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


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

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)


Spectra of outgoing radiation from earth observed by iris on nimbus 3

Spectra of outgoing radiation from Earth observed by IRIS on Nimbus 3


The enhanced greenhouse effect

The Enhanced Greenhouse Effect

SL

236236

SL

236232

SL

236236

SL

236236

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 climate system

The climate system


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


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

Coupled atmosphere / ocean climate model

Radiation

Atmosphere: Density

Motion

Water

Heat

Exchange of: Momentum

Water

Ocean: Density (inc. Salinity)

Motion

Sea

Ice

Land


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

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


Cloud radiation feedback

Cloud Radiation Feedback


Cloud radiation feedback1

Cloud radiation feedback


Global average change in t c

Global average change in T /C


Model estimates of cloud radiative forcing with co 2 doubling

Model Estimates of Cloud Radiative Forcing with CO2 Doubling


Effect of cloud feedback formulation on climate prediction

Effect of cloud feedback formulation on climate prediction

  • Feedback schemeGlobal Av Temp change,C for doubled CO2

    • RH5.3

    • CW2.8

    • CWRP1.9

    • after Senior & Mitchell, Hadley Centre


Net cloud forcing january to july

Net cloud forcing: January to July

Hadley Centre


Ship tracks under cloud

SHIP TRACKS UNDER CLOUD

Washington

state


Ocean interactions

Ocean Interactions


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

IPCC Synthesis Report


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

Strength of the thermohaline circulation in the North Atlantic.

Hadley Centre


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

Modelled transport of water in Atlantic conveyor belt

IPCC Third Assessment Report


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.


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

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

Hadley Centre


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

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

Surface Temperature

Cooling over UK: 1-3°C


The carbon cycle

The Carbon Cycle


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

IPCC Third Assessment Report


Human perturbation of the carbon cycle

Human Perturbation of the Carbon Cycle


Partitioning of co 2 uptake using o 2 measurements

Partitioning of CO2 uptake using O2 measurements


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


Carbon cycle feedbacks

Carbon cycle feedbacks


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

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

between 1860 and 2100

- predicted by Hadley Centre climate model

Hadley Centre


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

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

Hadley Centre


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

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


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

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


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

Photo: Tim Hewison


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

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


The climate of the 20 th century

The Climate of the 20th Century


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

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


Simulated annual global mean surface temperatures1

Simulated annual global mean surface temperatures


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


Climate projections for the 21st century

Climate Projections for the 21st century


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

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


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

Globally averaged tempertaure change for scenario SRES B2

IPCC Third Assessment Report


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

Globally averaged precipitation change for scenario SRES B2

IPCC Third Assessment Report


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

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


Simulated temperature rise and thermal expansion for the 4xco2 experiment

Simulated temperature rise and thermal expansion for the 4xCO2 experiment


Regional climate modelling

Regional Climate Modelling


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

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!


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

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

Hadley Centre - PRECIS brochure


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

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


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

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


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

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


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

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


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

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


Is the climate chaotic

Is the Climate Chaotic?


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