Transcript Global Warming

The Great Global Experiment
‘Climate Change and its Consequences’
The fragility of spaceship earth
Lecture outline
•The Science
•Empirical Support
•Adaptation
Some underlying drivers of the
world’s climate & weather
Gravity
Earth’s rotation
Solar radiation
Volcanoes
Topography
Life
Radiation, Chemistry & Dynamics
• Radiation: provides the heat source
• Chemistry/Biology: modifies atmospheric composition
• Dynamics: creates weather patterns & distributes heat
Integration: together produce a complex system
Radiation
Shortwave (solar) :
from the sun; dominates incoming sources
Longwave (terrestrial) :
from the earth, dominates outgoing sources
Without the Coriolis effect, the balance of incoming and
outgoing radiation gives a picture of the earth’s climate (i.e. if
we ignore dynamics)
THE GREENHOUSE EFFECT
The Met.Office Hadley Centre
SUN
high
temperature
Solar radiation
high temp’ source
-short wavelength
Some solar radiation is
reflected by the earth’s
surface and the atmosphere
Some of the infrared
radiation is absorbed
and re-emitted by the
greenhouse gases.
The effect of this is to
warm the surface
and the lower
atmosphere
ATMOSPHERE
Solar radiation
passes through the
clear atmosphere
Terrestrial radiation
low temperature source
longer wavelength
(Infrared)
EARTH
Low temperature
Most solar
radiation absorbed warming the surface
Early Contributors
 Fourier (1827) first advanced the idea that the
atmosphere acts like the glass of a greenhouse (Mem
de l’ Ac. R. de Sci de l’Inst de France Vol 7.)
 Tyndall (~1860) first to demonstrate & quantify the
impact of the greenhouse gases [infrared emitters]
 Arrhenius (1896) Provided first predictions of changes
in global temperature arising from increases in CO2
concentration. (Phil Trans 41, 237-276)
Breakdown of Warming caused by
Greenhouse Effect
without
Greenhouse
Surface
Temperature
-18oC
with
Greenhouse
+15oC
mean
Increase
33oC
Water Vapour responsible for 60-70% greenhouse effect
(~1% of atmosphere – a positive feedback of other GHGs))
Other Gases responsible for ~ 30-40% greenhouse effect
(~0.04% of atmosphere)
The Greenhouse Effect & Climate Change
The Greenhouse Effect is uncontested!
-without it the earth would be ~ 33K cooler.
Climate Change is uncontested!
-the balance of incoming and outgoing radiation has always fluctuated, with, for
example, changes in atmospheric constituents, their relative concentrations, solar
variations, etc.
Anthropogenic Climate Change is contested - a little.
-the disagreement centres on the degree to which human-induced changes in the
atmospheric make-up have altered the balance of incoming and outgoing radiation.
Future anthropogenic Climate Change is contested - a little.
-the level of future warming depends on the ‘climate sensitivity’ – i.e. how much
warming is likely for a doubling in CO2 concentration compared with pre-industrial
levels. (IPCC likely range is 2 to 4.5°C; most likely estimate is 3°C)
So what is changing?
Drivers:
 Position of the sun in relation to the earth
 Volcanic eruptions
 Solar cycle
 Concentration of greenhouse gases
What are the Greenhouse Gases
(those that absorb terrestrial, infrared, radiation)
•Water vapour
•Carbon Dioxide
•Methane
•Nitrous Oxide
•Hydrofluorocarbons
•Perfluorocarbons (PFCs)
•Sulphur hexafluoride (SF6)
Global Warming Potential (GWP)
The warming effect of Greenhouse gases
indexed to a molecule of CO2 integrated
over 100 yrs.
Global Warming Potential (GWP)
Lifetime
GWP(100)
Carbon Dioxide
100+
1
Methane
9-15
28
Nitrous Oxide
114
265
Hydrofluorocarbons
1-264
1000-12400
Perfluorocarbons
2600-5000
6500-9200
Sulphur hexafluoride
3200
23500
Global Warming Potential (GWP)
GWP(20)
Carbon Dioxide (1)
GWP(500)
1
1
Methane (28)
~80
8
Nitrous Oxide (114)
265
153
Data examples underpinning
climate change
- Tree rings – 10,000 years – reflect
water availability
- Ice cores –160,000 years – Oxygen
isotopes and air bubbles (with CO2)
provide information (e.g. 1ppm
difference in oxygen isotope is
equivalent to a 1.5ºC temp changes)
- Ocean sediment – million years –
proportion of heavy oxygen in sea
shells goes up when temperatures
drop
Trends of main greenhouse gases
atmospheric concentrations
pre-industrial
concentration
~2015/16
concentration
%
Increase
CO2
280ppmv
+400ppmv
~43%
CH4
700ppbv
~1835ppbv
~162%
N 20
270ppbv
328ppbv
~22%
Historical temperature trend
CO2 Concentration in Ice Core Samples and
CO2 concentration has increased
by ~42%
since
Projections
for Next
100 1750
Years - 280ppmv to ~400ppmv
Projected
(2100)
2050-2100?
700
The current CO2 concentration has not been exceeded during past 800 000yrs
and…probably
notRecord
during the past 5 million years
Vostok
600
650
500
Evidence for being human made - CO2 from fossil fuels contains no 14C unlike
the ‘background’ atmospheric CO2
450
2016:
400
Current
(2001)
350
300
250
200
150
400,000
300,000
200,000
Years Before Present
100,000
0
CO2 Concentration (ppmv)
550
IPCC IS92a Scenario
Law Dome Record
Mauna Loa Record
Greenhouse Gas Flows
Note: 1 Giga tonne (Gt) is 1000 million tonnes
•Global flow of CO2
~ 750 Gt p.a
•Human emissions of CO2
~ 40 Gt p.a.
• Human CO2 added to Atmosphere
~ 18 Gt p.a
This has led to a:
… ~ 42% increase in atmospheric carbon
concentration since ~1800
To Conclude the Science Section:
 Greenhouse effect is understood
 Atmospheric concentrations of
greenhouse gases are rising
 Empirical data tends to support the
science and the models
 Feedbacks are, to some degree,
understood (net effect exacerbates warming)
Where do human emissions come from ?
What can we do ?
• Learn to live with increased climate change (adaptation)
• Find ways to reduce carbon emissions (mitigation)
Adapt to What ?
• More severe weather events
• Destruction of Ecosystems
• Flooding
• Food shortages
• Fresh Water shortages
• Human Migration
• Increased Military tension
• Changes in Disease
Adaptation: Equity & Morals!
High Carbon emitters geographically & financially able to adapt
Low Carbon emitters suffer geographically and financially from
climate change impacts - also have less political influence
____________
Today’s generation are the Cause
Tomorrow’s generation suffer the Impacts
Adaptation: Equity & Morals!
 http://www.carbonmap.org/#Emissions