Level

Changes in atmosphere and Surface

1) Global mean surface temperatures have risen by 0.74°C ±0.18°C when estimated by a linear trend over the last 100years (1906–2005). The rate of warming over the last 50 years is almost double that over the last 100 years (0.13°C± 0.03°C vs. 0.07°C ± 0.02°C per decade).

2) Land regions have warmed at a faster rate than the oceans.

3) Recent warming is strongly evident at all latitudes in SSTs over each of the oceans.

5) Average arctic temperatures increased at almost twice the global average rate in the past 100 years.

6) Precipitation has generally increased over land north of 30°N over the period 1900 to 2005 but downward trends dominate the tropics since the 1970s.

7) Substantial increases are found in heavy precipitation events.

8) Droughts have become more common, especially in the tropics and subtropics, since the 1970s.

9) Tropospheric water vapour is increasing.10)Mid-latitude westerly winds have generally

increased in both hemispheres.

Changes in cryosphere

1) The amount of ice on the Earth is decreasing. There has been widespread retreat of mountain glaciers since the end of the 19th century. The rate of mass loss from glaciers and the Greenland Ice Sheet is increasing.

2) The extent of NH snow cover has declined. Seasonal river and lake ice duration has decreased over the past 150 years.

3) Since 1978, annual mean arctic sea ice extent has been declining and summer minimum arctic ice extent has decreased.

4) Temperature at the top of the permafrost layer has increased by up to 3°C since the 1980s in the Arctic.

Ocean and sea level

The global temperature (or heat content) of the oceans has increased since 1955.Large-scale regionally coherent trends in salinity have been observed over recent decades with freshening in subpolar regions and increased salinity in the shallower parts of the tropics and subtropics. These trends are consistent with changes in precipitation and inferred larger water transport in the atmosphere from low latitudes to high latitudes and from the Atlantic to the Pacific.Global average sea level rose during the 20th century. There is high confidence that the rate of sea level rise increased between the mid-19th and mid-20th centuries. During 1993 to 2003, sea level rose more rapidly than during 1961 to 2003.Thermal expansion of the ocean and loss of mass from glaciers and ice caps made substantial contributions to the observed sea level rise.The observed rate of sea level rise from 1993 to 2003 is consistent with the sum of observed contributions from thermal expansion and loss of land ice.The rate of sea level change over recent decades has not been geographically uniform.As a result of uptake of anthropogenic CO2 since 1750, the acidity of the surface ocean has increased.

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

What makes Climate

Change?

Internal forcings

External forcings

What makes Climate

Change?

Internal forcings

External forcings

Internal forcings

Some aspect of internal variability

El Niño Southern oscillation Pacific decadal oscillation North Atlantic oscillation Arctic oscillation Thermohaline circulation

What makes Climate

Change?

Internal forcings

External forcings

Internal Variability

Human activities

What makes Climate

Change?

Internal forcings

External forcings

Natural

Solar Variation

Orbital Variation

Volcanism

External Natural Forcings

Solar Variability

Orbital variation Obliquity (every 41,000 years)

Eccentricity (every 400,000 years)

Precession(20,000 years)

Ice age changes

occurs several times per century causing cooling for a period of a few years, cooling

by partially blocking the transmission of solar radiation to the Earth's surface

Huge eruptions, known as large igneous provinces, occur only a few times every hundred million years but can reshape climate for millions of years and cause mass extinctions

most of the dust thrown in the atmosphere returns to the Earth's surface within six months

Volcanic Eruption

Human activities

What makes Climate

Change?

Internal forcings

External forcings

Natural

Solar Variation

Orbital Variation

Volcanism

Natural Variability

Human activities

What makes Climate

Change?

Internal forcings

External forcings

Natural

Solar Variation

Orbital Variation

Volcanism

Natural Variability

Fossil fuel combustion Aircraft

Human Activities

Land use change (forest,

cropland, pasture)

Agriculture, Livestock,

Deforestation

Refrigeration agents

Surface Mining,

Industrial Process

Greenhouse gasses change

Albedo Change

Aerosol ChangeOzone

depletion

Contrails

CO2,N2O

CO2,CH4,N2O

CFC-11 CFC-12

Changes in Human drivers

Human activities

What makes Climate

Change?

Internal forcings

External forcings

Natural

Solar Variation

Orbital Variation

Volcanism

Natural Variability

Climate Change

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Attributing climate change

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

IPCCUnited Nations Environment

Program (UNEP)

World Meteorological Organization

Intergovermental Panel of Climate

Change(IPCC)

WGI WGII WGIII

The science of C.C Impact, Adaptation and vulnerability Mitigation

1990 –FAR1995 – SAR2001 – TAR2007 – AR42013- AR5

Definitions of termsProjection: any description of the future and the pathway leading to it.Forecast/Prediction: When a projection is designated "most likely" it becomes a forecast or predictionScenario: A scenario is a coherent, internally consistent and plausible description of a possible future state of the world. It is not a forecast; rather, each scenario is one alternative image of how the future can unfold. A projection may serve as the raw material for a scenario, but scenarios often require additional information (e.g., about baseline conditions).Baseline/reference: The baseline (or reference) is any datum against which change is measured.

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Socio-economic Scenario

Why do we need? They improve our understanding of the key

relationships among factors that drive future emissions.

They provide a realistic range of future emissions of net greenhouse gas and aerosol precursors

They offer a consistent framework of projections that can be applied in climate change impact assessments.

Socio-economic scenarios are projected for the globe up to 2100 and finally convert to emission scenarios

Emission scenarios1- IS92 (1992)

Emission scenarios 2- SRES (1998)

The four IPCC SRES scenario storylines

Some aspects of the SRES emissions scenarios and their implications

Anthropogenic emissions of CO2, CH4, N2O and sulphur dioxide for the six

illustrative SRES scenarios,

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Climate scenario

Criteria for selecting climate scenarios1: Consistency with global projections.2: Physical plausibility.3: Applicability in impact assessments.4: Representative5: Accessibility.

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Synthetic (incremental) scenario

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

palaeoclimate

Use information from the geological record -fossils, sedimentary deposits - to reconstruct past climates

1- the mid-Holocene (5000 to 6000 years BP) - Northern Hemisphere temperatures are estimated to have been about 1°C warmer than today

2- the Last (Eemian) Interglacial (125000 years BP) - about 2°C warmer

3-Pliocene (three to four million years BP) - about 3-4°C warmer

Disadvantages: changes in the past unlikely to have been caused by increased GHG concentrations data and resolution generally insufficient,i.e., extremely unlikely to get daily resolution and individual site information uncertainty about the quality of palaeoclimatic reconstructions higher resolution (and most recent) data generally lie at the low end of the range of anticipated future climatic warming

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Simple numerical model

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Atmosphere-Ocean General Circulation Model (AOGCM)

Relation between emission scenarios and AOGCM

AOGCMs SAR version

AOGCMs TAR version

AOGCMs AR4 version

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Applying AOGCM data in Impact Assessments

GCM outputs are not generally of a sufficient resolution or reliability to be applied

directly in impact assessment.

so we cannot use their output directly ...

Resolution problem of AOGCMs

Downscaling

developing regional GCM-based scenarios at sub-grid scale

1- Using original or interpolating grid box information

2- High resolution experiments3- Statistical downscaling

Using original or interpolating grid box information

Overcomes problems of discontinuities in change between adjacent sites in different grid boxes

But introduces a false geographical precision to the estimates

High resolution experiments

Numerical models at high resolution over region of interest

1- Time slice experiment: Run a full GCM at higher resolution for a limited number of years in "time slice" experiments.

2- Stretched grid experiments: running a GCM at varying resolution across the globe, with the highest resolution over the study region

3- nesting approach: use of a separate high resolution limited area model (LAM), using conventional GCM outputs (control simulation and experiment) to provide the boundary conditions for the LAM

Advantage: are able to account for important local

forcing factors, e.g., surface type & elevationDisadvantage dependent on a GCM to drive models computationally demanding few experiments may be ‘locked’ into a single scenario,

therefore difficult to explore scenario uncertainty, risk analyses

Statistical downscaling

More sophisticated downscaling techniques calculate sub-grid scale changes in climate as a function of larger-scale climate or circulation statistics.

Tobserved=f(MSLP,…) observed

Tfuture=f(MSLP,…) GCM

Advantage much less computationally demanding than physical

downscaling using numerical models ensembles of high resolution climate scenarios may be

produced relatively easilyDisadvantage

large amounts of observational data may be required to establish statistical relationships for the current climate

specialist knowledge required to apply the techniques correctly

relationships only valid within the range of the data used for calibration - projections for some variables may lie outside this range

may not be possible to derive significant relationships for some variables

a predictor which may not appear as the most significant when developing the transfer functions under present climate may be critical for determining climate change

Statistical downscaling

Change)

What makes C.C.?

Attribution of C.C.

Climate Scenario

in the future

Synthetic scenarios

Numerical Models

Analogue scenarios

(AOGCM)

Downscaling

Impact Assessment

Some questions

Which AOGCM model should we use in an impact study?Which emission scenario should be used in an impact study?Which downscaling techniques should we use?

Cascade of uncertainty in climate change research

My Research Projects and Work

Downscaling Techniques

Impact of climate change

Agriculture Surface Water

RunoffFlood Drought

Adaptation strategies

Water Productivity

Crop Yield

Ground Water

Evaluating different AOGCMs and downscaling procedures in climate change local impact assessment

studies

Results of Kriging and IDW with a different number of pixels around the original pixel didn’t show significant difference. Therefore, because of simplicity, the IDW method with 8 pixels was used to downscale the climate change scenarios of temperature and precipitation in future periods.

Comparison of the effects of future uncertainty of AOGCM-TAR and AOGCM-AR4 models on runoff

Results showed that the range of uncertainty of temperature, precipitation and consequently runoff of the basin due to AR4 models are less than TAR models

Evaluating difference between use of AOGCM multi-model ensembles and multi-model average for

assessment of climate change impacts on runoff (Case study: Qare Su sub-basin, Iran)

Overall results showed that in studies of climate change, average of temperature and precipitation derived from AOGCM models can be used to reduce the size of calculation, in addition to considering the uncertainty of these models which is one of the most important factors in climate change studies, and in many cases researchers are interested in this issue. However, it seems that in studies such as flood regime analysis that generally required the maximum flow series, using average of AOGCM models can not cover all range of uncertainty.

A Framework for Uncertainty Assessment of Climate Change Impacts on Runoff

(Case Study: Qareh-Soo Sub Basin, Iran)

For projection of precipitation, uncertainties of different AOGCMs were found more than downscaling techniques. However, considering the results, downscaling techniques seemed to be the main source of uncertainties for projection of runoff, compared with AOGCMs and hydrological models, predominantly. Final results showed that, different uncertainty sources exist that alter final simulation results, significantly. Therefore, a procedure seems to be necessary to determine uncertainty sources and their importance for assessment of climate change impacts on runoff and also other environmental hazards.

modeling climate change in future periods (gcm models and downscaling techniques)

attribution of c

changes unusual

global average rate

rate of warming

lake ice duration

greenland ice sheet

average arctic temperatures

global temperature

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