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The Modeling of Climate and Climate Change; can we trust model predictions?. University of California, Irvine 21 February 2003 by John Houghton. Outline. Introduction Cloud Radiation Feedback Ocean Interactions The Carbon Cycle The Climate of the 20th Century

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the modeling of climate and climate change can we trust model predictions

The Modeling of Climate and Climate Change;can we trust model predictions?

University of California, Irvine

21 February 2003

by

John Houghton

outline
Outline
  • Introduction
  • Cloud Radiation Feedback
  • Ocean Interactions
  • The Carbon Cycle
  • The Climate of the 20th Century
  • Climate Projections for the 21st Century
  • Regional Climate Modeling
  • Patterns of Climate Response
slide3

The greenhouse effect

Solar radiation

Long-wave

radiation

236 Wm-2

236 Wm-2

Equivalent T = 255 K (-18ºC)

390 Wm-2

T = 255 K (-15ºC)

the enhanced greenhouse effect
The Enhanced Greenhouse Effect

S L

236 236

S L

236 232

S L

236 236

S L

236 236

Solar (S) and longwave (L) radiation in Wm-2 at the top of the atmosphere

T = -18°C

CO2 x 2

+ Feedbacks

H2O (+60%) Ice/Albedo (+20%)

Cloud?

Ocean?

CO2 x 2

CO2 x 2

TS = 15°C

TS = 15°C

DTS ~ 1.2K

DTS ~ 2.5K

the development of climate models past present and future
The Development of Climate models, Past, Present and Future

Mid 1980s

Early 1990s

Late 1990s

Present day

Early 2000s?

Mid 1970s

Atmosphere

Atmosphere

Atmosphere

Atmosphere

Atmosphere

Atmosphere

Land surface

Land surface

Land surface

Land surface

Land surface

Ocean & sea-ice

Ocean & sea-ice

Ocean & sea-ice

Ocean & sea-ice

Sulphate

aerosol

Sulphate

aerosol

Sulphate

aerosol

Non-sulphate

aerosol

Non-sulphate

aerosol

Carbon cycle

Carbon cycle

Atmospheric

chemistry

Sulphur

cycle model

Non-sulphate

aerosols

Ocean & sea-ice

model

Off-line

model

development

Strengthening colours

denote improvements

in models

Land carbon

cycle model

Carbon

cycle model

Ocean carbon

cycle model

Atmospheric

chemistry

Atmospheric

chemistry

predicting impacts of climate change
Predicting impacts of climate change

Scenarios from population, energy,

economics models

Emissions

Concentrations

CO2, methane, sulphates, etc.

Global climate change

Temperature, rainfall, sea level, etc.

Regional detail

Mountain effects, islands, extreme weather, etc.

Impacts

Flooding, food supply, etc.

Carbon cycle and chemistry models

Coupled global climate models

Regional climate models

Impacts models

The main stages required to provide climate change scenarios for assessing the impacts of climate change.

Hadley Centre - PRECIS brochure

slide10

Coupled atmosphere / ocean climate model

Radiation

Atmosphere: Density

Motion

Water

Heat

Exchange of: Momentum

Water

Ocean: Density (inc. Salinity)

Motion

Sea

Ice

Land

slide12

30km

19 levels in

atmosphere

2.5

lat

3.75

long

THE HADLEYCENTRETHIRDCOUPLEDMODEL -HadCM3

1.25

1.25

20 levelsin ocean

-5km

physical feedbacks
Physical Feedbacks
  • Water vapour
  • Ice albedo
  • Clouds
  • Oceans
  • Ice sheets
effect of cloud feedback formulation on climate prediction
Effect of cloud feedback formulation on climate prediction
  • Feedback scheme Global Av Temp change,C for doubled CO2
    • RH 5.3
    • CW 2.8
    • CWRP 1.9
    • after Senior & Mitchell, Hadley Centre
projected changes in annual temperatures for the 2050s
Projected changes in annual temperatures for the 2050s

The projected change in annual temperatures for the 2050s compared with the present day, when the climate model is driven with an increase in greenhouse gas concentrations equivalent to about 1% increase per year in CO2

BW 11

The MetOffice. Hadley Center for Climate Prediction and Research.

slide27

Changes in surface air temperature, relative to the present day, 20 years after the hypothetical collapse of the thermohaline circulation.

Hadley Centre

slide28

Combined effect of THC collapse (2049-2059) and global warming

Surface Temperature

Cooling over UK: 1-3°C

global co 2 budgets in gtc per year
Global CO2 budgets in GtC per year

1980s 1990s

Atmospheric increase 3.3 ± 0.1 3.2 ± 0.1

Emissions (fossil fuel, cement) 5.4 ± 0.3 6.3 ± 0.4

Ocean-atmosphere flux -1.9 ± 0.6 -1.7 ± 0.5

Land atmosphere flux -0.2 ± 0.7 -1.4 ± 0.7

partitioned as follows:

Land-use change 1.7 (0.6 to 2.5) NA

Residual terrestrial sink -1.9 (-3.8 to 0.3) NA

IPCC Third Assessment Report

slide36

Change in carbon content of soil (top) and vegetation (bottom)

between 1860 and 2100

- predicted by Hadley Centre climate model

Hadley Centre

slide37

Simulated changes in the global total soil and vegetation carbon content (Gt C) between 1860 and 2100.

Hadley Centre

slide38

Influence of ENSO on CO2 Variability

  • Annual changes in atmospheric CO2 are dominated by ENSO
    • after removing anthropogenic rise
    • rise during El Nino
    • fall during La Nina

CO2 - black, Nino3 - red

slide39

Influence of Volcanoes on CO2 Variability

  • 2 notable exceptions to ENSO correlation
  • CO2 levels lower than expected
  • Coincide with major volcanic eruptions

El Chichon

Pinatubo

CO2 - black, Nino3 - red

constraint from enso sensitivity
Constraint from ENSO Sensitivity
  • Model with q10=2 has realistic sensitivity to ENSO.
  • Reconstructions for range of q10.
  • Infer q10=2.1±0.7.
constraint from sensitivity to volcanoes
Constraint from Sensitivity to Volcanoes
  • Model with q10=2 has realistic sensitivity to Pinatubo.
  • Reconstructions for range of q10.
  • Infer q10=1.9±0.4
enso and pinatubo variations as a constraint on climate carbon cycle feedback
ENSO and Pinatubo Variations as a constraint on climate-carbon cycle feedback

Model with

C cycle

Feedback

(q10= 2)

Grey region is estimate of uncertainty

related to q10 parameter for soil respiration

Model without

C cycle

Feedback

q10= 3

q10= 1

slide44

Estimated carbon uptake if suitable arable land north of 30º N were to be replaced with trees.

The additional effect on climate of the changes in surface reflectivity when trees are planted on suitable arable land north of 30º N, expressed as equivalent carbon emissions.

The difference between the two diagrams above. Negative values show where the net effect of planting trees is to warm climate.

Hadley Centre

net effect of planting trees expressed as equivalent carbon uptake
NET EFFECT OF PLANTING TREESexpressed as equivalent carbon uptake

50

0

50

100

150

200

tonnes of carbon per hectare

Met Office / Hadley Centre

Negative values show where the net effect of planting trees is to warm climate

emissions and concentrations of co 2 from unmitigated and stabilising emission scenarios

20

1000

950

900

850

15

emissions (GtC/yr)

800

750

700

CO concentration (ppm)

10

2

650

600

2

Anthropogenic CO

550

5

500

450

400

0

350

2000

2050

2100

2150

2200

2250

2300

2350

2000

2050

2100

2150

2200

2250

2300

2350

750 ppm stabilisation

550 ppm stabilisation

Unmitigated emissions

EMISSIONS AND CONCENTRATIONS OF CO2from unmitigated and stabilising emission scenarios

Source: IPCC

slide48
Global mean surface air temperature anomalies from 1,000 year control simulations with three different climate models, - Hadley, GFDL and Hamburg, compared to the recent instrumental record. No model control simulation shows a trend in surface air temperature as large as the observed trend. If internal variability is correct in these models, the recent warming is likely not due to variability produced within the climate system alone.

IPCC Third Assessment Report

simulated annual global mean surface temperatures
Simulated annual global mean surface temperatures

Natural forcing

Anthropogenic forcing

ipcc statements on detection
IPCC statements on Detection
  • “The balance of evidence suggests a discernible human influence on global climate” 1995 Report
  • “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities” 2001 Report
slide53

The solid line shows a GCM prediction of temperature change. Prior to 1990, historical emissions were used. Beyond 1990, the IS92a emissions scenario was used. The dashed line shows the results of scaling the model prediction to give the best fit to the most recent 50 years of observations. The shaded region is the uncertainty estimate.

Hadley Centre

sres scenario familys
SRES scenario familys

A1

More

economic

A2

B: balanced

FI: fossil intensive

T: non-fossil

More

global

More

regional

B1

B2

More

environmental

slide57

Area averaged changes in summer rainfall for the period 2071-2100 over southern Asia as predicted by nine coupled models forced by the A2 emissions scenario (taken from Chapter 10 of the Scientific Basis of the IPCC Third Assessment Report). In other areas predictions can show much greater differences in magnitude and even sign.

Hadley Centre - PRECIS brochure

observed and projected changes in extremes
Observed and projected changes in extremes

Changes in Phenomenon

Higher maximum temperatures and more hot days over nearly all land areas

Higher minimum temperatures, fewer cold days and frost days over nearly all land areas

Reduced diurnal temperature range over most land areas

Increase of heat indexover land areas

More intense precipitation events

Increased summer continental drying and associated risk of drought

Increase in tropical cyclone peak wind intensities

Increase in tropical cyclone mean and peak precipitation intensities

Confidence in projected changes (during the 21st century)

Very likely

Very likely

Very likely

Very likely, over most areas

Very likely, over many areas

Likely, over most mid-latitude continental interiors (Lack of consistent projections in other areas)

Likely, over some areas

Likely, over some areas

Confidence in observed

changes (latter half

of the 20th century)

Likely

Very likely

Very likely

Likely, over many areas

Likely, over many Northern Hemisphere mid- to high-latitude land areas

Likely, in a few areas

Not observed in the few analyses available

Insufficient data for assessment

IPCC Third Assessment Report

slide61

Schematic diagram of the resolution of the Earth’s surface and the atmosphere in the Hadley Centre regional climate model.

Hadley Centre - PRECIS brochure

regional climate model
Regional Climate Model
  • High resolution (50km) over limited area (Europe, Indian subcontinent)
  • Embedded in global model, so subject to same uncertainties
  • Takes account of local characteristics, e.g. mountains, coasts
  • Better regional detail, better prediction of extremes in weather (eg flooding)
  • Everybody wants one!
slide63

The representation of the Philippines in RCMs with resolutions of 400 km (the GCM), 50 km and 25 km.

Hadley Centre - PRECIS brochure

slide64

Patterns of present-day winter precipitation over Britain. Left, as simulated with the global model. Middle: as simulated with the 50 km regional model. Right, as observed.

Hadley Centre - PRECIS brochure

slide65

The frequency of winter days over the Alps with different daily rainfall thresholds. Purple bars, observed. Dark red bars simulated by the GCM. Green bars simulated by the RCM.

Hadley Centre - PRECIS brochure

slide66

A tropical cyclone is evident in the mean sea-level pressure field from the RCM (right) but not in the driving GCM (left) for the corresponding day (from an RCM over southern Africa, developed by the Hadley Centre in collaboration with the university of Cape Town).

Hadley Centre - PRECIS brochure

slide67

Predicted changes in summer surface air temperatures between the present day and the end of the 21st century. Left, from the global model. Right, from the regional model.

Hadley Centre - PRECIS brochure

slide68

Predicted changes in monsoon precipitation over India, between the present day and the middle of the 21st century from the GCM (left) and the RCM (right).

Hadley Centre - PRECIS brochure

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