Climate Change

Hype or Reality?

http://www.dimplex-resource.co.uk/gifs/energy_the_issues/eti_climateChange.jpg

Global System

Min MaxAtmosphere -50ºC 50ºC

No Atmosphere -230ºC 120ºC

Conceptual Global Climate System

Atmosphere

Earth

Consider energy and mass transfers across system boundaries and processes or events that may alter their magnitude

Consider alterations of processes within the system

Space

How do we know that climate is changing?

What is the best evidence??

Individual Events CAN NOT be usedAs evidence of a trend!!!

www.kreybaby.com

http://jrscience.wcp.muohio.edu/photos/hurricane-luis-dmsp.gif

www.nationwidepaging.co.uk/ boscastle_flooding.jpg

www.stormchasing.com

www.gi.alaska.edu

web.utk.edu

www.accustudio.com

www.blogula-rasa.com

images.encarta.msn.com

Ice Core Fossils

Tree Rings VineyardsPaintings

Mountain Treelines

Athabasca Glacier: Canadian Rockies: www.sonic.net

Mer de Glace: French Alps

1826

2004

http://www.royalhigh.edin.sch.uk/

http://www.swisseduc.ch/glaciersPainting by Birman

Famous Graph

Newer version in IPCC 2007 report Global records indicate 12 warmest years in the record have occurred since 1990 (record length 1881-2005)2005, 1998, 2003, 2002, 2004, 2001, 1999, 1995, 1990, 1997, 1991, 2000

http://cdiac.esd.ornl.gov/trends/temp/lugina/lugina.html

IPCC (Intergovernmental Panel on Climate Change) Verdict “Warming of the climate system is

unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea-level”

IPCC (2007) Summary for Policymakers, p5. Notice past changes identified are gradual,

not catastrophic storms/hazards etc

Past Temporal Fluctuations

Temporal Fluctuations

Source: Moran & Morgan (1994). Meteorology. Macmillan College Publishing Co., New York, NY

Temporal Fluctuations

Source: Moran & Morgan (1994). Meteorology. Macmillan College Publishing Co., New York, NY

Whether we consider ourselves to be in comparatively warm or cool period is dependent upon length of time scale under investigation. Last 10,000 years indicates current relative cooler phase, whereas last 1,000 years shows relative warmer phase. Climate System is always changing!

The Enhanced “Greenhouse Effect”

Heat increased due to elimination of advection, i.e. no heat is transported away

from the surface

Heat increased by re-emission of energy by

radiatively active gases

Historic Carbon Dioxide Levels

Accepted idea that CO2 levels trigger climate change, positive relationship with temperature

http://upload.wikimedia.org/wikipedia/en/c/c7/CO2-Mauna-Loa.png

Carbon Dioxide Levels vs Temperature?

Majority View: Sponge Effect?

Wavelength selective absorption

Many influences on climate but they work at different time scales

Source: Moran & Morgan (1994). Meteorology. Macmillan College Publishing Co., New York, NY

EXTERNAL FACTORS

Natural external forcing agents Global solar energy

Sunspot cycles Intergalactic dust

Impacts on global solar distribution Milankovitch theory

Solar Influence: SUNSPOTS A) Cycle (approximately

every 11 years) B) Longer term

fluctuation linked to European temperatures, e.g. Maunder minimum and the Little Ice Age (1645-1715)

Length of cycle linked to temperature?

Minor influence

0

50

100

150

200

250

1750 1800 1850 1900 1950 2000Year

Cou

nt

Source: http://science.nasa.gov/ssl/pad/solar/greenwch/spot_num.txt

http://www.astro.washington.edu/ivezic/Astr598/sunspot.gif

Climatic Aspects and Sunspot Cycle

Sunspot Cycle Length

Long-time scale

Milankovitch Hypothesis Obliquity of rotation to orbital plane

Currently 23.4º but varies between 22º and 24.5º over a 41,000 year cycle

Greater influence felt towards the poles Eccentricity of orbit around the sun

Varies from almost circular to more elliptical than present over two cycles, 96,000 and 413,000 years

Current annual variation of global solar energy approximately 5% but maximum variation of 30%

Precession of equinoxes Defines the season when closest to the sun over a

cycle of approximately 22,000 years

BUT TOTAL RADIATION REMAINS CONSTANT

Milankovitch Cycles Corresponds well with cycles from proxy data Theory, in terms of variation of global radiation,

insufficient to account for changes in global temperatures

Feedback effects must also contribute to climate change

Source: http://www.doc.mmu.ac.uk/aric/gccsg/2-5-2-4.html

Milankovitch Cycles Combined effect is to redistribute energy input Total amount of radiation received by Earth in a

year stays the same: so global effect? Snow and ice amplify effects In hemisphere with lower summer solar input and

higher winter solar input – snow does not melt and ice sheets develop

– initiates an ICE AGE. Dominance of N. Hemisphere

NATURAL INTERNAL FACTORS Natural Internal Forcing Agents

Solar Radiation forcing Volcanoes

Earth evolution Orogony (Mountain building) Continental Drift

Incr

easi

ng ti

me

scal

e

VolcanicEruptions

http://cas.hamptonu.edu/centerinfo/photo-album/ScienceGraphics/images/volcano.jpg

Only lasts a couple of years

Dust Veil Index (DVI)

Orogony and Continental Drift Orogony

Mountain building due to tectonic forces

Increases upland area which may hold snow longer, thus increasing solar reflection - cooling

Continental Drift Dictates ratio of land surface

to ocean areas: supercontinents

Dictates where land and sea are located

Land and sea heat up differently and influence climate

PangaeaVERY LONG TIMESCALE

Continental Drift

High Latitudes and Altitudes : Snow and Icemeans high albedo and cooling

Low Latitudes: Vegetation or Desert (depends on precipitation) – former means cooling through the CO2 effect, later means warming.

HUMAN INTERNAL FACTORS

Anthropogenic Internal Forcing Agents Human-based activity and land-use change

such as urbanisation Growth in existing natural background levels

of greenhouse gases

Humans: Land Use Change

http://www.bbc.co.uk/schools/gcsebitesize/geography/images/santiago.jpg

BUT: is this just local?

Deforestation

Urbanisation

Major Greenhouse Gases

Source: http://www.grida.no/climate/ipcc_tar

Major Greenhouse Gases

Classified by activity type

Humans: Greenhouse Gases

Current CO2 concentration: 380 ppmv – Parts per million volume

Between 1970 and 2004, emissions have increased by 70%

77% of total emissions is CO2

But also note methane (CH4)and nitrous oxide (N2O)

Forecast concentration, by 2100:500 – 1000 ppmv (wide range indicates economic uncertainty

GWP (Global Warming Potential)Time Horizon

20yrs 100yrs 500yrsCO2

MethaneNO2

CFC-11CFC-12HCFC-22

163

270450071004100

121

290350073001500

19

19015004500510

The warming effect of an emission of 1kg of each gas relative to that of CO2 = GWP (Global Warming Potential)

Note that methane is 63 times more powerful in the short term but has a relatively shorter atmospheric lifespan, hence only 9 times more powerful over 500 years

Composite Model

Combination of known factors appear to explain major changes in global climate

Some doubt cast upon validity – see Idso, K.E. (2001) Predicting the past: Its not that difficult at http://www.co2science.org/edit/v4_edit/v4n4edit.htm

Source: Gilliland, R.L.  1982.  Solar, volcanic, and CO2 forcing of recent climate changes.  Climatic Change 4: 111-131.

The Future? Predictions based on modelling

Energy Balance Models Global Climate Models

Scenarios of CO2 consumption used: modelling of economics as well as atmosphere AIFI scenario leads to doubling of CO2 by 2050, and 1550

ppm by 2100. Alternative lesser increases used to indicate global action:

B1 (600 ppm by 2100), AIT, B2, AIB, A2

Carbon Dioxide vs Temperature?NON-LINEAR

Fatalistic Viewpoint

Thresholds

Global Carbon Cycle

www.globalchange.umich.edu

Problem:Figures don’t balance

BIG

SMALL

Possible Feedback LoopsMore cloud

Less surface heating

Less convection

Less cloud?

-ve

Surface heating

Melting Less ice

Reduced albedo

+ve

Clouds

Ice/Snow

UNKNOWNS

http://www.geog.ucl.ac.uk/~jfogarty/GCM_essay.html

Permafrost: Methane Release

http://www.planetextinction.com/images/Permafrost.jpg

Problems with GCM’s Clouds not incorporated well

Serious deficiencies in treatment Changes in snow/ice cover badly modelled

Albedo of snow highly significan Coupling of ocean and atmosphere

Thermal inertia of ocean systems Polewards transport of energy

More confidence with temperature predictions than rainfall predictions: smooth vs spotty distribution

Feedbacks can lead to instability in the model

Future Predictions Intergovernmental Panel on Climate Change(IPCC)

Predictions updated 1990, 1996 and 2001, 2007 Global

Current rates of warming around 0.1-0.2 deg C/decade

Current mean estimate of 1.8ºC<>4.0ºC by 2100 (depends on scenario)

Constant 2000 concentrations: 0.6°C by 2100 (lag) Regional (see map)

Two main climate model types One way to avoid economic uncertainty is to

predict for 2 *CO2, NOT a date

Transient (time series) – takes time to adjust

Equilibrium: 1 * C02 vs 2 * CO2 Model allowed to come into equilibrium Take the difference between the two

predictions, i.e. + 2 deg C

Future Global change 2 times CO2

Most warming: Land, N hemisphere: Least certain: mid-latitudesGreen lines represent areas of uncertainty

Regional Detail: Europe: Hadley Centre GCM

Note relativelypoor grid resolution

Summer Precip Winter Precip

Annual Precip

Annual Temp

Most of the warming is focused in currently cold areas(snow and ice feedback) Logically this should reduce temporal and spatial variability of Earth’s climate at the surface

This may influence extreme events?

PREDICTING EFFECTS is not just temperature and precipitation?

Extreme Events: StorminessThunder

Wind

Waves

Rain Ice and Snow

Storm Tracks and GW

270

290

310

330

350

370

390

1948 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998year

num

ber

Frequency

Quinary mov.avg.

Timeseries of the number of storm events recorded at 24 hour intervals.

20

30

40

50

60

70

80

1948

1952

1956

1960

1964

1968

1972

1976

1980

1984

1988

1992

1996

2000

Year

Num

ber

Frequency

Quinary mov. avg.

Timeseries of the number of severe lows (max gradient greater than or equal to 45m/250km)

16

16.5

17

17.5

18

18.5

19

19.5

20

1948 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998year

geop

oten

tial h

eigh

t gra

dien

t (m

/250

km)

meanQuinary mov. avg.

Timeseries of average intensity (mean pressure gradients)

25

26

27

28

29

30

31

32

33

1948 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998year

inde

x va

lue

symmetry

Quinary mov. avg.

Timeseries of mean symmetry index

North Atlantic Cyclones: Western Europe

Source: Amanda Gibson (2006): Unpublished phD Thesis

F I

FSevere Sym

Hurricanes: Uncertain

Increase over N AtlanticFrom 1995 to present, butThere were similar high frequencies in the 1950s.

Maybe a cycle: Maybe not?

Statistics are inconclusive

Tornadoes:

Uncertain Data

Changes in reportingand better detectionmakes the data inhomogenous

Mountains

Complicated landscape

Glacial Change in East Africa

Polar Regions

Sensitive to change, snow is a natural cooling system, protects the groundas an insulator, frozen lakes can be used for transport, hunting etc.

Mediterranean: Desertification

Portsmouth: coastal flooding: Old Portsmouth 1989, but also both more and less rainfall?

So what can we do?

Figure 1. Global average temperature change projected from 16 different climate models for the 21st century if atmospheric CO2 levels are held constant at the year 2000 levels.

Figure 1. Global average temperature change projected from 16 different climate models for the 21st century if atmospheric CO2 levels are held constant at the year 2000 levels.

http://www.worldclimatereport.com/index.php/2006/04/Sceptic website!

Future scenarios

Source: IPCC 2007 Report: Mitigation of Climate Change

Sunspot CyclesOrbital CyclesInterstellar Dust

Conceptual Global Climate System

Global Circulation Systems

Solar EnergyTerrestrial Energy

Solar Energy

Short-wave and long-wave energy balance

Volcanic Dust

Gas Emissions

Surface Conditions

Atmospheric Chemistry Radiative Forcing

Thermodynamic Forcing

SUMMARY POINTS Climate change at many time scales: past changes have been

caused by many mechanisms superimposed upon one another

Changes in mean temperature and or precipitation may be seen in the past reconstructions and modelled in the GCMs, but this is not the whole description of climate

Extreme events are a real problem! to predict and understand! They are also not good to use as evidence of past or current climate change, and there is much uncertainty here.

Many unknowns concerning degree and extent of response – we are interfering with a complex system

Surely we should limit our interference as much as possible even though there are scientific and economic uncertainties?

Internet Resources

http://www.climnet.org/ A useful site belonging to Climate Action Network Europe, great links

http://www.ipcc.ch/ The Intergovernmental Panel on Climate Change: Read the 2007 Scientific Basis report

http://www.meto.gov.uk/research/hadleycentre/models/modeldata.html Met OfficeWeb site gives some model data and predictions for the future

http://www.realclimate.org/ Climate science from climate scientists

http://www.co2science.org/scripts/CO2ScienceB2C/Index.jsp Alternative viewpoint

http://www.portsmouthcan.co.uk/ Local action network for climate change mitigation

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