Water

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Water Civilisation the Future in a Changing
Climate?
Brian Hoskins Royal Society Research Professor
Professor of Meteorology University of Reading
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Two basic water themes

• Water plays a central role in the climate system
  in climate change
• Water is central to all life, in particular to
  human civilisation its development

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Water, Life and Civilisation An interdisciplinary
project funded by the Leverhulme Trust
EUPHRATES VALLEY Mesopotamian Civilisation
6500 BC
JORDAN VALLEY Origin of agriculture, 10,000
BC First towns, 8500 BC
NILE VALLEY Egyptian Civilisation, 3500 BC
Aim To assess the impact of changes in the
hydrological climate on past, present and future
societies in the semi-arid regions of the Middle
East and North Africa, with a case study of the
Jordan Valley
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Summer 2002 Flooding in Central Europe
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July 2002 Drought in India
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All-India Summer Monsoon Rainfall
(1871-2003)(Based on IITM Homogeneous Monthly
Rainfall Data Set)
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Water uses by humans food, household,
industry energy Vital for rest of nature also
for some diseases
Currently equivalent to 0.3 of global
precipitation, 1.5 of that on land, 10 of that
flowing to sea
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• The atmosphere contains a relatively minute
  amount of water (equivalent to 2.5cm)
• The average evaporation and precipitation is
  about 3mm per day
• Every year the atmosphere cycles about 40 times
  the amount stored in it, equivalent to about 1
  meter of water globally
• The rate of flow of water between the global
  atmosphere and ocean is about ¼ that in the Gulf
  Stream

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Global Water Cycle A Complex System

• The hydrological cycle, powered by energy from
  the sun, is a continuous exchange of moisture
  between the oceans, atmosphere and land.
• It operates on all time and space scales,
  involving many non-linear processes.

• Terrestrial biosphere
• Extracts water from the soils
• Returns water to the atmosphere
• BUT the biosphere is highly dependent on local
  rainfall

• Over land precipitation exceeds evaporation
• Water is returned to the ocean in a complex way
  on timescales from days to centuries

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Global Energy Balance
..IR is radiated to space from the atmosphere
leading to cooling...
SUN
most IR is absorbed by some gases in the air,
and re-radiated
Most solar radiation passes through the
atmosphere..
Infra-red/thermal radiation (IR) is given off by
the earth...
..and about ½ warms the earth.
The Greenhouse Effect
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The Natural Greenhouse Effect

• Earths surface more than 30C warmer because of
  it
• Major greenhouse gases water vapour, carbon
  dioxide, methane..

Fourier (1827) recognised named Tyndall (1860)
measured suggested possible cause of Ice Ages
Arrhenius (1896) calculated impact of doubling
CO2

• Other water related influences on energy balance
• high clouds warm low clouds cool surface
• snow and ice on surface reflect sunlight cool
  surface

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The Fluid Parts of the Climate System in Action
Energy is transferred polewards by the atmosphere
and ocean
SUNS RAYS
Regional climate depends on the circulation of
the ocean and atmosphere (the weather)
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Natural causes of climate change
Orbital parameters
Explosive volcanoes
Solar activity
Plus natural internal variability
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Possible human impact on large-scale climate?
Negligible direct impact of energy and water usage
Direct impact on level of greenhouse
gases Carbon dioxide fossil fuels,
deforestation (100 years) Methane
agriculture, natural gas (10
years) Other gases (nitrous oxide, CFCs,
ground-level ozone..)
Indirect effects through water a warmer
atmosphere can hold more water (3ºC warmer, 20
more water) a surface with less snow reflects
less of the suns radiation
Also small particles from power generation
transport (1-2 weeks), land use change
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Atmospheric concentrations of some greenhouse
gases over the past thousand years
IPCC (2001)
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Atmospheric concentrations of carbon dioxide and
methane over the last 400,000 years
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Estimates of northern hemisphere temperature for
the past 1000 years
Drawn by Tim Osborn using published data
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Globally averaged surface temperature since 1861
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Other observations that suggest climate may be
changing

• INCREASE
• Length of freeze free season
• Length of growing season
• Frequency of heat waves
• Greenland ice-sheet melt
• Sea level height
• River flow into Arctic
• Heavy precipitation events

• DECREASE
• Number of frosts
• Sea-ice amounts and thickness
• Extent of mountain glaciers

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Northern Hemisphere late summer minimum sea ice
extent changes Trend -8 per decade
Source National Snow and Ice Data Centre (Sep.
2005)
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Greeland Ice Sheet Melt Extent
Greenland ice sheet melt area increased on
average by 16 from 1979 to 2002. The smallest
melt extent was observed after the Mt. Pinatubo
eruption in 1992
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Surface Melt on Greenland
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Historical retreat of non-polar glaciers
World Glacier Monitoring Service
www.geo.unizh.ch/wgms
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Sea level has risen by 1020 cm/century
Source IPCC TAR
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Change in the number of days with heavy
precipitation
Significant trends
Consistent with more water in the atmosphere
Spatial average (relative to 1961-90)
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Making quantitative projections ( hindcasts) of
Climate Change
Scenarios from population, energy, economics
models Carbon cycle and chemistry models Gas
properties Coupled climate models Impacts
models
EMISSIONS
CONCENTRATIONS CO2, methane, etc.
HEATING EFFECT Climate Forcing.
feedbacks
CLIMATE CHANGE Temp, rain, sea level, etc.
IMPACTS Flooding, food supply, etc.
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Warming since 1860 observations models
NATURAL ONLY
HUMAN ACTIVITY ONLY
Observations
Spread from set of simulations
NATURAL HUMAN
Most of the observed warming over the last 50
years is likely to have been due to the increase
in greenhouse gas concentration(IPCC 2001)
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• Running models on the past helps give confidence
  in them and helps answer the question whether
  some of the changes seen can be attributed to
  human influence.

• Human influences will continue to change
  atmospheric composition throughout the 21st
  century
• What climate changes will occur in the future and
  at what rate depends on
• How much greenhouse gas emissions grow
• depends on population growth, energy use, new
  technologies, etc
• How sensitive the climate system actually is to
  emissions

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International Response
United Nations Framework Convention on Climate
Change (UNFCC) stop dangerous climate
change Kyoto Protocol discussions on what
next. Periodic scientific assessments by the
Intergovernmental Panel on Climate Change (IPCC)
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CO2 Emissions to 2000, and IPCC projections to
2100
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Global average surface warming due to this range
of future emissions according to one model
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Geographical distribution of warming for
2071-2100 for 1 model 1 scenario
Annual means relative to 1990. Global mean in
2085, 3.1C
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Changes in Climate Extremes
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Projections of 21st century global precipitation
from many models
? Predictions of change for global precipitation
more uncertain than for temperature. ? All
models predict an increase, but the amounts vary
e.g. 1.5 to 9 for 2100 .
Source IPCC, 2001
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Distribution of 2080s annual precipitation
changes relative to present day for 1 model 1
scenario
IPCC High (A1FI) emissions scenario
SD
Generally wetter regions get wetter drier
regions drier
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Arctic summer sea-ice would disappear by 2080s
according to 1 model with high emissions scenario
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One Projection of Permafrost Melting
Projected reductions in near-surface permafrost
in 21st century
Alaskan sinkhole caused by melting ice pocket
Lawrence and Slater, 2005
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Greenland ice sheet
Reduction over the next 3000 years following
quadrupling of CO2 leading to sea level rise of
7m
The disappearance of the ice sheet could become
inevitable in the next 100 years
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IPCC estimates of global mean sea-level rise
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• One projection of change in annual number of
  people flooded
• Change from the present day to the 2080s (no
  adaptation unmitigated emissions)

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One prediction of changes in water availability
in 2050s with consequences for droughts and
floods for A1 scenario

Source Arnell (2004)
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One projection of change in average crop yields
for staple crops wheat, maize and rice.
Yellow, brown and red areas denote lower
yields Increased yields in some northern
latitudes due to more favourable climate
2020s
2050s
2080s
-40 0 40 change
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Impacts on Human Health Transmission window for
malariaNPL, New Delhi
Projected with climate change
Base case
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The likely future for water

• Dry regions drier, wet regions wetter, some
  shifts
• Seasonal changes e.g drier summers wetter winters
• More heavy precipitation events
• Soil moisture river flow changes
• Arctic sea ice reduction
• Glacier retreats
• Greenland ice cap reduction (demise?)
• West Antarctic Ice sheet??
• Sea level rise
• Permafrost reduction

Plants higher temperature - more demand for
water higher carbon dioxide less demand for
water
Population rise and socio-economic development
imply higher demand for water
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• There is still much uncertainty in the detail,
  but it seems that any climate surprises are more
  likely to be nasty ones.
• Changes in averages and extremes in climate with
  significant impacts in the natural and human
  world appear to be almost inevitable
• Dangerous climate change is a socio-political
  concept not a scientific one the danger
  certainly increases with increased GHG emissions
• Both mitigation and adaptation are required
• Water is a strong reason for mitigation is at
  the centre of adaptation
• Energy production use is at the centre of both

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Future CO2 emission targets?
Recommendations of the Royal Commission on
Environmental Pollution, 22nd Report, June 2000

• Aim to stabilise long-term atmospheric CO2
  content at as low a level as possible given
  todays technology and growing economy
• Reduce back to 1995 global emissions by 2050
  (1t/person/year) with further reductions
  thereafter for 550ppmv stabilisation
• Equity an equal per-capita emission target
  worldwide

• Requires 60 reduction of UK emissions by 2050

Energy The Changing Climate, RCEP (2000)
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Water civilisation the future in a
changing climate?
Considerable uncertainty in the detail, but the
likelihood of real increasing problems

• Prescription
• Urgent action to limit the rate magnitude of
  climate change due to human activity
• Development of socio-political-technological
  systems to improve the handling of water other
  issues

Vital roles for governments industry,
commerce scientists, technologists,
economists, sociologists individuals